Epigenetic Regulation of RGS2 in Cystic Fibrosis

Abstract

Cystic fibrosis (CF) is a recessive autosomal disease that affects the respiratory, gastrointestinal and reproductive systems. At pulmonary level, the absence of CFTR function (cystic fibrosis transmembrane conductance regulator encoding an ion channel chlorine) leads to a decrease in mucociliary clearance, resulting in mucus accumulation. A new approach based on epigenetic regulation of gene expression has been investigated and we identified a list of hypermethylated genes in dF508 cell lines, the most frequently observed mutation in the CF population. Among the CF hypermethylated genes, RGS2 (Regulator of G protein signaling 2) gene demonstrated either transcript or protein downregulation. RGS2 is a key modulator of bronchial hyperresponsiveness, plays a critical role in fibrosis‐related diseases and inflammation.We hypothesized that variation in RGS2 protein expression could be the result of modulation of promoter methylation and has an impact on cytokine regulation. The first objective was to verify that methylation observed on RGS2 promoter in dF508 homozygous cell lines induces a modulation of protein expression. Then, to assess the consequences of this downregulation of RGS2, we performed an shRNA‐mediated RGS2 knockdown followed by DMNQ treatment in non‐CF cells and monitored the expression of inflammatory mediators.We confirmed that methylation of RGS2 promoter has an impact on RGS2 gene expression using azacythidine and oxidative stress treatments and that RGS2 is downregulated at the protein level in CF cells and in dF508 homozygous patients. We observed a relation between RGS2 downregulation by shRNA and the upregulation of 3 modulators of early inflammation: CHI3L1, S100A12 and TNFa.