Genetic pathways in cerebral palsy: a review of the implications for precision diagnosis and understanding disease mechanisms

Abstract

Cerebral palsy is a diagnostic term utilized to describe a group of permanent disorders affecting movement and posture. Patients with cerebral palsy are often only capable of limited activity, resulting from non-progressive disturbances in the fetal or neonatal brain. These disturbances severely impact the child's daily life and impose a substantial economic burden on the family. Although cerebral palsy encompasses various brain injuries leading to similar clinical outcomes, the understanding of its etiological pathways remains incomplete owing to its complexity and heterogeneity. This review aims to summarize the current knowledge on the genetic factors influencing cerebral palsy development. It is now widely acknowledged that genetic mutations and alterations play a pivotal role in cerebral palsy development, which can be further influenced by environmental factors. Despite continuous research endeavors, the underlying factors contributing to cerebral palsy remain are still elusive. However, significant progress has been made in genetic research that has markedly enhanced our comprehension of the genetic factors underlying cerebral palsy development. Moreover, these genetic factors have been categorized based on the identified gene mutations in patients through clinical genotyping, including thrombosis, angiogenesis, mitochondrial and oxidative phosphorylation function, neuronal migration, and cellular autophagy. Furthermore, exploring targeted genotypes holds potential for precision treatment. In conclusion, advancements in genetic research have substantially improved our understanding of the genetic causes underlying cerebral palsy. These breakthroughs have the potential to pave the way for new treatments and therapies, consequently shaping the future of cerebral palsy research and its clinical management. The investigation of cerebral palsy genetics holds the potential to significantly advance treatments and management strategies. By elucidating the underlying cellular mechanisms, we can develop targeted interventions to optimize outcomes. A continued collaboration between researchers and clinicians is imperative to comprehensively unravel the intricate genetic etiology of cerebral palsy.

Introduction

Cerebral palsy (CP) is an umbrella diagnostic term that describes a group of permanent disorders that affect movement and posture. Patients with CP often experience limited activity, attributed to non-progressive disturbances in the developing fetal or infant brain, along with accompanying conditions such as mental retardation, epilepsy, perceptual impairment, language impairment, and mental behavior abnormalities. CP is also a leading cause of motor disability in children (Rosenbaum et al., 2007). Recent reports indicate a current birth prevalence of CP in high-income countries of 1.6/1000 live births, with markedly higher rates of 3.3/1000 live births in low- and middle-income countries (McIntyre et al., 2022). Furthermore, it is noteworthy that approximately 40% children with CP are unable to walk independently (Kirby et al., 2011; Christensen et al., 2014), one-third are affected by epilepsy (Reid et al., 2016), up to one-third experience language impairment (Mei et al., 2016), and almost 50% suffer from some form of cognitive impairment (Christensen et al., 2014; Delobel-Ayoub et al., 2017).

The etiological pathways of CP have been extensively documented in terms of symptoms and consequences. However, our understanding of the role of genetic factors remains less comprehensive. While birth asphyxia and perinatal factors were once thought to be the primary causes of CP, recent studies have revealed that they only account for a minority of cases. It is now well-acknowledged that a significant contribution comes from various underlying genetic mutations and alterations (Jin et al., 2020). Understanding these complex and heterogeneous genetic factors, along with their interaction with environmental influences, necessitates an in-depth exploration to better understand the genetic foundations of CP.

The field of genetic research in CP has seen remarkable advancements, which have substantially expanded our knowledge of the disease substantially. Utilizing whole-genome sequencing and exome sequencing, researchers have identified various mutated genes and genetic alterations associated with CP (Moreno-De-Luca et al., 2021; Srivastava et al., 2022). Nevertheless, several gaps remain in our comprehension of how these genetic factors interact with and contribute to the overall clinical presentation of CP.

Herein, we provide a comprehensive review of the current understanding of the genetic factors influencing CP development. We aim to elucidate the role of various genetic factors and synthesize findings from different genetic studies conducted to date. Additionally, this review will identify areas that require further research to fully comprehend the genetic etiology of CP. By enhancing our understanding of the genetic causes of CP, we intend to highlight potential targets for therapeutic intervention and pave the way for personalized treatment approaches. Ultimately, our goal is to translate these insights into improved care and outcomes for individuals with CP.

Database Search Strategy

This review article aims to compile, elaborate on, and categorize research concerning genes implicated in CP. The literature incorporated here includes clinical diagnoses, research reviews, and experimental validation studies. We utilized databases such as OMIM (www.omim.org/) and ClinVar (www.ncbi.nlm.nih.gov/clinvar/) to identify genes associated with CP. Subsequently, an exhaustive literature search was conducted on the PubMed database. Our literature search strategy involved pairing “cerebral palsy” with each of the following: (a) genes, (b) whole exome sequencing, (c) whole genome sequencing, and (d) mutation. For instance, this resulted in search strings such as (1) + (a), which translates to “cerebral palsy and genes”, (1) + (b), (1) + (c) and (1) + (d). We focused on relevant clinical diagnoses and follow-up with a statistical analysis of the associated genes. Most of the studies chosen for review were published between 2011 and 2023.

Overview of Cerebral Palsy

In the 1940s, two American voluntary organizations, the National Society for Crippled Children/Easter Seals and the United CP, jointly sponsored two demographic surveys to estimate the prevalence of CP (Sandifer, 1953). These surveys conducted statistical analyses on the incidence of CP in selected counties in the United States and Europe. They found prevalence rates of 4/1000 and 5.9/1000 in Phelps and Schenectady in the United States, respectively, 1.0/1000 in Escher and Sknekel in the United Kingdom, respectively, 1.5/1000 in Thomas in Denmark, 0.6/1000 in Sweden, and 1.9/1000 in Norway. These variations in statistical prevalence suggest non-uniform criteria for defining CP, differentiating it from other movement disorders, and determining the severity of defined cases. Since 1958, a series of global conferences on the definition and classification of CP have been conducted, leading to a refined definition of CP (Figure 1; Perlstein, 1952; Balf and Ingram, 1955; Bax, 1964; Little, 1966; Mutch et al., 1992; Rosenbaum et al., 2007).

Figure 1.

Evolution of the definition and classification of CP over time.

This figure visually presents the historical development of the definition and classification of CP, spanning from 1958 to now. Key global conferences and their impact on the understanding of CP are depicted along the timeline, highlighting the continuous efforts to refine the definition and classification of this condition. These advancements contribute to establishing consistent diagnostic criteria and assessing the severity of CP across various organizations. Created using Microsoft PowerPoint. CP: Cerebral palsy.

Clinical Manifestations and Diagnostic Criteria of Cerebral Palsy

Typically, the diagnosis of CP is often established by a specialized physician during early infancy; however, it is susceptible to misdiagnosis because of various factors. The diagnosis is now considered more accurate after the age of 2 years. While the presence of persistent primitive reflexes or motor patterns beyond the expected age serve as a diagnostic indicator for CP, it is important to emphasize that the primary clinical feature defining this condition is motor impairment. This impairment encompasses a range of symptoms, including the persistence of primitive reflexes (Oskoui et al., 2017; Michael-Asalu et al., 2019); this inhibits or delays motor development and the acquisition of higher levels of neuromotor skills (Mohamed et al., 2023). Therefore, high-risk CP should be the prime diagnosis when milestone movements described below cannot be performed by the child at the expected age.

Infants aged 3–6 months raise their head while lying on their back which appears stiff and limp (Li et al., 2018). When held in someone's arms, the infant hyperextends its back and neck. When lifted, the infant's legs may become stiff, crossed, or scissor-like. Infants over the age of 6 months cannot roll in either direction, have difficulty closing their hands, struggle to reach their mouths, and can only reach out with one hand while tightly holding the other. Infants aged ≥ 10 months crawl in an unbalanced way, pushing forward with one arm and one leg while trailing the other arm and leg. Additionally, infants move or jump rapidly on their hips but cannot crawl on all fours.

Patients with CP are diagnosed by using four functional classification systems (Table 1). These classification systems assess their support and treatment needs in a standardized manner (Paulson and Vargus-Adams, 2017). The Gross Motor Function Classification System describes gross motor function, particularly walking ability, in children aged 2–18 years (Palisano et al., 1997; Rosenbaum et al., 2008). It also describes the child's ability to initiate movement autonomously and their motor ability with the aid of assistive devices such as walkers, crutches, canes, or wheelchairs (Palisano et al., 1997; Rosenbaum et al., 2008). The Manual Ability Classification System (MACS) helps describe how children aged 4–18 years utilize their hands or upper limbs when handling objects in daily life (Eliasson et al., 2006). Furthermore, the Communication Function Classification System describes the communication ability of individuals with CP, including their capacity to send or receive messages on a daily basis (Hidecker et al., 2011).

Table 1.

Four classifications of patients with cerebral palsy

Grade	GMFCS	MACS	CFCS	EDACS
1	Walk without restrictions.	Easy and successful picking up of objects.	Express and receive information effectively.	Eat safely and effectively.
2	Walk with restrictions (no mobility assistance for 4 years)	Handle most objects at a lower speed/quality.	Send and receive messages efficiently, but at a slow pace.	Safe dietary behavior, but limited efficiency.
3	Walk with mobile devices in hand.	Have difficulty in dealing with the subject and need help preparing or adjusting to activities.	Effective senders and receivers with familiar partners.	Limitations in safe eating and efficiency.
4	Limited ability to move autonomously, but may have other capabilities.	Handle a limited number of objects in an adapted environment.	Inconsistent communication and reception of information with familiar partners.	Dietary practices with significant safety restrictions.
5	Mobility with the help of a manual wheelchair.	Inability to handle objects.	Rarely communicate and receive information efficiently with familiar partners.	Inability to eat or drink safely, with the need for a feeding tube.

CFCS: Communication Function Classification System; EDACS: Eating and Drinking Ability Classification System; GMFCS: Gross Motor Function Classification System; MACS: Manual Ability Classification System.

The Communication Function Classification System encompasses all communication methods, such as vocalization, gestures, eye gaze, images, communication boards, or speech-generating devices (Reid et al., 2014). The Eating and Drinking Ability Classification System assists in describing the eating function of children aged ≥ 3 years by assessing eating safety (risk of aspiration or blockage) and eating efficiency (amount of food lost and time spent in eating) (Sellers et al., 2014).

CP encompasses a diverse range of neuropathological manifestations, reflecting its heterogeneous origins. Commonly observed neuropathological findings include periventricular leukomalacia, cortical or subcortical infarctions, malformations of cortical development, and hypoxic-ischemic lesions. These specific neuropathological changes can provide valuable clues to the underlying cause of CP and aid in differentiating between its various forms and etiologies. In-depth histopathological studies can reveal cellular-level abnormalities such as neuronal loss, gliosis, or inflammation, thereby further enhancing our understanding of the pathogenesis of CP (Adle-Biassette et al., 2017).

Numerous neuroimaging studies have been conducted in children with CP (Reid et al., 2014; Himmelmann et al., 2020). Brain abnormalities were observed in 86% of all magnetic resonance imaging (MRI) scans, with the lowest proportion seen in children with ataxia (24–57%). White matter damage was the most frequently identified imaging presentation (19–45%), despite significant heterogeneity. Other types of imaging presentations included gray matter damage (21%), focal vascular damage (10%), brain malformations (11%), and other outcomes (4–22%). Additionally, several clinical neuroimaging studies (Reid et al., 2015; White et al., 2018; Nakao et al., 2023) demonstrated a reduction in the incidence of white matter damage and an increase in the incidence of gray matter damage in cases of CP. Furthermore, the prevalence of CP in children has shown inconsistencies in recent years, which may be related to the lack of a uniform definition and criteria for determining CP, resulting in statistical bias.

Currently, the diagnosis of CP primarily relies on clinical manifestations, and imaging alone cannot be used as a major factor for confirmation. Therefore, a diagnosis of high-risk CP should be made in conjunction with clinical manifestations when white matter damage and other imaging manifestations are observed on MRI. Imaging provides greater accuracy in elucidating the pathological mechanism, thereby facilitating determination of the main cause of CP development. However, consensus regarding treatment methods for CP are yet to be reached, prompting further exploration of the pathogenesis of CP and the development of improved treatments.

Risk Factors for Cerebral Palsy

The risk factors contributing to CP are diverse, encompassing genetic and environmental aspects. These factors can be classified into prenatal, perinatal, and postnatal phases and may act independently or synergistically to increase the risk of CP. This section will focus on discussing key environmental risk factors.

Maternal factors

Several reports have demonstrated that socially disadvantaged children are more likely to develop CP than their non-disadvantaged counterparts (Maenner et al., 2012; Solaski et al., 2014; Oskoui et al., 2016; Tseng et al., 2018). For instance, African American children have a higher prevalence of CP than other children (Maenner et al., 2012). This may be attributed to divergences in maternal education attainment, which could account for the higher incidence of preterm birth among socially disadvantaged women compared with their non-socially disadvantaged counterparts. Additionally, the physical condition of the mother is also associated with CP to some extent.

Obesity

Analysis of a California database comprising 6 million newborns revealed a link between pre-pregnancy obesity and CP (Crisham Janik et al., 2013). The study classified mothers as morbidly obese or obese, with children born to morbidly obese mothers showing a significantly higher relative risk of CP than those born to obese mothers. Similar findings were observed in large studies conducted in South Carolina (USA) (Pan et al., 2014), Norway and Denmark (Forthun et al., 2016), and Sweden (Maenner et al., 2016). However, maternal obesity did not appear to be associated with an elevated risk of CP in infants born before 28 weeks of gestation (van der Burg et al., 2018). Therefore, it can be speculated that obesity-induced placental inflammation increases the risk of CP in the fetus.

Pre-eclampsia

An Australian study indicated a nuanced relationship between pre-eclampsia and CP risk among low-birth-weight infants. Specifically, when stratifying CP risk by birth weight, infants born to mothers with pre-eclampsia had a lower risk of CP. However, this pattern was not evident when the analysis was based on gestational age at birth, suggesting the greater importance of gestational age. Mothers with pre-eclampsia often give birth to infants who are smaller than expected for their gestational age, adding complexity to these relationships (Blair, 1996). Another Norwegian population-based prospective cohort study (Sun et al., 2020) involving 980,560 children born at term revealed that 28,068 (2.9%) children with CP were born to mothers with pre-eclampsia, clearly associating pre-eclampsia with CP. However, a systematic review and meta-analysis (Badagionis et al., 2022) including 10 studies found no statistically significant link between pre-eclampsia and CP. Therefore, it appears that pre-eclampsia is not directly associated with CP, rather may be linked to gestational age. Further research is needed to elucidate the specific relationship between the two.

Maternal infections

Maternal infections can lead to CP by transmitting pathogens to the fetus, even in the absence of detectable maternal inflammatory response (Leviton et al., 2010) and by inducing persistent systemic inflammation, which sensitizes the brain to subsequent injury (Dammann and Leviton, 2004; Dammann, 2016). Infections occurring during pregnancy, such as toxoplasma gondii, rubella, cytomegalovirus, and herpes simplex virus, are associated with an increased risk of CP (Smithers-Sheedy et al., 2014a, 2017). Perinatal maternal and infant chikungunya virus infection results in a subtype of CP with a predominant clinical presentation of microcephaly (Gérardin et al., 2014). In utero infection with the Zika virus may harm the fetal brain (Meneses et al., 2017), although the extent to which Zika virus affects CP is unknown. Clinical case studies and one cohort study investigated whether children with congenital Zika virus infection exhibited early signs of motor impairment and epilepsy. After 3–12 months of follow-up, 54% children developed seizures and impaired motor development (Pessoa et al., 2018). Additionally, various nonspecific indicators of infection, including maternal fever (Wu and Colford, 2000), maternal antibiotic administration (Gérardin et al., 2014), and chorioamnionitis (Wu and Colford, 2000) have been identified. Infections closer to delivery result in a higher risk of CP. Several studies have shown an association between early gestational infections and CP (Miller et al., 2013; Bear and Wu, 2016). However, another study concluded that early gestational infections did not affect the occurrence of CP (Brookfield et al., 2017). Furthermore, CP appears to be caused by a variety of brain developmental abnormalities, particularly neuronal migration disorders (Tsutsui et al., 1999), including cerebral fissure (Kułak et al., 2011) and bilateral perisylvian polymicrogyria (Clark et al., 2000). Cytomegalovirus infection may underlie these neuronal migration disorders (Smithers-Sheedy et al., 2014b).

Fetal factors

Birth asphyxia is closely linked to the development of CP (Roboz, 1962). The National Perinatal Collaborative further supports this finding, highlighting that abnormal neurological symptoms such as seizures, inability to suck, and respiratory distress observed in the neonatal period are primarily associated with asphyxia (Nelson and Ellenberg, 1986), particularly in neonates born at ≥ 35 weeks' gestation. Research has found that the incidence of CP is significantly higher in neonates with perinatal asphyxia than the healthy neonate population. This can be attributed to cerebral hypoxia and ischemia resulting from asphyxia. Prolonged exposure to these conditions can cause permanent neurological injury, which may eventually manifest as CP. Therefore, the prevention and treatment of perinatal asphyxia are essential for averting the development of CP (Zhang et al., 2020).

Birth weight, 5-minute, and 10-minute Apgar scores, as well as patterns of white matter injury associated with deep gray matter injury or near-total injury on MRI, are significantly higher in severe CP than mild CP (Zhang et al., 2020).

Together, these symptoms indicate that neonatal encephalopathy syndrome significantly increases the risk of CP. This syndrome is typically considered a result of hypoxic-ischemic brain damage, which can occur without identifiable factors during delivery and may also be closely related to pre-delivery factors. Hence, factors related to fetal asphyxia should be considered during delivery to implement necessary preventive measures.

Mechanical ventilation

Mechanical ventilation is commonly used in premature infants and has been linked to CP (Tsai et al., 2014). Ventilator settings that induce hypocapnia have been associated with brain injury on autopsy and an increased risk of CP (Giannakopoulou et al., 2004). Additionally, prenatal administration of steroids to stimulate lung maturation during preterm birth has been associated with a reduced risk of CP (Chawla et al., 2016). Conversely, postnatal steroid administration may increase the risk of CP (Linsell et al., 2016).

Up-regulation of inflammation-related protein levels

Up-regulation of one or more inflammation-related proteins during the neonatal period is associated with a two- to three-fold higher risk of CP in infants born before 28 weeks of gestation (Carlo et al., 2011). Inadequate levels of neurotrophic and/or angiogenic proteins in the blood may also influence the risk of CP and other neurodevelopmental disorders. For example, low levels of thyroid hormones may affect fetal cognitive function and are more likely to occur in cases of inadequate fetal synthesis or maternal iodine deficiency (Hong and Paneth, 2008).

Congenital brain malformations and CP

Congenital brain malformations are a significant yet understudied risk factor in the development of CP. These malformations are more prevalent among prematurely born children, and prematurity itself is recognized as a prominent risk factor for CP (Garne et al., 2008; Vassar et al., 2020). The complex and multifaceted association between congenital malformations and CP requires careful investigation and analysis.

Data extracted from the Canadian CP Registry indicate that approximately 23% children with CP also have accompanying congenital malformations. This prevalence establishes a compelling correlation, particularly considering the diverse impact these malformations have on the CP phenotype (Sévère et al., 2020).

A systematic review focused on the link between congenital anomalies and CP supports these findings. The review highlights a high prevalence of cerebral anomalies such as microcephaly and hydrocephaly and congenital anomalies are more common in term-born children with CP than in preterm children with CP. These data collectively emphasize the critical role of congenital anomalies, particularly cerebral malformations, as risk factors in the development of CP (Goldsmith et al., 2019).

Given the intricate interplay between congenital brain malformations and CP, further research is necessary to identify specific causal pathways and opportunities for prevention. Recognizing this connection enriches our understanding of CP etiology and brings us closer to the development of more precise and individualized therapeutic strategies.

Genetic factors and CP-related genes

In a notable subset of CP cases where known etiological factors such as jaundice, premature birth, or asphyxia are absent, genetic factors become plausible explanations. Therefore, elucidating potential genetic causes is crucial in these instances. Many children with clinical manifestations of CP do not have a history of known predisposing risk factors, while not all children with a history of multiple additional risk factors develop CP. This suggests the presence of unknown important risk factors that have not yet been identified. Recent meta-analyses investigating CP have provided valuable insights (Srivastava et al., 2022; Gonzalez-Mantilla et al., 2023). One study, comprising 13 studies, 15 cohorts, and 2612 cases, yielded a diagnostic rate of 31.1% for exome sequencing or genome sequencing (Gonzalez-Mantilla et al., 2023) Another analysis, including 15 studies with 2419 cases from 11 articles, revealed an overall diagnostic rate of 23% for exome sequencing (Srivastava et al., 2022). CP is typically considered a sporadic condition due to the diverse range of incidents causing static brain injury. However, familial aggregation in CP has been observed, with siblings of affected children having a disease risk up to 4.8 times higher than the general population. In twin cases, this risk increases up to 29 times compared with the control population. Importantly, a significant proportion of CP cases lack identified risk factors, making genetic causes potential contributors in such instances. This phenomenon may be related to the fact that multiple births themselves are a risk factor for CP. However, the impact of genetic factors on CP development has also been determined accordingly. Currently, genetic variants associated with CP have been identified, including single gene mutations, candidate genes, copy number variants, and single nucleotide polymorphisms, highlighting the critical role of genetic factors in the onset of CP (Mohandas et al., 2018; Jin et al., 2020).

Clinical genetic screening of children with CP using whole-genome sequencing and copy number variation studies has yielded crucial clinical data (Abe-Hatano et al., 2021) and identified numerous genetic mutations that cause early brain developmental delays or increased susceptibility. However, the exact causative mechanisms are yet to be explored. A search on the Genecards website (https://www.genecards.org) using the keyword “CP” yielded a total of 3955 CP-related genes. A combination of positive results from two cohorts (Moreno-De-Luca et al., 2021) revealed that 229 genes, constituting 29.5% of 1526 patients, were identified as containing pathogenic and possibly pathogenic variants. Additionally, 143 genes (62.4%) were mutated in a single case, and 86 genes (37.6%) had pathogenic and possibly pathogenic variants in two or more patients (20.1% of 1526 patients). In this study, the genes currently linked or suspected to be linked to CP were classified to explore the pathogenesis of CP based on their respective functions, offering a theoretical basis for the prevention and treatment of CP. An exome sequencing meta-analysis summarized the causative genes of CP (Srivastava et al., 2022). The most common molecular diagnosis was catenin beta 1 (CTNNB1)-related disorder, accounting for 23 of 667 patients (3%) with genetic disorders. The second-most frequent molecular diagnosis in the exome sequencing meta-analysis was SPAST-related disorder. In this study, the clinical phenotypes of patients remained stable and unchanged for decades, emphasizing the importance of studying CP genotypes for diagnosis and clinical treatment.

Coagulation factor V Leiden mutation

The coagulation factor V Leiden mutation (FVL) is characterized by an Arg506Gln mutation in coagulation factor V. Mutation at this locus, the site of action of activated protein C, inhibits activated protein C activity and prevents the inactivation of coagulation factor V (Thorarensen et al., 1997). The association between hemiplegic CP and placental thrombosis was first reported by Thorarensen et al. (1997). Their study identified three newborns presenting with cerebrovascular disease, including ischemic infarction and hemorrhagic stroke, associated with heterozygous FVL. One infant had multiple thrombi in the fetal placental vessels. FVL-induced activated protein C resistance to coagulation factor V production was the primary cause of familial thrombosis. This mutation is linked to arterial and venous thromboembolic illnesses in neonates, infants, and children; however, it is not a significant risk factor for ischemic stroke in adults. Furthermore, it has been proposed that activated protein C resistance might be a major factor responsible for intrauterine cerebrovascular disease and hemiplegic CP.

Additionally, Nelson et al. (1998) proposed an association of inflammatory mediators and markers of autoimmune and coagulation disorders with CP. They tested 53 analytes in neonatal dried blood from 31 children with spastic CP, mostly born at term, and 65 control children. Children with CP had higher concentrations of antibodies to antithrombin III, the translation product of FVL, and proteins C and S than the controls. Thus, both inflammation and coagulation abnormalities are involved in interacting pathways that may contribute to the etiology of CP in some cases. An ethical examination of 81 subjects in Ghana suggested that FVL may be associated with the onset of acute inflammation (Ababio et al., 2019).

The role of FVL in angioedema was recently proposed by Maroteau et al. (2020), who studied a total of 1066 samples from case and control groups with ACEI-induced angioedema (ACEI-AE) or ARB-induced angioedema (ARB-AE) and sequenced their genes. Their findings demonstrated a significant association between FVL and ACEI-AE and ARB-AE. Therefore, vascular inflammation caused by coagulation factor disorders may be associated with CP.

Moreover, numerous validation studies have been conducted on FVL in recent years. Neonatal screening of 443 Caucasian patients with CP and 883 normal Caucasians suggested that homozygous FVL may increase the risk of developing tetraplegia (O'Callaghan et al., 2013). Another study on spontaneous preterm birth indicated a higher risk of spontaneous preterm birth in Caucasians with fetal FVL (Gibson et al., 2005). However, several studies have also highlighted that homozygous FVL is not associated with the development of CP. A study on 61 Jewish and Arab children with CP and thrombophilia-associated gene mutations failed to demonstrate a significant correlation between homozygous FVL and CP, despite the high frequency of FVL in the studied population, as its mutation was common in this population (Yehezkely-Schildkraut et al., 2005).

Another case-control study with 94 patients with spastic hemiplegia and 120 healthy controls and their mothers showed that FVL was not a significant factor in the Mexican mixed-race population (Arenas-Sordo Mde et al., 2012). Similarly, a study involving 36 cases of hemiplegic CP and 41 controls without neurological deficits found no significant differences between the two groups with respect to FVL; methylenetetrahydrofolate reductase (MTHFR); prothrombin 20210A mutation frequency; and protein C, protein S, and antithrombin III levels (Türedi Yildirim et al., 2015). These studies evaluated each thrombotic disorder by correlating atrophy, periventricular white matter softening, infarction, congenital anomalies, and hilar cysts and found no significant correlation between thrombophilia and cranial imaging manifestations.

It is hypothesized that there may be ethnographic differences in the effects caused by FVL, which could be because of complex gene interactions. The effect of pre-delivery FVL on fetal development of CP is of significance, as manifested by intra-placental thrombosis, increased inflammatory factors in neonatal stem cells, and cerebrovascular edema, all of which can cause neonatal ischemia and hypoxia.

MTHFR mutation

5,10-Methylenetetrahydrofolate reductase is an essential enzyme involved in the folate metabolic pathway, converting 5,10-methylenetetrahydrofolate to the biologically functional 5-methylenetetrahydrofolate. This enzyme is responsible for maintaining low levels of homocysteine (Türedi Yildirim et al., 2015). However, gene mutations in MTHFR can result in elevated levels of homocysteine, which can lead to vascular endothelial cell damage and thrombotic disease (Fehlings et al., 2012).

A large case-control study conducted in Caucasians examined genomic DNA from 443 newborns with CP and 883 normal individuals. The study found that MTHFR C677T was associated with the onset of all types of CP (O'Callaghan et al., 2013). Additionally, MTHFR A1298C (heterozygous) reduced the risk of diplegia at 32–36 weeks of gestation, while MTHFR C677T doubled the risk of CP in preterm infants. Furthermore, the combination of purely heterozygous MTHFR C677T and heterozygous PGM increased the risk of tetraplegia by five-fold.

A study involving 169 healthy controls and 159 infants with CP in China demonstrated, for the first time, that MTHFR gene polymorphisms are a potential risk factor for the combination of CP and sub-intelligence (Cheng et al., 2011). Another study on 62 preterm infants with periventricular hemorrhagic infarction found polymorphisms in the MTHFR gene in these infants (Harteman et al., 2012). Similarly, a study genotyped 105 individuals with CP and 114 age-, sex-, and race-matched healthy controls, suggesting a possible relationship between MTHFR gene polymorphisms and CP pathogenesis in Chinese infants and children (Hou et al., 2016).

Nitric oxide synthase

Nitric oxide synthase (NOS) plays a crucial role in the nervous system and is found in endothelial cells, neuronal cells, and phagocytes (Xu et al., 2023; Zhao et al., 2023). There are three main subtypes of NOS: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS)(Berry, 2004). Among these, nNOS has been extensively studied. Each subtype is responsible for different functions, leading to the development of targeted drugs and therapies.

A study involving 443 children with CP and 549 infants born after spontaneous delivery in white South Australians found that prematurity was associated with iNOS in children without CP, while preterm birth was linked to eNOS in children with CP (Gibson et al., 2007). Another study using a highly selective nNOS inhibitor demonstrated its effectiveness in a rabbit model and its ability to prevent neurobehavioral symptoms of CP (Silverman, 2009). A study by El Ghazi et al. (2012) found that glutamate stimulated nNOS activity in the deep cortex of neonatal mice, and high levels of glutamate-induced NO production provided neuroprotection to neonatal mice compared to mature mice. An association study in the Chinese Han population found that nNOS gene polymorphism is likely involved in the pathogenesis of CP (Zhang et al., 2018).

Mitochondrion- and oxidative phosphorylation metabolism disorder-related genes

Mitochondria are energy-producing organelles involved in aerobic respiration. Mitochondrial and oxidative phosphorylation-related genes play a vital role in many ischemic and hypoxic diseases (Galluzzi et al., 2018). A study that collected biceps samples from 19 children with CP and 10 normally developing children revealed that children with CP had a lower ratio of mitochondrial DNA (mtDNA) to genomic DNA percentage compared to the control group. Additionally, reduced protein levels were observed in all mitochondrial respiratory chain complexes, except complex II. The number of mitochondria, mtDNA, and oxidative phosphorylation-related protein levels were also decreased in the muscles of children with CP compared with normally developing muscles (von Walden et al., 2021).

Abnormalities in mitochondria and oxidative phosphorylation-related genes not only contribute to abnormal muscle development and altered muscle tone but also have significant effects on the brain, as both the brain and muscles are high energy-consuming organs. Therefore, it is crucial to explore the effects of mitochondrial and oxidative phosphorylation genes on CP.

Mitochondrial fission factor

Mitochondrial fission factor (MFF) is a nuclear gene that encodes a protein involved in mitochondrial and peroxisomal fission. Disorders related to MFF include encephalopathy and mitochondrial encephalomyopathy caused by defects in mitochondrial and peroxisomal fission. MFF is associated with pathways such as apoptosis and autophagy. A rare case of an MFF gene mutation was reported in a family with CP, which was ultimately a variant of unknown significance (Sharma et al., 2021).

Neurons, particularly cortical long-range pyramidal neurons, exhibit compartment-specific organelle morphology. In these neurons, dendritic mitochondria are long and tubular, while axonal mitochondria are uniform and short in length (Lewis et al., 2018). Recent research has highlighted the functional significance of maintaining small mitochondria for axon development (Smith and Gallo, 2018). MFF plays an essential role in determining the size of mitochondria entering the axon and maintains that size along the distal portion of the axon without interfering with their transport properties, presynaptic capture, membrane potential, and ATP production ability. Down-regulation of MFF increases the size of presynaptic mitochondria, enhancing their function during neurotransmission Ca²⁺ uptake. This, in turn, leads to reduced presynaptic Ca²⁺ accumulation, decreased presynaptic release, and terminal axonal branching, providing a novel mechanism to control neurotransmitter release and axon branching through fission-dependent regulation of presynaptic mitochondrial size (Lewis et al., 2018).

Acyl-CoA dehydrogenase medium chain

Acyl-CoA dehydrogenase medium chain (ACADM) is a protein-coding gene involved in mitochondrial fatty acid beta-oxidation, a process that breaks down fatty acids into acetyl-CoA for energy production (Madeira et al., 2023). Through Whole Exon Sequencing, a study demonstrated the identification of mutations in the ACADM gene in one out of 50 patients with CP (Chopra et al., 2022), highlighting its potential role in the disorder (Chopra et al., 2022).

Fatty acyl-CoA reductase 1

Fatty acyl-CoA reductase 1 (FAR1) is a protein-coding gene associated with peroxisomal fatty acyl coenzyme triglyceride reductase 1 disorder, cataracts, spastic paraparesis, and bradylalia (Westenberger et al., 2023). A study investigated the etiology of amino acid changes in 12 patients with FAR1 variants, and all patients exhibited spastic diplegia, delayed speech and motor development, and trunk hypotonia. FAR1 deficiency caused by the mutation results in defective ether lipid synthesis and deficiency of plasmalogen. Therefore, FAR1 should be considered as a candidate gene for individuals with spastic CP and included in the gene set for hereditary spastic paraplegia (Ferdinandusse et al., 2021).

APOE genotypes

The APOE gene is responsible for synthesizing apolipoprotein E, which is abundant in the brain and extensively studied in Alzheimer's disease (Lee et al., 2023a). Several studies have indicated a role for APOE gene alleles in the pathogenic mechanism of CP (Wu et al., 2011; Gümüş et al., 2018). A study from Brazil and two reports from the United States suggested a higher relative risk of CP associated with the APOEε4 allele (Kuroda et al., 2007; Braga et al., 2020; Cotten et al., 2014). Another Brazilian report linked a higher risk of CP to the APOEε2 allele alone (Kuroda et al., 2007). In a large population-based study in Norway, the APOEε2 or APOEε3 alleles and the s59007384 polymorphism in the TOMM40 gene were associated with a reduction in CP severity (Lien et al., 2015). Another Norwegian study determined that the APOE*ε3 allele was most closely related to CP (Stoknes et al., 2015). The variability in APOE genetic subtypes is primarily attributed to changes in the definition and criteria for diagnosing CP.

The specific function of the APOE gene is still subject to speculation. One study suggested a critical role of ApoE in regulating systemic and central neuroinflammatory responses (Liu et al., 2015). Additionally, microglia from ApoE(–/–) mice exhibit more severe inflammation and cell death, while certain cytokines from microglia and astrocytes are significantly reduced following loss of ApoE function. APOE is also thought to be critical in transcriptional regulation through receptor-dependent and cholesterol-independent mechanisms. This mechanism activates specific signaling pathways that affect neuronal synapse production (Liu et al., 2015; Huang et al., 2017).

Pyruvate dehydrogenase complex component X

The pyruvate dehydrogenase complex component X (PDHX) gene encodes the E3 binding protein subunit, also known as component X, of the pyruvate dehydrogenase complex. This gene plays a crucial role in the pathway of pyruvate metabolism. The absence of this gene leads to fetal lactic acidosis and affects the development of the nervous system (Savvidou et al., 2022). In a cohort of 50 CP patients, a single individual was identified with mutations in both the PDHX and ACADM genes (Chopra et al., 2022).

Glutaryl-CoA dehydrogenase

The glutaryl-CoA dehydrogenase (GCDH) gene belongs to the acyl-CoA dehydrogenase family. GCDH-related disorders include glutaric aciduria I. In a clinical study, a patient was diagnosed with severe dystonia and identified as having glutaric aciduria I (Tsagkaris et al., 2023). This suggests that further investigation is warranted to explore the role of this gene as a recessive pathogenic gene in CP. Another experiment demonstrated that [¹⁸F] 2-fluoro-2-deoxy-D-glucose-PET may play a role in the dystonia of children with CP (Tsagkaris et al., 2023).

Angiogenesis-related genes

The COL4A1 and COL4A2 genes encode IV collagen, a crucial component of the basement membrane. COL4A1 encodes type IV alpha collagen, while the C-terminal portion of the COL4A2 protein, known as cantharidin, acts as an angiogenesis and tumor growth inhibitor. Mutations in these genes can lead to brain penetrance malformations, cerebrovascular disease, and renal and muscle defects (Yao et al., 2014). A study found that, apart from growth retardation, there was no significant correlation between the polymorphism of COL4A1 and COL4A2 genes and the phenotypic characteristics and disease severity of CP patients. However, a statistically significant correlation was observed between growth retardation and COL4A2 gene polymorphism in CP patients (Güvener et al., 2021). Further statistical analysis of clinical data is needed to examine the effect of gene polymorphism on the phenotype of CP.

Neuronal migration disorder-related genes

Cell migration, also known as cell crawling, cell movement, or cell motility, refers to the movement of cells in response to migration signals or sensing gradient changes of pro-migration substances. Neuronal migration is a fundamental process during the development of the brain (Fang et al., 2022), and disruptions to this process can contribute to CP (Selvanathan et al., 2023). However, the mechanisms of neuronal proliferation, migration, and differentiation in the brains of individuals with CP are not well understood.

Rodent studies have shown that prenatal brain injury affects neurogenesis and inhibits neural stem cell production, while postnatal models demonstrate increased proliferation of neural precursor cells. Improper neuronal migration leads to reduced survival of new neurons, resulting in brain dysfunction (Visco et al., 2021). In a clinical study that sequenced the whole exome of 250 families, cases of disruptive ab initio mutations were observed in multiple genes, with TUBA1A and CTNNB1 being of particular importance. Additionally, two novel single-gene causative factors, FBXO31 and RHOB, were identified (Jin et al., 2020). These findings support the genetically mediated dysregulation of neuronal connectivity in early CP. Studying genes associated with neuronal migration not only enhances our understanding of the genetic profile of CP but also provides insights into other cerebral disorders.

TRNA-YW synthesizing protein 1 homolog and glycerol-3-phosphate acyltransferase mitochondrial

TRNA-YW synthesizing protein 1 homolog (TYW1) is a tRNA super-modifying enzyme, while glycerol-3-phosphate acyltransferase mitochondrial (GPAM) is a mitochondrial enzyme. In a study involving two patients both with CP and intellectual disability, defective TYW1 was found to cause primary microcephaly, motor problems, and cognitive impairments by blocking neuronal proliferation and migration (Li et al., 2022). In another study, abnormal expression of the mitochondrial enzyme GPAM resulted in reduced myelination of corticospinal tracts in human and mouse models (Sun et al., 2021). Abnormal GPAM expression in mice disrupts lipid metabolism in astrocytes and inhibits astrocyte proliferation. These new genetic findings expand our understanding of the genetic spectrum of CP and provide new avenues for research.

Zinc finger DHHC-type palmitoyltransferase 15

Zinc finger DHHC-type palmitoyltransferase 15 (ZDHHC15) is a protein-coding gene associated with spastic diplegia and non-syndromic X-linked mental retardation 91 (MRX91; Lewis et al., 2021). A clinical trial tested four genetic mutation types of ZDHHC15, and functional abnormalities of the protein were observed in one patient among multiple genotypes tested. This patient exhibited hypotonic CP, as well as autism, epilepsy, and intellectual disability. Thus, the ZDHHC15 gene not only plays a crucial role in the pathogenesis of CP but may also be involved in the development of other diseases (Lewis et al., 2021). It mediates a palmitoylation process critical for lysosomal sorting and recycling in transport and regulates synaptic aggregation and synapse formation, participating in the differentiation of dopaminergic neurons and the development of the mesencephalon (Lewis et al., 2021).

Tenascin R

The tenascin R (TNR) gene encodes a member of the Tenascin family of extracellular matrix glycoproteins, which is exclusively found in the central nervous system. This protein is involved in neural protrusions, neural cell adhesion, and the regulation of sodium channel function (Roll and Faissner, 2019). Thirteen individuals from eight unrelated families with phenotypes including spastic diplegia or quadriplegia, hypotonia, and developmental delay were identified with mutations in the TNR gene (Wagner et al., 2020). However, research on this gene in the field of CP is still in its preliminary stage, and further investigation is warranted.

Autophagy: SPG-related genes

Spastic CP is a common clinical subtype of CP. In a study conducted in Spain in 2019, 70.9% CP population exhibited ataxia, while 29.1% had hereditary spastic paraplegia. The estimated prevalence rates of ataxia and hereditary spastic paraplegia were 5.48 and 2.24 cases per 100,000 people, respectively (Ortega Suero et al., 2023). It should be noted that while some cases may appear to overlap with CP, they can only be classified as such if the symptoms are non-progressive, adhering to the standard diagnostic criteria for CP. The predominant types of hereditary spastic paraplegia in the sample were SPG4 and SPG7. Similar findings have been reported in clinical studies conducted in other countries, highlighting common mutant types of the SPG gene (Dong et al., 2021; Erfanian Omidvar et al., 2021).

The roles of SPG-related genes and their associated mutation outcomes were summarized in Table 2. Among them, genes such as SPG10, SPG11, SPG15, SPG30, SPG47, SPG48, SPG49, SPG50, SPG51, SPG52, SPG69, and SPG78 play a crucial role in cell autophagy, influencing autophagy formation and the number of lysosomes in cells. Other genes primarily contribute to protein transport processes, including endosome assembly and transport barriers (SPG4, SPG8, SPG20, SPG53, and SPG80). Genes such as SPG3A, SPG5A, SPG6, SPG7, SPG35, SPG39, SPG42, SPG54, and SPG58, and others are more involved in the synthesis of their encoded proteins and metabolic pathways. Several genes are associated with abnormal protein transport and dysfunction of the cellular autophagosome (Alderson et al., 2004; Maruyama et al., 2018; Bogdanova-Mihaylova et al., 2021; Toupenet Marchesi et al., 2021).

Table 2.

Functions of SPG-related genes and the consequences of their mutational disorders

SPG	Genes	Proteins	Roles	Mutation outcomes
SPG3A	ATL1	Atlastin-1	Bone morphogenetic protein cycling and signaling between the endoplasmic reticulum-Golgi apparatus	Overactivation of bone morphogenetic protein signaling; Impairment of endoplasmic reticulum-Golgi transport and Golgi morphogenesis
SPG4	SPAST	Spastin	Regulation of ESCRT-III	Disturbance of endosomal assembly; Overactivation of bone morphogenetic protein signaling
SPG5A	CYP7B1	Cytochrome P450 7B1	Oxidation of cytochrome P450	Apo-P450 (without heme) protein formation
SPG6	NIPA1	NIPA1	Protein signaling regulation of bone morphology	Overactivation of protein signaling in bone morphology
SPG7	SPG7	Mitochondrial metalloprotease protein	Membrane transport, intracellular motility, organelle biogenesis, protein folding, and protein hydrolysis.	Length-dependent neuropathy of large fiber axons
SPG8	KIAA0196/WASHC5	Strumpellin/WASHC5	Member of the WASH complex	Disruption of non-dependent pathways of lattice proteins; Impairment of endosome assembly
SPG10	KIF5	KIF5A	Kinesin and motor protein	Impaired axonal transport and autophagic pathways
SPG11	SPG11	Spatacsin	Dynamin recruitment; Interaction with spastizin and AP-5	Defective autophagy because of reduced autolysosome assembly; Accumulation of autophagosomes; Defective clearance of ganglioside lysosomes
SPG15	ZFYVE26	Spastizin	Interaction with spatacsin and AP-5; Interaction with Rab5A and Rab11	Defective autophagy due to reduced autolysosome assembly; Accumulation of autophagosomes; Altered autophagosome maturation
SPG20	SPART	Spartin	Regulation of ESCRT-III	Disturbance of endosome assembly; Overactivation of protein signaling of bone morphology
SPG30	KIF1A	KIF1A/Unc104	Kinesin and motor protein	Impaired transport of ATG-9-positive vesicles leading to defective autophagosome biogenesis
SPG35	FA2H	Fatty acid 2-hydroxylase	Synthesis of galactose sphingolipids from myelin sheaths	Leukodystrophic myelin disorder
SPG39	PNPLA6	PNPLA6	Regulation of protein signaling in bone morphology	Overactivation of protein signaling in bone morphology
SPG42	SLC33A1	SLC33A1	Regulation of protein signaling in bone morphology	Overactivation of protein signaling in bone morphology
SPG47	AP4B1	AP4B1	Subunit of the AP-4 complex	Impaired sorting of ATG9A leading to diminished autophagosome biogenesis
SPG48	AP5Z1	AP5Z1	AP-5 subunit; Spatacsin-spastizin interaction	Reduction of autolysosome loading; Impaired endolysosomal system due to accumulation of endolysosomes; Impairment of CIMPR transport to TGN
SPG49	TECPR2	TECPR2	Interaction between HOPS and ATG8 family members	Autophagosome accumulation due to impaired autophagosome-lysosome fusion
SPG50	AP4M1	AP4M1	Subunit of the AP-4 complex	Impaired sorting of ATG9A leading to diminished autophagosome biogenesis
SPG51	AP4E1	AP4E1	Subunit of the AP-4 complex	Impaired sorting of ATG9A leading to diminished autophagosome biogenesis
SPG52	AP4S1	AP4S1	Subunit of the AP-4 complex	Impaired sorting of ATG9A leading to diminished autophagosome biogenesis
SPG53	VPS37A	VPS37A	ESCRT-I subunit	Disturbance of endosomal sorting
				Altered ability to recruit ESCRT-I subunits at PAS, leading to impaired autophagosome closure
SPG54	DDHD2	DDHD2	Membrane transport between the endoplasmic reticulum and the Golgi apparatus	Significant reduction in phospholipid content in the cell center and increased production of reactive oxygen species
SPG58	KIF1C	KIF1C	Kinesin and motor protein	Impaired Golgi transport
SPG69	RAB3GAP2	RAB3GAP2	Subunits of the Rab3GAP complex	Autophagy defects
SPG78	ATP13A2/PARK9	ATP13A2	Unknown	Autophagy defects due to the accumulation of autophagosomes
SPG80	UBAP1	UBAP1	ESCRT-I subunit	Disorders of endosomal sorting
\	VCP	VCP	Interaction with strumpellin; Autophagosome maturation	Perturbation of strumpellin protein localization and function; Autophagy defects
\	VPS53	VPS53	Subunit of the GARP complex	Unknown

Ataxia telangiectasia mutated

The ataxia telangiectasia mutated (ATM) gene is understood to be related to ataxia-telangiectasia and mantle cell lymphoma. In recent years, its role in cell cycle regulation has been confirmed. The protein products of this gene play a crucial role in regulating key substrates involved in DNA repair and cell cycle control (Cortez et al., 1999). In clinical screenings, a correlation between CP and limb ataxia in patients with ataxia-telangiectasia were observed (Mandola et al., 2019). It is important to note that ataxia-telangiectasia is a distinct and progressive condition, although it shares some initial symptoms with CP. The early nervous system symptoms experienced by individuals with ataxia-telangiectasia often serve as primary indications, leading to frequent misdiagnoses as CP. It is crucial to conduct a careful differential diagnosis to avoid such misinterpretations (Zouvelou et al., 2019; Petley et al., 2022).

CTNNB1

The protein encoded by the CTNNB1 gene is part of a complex of proteins that form adherens junctions (AJs). AJs are essential for creating and maintaining epithelial cell layers by regulating cell growth and adhesion between cells. This protein may transmit the contact inhibition signal that halts cell division once the epithelial sheet is complete (Lillehoj et al., 2007; Weiske et al., 2007). Clinical exon sequencing studies have also confirmed the role of this gene in CP pathogenesis (Takezawa et al., 2018; Zech et al., 2020; Lee et al., 2023b). Furthermore, one study demonstrated that disruption of neuronal adhesion caused by this gene is closely associated with CP (Jin et al., 2020).

Potassium voltage-gated channel subfamily Q member 2

The M channel, a slowly activating and deactivating potassium channel, plays a critical role in regulating neuronal excitability. Mutations in the potassium voltage-gated channel subfamily Q member 2 (KCNQ2) gene are known to cause benign familial neonatal seizures (Saviola et al., 2018). KCNQ2 mutations are found in a significant proportion of patients with neonatal epilepsy encephalopathy. In a whole-exome sequencing study on four members of a family, one individual exhibited epileptic-like seizures since birth, accompanied by CP, severe neuromotor and developmental retardation, dystonia, quadriplegia, axonal motor effects, and unexplained hyperexcitability (Lazo et al., 2020).

G protein subunit alpha O1

The protein encoded by the G protein subunit alpha O1 (GNAO1) gene represents the alpha subunit of the Go heterotrimeric G-protein signal-transducing complex. Among 17 cases involving nine genes, 9.1% exhibited pathogenic or potentially pathogenic candidate mutations, including GNAO1 (Takezawa et al., 2018). Recently, GNAO1 mutations have been found to cause epileptic encephalopathy and a severe early-onset hyperkinetic syndrome characterized by prominent chorea, dystonia, and orofacial dyskinesia (Schirinzi et al., 2019). Dyskinesia CP is the predominant manifestation of this condition (Malaquias et al., 2019).

Tubulin beta 4A class IVa

The tubulin beta 4A class IVa (TUBB4A) gene encodes a member of the beta tubulin family and plays a role in GTP binding and cytoskeleton formation. Sequencing studies have indicated the significance of TUBB4A mutations in CP pathogenesis (Zech et al., 2020).

In summary, this comprehensive review explores the genes associated with CP, providing a systematic analysis of their functions and their individual and collective contributions to CP development. This review provides a comprehensive summary of the current evidence concerning genetic factors influencing CP pathogenesis. Thrombosis-related genes such as FVL and MTHFR have been tentatively associated with an increased risk of thrombosis. Mutations in COL4A1/COL4A2 may elevate the risk of hemorrhagic and ischemic strokes, resulting in CP-like presentations; however, the variability in outcomes requires further investigation. Hypotheses suggesting the involvement of mitochondrial and oxidative phosphorylation genes in neural injury in CP lack sufficient functional evidence in human patients. To firmly establish causality, neuronal migration genes implicated in developmental disorders need large-scale validation in CP cohorts.

In terms of exploring promising avenues for additional research, calcium ion channels, GTP/ATP homeostasis, and fundamental cellular processes like transcription and RNA processing warrant further investigation. In the future, multifaceted research incorporating genetic epidemiology, functional assays, and animal models is necessary to substantiate the pathophysiological roles of these genes in CP subtypes. This approach will pave the way for novel diagnostics and treatments tailored to the genetic profiles underlying CP in each patient. The discussion expands our understanding of the involved genetic factors and sheds light on the complex mechanisms driving this disorder.

Gaining comprehensive insights into CP genetics will empower clinicians to develop targeted interventions based on each patient's specific genetic risk factors. The future of evidence-based care for this heterogeneous disorder lies in personalized treatment approaches, informed by the distinct biological pathways disrupted in individual CP patients. Achieving this goal necessitates further interdisciplinary collaboration, leveraging robust functional studies in model systems, high-throughput human genetic analysis, and integrative bioinformatics. These efforts will be the key to unlocking CP's complex genetic architecture and paving the way for precision medicine.

To facilitate easy reference and summarize our findings in a structured format, we have included detailed data (Figure 2 and Table 3). This data concisely presents the identified genes, outlining their known functions and potential impact on the disease process. By providing this resource, we aim to stimulate further research and advance our understanding of CP genetics (Lee et al., 2011; Parolin Schnekenberg et al., 2015; Zennaro and Jeunemaitre, 2016; Das et al., 2017; Suzuki-Muromoto et al., 2018; Giri et al., 2019; Zouvelou et al., 2019; Ferdinandusse et al., 2021; Tsagkaris et al., 2023).

Figure 2.

Pathway analysis of cerebral palsy-related genes.

This figure employs a circular packing layout to depict the associations between genes and pathways identified in our study. Each gene is represented by a colored circle, with the color indicating the corresponding pathway. The key on the right provides a clear reference to the pathways. This figure was generated using the open-source R software package “graph.”

Table 3.

Systematic analysis of the genes currently associated with CP

Category	Abbreviation	Full name or alias	Function	Mechanistic link with CP
Thrombosis-related genes	FVL	The coagulation factor V Leiden mutation	Inhibits the activated protein C activity and prevents inactivation of coagulation factor V.	Thrombophilic genetic factors, particularly FVL and MTHFR, are more frequent in infants with ischemic and hemorrhagic lesions, which are frequently observed in CP. These genetic factors are associated with an increased risk of thrombosis, which can lead to ischemic and hemorrhagic brain lesions, potentially contributing to the development of CP. However, the exact mechanisms are not fully understood and more research is needed to confirm these findings.
			Leading to the overproduction of thrombin, excessive blood clotting, and increased risk of thrombosis.
	MTHFR	5,10-methylenetetrahydrofolate reductase	Associated with the maintenance of low levels of homocysteine.
			Gene mutation results in unregulated homocysteine levels.
			Elevated homocysteine levels can damage vascular endothelial cells
	NOS	Nitric oxide synthase	Neuronal NOS which participates in cellular communication within the nervous tissue; inducible NOS which assists macrophages to participate in immune actions; endothelial NOS which participates in the vascular function regulation.
Mitochondrion- and oxidative phosphorylation metabolism disorder-related genes	MFF	Mitochondrial fission factor	A nuclear gene that encodes a protein involved in mitochondrial and peroxisomal fission.	The relationship between mitochondrial- and oxidative phosphorylation metabolism disorder-related genes and CP is intricate. Studies have shown that mitochondrial dysfunction and oxidative stress can lead to neuronal damage, a key feature of CP. In particular, the genes involved in mitochondrial and oxidative phosphorylation metabolism are often found to be dysregulated in CP patients. This dysregulation can lead to energy metabolism disorders, which can further exacerbate neuronal damage and contribute to the symptoms of CP.
	ACADM	Acyl-CoA dehydrogenase medium chain	Mitochondrial fatty acid beta-oxidation and PPAR-α activates gene expression.
	FAR1	Fatty acyl-CoA reductase 1	FAR1-related disorders include peroxisomal fatty acyl coenzyme triglyceride reductase 1 disorder, cataracts, spastic paraparesis, and bradylalia.
	APOE	apolipoprotein E	Controls the synthesis of apolipoprotein E
	PDHX	Pyruvate dehydrogenase complex component X	Pyruvate metabolism and ESR-mediated signaling.
	GCDH	Glutaryl-CoA dehydrogenase	Super pathway of tryptophan utilization and metabolism
Angiogenesis-related genes	COL4A1/COL4A2	Encode IV collagen	The COL4A1 gene encodes type IV alpha collagen. The C-terminal portion of the COL4A2 protein, called cantharidin, is an angiogenesis and tumor growth inhibitor.	The relationship between angiogenesis-related genes (COL4A1/COL4A2) and CP is quite significant. Mutations in the collagen genes COL4A1 and COL4A2 can lead to arterial basement membrane thickening, resulting in a multisystem microangiopathy that targets the central nervous system and potentially affects other systems such as the ocular, renal, cardiac, and muscular systems. Within the brain, these changes predispose individuals to recurrent ischemic and/or hemorrhagic strokes, which can begin during early fetal development and extend into the postnatal period and even into adulthood. These stroke-related complications may be insidious and clinically silent. Neuroimaging phenotypes of COL4A-associated disease include chronic white matter disease, porencephaly/ hydranencephaly, encephalomalacia, cerebral calcifications, schizencephaly, and hydrocephalus. The corresponding clinical diagnoses include CP intellectual disability, cortical visual impairment, and epilepsy. Therefore, mutations in the COL4A1 and COL4A2 genes significantly contribute to the development of CP and other neurological conditions.
Neuronal migration disorder-related genes	TYW1	TRNA-YW synthesizing protein 1 homolog	TRNA-YW synthesizing protein 1 homolog (TYW1) is a tRNA super-modifying enzyme; The recombinant glycerol-3-phosphate acyltransferase, mitochondrial (GPAM) is a mitochondrial enzyme.	Neuronal migration, a critical process in brain development, has been linked to CP. Disruptions in neuronal migration can cause issues in motion and cognition by hindering neuronal proliferation and migration, as observed in some CP patients. Moreover, evidence suggests that there may be attempts at neuronal repair or regeneration in neonatal white matter injury, a characteristic of CP.
	ZDHHC15	Zinc finger DHHC-type palmitoyltransferase 15	ZDHHC15-related disorders include spastic diplegia and non-syndromic X-linked mental retardation 91 (MRX91).
	TNR	The tenascin R	Encodes a member of the tenascin family of extracellular matrix glycoproteins.
	CTNNB1	Catenin Beta 1	Part of a complex of proteins that constitute adherens junctions.
Calcium ion correlation	ITPR1	Inositol 1,4,5-Trisphosphate Receptor Type 1	Release of calcium ions from endoplasmic reticulum.	Calcium ions play a significant role in various neurological functions, including neural cell-cell interactions, synaptic transmission, and axon guidance. Disruptions in these functions, such as those caused by genetic alterations affecting calcium ion channels, can contribute to the development of CP.
	CACNA1A/D	Calcium voltage-gated channel subunit alpha 1 A/D.	Voltage-dependent calcium channels
	PCDH12	Protocadherin 12	A subfamily of the cadherin superfamily.
GTP/ATP	ATL1	Atlastin GTPase 1	GTPase and a Golgi body transmembrane protein.	GTP and ATP are essential energy sources for various biological processes. In the context of CP, a condition characterized by motor impairment, the role of ATP is particularly significant. ATP is primarily produced by mitochondrial organelles within muscle fibers, powering the force generation needed for movement. In children with CP, there is a marked reduction in mitochondrial function, which can lead to decreased ATP production. This reduction in ATP can contribute to the increased energetics of movement, reduced endurance capacity, and increased perceived effort observed in CP patients. Therefore, the correlation between GTP/ATP and CP is largely tied to energy production and muscle function
	GCH1	GTP cyclohydrolase 1	A member of the GTP cyclohydrolase family, and the first and rate-limiting enzyme in tetrahydrobiopterin (BH4) biosynthesis
	GNAO1	G protein subunit alpha O1	The alpha subunit of the Go heterotrimeric G-protein signal-transducing complex.
	SPATA5L1	Spermatogenesis associated 5 Like 1	Enable ATP binding activity. Located in cytoplasm and spindle.
Gene transcription related factor	AUTS2	Autism susceptibility gene 2 protein	Gene expression (transcription) and assembly of the pre-replicative complex.	The processes of pre-mRNA, tRNA processing, and cell cycle regulation are fundamental to cellular function and development. Disruptions in these processes can lead to various disorders, including CP. For instance, tRNA-derived fragments (tRFs), generated by the specific cleavage of pre- and mature tRNAs, have been found to play crucial roles in cellular processes such as inhibiting protein translation, modulating stress response, regulating gene expression, and involvement in cell cycles. Dysregulation of these tRFs has been associated with various diseases. While direct links between these processes and CP are not explicitly stated in the literature, it is plausible that abnormalities in these fundamental cellular processes could contribute to the neuronal dysfunction observed in CP
	TRMT5	TRNA methyltransferase 5	tRNA Processing and processing of capped intron-containing pre-mRNA.
	NSRP1	Nuclear speckle splicing regulatory protein 1	Processing of capped intron-containing pre-mRNA.
	SOX10	SRY-box transcription factor 10	Nervous system development and ERK signaling.
	DDX3X	DEAD-Box helicase 3 X-linked	Innate immune system and Toll-like receptor signaling pathway.
	RNASEH2B	Ribonuclease H2 subunit B	Pathways of nucleic acid metabolism and innate immune sensing.
	ATM	Ataxia telangiectasia mutated	Cell cycle regulation related to ataxia-telangiectasia and mantle cell lymphoma
Other proteins	ARG1	Arginase 1	Super pathway of L-citrulline metabolism and innate immune system.
	UBE3A	Ubiquitin protein ligase E3A	Class I MHC-mediated antigen processing and presentation and MIF-mediated glucocorticoid regulation.
	ZC4H2	Zinc finger C4H2-type containing	Plays a role in interneurons differentiation. Involved in neuronal development and in neuromuscular junction formation.
	HPRT1	Hypoxanthine phosphoribosyltransferase 1	Nucleotide salvage and thiopurine pathway, Pharmacokinetics/pharmacodynamics.
	FAR1	Fatty Acyl-CoA Reductase 1	Metabolism and wax and plasmalogen biosynthesis.
	PDHA1	Pyruvate dehydrogenase E1 subunit alpha 1	Pyruvate metabolism and glycolysis (BioCyc).
	KCNQ2	Potassium voltage-Gated channel subfamily Q member 2	A slowly activating and deactivating potassium channel
	TUBB4A	Tubulin beta 4A class IVa	A member of the beta tubulin family

ATP: Adenosine triphosphate; CP: cerebral palsy; GTP: guanosine triphosphate.

Limitations

This study has some limitations. First, the reliance on small-scale candidate gene studies and case reports may have introduced bias, hindering the establishment of definitive causal links between genes and CP subtypes. To address this, future research should involve large-scale genomic analyses in well-phenotyped CP cohorts. Second, the absence of functional validation for most implicated genes obscures their relevance to CP pathogenesis. To overcome this limitation, it is recommended that future work undertake validation using cellular and animal models to discern causative impacts. Last, the genetic heterogeneity of CP suggests a diverse array of implicated genes, demanding large-scale collaborative studies to elucidate their relative contributions. Addressing these challenges will require robust genomic analyses and mechanistic studies in subsequent research, enriching our understanding of CP and potentially advancing diagnostic and therapeutic approaches.

Conclusions

Pinpointing the precise mechanisms involved in the development of CP is a substantial challenge given the complexity of its underlying genetic causes. Although genetic factors may not always be the primary contributors in every CP case, their significance becomes particularly pronounced when traditional risk factors are absent. In such scenarios, it is crucial to acknowledge and thoroughly investigate the potential role of these genetic elements. Despite this challenge, advancements in genetic research have identified several mutations affecting different cellular signaling pathways involved in CP pathogenesis. However, further refinement is necessary to fully understand the specific pathogenesis resulting from these genetic mutations. Understanding these mutations is essential to develop effective therapies and treatments for individuals with CP. Additionally, comprehending the specific cellular signaling pathways involved in CP enables clinicians to identify potential comorbidities associated with the disorder, facilitating targeted interventions to improve overall outcomes. Despite ongoing research, there is still much to be understood regarding the genetics and cellular mechanisms underlying CP, highlighting the need for continued collaboration and investigation among researchers and clinicians.

Funding Statement

Funding: This work was supported by the National Natural Science Foundation of China, No. U21A20347 (to CZ); the National Key Research and Development Program of China, No. 2022YFC2704801 (to CZ); the Henan Key Laboratory of Population Defects Prevention, No. ZD202103 (to YX); and the Department of Science and Technology of Henan Province of China, No. 212102310221 (to YX).