Molecular investigation of primary aldosteronism: exploring genetic heterogeneity in understudied populations

Abstract

Objective: Genetic abnormalities in ion channels that regulate the depolarization of adrenal glomerular cell plasma membranes have been identified as a cause of primary aldosteronism (PA) due to aldosterone-producing adenoma (APA). This study aimed to evaluate somatic variants in the KCNJ5, CACNA1D, CLCN2, ATP1A1, ATP2B3, GNAQ, GNA11, and CTNNB1 genes, assess the genotype-phenotype correlation, and analyze the outcomes in patients with APA from a heterogenic ethnic population.

Subjects and methods: Clinical, biochemical, and molecular data were obtained from 32 patients.

Results: Pathogenic variants (PVs) were identified in 43.7% (14/32) of the patients. PVs occurred in 31.2% (10/32) of the KCNJ5 gene: p.Leu168Arg (15.6%), p.Gly151Arg (9.3%), p.Glu145Gln (3.2%), and p.Gly151_Tyr152del (3.2%). In the CLCN2 gene, two PVs (6.25%), p.Pro48Arg and p.Ala195Thr, were identified; the latter was found in association with p.Glu145Gln in the KCNJ5 gene within the same APA. Additionally, two PVs were found in ATPase genes: p.Leu104Arg in ATP1A1 (3.2%) and p.Leu425_Val426del in ATP2B3 (3.2%). No PVs were identified in the other examined genes. Patients with KCNJ5 PVs were predominantly female (90% vs. 45.5%; p = 0.01), had an earlier age of PA diagnosis (38 vs. 54 years; p = 0.04), and exhibited fewer electrocardiogram abnormalities (20% vs. 59%; p = 0.04). Patients with PVs across all studied genes also showed an earlier age at PA diagnosis (p = 0.02). The Primary Aldosteronism Surgical Outcome score revealed that 37.5% of patients met clinical/biochemical cure criteria, 12.5% showed partial improvement in both, while 50% achieved complete biochemical but not clinical remission. Patients carrying PVs had a higher rate of complete clinical and biochemical cure (66.7% vs. 33.3%; p = 0.05).

Conclusion: Identifying PVs in this study enhances our understanding of the genetic landscape in Brazilian patients with primary aldosteronism.

Keywords: APA; Primary aldosteronism; adrenalectomy; pathogenic variations in channel-encoding genes.

Figure 1

Electropherograms obtained by Sanger sequencing method from three patients with aldosterone-producing adenoma presenting the pathogenic variants (A) p.Leu168Arg, (B) p.Gly151Arg, and (C) p.Glu145Gln in the KCNJ5.

Figure 2

(A) Sanger sequencing chromatogram of one patient with aldosterone-producing adenoma showing the novel somatic heterozygous KCNJ5 variant, which consists of a 6 bp in-frame deletion (c.453_458delGTATGG) resulting in an in-frame deletion of two amino acids, glycine 151 and tyrosine 152, in the protein sequence (p.Gly151_Tyr152del), without altering the downstream reading frame (top), compared to the wild-type sequence (bottom). (B) Multiple sequence alignment demonstrating the evolutionary conservation of residues G151 and Y152 in the KCNJ5 protein across different species. (C) Predicted 3D structure of the KCNJ5 protein highlighting the location of the deleted residues G151 and Y152 (indicated by arrows), which correspond to the first glycine and the tyrosine of the highly conserved GYG motif within the K^⁺ channel selectivity filter.

Figure 3

Electropherograms obtained by Sanger sequencing method from a patient with aldosterone-producing adenoma presenting the pathogenic variant (A) p.P48R and the pathogenic variants (B) p.Ala195Thr in the CLCN2 gene, and (C) p.Glu145Gln in the KCNJ5 gene.

Figure 4

Electropherograms obtained by Sanger sequencing method of a normal control and (A) a patient with aldosterone-producing adenoma presenting the pathogenic p.L104R variant in the ATP1A1 gene, and of a normal control and (B) a patient with aldosterone-producing adenoma presenting the pathogenic p.Leu425_Val426del variant in the ATP2B3 gene.