Haploinsufficiency of ARHGAP42 is associated with hypertension

Abstract

Family studies have established that the heritability of blood pressure is significant and genome-wide association studies (GWAS) have identified numerous susceptibility loci, including one within the non-coding part of Rho GTPase-activating protein 42 gene (ARHGAP42) on chromosome 11q22.1. Arhgap42-deficient mice have significantly elevated blood pressure, but the phenotypic effects of human variants in the coding part of the gene are unknown. In a Danish cohort of carriers with apparently balanced chromosomal rearrangements, we identified a family where a reciprocal translocation t(11;18)(q22.1;q12.2) segregated with hypertension and obesity. Clinical re-examination revealed that four carriers (age 50-77 years) have had hypertension for several years along with an increased body mass index (34-43 kg/m²). A younger carrier (age 23 years) had normal blood pressure and body mass index. Mapping of the chromosomal breakpoints with mate-pair and Sanger sequencing revealed truncation of ARHGAP42. A decreased expression level of ARHGAP42 mRNA in the blood was found in the translocation carriers relative to controls and allele-specific expression analysis showed monoallelic expression in the translocation carriers, confirming that the truncated allele of ARHGAP42 was not expressed. These findings support that haploinsufficiency of ARHGAP42 leads to an age-dependent hypertension. The other breakpoint truncated a regulatory domain of the CUGBP Elav-like family member 4 (CELF4) gene on chromosome 18q12.2 that harbours several GWAS signals for obesity. We thereby provide additional support for an obesity locus in the CELF4 domain.

Fig. 1

a Pedigree of the family with the proband (III.5, indicated with an arrow), her mother (II.2), two brothers (III.2 and III.4), niece (IV.4) and nephew (IV.3) carrying a t(11;18) reciprocal translocation. Individuals with normal karyotypes are indicated in grey, whereas individuals not analysed are indicated in white. Phenotypes are as annotated with hypertension indicated by a white dot and body mass index (BMI) written below. Underneath each translocation carrier, except individuals IV.3 and IV.4, who were unavailable for investigation, the SNP haplotypes from Sanger sequencing of genomic DNA are shown. b Partial karyogram of the t(11;18)(q22.1;q12.2) translocation, showing the normal and derivative (der) chromosomes 11 and 18. The approximate breakpoint positions are indicated by arrows

Fig. 2

a The chromosome 11 breakpoint truncates ARHGAP42 between exons 4 and 5 as illustrated in the GRCh38/hg38 UCSC Genome Browser [20] view of the 11q22.1 breakpoint and indicated with a black arrow. The positions of the SNPs known to be associated with hypertension and discussed in the main text are illustrated below the gene. The position of the qPCR primers are indicated with arrows: the black arrows show the position of the ARHGAP42E1 qPCR primers and the grey arrows show the position of the ARHGAP42E21 qPCR primers. b, c ARHGAP42 mRNA expression in blood from translocation carriers (grey) and unrelated controls (white) using the two different primer sets: b proximal primer pair (ARHGAP42E1), p-value = 0.0828 and c distal primer pair (ARHGAP42E21), p-value = 0.0219. For the experiments, four translocation carriers (II.2, III.2, III.4, and III.5 in Fig. 1A) and six unrelated controls were investigated, and values represent the mean rescaled normalized relative quantities ± SD. Results are depicted as fold change relative to the minimum ARHAGP42 expression level

Fig. 3

The chromosome 18 breakpoint (black arrow) truncates the putative regulatory domain of the CUGBP Elav-Like Family Member 4 (CELF4) gene. The HiC-heatmap of neural progenitor cells (NPC) and the Virtual 4C-profile with CELF4 as anchor point [25] show that CELF4 has cis-interactions within a > 5 megabase (Mb) region on 18q12.2 (tented region), within topological associating domain (TAD) boundaries in embryonic (hESC) and IMR90 fibroblasts. Four obesity-associated genome-wide association study (GWAS), signals are located within the CELF4 -domain, including three single-nucleotide polymorphisms (SNPs; rs4327120:T > C, rs9304204:G > A, rs7226835:C > A) surrounding the translocation breakpoint. Moreover, Capture-HiC from GM12878 cells show the interactions of CELF4, where both the translocation breakpoints and the cluster of three obesity-associated SNPs are located within the CELF4 interaction range