Molecular Medicine Program-Neurobiology and Anatomy Department, University of Utah, Salt Lake City, Utah, United States of America.
University of Minnesota, Morris, Minnesota, United States of America.
PLoS Biol. 2019 Sep 3;17(9):e3000087. doi: 10.1371/journal.pbio.3000087. eCollection 2019 Sep.
Kabuki Syndrome patients have a spectrum of congenital disorders, including congenital heart defects, the primary determinant of mortality. Seventy percent of Kabuki Syndrome patients have mutations in the histone methyl-transferase KMT2D. However, the underlying mechanisms that drive these congenital disorders are unknown. Here, we generated and characterized zebrafish kmt2d null mutants that recapitulate the cardinal phenotypic features of Kabuki Syndrome, including microcephaly, palate defects, abnormal ear development, and cardiac defects. The cardiac phenotype consists of a previously unknown vasculogenesis defect that affects endocardium patterning and, consequently, heart ventricle lumen formation. Additionally, zebrafish kmt2d null mutants have angiogenesis defects depicted by abnormal aortic arch development, hyperactive ectopic blood vessel sprouting, and aberrant patterning of the brain vascular plexus. We demonstrate that zebrafish kmt2d null mutants have robust Notch signaling hyperactivation in endocardial and endothelial cells, including increased protein levels of the Notch transcription factor Rbpj. Our zebrafish Kabuki Syndrome model reveals a regulatory link between the Notch pathway and Kmt2d during endothelium and endocardium patterning and shows that pharmacological inhibition of Notch signaling rebalances Rbpj protein levels and rescues the cardiovascular phenotype by enhancing endothelial and endocardial cell proliferation and stabilizing endocardial patterning. Taken together, these findings demonstrate that Kmt2d regulates vasculogenesis and angiogenesis, provide evidence for interactions between Kmt2d and Notch signaling in Kabuki Syndrome, and suggest future directions for clinical research.
歌舞伎综合征患者存在一系列先天性疾病，包括先天性心脏病，这是导致死亡率的主要因素。70%的歌舞伎综合征患者存在组蛋白甲基转移酶 KMT2D 的突变。然而，导致这些先天性疾病的潜在机制尚不清楚。在这里，我们生成并鉴定了斑马鱼 kmt2d 缺失突变体，这些突变体重现了歌舞伎综合征的主要表型特征，包括小头畸形、腭裂、耳朵发育异常和心脏缺陷。心脏表型包括以前未知的血管发生缺陷，影响心内膜的模式形成，进而影响心室腔的形成。此外，斑马鱼 kmt2d 缺失突变体还存在血管生成缺陷，表现为主动脉弓发育异常、异位血管过度出芽和脑血管丛异常模式。我们证明斑马鱼 kmt2d 缺失突变体在心内膜和内皮细胞中存在强烈的 Notch 信号过度激活，包括 Notch 转录因子 Rbpj 的蛋白水平增加。我们的斑马鱼歌舞伎综合征模型揭示了 Notch 通路和 Kmt2d 在血管内皮细胞和心内膜细胞的模式形成过程中的调节关系，并表明 Notch 信号通路的药理学抑制通过增强内皮细胞和心内膜细胞的增殖以及稳定心内膜的模式形成来重新平衡 Rbpj 蛋白水平并挽救心血管表型。总之，这些发现表明 Kmt2d 调节血管发生和血管生成，为 Kmt2d 和 Notch 信号通路在歌舞伎综合征中的相互作用提供了证据，并为临床研究提供了未来的研究方向。
