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. 2021 Apr 27;118(17):e2014876118.
doi: 10.1073/pnas.2014876118.

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

Affiliations

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

Eric Seidel et al. Proc Natl Acad Sci U S A. .

Abstract

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.

Keywords: CaV3.2; adrenal gland; calcium imaging.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.
Fig. 1.
Generation of Cacna1hM1560V/+ and Cacna1h−/− mouse models. (A) Alignment of Mus musculus and Homo sapiens genomic and amino acid sequences surrounding human Met1549 (box) mutated in FH-IV. Identical nucleotides are shown in yellow. The protein sequence is completely conserved. (B) Representation of the mouse Cacna1h locus targeted on exon 25. Sequences of protospacer used to target Cas9 nuclease to exon 25 and repair template used to introduce Cacna1hM1560V/+ via homology-directed repair are listed below target sequence. The guide binding site is underlined, and intended mutations (including three silent mutations) are shown in red letters. (C, Upper) Sanger sequences of genomic DNA (gDNA, from ear biopsies) from a WT control, a Cacna1hM1560V/+ mouse, and a Cacna1h−/− mouse (knockout). (Lower) Sanger sequences of adrenal complementary DNA (cDNA) from the identical animals shown above, demonstrating adrenal expression of the mutant alleles. Bases adjacent to the 8-bp deletion in Cacna1h−/− are underlined.
Fig. 2.
Fig. 2.
Adrenal glands of Cacna1hM1560V/+ and Cacna1h−/− mice show unchanged morphology. (A) Adrenal weight (normalized to body weight) is unchanged between WT, Cacna1hM1560V/+, and Cacna1h−/− mice (WT: n = 21; M1560V: n = 29; P = 0.69; knockout [KO]: n = 17; P = 0.17; Kruskal–Wallis test with Dunn’s multiple comparisons test [MCP]). (B) Adrenal expression of Cacna1h is not changed in Cacna1hM1560V/+ compared to WT (M1560V: n = 41; WT: n = 40; P = 0.95; unpaired two-tailed t test of log-transformed fold-change). (C) Cacna1h expression is unchanged between WT and Cacna1hM1560V/+ in both sexes (male WT: n = 24; male M1560V: n = 17; P > 0.99; female WT: n = 16; female M1560V: n = 24; P > 0.99; Kruskal–Wallis test with Dunn’s MCP of log-transformed fold-change). All data are shown as box plots (box, interquartile range; whiskers, 1.5 times the interquartile range; line, median; dots, outliers); n values represent animals. ns, P > 0.05. (D and E) H&E staining of adrenal sections show unaltered morphology of Cacna1hM1560V/+ and Cacna1h−/− mice compared to WT (three mice each, representative images, pictures of male mice at 15 to 16 wk of age are shown). C, capsule; F, fasciculata; G, glomerulosa; M, medulla. (Scale bars, 500 μm in D and 100 μm in E.).
Fig. 3.
Fig. 3.
Adrenal sections of Cacna1hM1560V/+ and Cacna1h−/− mice show normal Cyp11b2 staining. (A and B) In situ hybridization with corresponding negative controls (see Materials and Methods). One of four to five animals of each genotype is shown. C: capsule; F: fasciculata; G, glomerulosa; M: medulla. (Scale bars, 500 μm in A and 100 μm in B.)
Fig. 4.
Fig. 4.
Cacna1hM1560V/+ mice have elevated adrenal Cyp11b2 expression. (A) Adrenal Cyp11b2 expression is increased in Cacna1hM1560V/+ mice during NSD (WT: n = 43; Cacna1hM1560V/+: n = 43; P = 0.004 vs. WT; KO: n = 11; P = 0.996 vs. WT; one-way ANOVA with Dunnett’s MCP). (B) Cyp11b2 expression is only increased in male Cacna1hM1560V/+ mice (male WT: n = 24; male Cacna1hM1560V/+: n = 18; P = 0.004; female WT: n = 19; female Cacna1hM1560V/+: n = 25; P = 0.294; one-way ANOVA and Sidak’s MCP). (C) Adrenal Cyp11b2 expression remains elevated in Cacna1hM1560V/+ mice during HSD (WT: n = 12; Cacna1hM1560V/+: n = 9; P = 0.008; unpaired two-tailed t test). (D) Plasma aldosterone is not significantly changed in Cacna1hM1560V/+ mice or Cacna1h−/− mice during NSD (WT: n = 42; Cacna1hM1560V/+: n = 41; P = 0.090; KO: n = 13; P = 0.895; Kruskal–Wallis test and Dunn’s MCP). (E) Plasma aldosterone is significantly increased in male, but not in female Cacna1hM1560V/+ mice (male WT: n = 23; male Cacna1hM1560V/+: n = 17; P = 0.016; female WT: n = 19; female Cacna1hM1560V/+: n = 24; P > 0.999; Kruskal–Wallis test and Dunn’s MCP). (F) There is no significant difference in aldosterone between Cacna1hM1560V/+ and WT during HSD (WT: n = 8; Cacna1hM1560V/+: n = 9; P = 0.393; unpaired two-tailed t test). Box plots (box, interquartile range; whiskers, 1.5 times the interquartile range; line, median; dots, outliers) are shown in the figure; n values are animals. ns, P > 0.05; *P < 0.05; **P < 0.01.
Fig. 5.
Fig. 5.
Cacna1h−/− mice show elevated Ren1 expression; Cacna1hM1560V/+ mice have elevated ARRs. (A–C) Kidney expression of Ren1 is increased in KO mice but not significantly changed in Cacna1hM1560V/+ mice during NSD (WT: n = 43; Cacna1hM1560V/+: n = 43; P = 0.095 vs. WT; KO: n = 11; P = 0.026 vs. WT; one-way ANOVA and Dunnett’s MCP; male WT: n = 24; male Cacna1hM1560V/+: n = 18; P = 0.688; female WT: n = 19; female Cacna1hM1560V/+: n = 25; P = 0.078; one-way ANOVA and Sidak’s MCP) or HSD (WT: n = 12; Cacna1hM1560V/+: n = 9; P = 0.425; Mann–Whitney test). (D–F) PRC is not significantly changed in Cacna1hM1560V/+ and Cacna1h−/− mice during NSD (WT: n = 39; Cacna1hM1560V/+: n = 40; P = 0.115; KO: n = 13; P > 0.999; Kruskal–Wallis test and Dunn’s MCP). In subgroup analysis, PRC is decreased in female Cacna1hM1560V/+ mice only (male WT: n = 22; male Cacna1hM1560V/+: n = 17; P = 0.821; female WT: n = 17; female Cacna1hM1560V/+: n = 23; P = 0.046; Kruskal–Wallis test and Dunn’s MCP). PRC is reduced in Cacna1hM1560V/+ mice during HSD (WT: n = 10; Cacna1hM1560V/+: n = 8; P = 0.008; unpaired two-tailed t test). (GI) The ratio of Cyp11b2 and Ren1 expression was calculated using fold-change. (G) Expression ratio is significantly increased in Cacna1hM1560V/+ compared to WT mice and not significantly changed in Cacna1h−/− compared to WT (WT: n = 43; M1560V: n = 43; P = 0.005; Cacna1h−/−: n = 11, P = 0.176; Kruskal–Wallis test, Dunn’s MCP). (H) The ratio is significantly increased in male Cacna1hM1560V/+ mice compared to WT (WT: n = 24; Cacna1hM1560V/+: n = 18; P = 0.010; Kruskal–Wallis test and Dunn’s MCP), but not in female mice (WT: n = 19; Cacna1hM1560V/+: n = 25; P = 0.074; Kruskal–Wallis test and Dunn’s MCP). (I) After HSD, the ratio is significantly increased in Cacna1hM1560V/+ mice compared to WT (WT: n = 12; Cacna1hM1560V/+: n = 9; P = 0.009; Mann–Whitney test). (J) ARRs (calculated using plasma aldosterone levels and PRC) are increased in Cacna1hM1560V/+ mice compared to WT under NSD (WT: n = 39; M1560V: n = 39; P = 0.033; Kruskal–Wallis test with Dunn’s MCP). In Cacna1h−/− mice, ARR is not significantly changed compared to WT (WT: n = 39; KO: n = 13; P = 0.540; Kruskal–Wallis test, Dunn’s MCP). (K) ARR levels are not significantly changed in subgroup analyses (male WT: n = 22; M1560V: n = 17; P = 0.070; female mice WT: n = 17; M1560V: n = 22; P = 0.353; Kruskal–Wallis test, Dunn’s MCP). (L) After HSD, ARR remains elevated in Cacna1hM1560V/+ mice (WT: n = 8; Cacna1hM1560V/+: n = 8; P = 0.015; unpaired two-tailed t test). All data are shown in box plots (box, interquartile range; whiskers, 1.5 times the interquartile range; line, median; dots, outliers); n values are animals. ns, P > 0.05; *P < 0.05; **P < 0.01.
Fig. 6.
Fig. 6.
Blood pressure is higher in Cacna1hM1560V/+ mice. Blood pressure (BP) and heart rate (HR) of animals were assessed during NSD and HSD through common carotid artery telemetry. Graphs show loess regressions of BP or HR of WT (black, n = 8 animals on NSD and n = 7 on HSD) and Cacna1hM1560V/+ (red, n = 7 animals for both conditions) mice. Gray intervals denote 95% confidence intervals for loess regressions. Horizontal axis shows time, with black lines noting nights (6:00 PM to 6:00 AM). Horizontal lines show means for the entire NSD and HSD period, respectively, for WT (black) and Cacna1hM1560V/+ (red dashed) animals. Nested-model likelihood ratio comparisons revealed significantly higher SBP (P = 0.001) and MAP (P = 0.002) during NSD; DBP (P = 0.139) and HR (P = 0.135) were not significantly changed. n = 9 WT, n = 8 Cacna1hM1560V/+ animals. Mean ± SD values: NSD-SBP, 115.9 ± 13.7 mmHg (WT), 124.2 ± 14.7 mmHg (Cacna1hM1560V/+); NSD-DBP, 85.0 ± 12.1 mmHg (WT) and 87.7 ± 11.9 mmHg (Cacna1hM1560V/+); NSD-MAP, 99.9 ± 12.5 mmHg (WT) and 105.2 ± 13.1 mmHg (Cacna1hM1560V/+); NSD-HR, 462.2 ± 100.4 beats per minute (BPM, WT) and 482.1 ± 111.1 BPM (Cacna1hM1560V/+). Similarly, during HSD, SBP (P = 0.0008) and MAP (P = 0.021) were increased in Cacna1hM1560V/+ mice, while DBP (P = 0.65) and HR (P = 0.92) were unchanged. One WT mouse failed HSD recording. Mean ± SD: HSD-SBP, 122.2 ± 15.7 mmHg (WT) and 128.8 ± 18.1 mmHg (Cacna1hM1560V/+); HSD-DBP, 88.2 ± 13.4 mmHg (WT) and 89.2 ± 13.7 mmHg (Cacna1hM1560V/+); HSD-MAP, 104.5 ± 14.2 mmHg (WT) and 108.0 ± 15.4 mmHg (Cacna1hM1560V/+); HSD-HR, 450.9 ± 92.3 BPM (WT) and 451.8 ± 100.9 BPM (Cacna1hM1560V/+).
Fig. 7.
Fig. 7.
Cacna1hM1560V/+ mice have higher intracellular calcium concentrations than controls. (A and B) Representative average projections over 20 s from a WT or M1560V adrenal slice stained with Fura-2 AM (Upper). Intensity corresponds to the intracellular calcium concentration. (Scale bars, 10 µm.) The concentration changes of one representative cell each (both at 5 mM K+ and 1 nM Ang II) are shown below. The trace is color-coded to represent baseline concentrations (purple), spiking activity (black) and peak concentrations (center of red circles). (C) Baseline as well as peak intracellular calcium concentrations are higher in Cacna1hM1560V/+ compared to WT mice under all tested conditions. (D) The mean overall intracellular calcium concentrations (including baseline, spiking and peak segments) are also elevated in Cacna1hM1560V/+ mice. (E) Mean frequencies of calcium spikes during the corresponding perfusions are lower in Cacna1hM1560V/+ than in WT mice at supraphysiological concentrations of Ang II only. P values (likelihood ratio test of linear mixed models) are indicated as follows: ns, P ≥ 0.05; *P < 0.05; **P < 0.01; ***P < 0.001. See SI Appendix, Table S1 for statistical information. Data in C and D are shown as bars (mean) ± SD. Data in E are shown in box plots (box, interquartile range; whiskers, 1.5 times the interquartile range; line, median; dots, outliers).

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