Enhanced Ca2+signaling, mild primary aldosteronism, and hypertension in a familial hyperaldosteronism mouse model (Cacna1hM1560V/+)

Abstract

Gain-of-function mutations in theCACNA1Hgene (encoding the T-type calcium channel CaV3.2) cause autosomal-dominant familial hyperaldosteronism type IV (FH-IV) and early-onset hypertension in humans. We used CRISPR/Cas9 to generateCacna1hM1560V/+knockin mice as a model of the most common FH-IV mutation, along with corresponding knockout mice (Cacna1h−/−). Adrenal morphology of bothCacna1hM1560V/+andCacna1h−/−mice was normal.Cacna1hM1560V/+mice had elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism). Their adrenalCyp11b2(aldosterone synthase) expression was increased and remained elevated on a high-salt diet (relative autonomy, characteristic of primary aldosteronism), but plasma aldosterone was only elevated in male animals. The systolic blood pressure ofCacna1hM1560V/+mice was 8 mmHg higher than in wild-type littermates and remained elevated on a high-salt diet.Cacna1h−/−mice had elevated renalRen1(renin-1) expression but normal adrenalCyp11b2levels, suggesting that in the absence of CaV3.2, stimulation of the renin-angiotensin system activates alternative calcium entry pathways to maintain normal aldosterone production. On a cellular level,Cacna1hM1560V/+adrenal slices showed increased baseline and peak intracellular calcium concentrations in the zona glomerulosa compared to controls, but the frequency of calcium spikes did not rise. We conclude that FH-IV, on a molecular level, is caused by elevated intracellular Ca2+concentrations as a signal for aldosterone production in adrenal glomerulosa cells. We demonstrate that a germlineCacna1hgain-of-function mutation is sufficient to cause mild primary aldosteronism, whereas loss of CaV3.2 channel function can be compensated for in a chronic setting.