X-chromosome variants are associated with aldosterone producing adenomas

Abstract

Aldosterone-producing adenomas (APAs) are a major cause of primary aldosteronism (PA) and are characterized by constitutively producing aldosterone, which leads to hypertension. Several mutations have been identified in ion channels or ion channel-associated genes that result in APAs. To date, no studies have used a genome-wide association study (GWAS) approach to search for predisposing loci for APAs. Thus, we investigated Scandinavian APA cases (n = 35) and Swedish controls (n = 60) in a GWAS and discovered a susceptibility locus on chromosome Xq13.3 (rs2224095, OR = 7.9, 95% CI = 2.8-22.4, P = 1 × 10^-7) in a 4-Mb region that was significantly associated with APA. Direct genotyping of sentinel SNP rs2224095 in a replication cohort of APAs (n = 83) and a control group (n = 740) revealed persistently strong significance (OR = 6.1, 95% CI = 3.5-10.6, p < 0.0005). We sequenced an adjacent gene, MAGEE1, of the sentinel SNP and identified a rare variant in one APA, p.Gly327Glu, which is complementary to other mutations in our primary cohort. Expression quantitative trait loci (eQTL) were investigated on the X-chromosome, and 24 trans-eQTL were identified. Some of the genes identified by trans-eQTL point towards a novel mechanistic explanation for the association of the SNPs with APAs. In conclusion, our study provides further insights into the genetic basis of APAs.

Figure 1

Manhattan plot. Genome-wide association results for aldosterone-producing adenomas (APAs). Manhattan plot of P values in –log₁₀ scale from the logistic regression with sex as a covariate on 727,307 SNPs (from 33 cases and 58 controls). The horizontal lines indicate the genome-wide significance threshold (red line = 1X10^–8, blue line = 1X10^–6). Green dots show the 100 most significant SNPs in the region of the susceptibility loci.

Figure 2

(A) Regional association plot. The plot shows the association results of SNPs of the GWAS samples and the recombination rates. The –log10 P values (y axis) of the SNPs are shown according to their X-chromosome positions (X axis). The lead SNP (rs2224095) is shown as a diamond. The intensity of each symbol reflects the extent of LD with rs2224095. Genetic recombination rates were estimated using HapMap samples from Utah residents of Western and Northern European ancestry (CEU) and are shown as a blue line. Physical positions are based on hg18. (B) A summary of mutations and genotype of sentinel SNP (rs2224095) identified in 24/35 of our cohort of APAs. The remaining APAs had no mutations in the known susceptibility genes.

Figure 3

Sequencing of MAGEE1 and eQTL analysis. (A) The germline sequence variant identified in MAGEE1 (left) in comparison to the normal sequences from a non-mutated sample (right). (B-G) Log2 expression of MAGEE1, TMEM47, KCNE5, CASK, ATP2B3, and REELIN after normalization of mRNA microarray data from patient tissue. *P < 0.05, **P < 0.005, ***P < 0.0005, 2-tailed student t-test.