Pathogenic variants in PRDM16 impair cardiomyocytes maturation and cause cardiomyopathy phenotypes in humans

Loss of the PR domain 16 (PRDM16) genetic locus has been suggested as the needed trigger for the development of left ventricular non-compaction cardiomyopathy (LVNC) and dilated cardiomyopathy (DCM) in patients with 1p36 deletion syndrome. Furthermore, lack of Prdm16 in the murine heart has recently been shown to cause a spectrum of cardiomyopathy phenotypes. In spite of these advances, our understanding of the downstream transcriptional pathways regulated by PRDM16 that lead to these cardiac phenotypes is limited. OBJECTIVE: to unveil the downstream transcriptional pathways involved in the development of cardiomyopathy phenotypes associated with PRDM16 mutations/deletion in human and mice. METHODS AND RESULTS: We hypothesized that PRDM16 acts as an upstream regulator of key transcriptional pathways involved in cardiac maturation. Induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with a PRDM16 variant, cardiac tissue from mice expressing the human variant, mice with cardiac-specific deletion of Prdm16 and in vitro gain and loss of Prdm16 function were employed. Here we show that de novo pathogenic variants in PRDM16 are sufficient to cause LVNC in humans. In contrast, haploinsufficiency or complete deletion of Prdm16 in cardiomyocytes in mice led to pathological hypertrophy and dilated cardiomyopathy respectively. We demonstrated that PRDM16 regulates cardiac maturation through the maintenance of estrogen-related receptors (ERRs) expression. By contrast, PRDM16 acts as a supressor of transforming growth factor beta (TGFB) signaling. CONCLUSIONS: PRDM16 is a novel regulator of cardiac maturation acting upstream of ERRs and their regulators, and a suppressor of fibrotic signaling including TGFB. Overall design: Induced pluripotent stem cells (iPSCs) were prepared from periferal blood of a control subject and a subject with PRDM16Q187X variant. iPSCs were differentiated into cardiomyocytes (iPSC-CMs) before performing the RNAseq