Abstract 210: Transcriptomic Changes During Induced Pluripotent Stem Cell-derived Neural Crest Cell Differentiation Highlight Genes Involved in Endocardial Cushion and Cardiac Outflow Tract Development

Abstract

Rationale: Neural crest cells (NCCs) play a critical role in normal cardiac development, and defects in NCCs likely cause congenital heart disease (CHD). NCCs are transient and multipotent migratory stem cells that give rise to diverse tissues, including cardiac structures such as the smooth muscles of the great arteries and semilunar valves. Induced pluripotent stem cells (iPSC) can be differentiated into NCCs, as demonstrated by expression of several marker proteins including NGFR and HNK1. To better define iPSC-NCCs and to better understand the progression of iPSCs to NCCs, we have compared the transcriptomes of iPSC and iPSC-NCCs. We have also begun to investigate the consequences of loss-of-function mutations in genes implicated in CHD on the differentiation of iPSC-NCCs. Methods and Results: PGP1 iPSCs were differentiated to NCCs and RNA was collected at 0, 5, 10, and 15 days of differentiation. RNAseq analysis showed that by day 15, 6483 genes were upregulated in NCC vs iPSCs, 6406 downregulated, and 6715 unchanged (FDR 5%). Enrichment analysis for the top 500 upregulated genes showed 4 cardiac gene ontology (GO) terms in the top 10, including ‘endocardial cushion morphogenesis’ (fold enrichment 11.85, p = 0.012). Notably, of 45 genes under GO term ‘endocardial cushion development’, 38 (84%) differentially expressed in NCCs by day 15 (FDR 5%). Next, we compared this RNAseq data with that of iPSC-derived cardiomyocyte (CM) differentiation in a subset of 253 genes previously implicated in CHD. Of these, 143 genes were differentially expressed in both iPSC-CMs and iPSC-NCCs. However, 27 genes (10.6%) including MYH6, PITX2, and TBX5 were uniquely upregulated during CM differentiation, while 65 genes (25.7%) including CHD4 and NOTCH1 were uniquely upregulated during NCC differentiation. Conclusion: Transcriptomic changes during iPSC-NCC differentiation, assessed by both bulk and single cell RNAseq, reveal an upregulation of genes involved in cardiac development, particularly endocardial cushions and the outflow tract. Importantly, a subset of genes implicated in CHD are altered during iPSC-NCC differentiation but not in iPSC-CM differentiation. Thus, iPSC-NCCs offer a new model with which to investigate the pathogenesis and mechanisms of CHD.