Loss-of-Function ABCC8 Mutations in Pulmonary Arterial Hypertension

Abstract

Background: In pulmonary arterial hypertension (PAH), pathological changes in pulmonary arterioles progressively raise pulmonary artery pressure and increase pulmonary vascular resistance, leading to right heart failure and high mortality rates. Recently, the first potassium channelopathy in PAH, due to mutations in KCNK3, was identified as a genetic cause and pharmacological target. Methods: Exome sequencing was performed to identify novel genes in a cohort of 99 pediatric and 134 adult onset group I pulmonary arterial hypertension patients. Novel rare variants in the gene identified were independently identified in a cohort of 680 adult onset patients. Variants were expressed in COS cells and function assessed by patch-clamp and rubidium flux analysis. Results: We identified a de novo novel heterozygous predicted deleterious missense variant c.G2873A (p.R958H) in ABCC8 (ATP-binding cassette, subfamily C, member 8) in a child with idiopathic PAH. We then evaluated all individuals in the original and a second cohort for rare or novel variants in ABCC8 and identified 11 additional heterozygous predicted damaging ABCC8 variants. ABCC8 encodes sulfonylurea receptor 1 (SUR1), a regulatory subunit of the ATP-sensitive potassium channel (KATP). We observed loss of KATP function for all ABCC8 variants evaluated, and pharmacological rescue of all channel currents in vitro by the SUR1 activator, diazoxide. Conclusions: Novel and rare missense variants in ABCC8 are associated with pulmonary arterial hypertension. Identified ABCC8 mutations decreased KATP channel function, which was pharmacologically recovered.

Molecular genetic framework underlying pulmonary arterial hypertension

“…Screening of ABCC8 mutations in an extended cohort identified likely deleterious, heterozygous, missense mutations distributed across the length of the gene in paediatric patients with IPAH, familial PAH or congenital heart diseaseassociated PAH. Expression of the identified ABCC8 variants in a fibroblast-like cell line decreased the function of the ATP-sensitive potassium channel, further indicating that a subset of PAH might be mechanistically described as a potassium channelopathy 97 . Of interest, treatment of these cells with the pharmacological agent diazoxide, a selective ABCC8 activator, resulted in the recovery of channel function to normal levels 97 .…”

“…A follow-up report in a cohort of patients with childhood-onset (n = 99) and adult-onset (n = 134) PAH who were negative for BMPR2 or ACVRL1 mutations, identified a de novo missense variant in ABCC8 (encoding the ATP binding cassette subfamily C member 8 (ABCC8); also known as sulfonylurea receptor 1) in a patient with childhood-onset IPAH 97 .…”

“…The mutation (c.2873G>A; p.R958H) was predicted to be deleterious, occurring at a highly conserved site within a critical domain of the encoded protein, which is a regulatory subunit of the ATP-sensitive potassium channel 97 . Screening of ABCC8 mutations in an extended cohort identified likely deleterious, heterozygous, missense mutations distributed across the length of the gene in paediatric patients with IPAH, familial PAH or congenital heart diseaseassociated PAH.…”

Novel risk genes and mechanisms implicated by exome sequencing of 2,572 individuals with pulmonary arterial hypertension

“…The data and resources are made available to the research community for hypothesis-driven projects via an application process (www.pahbiobank.org). A subset including 183 affected participants were included in previous publications from our group 14,20,22 . MLPA was performed with 100 ng of genomic DNA according to manufacturer's instructions using the P093 Salsa MLPA probe sets (MRC-Holland, Amsterdam, The Netherlands).…”

“…Germline mutations in other genes are individually rare causes of PAH. These include other genes in the TGF-β/BMP signaling pathway 15 , hereditary hemorrhagic telangiectasia (HHT) genes activin A receptor type II-like 1 (ACVRL1) and endoglin (ENG) 7 , eukaryotic initiation translation factor (EIF2AK4) associated with pulmonary veno-occlusive disease (PVOD)/pulmonary capillary hemangiomatosis (PCH) 16,17 , caveolin-1 (CAV1) 18 , and channel genes including potassium two pore domain channel (KCNK3) 19 , ATP-binding cassette subfamily member 8 (ABCC8) 20 and voltage-dependent potassium channel 1.5 (KCNA5) 21 .…”