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CHD-associated enhancers direct human cardiomyocyte lineage commitment.

ABSTRACT: Enhancers orchestrate gene expression programs that drive multicellular development and lineage commitment. Thus, genetic variants at enhancers are thought to contribute to developmental diseases by altering cell fate commitment. However, while many variant-containing enhancers have been identified, systematic studies to endogenously test the impact of these enhancers on lineage commitment have been lacking. We performed a single-cell CRISPRi screen to directly assess the roles of 25 enhancers and putative cardiac target genes implicated in genetic studies of congenital heart defects (CHD). We identified 16 enhancers whose repression leads to delayed differentiation of human cardiomyocytes. A focused analysis on 6 TBX5 enhancers showed that TBX5 enhancer perturbation delays the transcriptional switch from mid-CM to late-CM states. Knockout of two TBX5 enhancers resulted in X and Y, which phenocopy expected CHD phenotypes. Together, these results identify critical enhancers of cardiac development and suggest that misregulation of these enhancers could contribute to cardiac defects in human patients.

ORGANISM(S): Homo sapiens

PROVIDER: GSE190475 | GEO | 2022/05/15

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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CHD-associated enhancers direct human cardiomyocyte lineage commitment.

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