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Systems analysis of de novo mutations in congenital heart diseases identified a protein network in the hypoplastic left heart syndrome

ABSTRACT: Congenital heart diseases (CHD) are a class of birth defects affecting ~1% of live births. These conditions are hallmarked by extreme genetic heterogeneity, and therefore, despite a strong genetic component, only a very handful of at-risk loci in CHD have been identified. We herein introduced systems analyses to uncover the hidden organization on biological networks of genomic mutations in CHD, and leveraged network analysis techniques to integrate the human interactome, large-scale patient exomes, the fetal heart spatial transcriptomes, and single-cell transcriptomes of clinical samples. We identified a highly connected network in CHD where most of the member proteins had previously uncharacterized functions in regulating fetal heart development. While genes on the network displayed strong enrichment for heart-specific functions, a sub-group, active specifically at early developmental stages, also regulates fetal brain development, thereby providing mechanistic insights into the clinical comorbidities between CHD and neurodevelopmental conditions. At a small scale, we experimentally verified previously uncharacterized cardiac functions of several novel proteins employing cellular assays and gene editing techniques. At a global scale, our study revealed developmental dynamics of the identified CHD network and observed the strongest enrichment for pathogenic mutations in the network specific to hypoplastic left heart syndrome (HLHS). Our single-cell transcriptome analysis further identified pervasive dysregulation of the network in cardiac endothelial cells and the conduction system in the HLHS left ventricle. Taken together, our systems analyses identified novel factors in CHD, revealed key molecular mechanisms in HLHS, and provides a generalizable framework readily applicable to studying many other complex diseases.

ORGANISM(S): Homo sapiens

PROVIDER: GSE197709 | GEO | 2022/09/26

REPOSITORIES: GEO

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Project description:Hypoplastic left heart syndrome (HLHS) is the most lethal congenital heart disease (CHD). The pathogenesis of HLHS is poorly understood and due to the likely oligogenic complexity of the disease, definitive HLHS-causing genes have not yet been identified. Postulating that impaired cardiomyocyte proliferation as a likely important contributing mechanism to HLHS pathogenesis, and we conducted a genome-wide siRNA screen to identify genes affecting proliferation of human iPSC-derived cardiomyocytes (hPSC-CMs). This yielded ribosomal protein (RP) genes as the most prominent class of effectors of CM proliferation. In parallel, whole genome sequencing and rare variant filtering of a cohort of 25 HLHS proband-parent trios with poor clinical outcome revealed enrichment of rare variants of RP genes. In addition, in another familial CHD case of HLHS proband we identified a rare, predicted-damaging promoter variant affecting RPS15A that was shared between the proband and a distant relative with CHD. Functional testing with an integrated multi-model system approach reinforced the idea that RP genes are major regulators of cardiac growth and proliferation, thus potentially contributing to hypoplastic phenotype observed in HLHS patients. Cardiac knockdown (KD) of RP genes with promoter or coding variants (RPS15A, RPS17, RPL26L1, RPL39, RPS15) reduced proliferation in generic hPSC-CMs and caused malformed hearts, heart-loss or even lethality in Drosophila. In zebrafish, diminished rps15a function caused reduced CM numbers, heart looping defects, or weakened contractility, while reduced rps17 or rpl39 function caused reduced ventricular size or systolic atrial dysfunction, respectively. Importantly, genetic interactions between RPS15A and core cardiac transcription factors TBX5 in CMs, Drosocross, pannier and tinman in flies, and tbx5 and nkx2-7 (nkx2-5 paralog) in fish, support a specific role for RP genes in heart development. Furthermore, RPS15A KD-induced heart/CM proliferation defects were significantly attenuated by p53 KD in both hPSC-CMs and zebrafish, and by Hippo activation (YAP/yorkie overexpression) in developing fly hearts. Based on these findings, we conclude that RP genes play critical roles in cardiogenesis and constitute an emerging novel class of gene candidates likely involved in HLHS and other CHDs.

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Systems analysis of de novo mutations in congenital heart diseases identified a protein network in the hypoplastic left heart syndrome

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