Abstract 16626: Endothelial Zinc Transporter Zip8 Regulates Ventricular Trabeculation and Compaction

Abstract

Trabeculation and subsequent compaction of the ventricular wall are essential for normal heart morphogenesis. In human, excessive trabeculation and impaired myocardial compaction during earlyheart development lead to left ventricular non compaction (LVNC), a third most common cardiomyopathies after dilated and hypertrophic cardiomyopathies. LVNC is also associated with cardiac arrhythmia and sudden cardiac death. The etiology of LVNC is poorly understood. Recently our group identified that Zip8, a Zinc transporter, implicated in ventricular trabeculation and compaction (JCI, 2018,PMID: 29337306). However, it remains elusive how Zip8 regulates these processes through cellular and molecular mechanisms. We conditionally ablated Zip8 in the endothelial cells, epicardial cells and cardiomyocytes in the developing heart respectively. Strikingly, deletion of Zip8 in the endothelial cellsgave rise to LVNC phenotypes, identical to cardiac phenotypes from the global Zip8 knockouts. Incontrast, hearts with deletions of Zip8 in either epicardium or myocardium developed normally. Further,we found only conditional deletion of Zip8 in the endothelium in the early developing hearts (at E8.5)generated LVNC but not in the late gestation stage (E13.5), suggesting that Zip8 plays critical roles during the initial trabeculation stage. Interestingly, we found that endocardial Zip8 deficiency resulted inthe upregulation of Notch signaling, as evidenced by the increase of intracellular domain of notch protein(NICD) and its downstream target gene, bone morphogenetic protein 10 (BMP10). When the notch signaling is inhibited in the endothelial Zip8 knockout hearts either by DAPI, a γ secretase inhibitor, or by genetic deletion of Rbpj, the LVNC cardiac phenotypes are partially rescued. These results suggest thatZip8 orchestrates myocardial trabeculation and compaction by regulating notch signaling.Collectively, our study provides novel insights into the mechanisms of LVNC, suggesting that genetic mutations in Zip8 or zinc deficiency may contribute to LNVC in humans.