Endocrine Abstracts

The renin-angiotensin-aldosterone system (RAAS) is an endocrine system within the body that is essential for regulation of blood pressure (BP) and fluid balance. The system is mainly comprised of three hormones renin, angiotensin II (Ang II) and aldosterone. The RAAS pathway is initiated in the kidney with the proteolytic conversion of liver derived angiotensinogen to angiotensin I (Ang I) by renin secreted by juxtaglomerular apparatus of the nephron. Ang I is cleaved by angiotensin converting enzyme to produce Ang II, the physiologically active component of the system. Ang II acts on the adrenal cortex through its receptors, AT-1 and AT-2, to stimulate the release of aldosterone. Aldosterone is a mineralocorticoid, a steroid hormone released from the zona glomerulosa of the adrenal cortex and plays a central role in regulation of BP mainly by acting on distal tubules and collecting ducts of the nephron, increasing reabsorption of sodium and water in the kidney and secretion of potassium. Increase in water retention causes increase in the blood volume and hence BP. In this study, whole exome sequencing (WES) was used to identify pathogenic mutations in different genes of RAAS pathway, whose dysfunction may lead to hypertension and related cardiovascular diseases. Thirteen hypertensive cardiovascular patients from three families (3 patients in 1^st from 21-48, 5 in 2^nd from 43-72 and 5 in 3^rd from 19-47 years of age) were selected for WES. Genomic DNA was extracted (DNA Isolation Kit from QIAamp DNA mini Kit) at University of Wah (UOW), Wah Cantt, 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. Our results revealed pathogenic mutations in different routes of RAAS pathway; gene mutations in DGKB in all 13 patients, NCOR2 in 12 patients, ESRRA in 10 patients, SEC63 in 10 patients, RYR3 in 3 patients of 2 families and CAMKK2 in 1 patient. Novel variants were identified in NCOR2, SEC63 and CAMKK2 genes. Missense variants were found in RYR3 and ESSRA genes, splice region variants in DGKB and SEC63 genes and frameshift variants were identified in NCOR2 and CAMKK2 genes. All the variants were found to be heterozygous except NCOR2 gene. In conclusion, our results identified non-synonymous mutations in 6 genes involved in different steps of RAAS pathway in patients with hypertensive cardiovascular diseases.