OR04-2 WNT2B Deficiency Results in Hyperreninemic Hypoaldosteronism in Humans and Mice

Abstract

Abstract Proper development and zonation of the adrenal cortex is intimately connected with its lifelong capacity to produce steroid hormones. Both adrenocortical development and homeostasis are mediated in part by paracrine WNT/β-catenin signaling, an essential pathway for zonal maintenance and aldosterone production. Patients harboring homozygous or compound heterozygous loss-of-function (LOF) mutations in the WNT ligand WNT2B present with congenital diarrhea and require parenteral nutrition. Despite evidence for euvolemia, WNT2B-null patients exhibit markedly elevated plasma renin levels with no corresponding increase in aldosterone, suggesting a primary adrenal defect in aldosterone synthesis. To test this hypothesis, we generated both global and conditional Wnt2b knockout mouse models. In the mouse adrenal, Wnt2b is expressed exclusively in the capsule, the outer compartment of mesenchymal cells that overlay and signal to the subcapsular zona glomerulosa (zG), the adrenocortical zone that harbors aldosterone-producing cells and critical long-term progenitor cells. Global loss of Wnt2b from early mouse development results in a near-complete absence of the histological zG. Moreover, Wnt2b-null mice exhibit significantly increased plasma renin but normal aldosterone levels compared to wild-type controls. These data suggest that WNT2B-null patients indeed have an adrenocortical phenotype caused by apparent zG hypofunction. To further define the mechanism(s) by which Wnt2b LOF leads to zG hypofunction, we temporally deleted Wnt2b in the adrenal capsule of adult mice. Wnt2b conditional knockout (cKO) adrenals exhibit a zG-restricted decrease in Wnt/β-catenin signaling as determined by decreased β-catenin activity and target gene expression. Moreover, Wnt2b cKO mice demonstrated a disorganized zG and disrupted adrenocortical zonation. To determine the contribution of WNT2B to aldosterone production, we administered a sodium-deficient diet to control and Wnt2b cKO mice to activate the renin-angiotensin-aldosterone system. Indeed, while control mice exhibited the expected increase in both plasma renin and aldosterone, Wnt2b cKO mice showed marked elevation of renin despite normal aldosterone compared to controls, consistent with hyperreninemic hypoaldosteronism. Together, our work supports a WNT2B-dependent mechanism for adrenal zG development and maintenance in mice and humans and provides relevant models to study the consequences of WNT2B deficiency within the zG. Presentation: Saturday, June 11, 2022 11:45 a.m. - 12:00 p.m.