CLC-2 single nucleotide polymorphisms (SNPs) as potential modifiers of cystic fibrosis disease severity

Carol J Blaisdell,Timothy D Howard,O Colin Stine,Augustus Stern,Eugene R Bleecker,Penelope Bamford

doi:10.1186/1471-2350-5-26

Abstract

BackgroundCystic fibrosis (CF) lung disease manifest by impaired chloride secretion leads to eventual respiratory failure. Candidate genes that may modify CF lung disease severity include alternative chloride channels. The objectives of this study are to identify single nucleotide polymorphisms (SNPs) in the airway epithelial chloride channel, CLC-2, and correlate these polymorphisms with CF lung disease.MethodsThe CLC-2 promoter, intron 1 and exon 20 were examined for SNPs in adult CF dF508/dF508 homozygotes with mild and severe lung disease (forced expiratory volume at one second (FEV1) > 70% and < 40%).ResultsPCR amplification of genomic CLC-2 and sequence analysis revealed 1 polymorphism in the hClC -2 promoter, 4 in intron 1, and none in exon 20. Fisher's analysis within this data set, did not demonstrate a significant relationship between the severity of lung disease and SNPs in the CLC-2 gene.ConclusionsCLC-2 is not a key modifier gene of CF lung phenotype. Further studies evaluating other phenotypes associated with CF may be useful in the future to assess the ability of CLC-2 to modify CF disease severity.

Highlights

Cystic fibrosis (CF) lung disease manifest by impaired chloride secretion leads to eventual respiratory failure
Expression of CLC-2 protein in CF nasal cells CLC-2 protein is nearly undetectable in postnatal rat lung [2], we hypothesized that postnatal expression of CLC-2 in CF individuals might confer a protective advantage for the respiratory epithelium of CF individuals
The expression of ClC-2 protein was diminished in transformed bronchial epithelial IB3-1 cells [11], which were derived from primary nasal epithelial cells of a subject with delF508/ W1282X

Summary

Introduction

Cystic fibrosis (CF) lung disease manifest by impaired chloride secretion leads to eventual respiratory failure. Candidate genes that may modify CF lung disease severity include alternative chloride channels. The objectives of this study are to identify single nucleotide polymorphisms (SNPs) in the airway epithelial chloride channel, CLC-2, and correlate these polymorphisms with CF lung disease. Because CF is a disease of chloride transport in respiratory epithelia, alternative chloride channels present in the airway may be able to partially compensate for the CF defect. CLC-2 is one candidate alternative chloride channel in respiratory epithelia. A splice variant of CLC-2 skipping exon 20 occurs in rat lung, suggesting that alternative splicing may have functional significance in this tissue [6]. Because investigation of human CLC-2 genomic structure would be important for studies of gene regulation, we sought to identify single nucleotide polymorphisms in potential regulatory domains of human CLC-2. Genomic DNA was isolated from CF adults with severe and mild obstructive lung disease in order to determine if SNPs segregate with CF lung phenotype

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