CLCA1 gene polymorphisms in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), including chronic bronchitis and emphysema, is a major cause of morbidity and mortality in many countries. The most important risk factor for COPD is cigarette smoking, and nearly 90% of COPD patients are smokers.1 However, only 15% of cigarette smokers develop clinically significant COPD.2 COPD is known to aggregate in families,3 and twin studies have shown that obstructive airway disease correlates directly with genetic similarities.4 In contrast, there are differences in the prevalence of COPD between different ethnic groups.5 All these results support the notion that genetic factors are involved in the pathogenesis of COPD. Recent segregation analysis has demonstrated that the genetic components determining forced expiratory volume in 1 second (FEV1) consist of multiple genes, each of which has a small influence, rather than a single Mendelian gene.6 An intensive search has been ongoing to find the genetic factors responsible for COPD development. Until now, more than 20 polymorphisms of candidate genes have been reported to have an association with COPD. They include genes for proteinases,7 anti-proteinases,8–10 anti-oxidants,11 xenobiotic metabolising enzymes,12,13 and inflammatory mediators.14,15 For most of these loci, however, there have been contradictory results.16 Although genetic heterogeneity among different ethnic groups under different environmental conditions could explain this inconsistency, it is still necessary to confirm the associations of the polymorphisms in different populations. Recently the human CLCA1 gene and its murine counterpart, m CLCA3 , have been isolated.17,18 To date, the human CLCA family consists of four homologous genes ( hCLCA1 , hCLCA2 , hCLCA3 , and hCLCA4 ), all clustered on the short arm of chromosome 1 (1p 22–31).19 The region around 120 cM on chromosome 1 has been identified to show moderate linkage to …