Utilization of induced pluripotent stem cells to model the molecular network regulating congenital heart disease

This editorial refers to ‘Patient-specific iPSC-derived cardiomyocytes reveal abnormal regulation of FGF16 in a familial atrial septal defect’ by L. Ye et al., pp. 859–871.

Congenital heart disease (CHD) occurs when the atria and ventricles are abnormal during the earlier stages of development, leading to atrial septal defect (ASD), ventricular septal defect, or both. ASD is among the most frequently diagnosed forms of CHD and is typically characterized by left-to-right shunting and increased right ventricular output.¹ CHD can result in chronic or acute heart disease depending on the degree of malformation. CHD is the most commonly occurring congenital birth defect. Although technological advances in healthcare have made a difference, children afflicted with CHD are still confronted with significant morbidity and mortality.^2,3 Cardiac malformations present at birth are a substantial component of pediatric cardiovascular disease that makes up a considerable percentage of clinically relevant congenital disabilities, occurring in ∼4–50 per 1000 live births.^4,5 Recent progress has led to a better understanding of the aetiology of CHD, allowing clinicians to implement new approaches that decrease morbidity and mortality rates among affected infants. Nevertheless, to date, the overall mechanisms that regulate cardiac development leading to CHD remain poorly understood. A powerful novel paradigm in cardiovascular disease modeling is the application of induced pluripotent stem cells (iPSCs) and their differentiated cardiovascular cells to develop in vitro models of human physiology.^1,6 iPSCs are a valuable tool for evaluating highly sensitive dysregulation of multiple pathways (e.g. genes associated with heart development, cardiomyocyte function, and CHD genetics) in specific subpopulations of cardiomyocytes.⁷ Specifically, iPSC-derived cardiomyocytes (iPSC-CMs) have gained popularity as experimental models because they are human derived and readily available and can be cultured in vitro for weeks to months.⁷

Ye et al.¹ used the iPSC-CM model to better elucidate the role of the GATA4–FGF16 axis in promoting the CHD during heart development, as it relates to ASD (Figure 1). GATA4 is a critical transcription factor involved in coordinating heart development. FGF16 belongs to the fibroblast growth factor (FGF) family, containing 22 structurally related members known for cell proliferation, migration, and differentiation in embryonic development.⁶ To model the GATA4 mutation-associated ASD, both GATA4-mutant iPSCs and embryonic stem cells (ESCs) were differentiated into cardiomyocytes (CMs). In 2010, a study utilized genetic analysis to reveal that the GATA4 T280M mutation is associated with familial ASD in an autosomal dominant inheritance.⁸ Ye et al.¹ built upon this previous study by generating a patient-specific iPSC line (iPSC-G4 T280M) from a family cohort carrying a hereditary ASD mutation in the GATA4 gene (T280M). They also generated a human ESC line (ESC-G4 T280M) carrying the isogenic T280M mutation using the CRISPR/Cas9 genome editing method.¹ This study represents the first time that the human iPSC model was used to show the direct relationship between GATA4 T280M and ASD, in which overexpression of FGF16 in GATA4-mutant cardiomyocytes rescued the cell proliferation defect.¹ In addition to using the iPSC model to reveal the crosstalk between GATA4 and FGF16, they detected significantly lower DNA occupancy of the GATA4 T280M protein, which disrupts activation or suppression of GATA4-targeted genes in iPSC-G4 T280M-CMs.¹ Loss-of-function mutations are the direct causes of GATA4 mutation-induced cardiovascular diseases such as CHD.

Figure 1.

Application of human-based induced pluripotent stem cells to model congenital heart disease. Utilization of the generation and characterization of patient-specific iPSCs allowed Ye et al. to discover that FGF16 mediates the GATA4 mutation in CHD. The GATA4 is an atrial septal defect hereditary mutation of the heart that influences development, thus contributing to CHD. This represents the first time that the human iPSC model was used to show the direct relationship between GATA4 T280M and ASD, in which overexpression of FGF16 in GATA4-mutant cardiomyocytes rescued the cell proliferation defect. ASD, atrial septal defect; CHD, congenital heart disease; CRISPR/Cas9, clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9; FGF16, fibroblast growth factor 16; iPSC, induced pluripotent stem cell; iPSC-CM, induced pluripotent stem cell-derived cardiomyocytes.

This study by Ye et al. successfully showed that patient-specific iPSC-CMs harboring a mutation of T280M in the GATA4 protein displayed cell proliferation deficiency in CHD models. Dysregulation of the GATA4-FGF16 axis directly results in defects in iPSC-G4 T280M-CMs.¹ Furthermore, this study revealed additional roles of the GATA4 T280M protein, which binds to novel DNA regions, gaining specific functions through activation of genes involved in regulating cholesterol metabolism and neuronal cell body (e.g. KCNH2, which contribute to the regulation of heart contraction).¹ This evaluation allows researchers to understand better the critical developmental factors that lead to CHD and how specific genes play a vital role in cardiogenesis. The identification of underlying genetic patterns (e.g. deletions, duplications, or mutations) is essential for CHD for the following reasons: (i) there may be systemic organ involvement; (ii) there may be important prognostic factors to understand for clinical outcomes; (iii) there may be reproductive genetic risks that the family should understand; and (iv) there may be other family members for whom genetic testing is recommended.⁵

Although this recent development sheds new light on critical genes that influence CHD development, a deeper analysis is needed to identify more of the factors contributing to the development of this disease in infants. Healthcare professionals should continue to consult and perform multi-omic studies on patients with CHD to elucidate further the full spectrum of genes involved and identify the most relevant factors. Future application of genome-editing technologies such as CRISPR with extensive capabilities to genetically modify cardiomyocytes or iPSCs will add another potent tool to address CHD.⁹ Researchers now have the ability to precisely edit or introduce mutations in disease-causing genes and evaluate the relative contribution of a single mutation on the severity of the disease phenotype (e.g. mutations associated with CHD).¹⁰ The work presented in this issue of Cardiovascular Research reveals an innovative approach to understand the genetic variant that causes CHD, establishing a role for iPSCs in modeling cardiovascular disease. The clinical application of genome-edited iPSC lines whose cardiovascular disease-associated mutations/variants are engineered into the same genetic background by CRISPR/Cas9 will be instrumental for creating libraries of disease-specific cardiomyocytes for drug testing and disease modeling, bringing a new age of personalized medicine customized to treat each patient based on the genetic mutation responsible for the condition.^4,11,12 This paradigm-shifting approach to therapy represents the future of healthcare regarding CHD and other previously incurable cardiovascular diseases.

Funding

This work was supported by National Institutes of Health R01 HL141371, R01 HL145676, and R01 HL150693 (Joseph C. Wu) and Propel Postdoctoral Scholars Program (McKay M.S. Mullen).

Conflict of interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

 

The opinions expressed in this article are not necessarily those of the Editors of Cardiovascular Research or of the European Society of Cardiology.