AGER -429T/C is associated with an increased lung disease severity in cystic fibrosis

Abstract

The clinical course of cystic fibrosis (CF) varies between patients bearing identical CFTR mutations, suggesting the involvement of modifier genes. We assessed the association of lung disease severity with the variant AGER -429 T/C, coding for RAGE, a pro-inflammatory protein, in CF patients from the French CF Gene Modifier Study. We analyzed the lung function of 967 CF patients p.Phe508del homozygous. FEV(1) was analyzed as CF-specific percentile adjusted on age, height and mortality. AGER -429T/C polymorphism was genotyped and its function was evaluated in vitro by measurement of the luciferase activity. AGER -429 minor allele (C) was associated with poorer lung function (p = 0.03). In vitro, the promoter activity was higher in cells transfected with AGER -429C compared to cells transfected with the AGER -429T allele (p = 0.016 in BEAS-2B cells). AGER seems to be a modifier gene of lung disease severity in CF, and could be an interesting biomarker of CF airway inflammation. The functional promoter AGER -429C variant is associated with an increased RAGE expression that can lead to an increased lung inflammation and a more severe lung disease.

Figure 1. FEV₁ survival adjusted CF specific percentiles (KNoRMA) distribution in CF subjects according to AGER

-429 T/C genotype. Distribution of the lung function according to the FEV₁ adjusted on the age, the height and the mortality; expressed in KNoRMA in AGER -429 CC and CT carriers (light-grey bars, n = 258) and AGER -429 TT carriers (dark-grey bars, n = 709).

Figure 2. In vitro influence of AGER

-429T/C polymorphism on the promoter activity. Constructs containing either AGER-429C or AGER-429T and a luciferase reporter gene were transfected into BEAS-2B (A) and A549 (B) cells. Luciferase activity assays were performed in triplicate in six independent experiments. Relative luciferase activity is represented as a ratio against the luciferase activity in cells transfected with the AGER-429T plasmid. Luciferase activity, reflecting activity of the AGER gene promoter, was significantly higher in cells containing AGER-429C plasmid compared to the cells containing AGER-429T plasmid (p = 0.016 and 0.031 respectively in BEAS-2B (A) and A549 (B) cells).