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. 2020 Jan 24;99(4):e18838. doi: 10.1097/MD.0000000000018838

Association of human serotonin receptor 4 promoter methylation with autism spectrum disorder

Zhenyu Hu a,∗, Xiuru Ying b, Ling Huang a, Yuanzhi Zhao a, Dongsheng Zhou a, Jing Liu b, Jie Zhong b, Tianyi Huang b, Wenwu Zhang a, Fang Cheng a, Shiwei Duan b,∗
Editor: Yi Zhu
PMCID: PMC7004686  PMID: 31977880

Abstract

Human serotonin receptor 4 (HTR4) encodes a 5-HT4 receptor involved in learning, memory, depression, anxiety, and feeding behavior. The aim of this study was to investigate the association between the deoxyribonucleic acid (DNA) methylation of HTR4 promoter and autism spectrum disorder (ASD), a disease characterized by communication disorder and repetitive or restrictive behavior.

Peripheral blood DNA was obtained from 61 ASD children and 66 healthy children, and the DNA methylation of HTR4 promoter was assessed by quantitative methylation-specific polymerase chain reaction. We used percentage of methylated reference (PMR) to represent DNA methylation level.

Due to significant age differences between ASD cases and controls (3 [2, 5] years and 6 [5, 6] years, P = 3.34E-10), we used binary logistic regression analysis for adjustment. Our results showed that the DNA methylation levels of HTR4 promoter were significantly lower in children with ASD than in healthy children (median PMR: 66.23% vs 94.31%,P = .028, age-adjusted P = .034). In addition, the DNA methylation of HTR4 promoter was inversely associated with age in male ASD cases (total cases: r = –0.283, P = .027; male cases: r = –0.431, P = .002; female cases: r = –0.108, P = .752). Dual-luciferase reporter gene assay showed that the reporter gene expression in the strain with recombinant pGL3-promoter-HTR4 plasmid was significantly higher than that in the strain with pGL3-promoter plasmid (fold change = 2.01, P = .0065), indicating that the HTR4 promoter fragment may contain transcription factors to upregulate promoter activity.

Our study suggested that hypomethylation of the HTR4 promoter is a potential biomarker for predicting the risk of male ASD.

Keywords: autism spectrum disorder, DNA methylation, HTR4, promoter, qMSP

1. Introduction

Autism spectrum disorder (ASD) is a progressive neurological disorder characterized by social communication disorder and special repetitive behavior that can ultimately lead to permanent disability.[1,2] Recent epidemiological studies have shown that ASD is estimated to be 1% of the general population in the United Kingdom.[3] In China, among children aged 18 to 36 months, the prevalence of ASD in Tianjin city of China is 0.275%, and the ratio of male to female is 4:1.[4] Although drug and behavioral training program are used to treat ASD, side effects and excessive cost limit the prognosis and recovery of ASD.[5] Therefore, it is important to find biomarkers for the early diagnosis and treatment of ASD in the context of increased social burden.[6]

The etiology of ASD is complex, including genetic and environmental factors.[7] The global incidence of soaring ASD may be caused by the deterioration of environment.[3,6] Epigenetic modifications are mediators of genetic and environmental elements.[8] Among them, deoxyribonucleic acid (DNA) methylation has been shown to play an important role in the development of ASD.[9] Studies have shown that in nearly 15% of ASD brain tissues, the CpG island at the SHANK3 promoter was found to be hypermethylated, and this subsequently altered the expression of SHANK3.[10] As a member of the Shank gene family, SHANK3 codes Shank proteins which are multidomain scaffold proteins of the postsynaptic density. Mutations in this gene are a cause of ASD. OXTR encodes protein who acts as a receptor for oxytocin. And the oxytocin-oxytocin receptor system plays an important role in the uterus during parturition. ASD is associated with preterm birth,[11] and the promoter methylation of OXTR (a ASD candidate gene) was found to be higher in premature fetal membranes.[12] Immunohistochemical analysis showed that increased methylation and decreased protein expression of RORA and BCL2 genes were found in the brain of ASD patients.[13] The protein encoded by RORA is a member of the NR1 subfamily of nuclear hormone receptors and BCL2 encodes a outer mitochondrial membrane protein blocking apoptosis.

Human serotonin receptor 4 (HTR4) encodes a member of the serotonin receptor family that can stimulate cAMP production and plays an important role in the regulation of releasing various neurotransmitters in the peripheral and central nervous systems.[14,15] Serotonin in the brain promotes prosocial behavior and correctly assesses social emotional information.[16] Peripheral high serotoninemia is one of the few consistent findings in autism, since it may deplete the serotonin in the central nervous system.[17] Serotonin receptor 4 controls many physiological effects, including the central nervous system.[18]HTR4 has been found to be involved in many genetic studies of neuropsychiatric disorders, including bipolar disorder and schizophrenia.[19,20] However, there are few studies of HTR4 with autism.

The serotonin system was found to be associated with ASD.[17] A disruption of the serotonin system in ASD leads to elevated levels of serotonin.[17,21,22] Selective serotonin reuptake inhibitors have been reported to successfully treat a variety of symptoms of ASD, including repetitive behavior and compulsion, depression and insomnia.[23,24] The serotonin concentrations in the brains of ASD patients were significantly lower than those in the brains of controls.[25,26] The serotonin depletion may be due to genetic abnormalities in the serotonin related genes. The ITGB3 gene encodes the integrin β3 subunit, and variations in this gene reduce the integrin β3 signaling that subsequently affect serotonin function via its modification of the 5-HT level in the blood.[27] A chromosomal break-point near the HTR4 gene was found in the genome of an ASD male patient.[17]

However, there is no study on the DNA methylation of HTR4 promoter in ASD. Based on the above findings, we aimed to investigate the association between the DNA methylation of HTR4 promoter and ASD, and to explore whether age is an influencing factor for ASD related to the methylation level of the promoter of HTR4.

2. Methods and materials

2.1. Subjects

A total of 61 ASD children and 66 healthy children were collected from the Kangning Hospital of Ningbo City, Zhejiang Province. The ASD cases consisted of 50 males and 11 females. The age of the case was 4.02 ± 2.83 (mean ± standard deviation) years. The age of control group was 5.76 ± 0.72 years. The age differences between ASD cases and controls is significant (P = 3.34E-10). According to the diagnostic and Statistical Manual of Mental Disorders 5 (American Psychiatric Association, 2013), patients were diagnosed with ASD by at least 2 psychiatric physicians in Ningbo Kangning Hospital (Ningbo, Zhejiang, China). At the same time, the child autism rating scale (CARS) and the autism behavior checklist (ABC) were used to confirm the accuracy of the diagnosis.[28] The tested phenotypes included 20 clinical features including sensory ability, communication ability, exercise ability, language ability, self-care ability, interpersonal relationship, imitative ability (words and actions), emotional response, physical exertion, relationship with non-living objects, adaptation to environmental changes, visual response, auditory response, near-sensory response, anxiety response, verbal communication, nonverbal communication, activity level, intellectual function and overall impression. The scores of the ABC scale of the 61 ASD children were 74.98 ± 34.91, and the score of the CARS scale was 34.18 ± 14.57. The study case had an ABC score of >31 and a CARS score of >30. Patients with mental retardation, congenital/hereditary disease or severe physical illness were excluded from the study. In the control group, 66 children (55 males and 11 females) had complete physical examination and no family or individual history of neurological or psychiatric illness. Besides, the sex distribution between cases and controls is not significant (P = .135). Our research was approved by the ethics committee of Ningbo university. Written informed consent forms were signed by the guardians of all participants.

2.2. Methods

Quantitative methylation-specific polymerase chain reaction (qMSP): Peripheral blood was collected from tubes treated with 3.2% sodium citrate and stored at –80°C. Our previous article described the details of blood DNA separation and bisulfite conversion.[29] qMSP was used to detect the DNA methylation of HTR4 promoter. The forward and reverse sequences of HTR4 were 5’-GTGTCGTATAGGGTAGTAAGTT-3’ and 5’-GATACTCGCAACCATCCT-3’, respectively. The forward and reverse sequences of ACTB were 5’-TGGTGATGGAGGAGGTTTAGTAAGT-3’ and 5’-AACCAATAAAACCTACTCCTCCCTTAA-3’, respectively. Our previous work showed the details of qMSP.[30] Each 384 plate contained the participant's DNA sample, a positive control, and multiple water sample as a blank control. The percentage of methylated reference (PMR) value was calculated using the method described previously.[31]

Plasmid transfection and dual luciferase reporter assay: We chemically synthesized a fragment of the HTR4 promoter (–657 bp to –566 bp) and digested with XhoI and KpnI (New England Biolabs, Ipswich, MA). Purified by cycle pure kit (Omega, Norcross, GA), the target DNA fragment was cloned into the pGL3 promoter vector (Promega, Madison city, WI) using a DNA ligation kit (TaKaRa, Japan). We used the empty pGL3 Basic vector as a negative control and used the pGL3 promoter vector containing the SV40 promoter upstream of the luciferase gene as a positive control. We prepared cells using 96-well plates, and the details of plasmid transfection of human embryo kidney 293T (HEK293T) cells were as previously described.[32] The culture method of the HEK293T cell line was as described previously.[33] After 18 to 72 hours of HEK293T cell transfection, luciferase activity was determined using a dual luciferase reporter assay system (dual-luciferase reporter assay systems, Promega). Renilla and firefly luciferase activities were measured by SpectraMax 190 (Molecular devices, Sunnyvale).

2.3. Statistical analysis

The non-parametric Mann–Whitney U test was used to compare the DNA methylation of HTR4 promoter, age, and sex between ASD cases and healthy controls. Binary logistic regression analysis was used for adjustment of age differences. The Spearman rank correlation coefficient method was used to quantify the relationship of HTR4 DNA methylation with age and HTR4 expression. A P value of less than .05 was considered to be significant.

3. Results

As shown in Figure 1, we selected a fragment of the promoter region (hg38, chr5: 148032968–148033058) for HTR4 DNA methylation assay, which contained 2 CpG sites. Due to age differences between cases and controls (3 [2, 5] years and 6 [5, 6] years, P = 3.34E-10), binary logistic regression analysis was used to adjust age differences. Our results showed that the DNA methylation levels of HTR4 promoter were significantly lower in ASD cases than in healthy controls (Fig. 2, median PMR: 66.23% versus 94.31%, P = .028, age-adjusted P = .034).

Figure 1.

Figure 1

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Target sequence on HTR4 CpG island (CGI) region. Two CpG sites are located on HTR4 gene promoter. F: forward primer; R: reverse primer. The genomic positions and function annotations of HTR4 were obtained from UCSC genome browser according to human 2013 (GRCh38/hg38). (B) Sequencing validation of the qMSP product. The first row of the sequences represents the original gene sequence, and the second row shows the converted sequence. The fragment length of qMSP product was 91 bp as expected. HTR4 = human serotonin receptor 4, qMSP = quantitative methylation-specific polymerase chain reaction, UCSC = University of California, Santa Cruz.

Figure 2.

Figure 2

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Comparisons of the DNA methylation of HTR4 promoter levels between cases and controls. The percentage of methylated reference (PMR) values were 66.23 (50.97, 110.85) and 94.31 (60.19, 180.33) in cases and controls, respectively. And the PMR values of cases and controls were 65.38 (45.54, 101.03), 93.07 (59.18, 191.70) in males, and 120.40 (68.22, 226.00), 96.93 (67.32, 134.40) in females. The levels of the DNA methylation of HTR4 promoter were represented by the PMR. DNA = deoxyribonucleic acid, HTR4 = human serotonin receptor 4, P∗ stood for the age-adjusted P.

We also observed gender differences in the DNA methylation of HTR4 promoter. The level of the DNA methylation of HTR4 promoter in male ASD cases was significantly lower than in the male control group (Fig. 2, median PMR: 65.38% vs 93.07%, P = .008, age-adjusted P = .014). However, we did not find a link between the DNA methylation of HTR4 promoter and ASD in females (P > .05, age-adjusted P > .05, Fig. 2). The DNA methylation of HTR4 promoter was found to be significantly higher in female cases than in male cases (Fig. 2, median PMR: 120.40% vs 65.38%, P = .013, age-adjusted P = .013). In addition, no differences in the DNA methylation of HTR4 promoter were found between male and female controls (P > .05, age-adjusted P > .05, Fig. 2).

We observed a significant inverse correlation between age and the DNA methylation of HTR4 promoter in the ASD cases (Fig. 3, r = –0.283, P = .027). A gender-based subgroup analysis found that the significant association between age and the DNA methylation of HTR4 promoter only existed in male cases, but not in female cases (Fig. 3, male cases: r = –0.431, P = .002; female cases: r = –0.108, P = .752). There was a moderate inverse correlation between age and the DNA methylation of HTR4 promoter in the controls (r = –0.224, P = .071).

Figure 3.

Figure 3

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Correlation between the DNA methylation of HTR4 promoter and age in cases. DNA = deoxyribonucleic acid, HTR4 = human serotonin receptor 4.

Subsequently, a dual luciferase reporter gene assay was performed to examine whether the HTR4 gene fragment (–657 bp to –566 bp) was able to increase promoter activity. Our results showed that the transcriptional activity of the recombinant pGL3-Promoter-HTR4 plasmid was significantly higher than that of the pGL3-promoter plasmid (Fig. 4, fold change = 2.01, P = .0065). In addition, TCGA data (http://www.cbioportal.org/) also demonstrated an inverse correlation between HTR4 expression and HTR4 DNA methylation (Fig. 5, r = –0.215, P = .002).

Figure 4.

Figure 4

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Dual-luciferase reporter assay in HEK-293T cell line. The pGL3 basic and promoter vectors were used as negative and positive control, respectively. Relative luciferase activity was performed in triplicates. HEK-293T = human embryo kidney 293T.

Figure 5.

Figure 5

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Correlation between HTR4 DNA methylation and HTR4 expression in 214 individuals from the TCGA dataset. DNA = deoxyribonucleic acid, HTR4 = human serotonin receptor 4.

Finally, we have checked the influence of the outliers on the statistics, including four points in Figure 2 and 2 points in Figure 5, and have found that these samples did not make big differences to the results (all P < .05).

4. Discussion

This study demonstrated that the DNA hypomethylation of HTR4 promoter was significantly associated with ASD. Our results also showed that the DNA methylation of HTR4 promoter was significantly lower in male patients with ASD than in healthy male controls, and that the DNA methylation of HTR4 promoter was significantly lower in male ASD patients than in female ASD patients. In addition, a significant inverse correlation between age and DNA methylation was found in ASD cases, especially in male cases.

HTR4 encodes a serotonin receptor expressed in the central nervous system. HTR4 is involved in learning and memory, depression, anxiety, and feeding behavior.[34] HTR4 is known to be involved in the regulation of neurotransmitter release, and irregular neurotransmission of serotonin has been shown to be involved in a variety of neuropsychiatric disorders.[20] Although there is little research between HTR4 and ASD, HTR4 is associated with other neurological diseases. ASD, schizophrenia spectrum disorders and symptoms of bipolar disorder may overlap with biopsychosocial risk factors.[35–37] Previous studies found that HTR4 polymorphism may contribute to bipolar disorder[20] and ADHD.[38]

The number of ASD boys diagnosed in all ethnic, and socioeconomic groups is 4 to 5 times higher than that of girls, but the underlying mechanisms for gender differences have not been established.[39] Early studies have found that females have higher levels of serotonin in their brains compared to males, which can be observed on the second day of neonatal early days and persist throughout adulthood.[40,41] The serum serotonin concentration in patients with ASD was significantly lower,[25,26] suggesting that men with a lower serum serotonin concentration are more susceptible to ASD. Our work suggested that the DNA of HTR4 promoter was significantly hypomethylated in ASD men, and this finding may help elucidate the molecular mechanisms of ASD.

Studies have shown that folic acid can regulate DNA methylation and affect gene expression. In order to determine whether folate intake during pregnancy changes the gene expression of neonatal cerebral hemispheres, scientists examined HTR4 methylation in mice, and confirmed a downregulation of HTR4 in folate changes.[42] A recent report shows that folic acid intake in Norwegian pregnant women from 4 weeks before pregnancy to 8 weeks after pregnancy helps reduce the risk of autism in newborns.[43] Lack of pleasure may be associated with down-regulation of HTR4 expression in the hippocampus.[44] In patients with pulmonary embolism, a negative feedback mechanism showed that the expression of HTR4 was downregulated.[45] However, studies have also found that HTR4 is highly expressed in patients with functional dyspepsia.[46] Increased expression of 5-HTR4 in high Gleason grade tumours may be involved in tumor progression through 5-HT-induced increases in hormone or growth factor levels.[47] Our dual luciferase reporter assay indicated that the HTR4 promoter-specific region contains potential regulatory elements. The HTR4 promoter fragment may contain a transcription factor capable of upregulating promoter activity.

The current age threshold for diagnosing ASD is 2 years and the typical age for diagnosis is 4. Adaptive behavior includes important behaviors of independent living, including daily life skills, social skills, and communication skills. Children with ASD show adaptive behavioral disorders in all areas. Previous studies have found that patients with ASD have lower adaptive behavior scores.[48] Age showed an inverse correlation with adaptive behavior of ASD.[49] In young children, there is a moderate to strong association between ASD severity and adaptive behavior.[50] In the current study, an inverse correlation between the DNA methylation of HTR4 promoter and age was found in male ASD cases. This may help explain the contribution of the DNA methylation of HTR4 promoter to ASD risk in different age groups.

To the best of our knowledge, this is the first report of the association between the DNA methylation of HTR4 promoter and ASD, but there are some limitations. First of all, our sample size is limited, especially for female samples. More female samples are needed in the future to investigate whether the DNA methylation of HTR4 promoter is associated with ASD in females. Second, since our work involves only Chinese people, it is necessary to confirm the correlation between the DNA methylation of HTR4 promoter and ASD in other ethnic groups in the future. Finally, although TCGA data analysis confirmed that HTR4 DNA methylation was negatively correlated with expression, we did not conduct experiments to assess the correlation between HTR4 DNA methylation and expression due to sample limitations, and future work needs to validate this association.

5. Conclusion

Taken together, our study suggested that hypomethylation of the HTR4 promoter is a potential biomarker for predicting the risk of male ASD. Our findings may provide new insights into the pathogenesis of ASD.

Author contributions

Conceptualization: Shiwei Duan.

Data curation: Ling Huang, Dongsheng Zhou.

Formal analysis: Jing Liu.

Funding acquisition: Yuanzhi Zhao.

Investigation: Yuanzhi Zhao.

Methodology: Jie Zhong, Tianyi Huang, Wenwu Zhang.

Project administration: Fang Cheng.

Resources: Dongsheng Zhou, Wenwu Zhang.

Software: Jing Liu, Jie Zhong.

Visualization: Tianyi Huang, Fang Cheng.

Writing – original draft: Zhenyu Hu, Xiuru Ying.

Writing – review and editing: Shiwei Duan.

Shiwei Duan orcid: 0000-0001-7682-2877.

Footnotes

Abbreviations: ABC = the autism behavior checklist, ASD = autism spectrum disorder, CARS = child autism rating scale, HTR4 = human serotonin receptor 4, PMR = percentage of methylated reference, qMSP = quantitative methylation-specific polymerase chain reaction.

How to cite this article: Hu Z, Ying X, Huang L, Zhao Y, Zhou D, Liu J, Zhong J, Huang T, Zhang W, Cheng F, Duan S. Association of human serotonin receptor 4 promoter methylation with autism spectrum disorder. Medicine. 2020;99:4(e18838).

ZH and XY are co-first authors of this work.

The clinical data used to support the findings of this study are restricted by the Ningbo Kangning Hospital in order to protect patient privacy. Data are available from Yuanzhi Zhao, 139-5789-2878 for researchers who meet the criteria for access to confidential data.

Informed consent was obtained from all individual participants included in the study. Compliance with Ethical Standards.

All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

The research was supported by the Medical Science and Technology Project of Zhejiang Province (2017207569) and the K. C. Wong Magna Fund in Ningbo University.

The authors have no conflicts of interest to disclose.

References

  • [1].Noroozi R, Ghafouri-Fard S, Omrani MD, et al. Association study of the vesicular monoamine transporter 1 (VMAT1) gene with autism in an Iranian population. Gene 2017;625:10–4. [DOI] [PubMed] [Google Scholar]
  • [2].Ye BS, Leung AOW, Wong MH. The association of environmental toxicants and autism spectrum disorders in children. Environ Pollut 2017;227:234–42. [DOI] [PubMed] [Google Scholar]
  • [3].Zhou B, Zhou H, Wu L, et al. Assessing the accuracy of the modified chinese autism spectrum rating scale and social responsiveness scale for screening autism spectrum disorder in Chinese children. Neurosci Bull 2017;33:168–74. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [4].Huang JP, Cui SS, Han Y, et al. Prevalence and early signs of autism spectrum disorder (ASD) among 18-36 month-old children of Tianjin in China. Biomed Environ Sci 2014;27:453–61. [DOI] [PubMed] [Google Scholar]
  • [5].Kouijzer ME, van Schie HT, Gerrits BJ, et al. Is EEG-biofeedback an effective treatment in autism spectrum disorders? A randomized controlled trial. Appl Psychophysiol Biofeedback 2013;38:17–28. [DOI] [PubMed] [Google Scholar]
  • [6].Kichukova TM, Popov NT, Ivanov IS, et al. Profiling of circulating serum microRNAs in children with autism spectrum disorder using stem-loop qRT-PCR assay. Folia Med 2017;59:43–52. [DOI] [PubMed] [Google Scholar]
  • [7].Ivanov HY, Stoyanova VK, Popov NT, et al. Autism spectrum disorder - a complex genetic disorder. Folia Med 2015;57:19–28. [DOI] [PubMed] [Google Scholar]
  • [8].Vogel Ciernia A, LaSalle J. The landscape of DNA methylation amid a perfect storm of autism aetiologies. Nat Rev Neurosci 2016;17:411–23. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [9].Keil KP, Lein PJ. DNA methylation: a mechanism linking environmental chemical exposures to risk of autism spectrum disorders? Environ Epigenet 2016;2:1–5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [10].Zhu L, Wang X, Li XL, et al. Epigenetic dysregulation of SHANK3 in brain tissues from individuals with autism spectrum disorders. Hum Mol Genet 2014;23:1563–78. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [11].Agrawal S, Rao SC, Bulsara MK, et al. Prevalence of autism spectrum disorder in preterm infants: a meta-analysis. Pediatrics 2018;142:e20180134. [DOI] [PubMed] [Google Scholar]
  • [12].Behnia F, Parets SE, Kechichian T, et al. Fetal DNA methylation of autism spectrum disorders candidate genes: association with spontaneous preterm birth. Am J Obstet Gynecol 2015;212:e1–9. [DOI] [PubMed] [Google Scholar]
  • [13].Nguyen A, Rauch TA, Pfeifer GP, et al. Global methylation profiling of lymphoblastoid cell lines reveals epigenetic contributions to autism spectrum disorders and a novel autism candidate gene, RORA, whose protein product is reduced in autistic brain. FASEB J 2010;24:3036–51. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [14].Medhurst AD, Lezoualc’h F, Fischmeister R, et al. Quantitative mRNA analysis of five C-terminal splice variants of the human 5-HT4 receptor in the central nervous system by TaqMan real time RT-PCR. Brain Res Mol Brain Res 2001;90:125–34. [DOI] [PubMed] [Google Scholar]
  • [15].Rosel P, Arranz B, Urretavizcaya M, et al. Altered 5-HT2A and 5-HT4 postsynaptic receptors and their intracellular signalling systems IP3 and cAMP in brains from depressed violent suicide victims. Neuropsychobiology 2004;49:189–95. [DOI] [PubMed] [Google Scholar]
  • [16].Crockett MJ. The neurochemistry of fairness: clarifying the link between serotonin and prosocial behavior. Ann N Y Acad Sci 2009;1167:76–86. [DOI] [PubMed] [Google Scholar]
  • [17].Vincent JB, Noor A, Windpassinger C, et al. Characterization of a de novo translocation t(5;18)(q33.1;q12.1) in an autistic boy identifies a breakpoint close to SH3TC2, ADRB2, and HTR4 on 5q, and within the desmocollin gene cluster on 18q. Am J Med Genet B Neuropsychiatr Genet 2009;150B:817–26. [DOI] [PubMed] [Google Scholar]
  • [18].Hegde SS, Eglen RM. Peripheral 5-HT4 receptors. FASEB J 1996;10:1398–407. [DOI] [PubMed] [Google Scholar]
  • [19].Suzuki T, Iwata N, Kitamura Y, et al. Association of a haplotype in the serotonin 5-HT4 receptor gene (HTR4) with Japanese schizophrenia. Am J Med Genet B Neuropsychiatr Genet 2003;121B:7–13. [DOI] [PubMed] [Google Scholar]
  • [20].Ohtsuki T, Ishiguro H, Detera-Wadleigh SD, et al. Association between serotonin 4 receptor gene polymorphisms and bipolar disorder in Japanese case-control samples and the NIMH genetics initiative bipolar pedigrees. Mol Psychiatry 2002;7:954–61. [DOI] [PubMed] [Google Scholar]
  • [21].Zafeiriou DI, Ververi A, Vargiami E. The serotonergic system: its role in pathogenesis and early developmental treatment of autism. Curr Neuropharmacol 2009;7:150–7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [22].Anderson GM. Genetics of childhood disorders: XLV. Autism, part 4: serotonin in autism,. J Am Acad Child Adolesc Psychiatry 2002;41:1513–6. [DOI] [PubMed] [Google Scholar]
  • [23].Williams K, Wheeler DM, Silove N, et al. Selective serotonin reuptake inhibitors (SSRIs) for autism spectrum disorders (ASD). Cochrane Database Syst Rev 2010;8:CD004677. [DOI] [PubMed] [Google Scholar]
  • [24].Chen R, Chen M, Xiong J, et al. Influence of the deqi sensation by suspended moxibustion stimulation in lumbar disc herniation: study for a multicenter prospective two arms cohort study. Evid Based Complement Alternat Med 2013;2013:718593. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [25].McBride PA, Anderson GM, Hertzig ME, et al. Serotonergic responsivity in male young adults with autistic disorder. Results of a pilot study. Arch Gen Psychiatry 1989;46:213–21. [DOI] [PubMed] [Google Scholar]
  • [26].Chugani DC, Muzik O, Behen M, et al. Developmental changes in brain serotonin synthesis capacity in autistic and nonautistic children. Ann Neurol 1999;45:287–95. [DOI] [PubMed] [Google Scholar]
  • [27].Dohn MR, Kooker CG, Bastarache L, et al. The gain-of-function integrin beta3 Pro33 variant alters the serotonin system in the mouse brain. J Neurosci 2017;37:11271–84. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [28].Rellini E, Tortolani D, Trillo S, et al. Childhood autism rating scale (CARS) and autism behavior checklist (ABC) correspondence and conflicts with DSM-IV criteria in diagnosis of autism. J Autism Dev Disord 2004;34:703–8. [DOI] [PubMed] [Google Scholar]
  • [29].Chang L, Wang Y, Ji H, et al. Elevation of peripheral BDNF promoter methylation links to the risk of Alzheimer's disease. PLoS One 2014;9:e110773. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [30].Chen R, Hong Q, Jiang J, et al. AGTR1 promoter hypermethylation in lung squamous cell carcinoma but not in lung adenocarcinoma. Oncol Lett 2017;14:4989–94. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [31].Abrams DJ. How to develop a clinic for sudden cardiac arrest survivors and families of non-survivors. Cardiol Young 2017;27(S1):S3–9. [DOI] [PubMed] [Google Scholar]
  • [32].Ji H, Wang Y, Liu G, et al. OPRK1 promoter hypermethylation increases the risk of Alzheimer's disease. Neurosci Lett 2015;606:24–9. [DOI] [PubMed] [Google Scholar]
  • [33].Shen Z, Chen X, Li Q, et al. Elevated methylation of CMTM3 promoter in the male laryngeal squamous cell carcinoma patients. Clin Biochem 2016;49:1278–82. [DOI] [PubMed] [Google Scholar]
  • [34].Bockaert J, Claeysen S, Compan V, et al. 5-HT(4) receptors: history, molecular pharmacology and brain functions. Neuropharmacology 2008;55:922–31. [DOI] [PubMed] [Google Scholar]
  • [35].Millan MJ, Agid Y, Brune M, et al. Cognitive dysfunction in psychiatric disorders: characteristics, causes and the quest for improved therapy. Nat Rev Drug Discov 2012;11:141–68. [DOI] [PubMed] [Google Scholar]
  • [36].Stefanik L, Erdman L, Ameis SH, et al. Brain-behavior participant similarity networks among youth and emerging adults with schizophrenia spectrum, autism spectrum, or bipolar disorder and matched controls. Neuropsychopharmacology 2018;43:1180–8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [37].Gadow KD, Drabick DA. Symptoms of autism and schizophrenia spectrum disorders in clinically referred youth with oppositional defiant disorder. Res Dev Disabil 2012;33:1157–68. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [38].Li J, Wang Y, Zhou R, et al. Association of attention-deficit/hyperactivity disorder with serotonin 4 receptor gene polymorphisms in Han Chinese subjects. Neurosci Lett 2006;401:6–9. [DOI] [PubMed] [Google Scholar]
  • [39].Autism, Developmental Disabilities Monitoring Network Surveillance Year Principal, I., Centers for Disease, C., Prevention, Prevalence of autism spectrum disorders--Autism, Developmental Disabilities Monitoring Network, 14 sites, United States, 2008. Morbidity and mortality weekly report. Surv Sum 2012;61:1–9. [PubMed] [Google Scholar]
  • [40].Carlsson M, Carlsson A. A regional study of sex differences in rat brain serotonin. Prog Neuropsychopharmacol Biol Psychiatry 1988;12:53–61. [DOI] [PubMed] [Google Scholar]
  • [41].Carlsson M, Svensson K, Eriksson E, et al. Rat brain serotonin: biochemical and functional evidence for a sex difference. J Neural Transm 1985;63:297–313. [DOI] [PubMed] [Google Scholar]
  • [42].Barua S, Chadman KK, Kuizon S, et al. Increasing maternal or post-weaning folic acid alters gene expression and moderately changes behavior in the offspring. PloS One 2014;9:e101674. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [43].Suren P, Roth C, Bresnahan M, et al. Association between maternal use of folic acid supplements and risk of autism spectrum disorders in children. JAMA 2013;309:570–7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [44].Bai M, Zhu XZ, Zhang Y, et al. Anhedonia was associated with the dysregulation of hippocampal HTR4 and microRNA Let-7a in rats. Physiol Behav 2014;129:135–41. [DOI] [PubMed] [Google Scholar]
  • [45].Jin Y, Wang L, Duan Q, et al. Differential expression of 5-HT-related genes in symptomatic pulmonary embolism patients. Int J Clin Exp Med 2015;8:512–8. [PMC free article] [PubMed] [Google Scholar]
  • [46].Witte AB, D’Amato M, Poulsen SS, et al. Duodenal epithelial transport in functional dyspepsia: Role of serotonin. World J Gastrointest Pathophysiol 2013;4:28–36. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [47].Dizeyi N, Bjartell A, Hedlund P, et al. Expression of serotonin receptors 2B and 4 in human prostate cancer tissue and effects of their antagonists on prostate cancer cell lines. Eur Urol 2005;47:895–900. [DOI] [PubMed] [Google Scholar]
  • [48].Kenworthy L, Case L, Harms MB, et al. Adaptive behavior ratings correlate with symptomatology and IQ among individuals with high-functioning autism spectrum disorders. J Autism Dev Disord 2010;40:416–23. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [49].Pathak M, Bennett A, Shui AM. Correlates of adaptive behavior profiles in a large cohort of children with autism: the autism speaks autism treatment network registry data. Autism 2019;23:87–99. [DOI] [PubMed] [Google Scholar]
  • [50].Perry A, Flanagan HE, Dunn Geier J, et al. Brief report: the vineland adaptive behavior scales in young children with autism spectrum disorders at different cognitive levels. J Autism Dev Disord 2009;39:1066–78. [DOI] [PMC free article] [PubMed] [Google Scholar]

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