Endocrine Abstracts

Hypertension is associated with vascular changes characterized by endothelial dysfunction, increased vascular contraction, and arterial remodelling. Vascular smooth muscle (VSM) cells, which constitute bulk of vascular wall, are critically involved in these processes through their highly plastic and dynamic features and ability to undergo phenotypic differentiation. Stimulation of VSM cells by pro-hypertensive neurohumoral stimuli such as acetylcholine and norepinephrine, and vasoactive peptides like angiotensin-II and endothelin-1 induce activation of receptors coupled to phospholipase C (PLC), leading to generation of second messengers, inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 increases intracellular Ca2+ and causes vasoconstriction. VSM contraction plays an important role in regulation of peripheral vascular resistance and blood pressure. Vascular dysfunction, excessive vasoconstriction and vasospasm could lead to major cardiovascular disorders such as hypertension and coronary artery disease. In this study, hypertensive cardiovascular patients were screened using whole exome sequencing (WES) to find possible pathogenic mutations in different genes involved in vasoconstriction. Thirteen hypertensive cardiovascular patients from three families (3 patients in 1st, 21-48 years; 5 in 2nd, 43-72 years and 5 patients in 3rd, 19-47 years of age) were selected for WES. Genomic DNA was extracted (DNA Isolation Kit, QIAamp DNA mini-Kit) at City Lab, Rawalpindi, Pakistan. DNA obtained was taken to Genome Institute of Singapore (GIS), Singapore, where final dilutions of 25μl DNA were outsourced to Proteomics Lab, Macrogen Asia Pacific, Singapore for WES. Subsequent bioinformatics analysis was performed at GIS, Singapore. We identified a novel splicing variant in SARAF gene (in two patients of family 1) involved in norepinephrine signalling pathway and a novel frameshift variant in NOX4 gene (in all patients of family 1 and 3, and two patients of family 2) involved in angiotensin-II signalling pathway. This study also found a missense variant in ADCY10 gene (in three patients each of family 2 and 3) involved in norepinephrine signalling pathway, a missense variant in TLR4 gene (in one patient of family 1 and three patients of family 2), which is upregulated by angiotensin-II and a splicing variant in GNAQ gene (in all patients of family 1 and two patients each of family 2 and 3) that encodes a protein associated with α-adrenergic receptor and angiotensin-II receptor. Variants identified in ADCY10, TLR4 and GNAQ genes were reported earlier but are extremely rare in GnomAD database. In conclusion, we report novel mutations in two genes and variants in three genes involved in vasoconstriction in hypertensive cardiovascular patients.