Enhanced Ca²⁺ signaling, mild primary aldosteronism, and hypertension in a familial hyperaldosteronism mouse model (<i>Cacna1h</i>^{<i>M1560V/+</i>} ).

Abstract

Gain-of-function mutations in the <i>CACNA1H</i> gene (encoding the T-type calcium channel Ca_V3.2) cause autosomal-dominant familial hyperaldosteronism type IV (FH-IV) and early-onset hypertension in humans. We used CRISPR/Cas9 to generate <i>Cacna1h</i>^{<i>M1560V/+</i>} knockin mice as a model of the most common FH-IV mutation, along with corresponding knockout mice (<i>Cacna1h</i>^<i>-/-</i> ). Adrenal morphology of both <i>Cacna1h</i>^{<i>M1560V/+</i>} and <i>Cacna1h</i>^<i>-/-</i> mice was normal. <i>Cacna1h</i>^{<i>M1560V/+</i>} mice had elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism). Their adrenal <i>Cyp11b2</i> (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 of <i>Cacna1h</i>^{<i>M1560V/+</i>} mice was 8 mmHg higher than in wild-type littermates and remained elevated on a high-salt diet. <i>Cacna1h</i>^<i>-/-</i> mice had elevated renal <i>Ren1</i> (renin-1) expression but normal adrenal <i>Cyp11b2</i> levels, suggesting that in the absence of Ca_V3.2, stimulation of the renin-angiotensin system activates alternative calcium entry pathways to maintain normal aldosterone production. On a cellular level, <i>Cacna1h</i>^{<i>M1560V/+</i>} 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 germline <i>Cacna1h</i> gain-of-function mutation is sufficient to cause mild primary aldosteronism, whereas loss of Ca_V3.2 channel function can be compensated for in a chronic setting.