The role of ZIC3 within cardiomyocyte precursors in cardiac morphogenesis

项目总结

PROJECT SUMMARY Despite an increasingly sophisticated understanding of cardiac development, the mechanisms underlying the causes, penetrance, and phenotypic diversity of congenital heart defects (CHDs), the most common birth defect, are not well understood. This represents a barrier to risk stratification, improved therapeutics, and prevention of CHD. We have studied the genetic and developmental basis of heterotaxy syndrome, a multisystem disorder with a spectrum of CHDs that are attributable, at least in part, to abnormal cardiac looping morphogenesis. Although it has been proven that abnormalities in left-right (LR) axis formation during early embryonic development lead to CHDs in heterotaxy, the ventricular chamber morphogenic defects encountered are more diverse than would be expected from simple disruption of the LR axis. We hypothesize that severe heterotaxy CHDs result from abnormal cell fate of cardiac progenitors and that this is a distinct CHD causing mechanism from later LR patterning-mediated CHDs. Single cell RNA sequencing (scRNA-seq) from a mouse model of X- linked heterotaxy, Zic3 null mice, supports this hypothesis. The data demonstrate an abnormal mesoderm versus neuroectoderm allocation prior to cardiogenesis that results in abnormal cardiomyocyte cell fate. Combined with our data on abnormal primitive streak formation in Zic3 null mice, these studies reveal an essential need to investigate the ZIC3 gene regulatory networks (GRNs) during the transition from cell pluripotency through LR patterning to understand the mechanistic underpinnings of a diverse set CHDs. We will pair this investigation with our expertise in genomic analyses and whole genome sequencing (WGS) data in our well-phenotyped cohort of heterotaxy CHD patients. Our preliminary data demonstrate increased rare variant burden in CHD candidate genes, suggesting that complex CHD can result from combinatorial interactions of multiple susceptibility alleles. This approach will be used to test candidate genes for monogenic and oligogenic disease association. The aims of this study are to: 1) test the hypothesis that integrating ZIC3 DNA-occupancy data with transcriptional and epigenetic changes caused by ZIC3 loss-of-function will identify novel GRNs for cardiac morphogenesis; and 2) test the hypothesis that genetic variation within the ZIC3 GRN is associated with CHD. The overarching hypothesis of this proposal is that ZIC3 regulatory network genes are risk factors for ventricular morphogenesis defects that result in CHD. By identifying ZIC3 pathways during transition states from gastrulation to cardiogenesis, we will discover distinct ZIC3 GRNs required for heart formation. The integration of this multiomics data will provide novel insight into cardiac progenitor cell specification. Investigating the importance of these ZIC3 GRNs and developmental-stage specific pathways to human CHD susceptibility will provide critical translational information. Collectively, we will have identified novel ZIC3 GRNs important for chamber morphogenesis and provided essential information on monogenic and oligogenic contributions of pathways regulating cardiac cell fate to the development of human heterotaxy CHDs.