Inhibition of Notch signaling rescues cardiovascular development in Kabuki Syndrome

Abstract

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.

Chromatin Regulator SPEN/SHARP in X Inactivation and Disease

“…Following the same line of reasoning, mutations of the genes encoding for SHARP interactors might have a deleterious ending. This might be the case of subunits of the KMT2D complex; in fact, KMT2D and lysine demethylase 6A / ubiquitously transcribed tetratricopeptide repeat protein X-linked ( KDM6A / UTX ) mutations have been observed in patients that are affected by Kabuki Syndrome [ 229 , 230 , 231 , 232 , 233 , 234 , 235 , 236 , 237 ] and, in line with that, kmt2d knockout in zebrafish recapitulates the Kabuki phenotype and it is characterized by the deregulation of the Notch pathway [ 238 ].…”

Kabuki Syndrome—Clinical Review with Molecular Aspects

“…Notch pathway inhibition leads to physiological cardiovascular development. Extrapolating on this finding, KMT2D may play a role in regulating vasculogenesis and angiogenesis (connective tissue development) [ 77 ]. Yet, KMT2D ’s function as a cardioregulatory gene in humans is not yet fully understood, nor is its role in the development of specific congenital cardiac diseases [ 74 , 76 , 77 ].…”

“…Extrapolating on this finding, KMT2D may play a role in regulating vasculogenesis and angiogenesis (connective tissue development) [ 77 ]. Yet, KMT2D ’s function as a cardioregulatory gene in humans is not yet fully understood, nor is its role in the development of specific congenital cardiac diseases [ 74 , 76 , 77 ]. Fewer than half of patients with KDM6A variants present with CHD, and those who do show mostly right-sided lesions [ 70 ].…”

Capillary Malformation–Arteriovenous Malformation Combined Alagille Syndrome in a Patient With Double Gene Variations of RASA1 and NOTCH2

“…RASA1 encodes the RAS GTPase activating protein, which negatively regulates the RAS-MAPK signal pathway. Both RAS-MAPK and Notch signaling pathways are involved in the vascular development (Chen et al, 2019; Serrano and Demarest, 2019). In addition, a single variant in NOTCH2 or RASA1 may cause phenotypes associated with vascular malformations.…”