Genetic variation in the FAS gene and associations with acute lung injury

Abstract

Rationale: Fas (CD95) modulates apoptosis and inflammation and is believed to play an important role in lung injury.

Objectives: To determine if common genetic variation in FAS is associated with acute lung injury (ALI) susceptibility, risk of death, and FAS gene expression.

Methods: We genotyped 14 single nucleotide polymorphisms (tagSNPS) in FAS in samples from healthy white volunteers (control subjects, n = 294) and patients with ALI (cases, n = 324) from the ARDSnet Fluid and Catheter Treatment Trial (FACTT). FAS genotypes associated with ALI in the discovery study were confirmed in a nested case-control validation study of critically ill patients at risk for ALI (n = 657). We also tested for associations between selected tagSNPS and FAS mRNA levels in whole blood from healthy control subjects exposed to media alone or LPS ex vivo.

Measurements and main results: We identified associations between four tagSNPs in FAS (FAS(-11341A>T) [rs17447140], FAS(9325G>A) [rs2147420], FAS(21541C>T) [rs2234978], and FAS(24484A>T) [rs1051070]) and ALI case status. Haplotype-based analyses suggested that three of the tagSNPs (FAS(9325G>A), FAS(21541C>T), and FAS(24484A>T)) function as a unit. The association with this haplotype and ALI was validated in a nested case-control study of at-risk subjects (P = 0.05). This haplotype was also associated with increased FAS mRNA levels in response to LPS stimulation. There was no association between FAS polymorphisms and risk of death among ALI cases.

Conclusions: Common genetic variants in FAS are associated with ALI susceptibility. This is the first genetic evidence supporting a role for FAS in ALI.

Figure 1.

FAS gene expression in blood leukocytes by FAS haplotype 4 copy number. Bars represent the mean fold change (± SD) in FAS mRNA level measured using duplicate reverse transcription polymerase chain reaction measurements of ΔCt (cycle threshold) values normalized to a control mRNA (glyceraldehyde-3-phosphate dehydrogenase) in whole blood incubated with LPS relative to whole blood incubated with media. The P value reflects an unadjusted additive linear regression model.