Gain-of-function mutations in the CACNA1H gene (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 generate Cacna1hM1560V/+ knockin mice as a model of the most common FH-IV mutation, along with corresponding knockout mice (Cacna1h−/−). Adrenal morphology of both Cacna1hM1560V/+ and Cacna1h−/− mice was normal. Cacna1hM1560V/+ mice had elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism). Their adrenal Cyp11b2 (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 Cacna1hM1560V/+ mice was 8 mmHg higher than in wild-type littermates and remained elevated on a high-salt diet. Cacna1h−/− mice had elevated renal Ren1 (renin-1) expression but normal adrenal Cyp11b2 levels, 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 germline Cacna1h gain-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.

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The zona glomerulosa of the adrenal gland is responsible for the synthesis and release of the mineralocorticoid aldosterone. This steroid hormone regulates salt reabsorption in the kidney and blood pressure. The most important stimuli of aldosterone synthesis are the serum concentrations of angiotensin II and potassium. In response to these stimuli, voltage and intracellular calcium levels in the zona glomerulosa oscillate, providing the signal for aldosterone synthesis. It was proposed that the voltage-gated T-type calcium channel CaV3.2 is necessary for the generation of these oscillations. However, Cacna1h knockout mice have normal plasma aldosterone levels, suggesting additional calcium entry pathways. We used a combination of calcium imaging, patch clamp and RNA sequencing to investigate such pathways in the murine zona glomerulosa. Cacna1h-/- glomerulosa cells showed similar calcium levels as wild-type mice in response to stimulation with angiotensin II or potassium. No calcium channels or transporters were upregulated to compensate for the loss of CaV3.2. The calcium oscillations observed in the zona glomerulosa of Cacna1h-/- mice were instead dependent on L-type voltage-gated calcium channels. Furthermore, we found these channels also in the wild-type zona glomerulosa where they can partially compensate for an acute inhibition of CaV3.2. Inhibition of both, T- and L-type calcium channels abolished the increase of intracellular calcium caused by angiotensin II. Our study demonstrates that T-type calcium channels are not required to maintain glomerulosa calcium oscillations and aldosterone production.