EDNRA variants associate with smooth muscle mRNA levels, cell proliferation rates, and cystic fibrosis pulmonary disease severity

Abstract

Airway inflammation and pulmonary disease are heterogeneous phenotypes in cystic fibrosis (CF) patients, even among patients with the same cystic fibrosis transmembrane conductance regulator (CFTR) genotype. Endothelin, a proinflammatory peptide and smooth muscle agonist, is increased in CF airways, potentially contributing to the pulmonary phenotype. Four cohorts of CF patients were screened for variants in endothelin pathway genes to determine whether any of these variants associated with pulmonary function. An initial cohort of 808 CF patients homozygous for the common CF mutation, DeltaF508, showed significant association for polymorphisms in the endothelin receptor A gene, EDNRA (P = 0.04), but not in the related endothelin genes (EDN1, EDN2, EDN3, or EDNRB) or NOS1, NOS2A, or NOS3. Variants within EDNRA were examined in three additional cohorts of CF patients, 238 patients from Seattle, WA, 303 from Ireland and the U.K., and 228 from Cleveland, OH, for a total of 1,577 CF patients. The three additional groups each demonstrated a significant association between EDNRA 3'-untranslated region (UTR) variant rs5335 and pulmonary function (P = 0.002). At the molecular level, single nucleotide primer extension assays suggest that the effect of the variants is quantitative. EDNRA mRNA levels from cultured primary tracheal smooth muscle cells are greater for the allele that appears to be deleterious to lung function than for the protective allele, suggesting a mechanism by which increased receptor function is harmful to the CF airway. Finally, cell proliferation studies using human airway smooth muscle cells demonstrated that cells homozygous for the deleterious allele proliferate at a faster rate than those homozygous for the protective allele.

Disrupted posttranscriptional regulation of the cystic fibrosis transmembrane conductance regulator (CFTR) by a 5′UTR mutation is associated with a cftr-related disease

“…One such CF-disease modifier gene mutation was recently identified in the endothelin receptor A gene (EDNRA). A 3´UTR sequence variation, that increased pulmonary EDNRA expression and airway inflammation, was significantly associated with decreased pulmonary function in ΔF508 homozygous CF patients [Darrah, et al, 2009]. Sequence variations in other genes with roles in inflammation/immune function, such as TGFB1 [Drumm, et al, 2005], IL8 [Hillian, et al, 2008] and IFRD1 [Gu, et al, 2009], have also been identified as CF modifier genes.…”

The Influence of Genetics on Cystic Fibrosis Phenotypes

“…Genetic variation in the endothelial receptor type A (EDNRA) has been associated with CF lung disease severity (Table 2), and replicated in three additional populations of CF patients (1478 total) (Darrah et al 2010). The variant EDNRA (rs5335) is in the 3 0 UTR, and the risk allele for worse lung disease is associated with increased expression of EDNRA in cultured human tracheal smooth muscle cells, as well as increased proliferation of smooth muscle cells that are homozygous for the risk variant.…”

Genetic Modifiers and Oligogenic Inheritance

“…Despite the majority of patients carrying identical genotypes (homozygosity for CFTR F508del), striking differences in lung function have been described (Kerem et al 1990). Candidate modifier studies reported that functional variants in MBL2 and alleles in the promoter and first exon of TGFb1 were associated with lower lung function measures (Garred et al 1999;Drumm et al 2005;Darrah et al 2010). More recently, genome-wide association studies revealed additional modifiers of lung function; IL-8, IFRD1 and ENDRA associated with neutrophil function (Vanscoy et al 2007;Hillian et al 2008).…”