Association of an intragenic microsatellite marker in the CC16 gene with asthma in the Indian population.

The gene for Clara cell secretory protein (CC16) is an ideal candidate for investigating genetic predisposition to asthma because of its role in the airway as an anti-inflammatory molecule, differences in its levels between asthmatics and healthy controls, and its genetic location (11q13). We investigated the association of an SNP (A38G) and an intragenic repeat polymorphism in the CC16 gene with asthma and its associated traits, such as total serum IgE levels, in a case control as well as in a family based study design. A significant association was observed for the microsatellite repeat at the level of alleles and genotypes with asthma (P<0.05) in both the study designs. However, no association was observed for the A38G SNP with asthma. When haplotypes were constructed for these two loci and compared, the haplotype A_18 was found at higher frequency in patients (OR=1.59, 95%CI=1.08, 2.33, P=0.016). Also, in the family based design, a biased transmission was observed for haplotypes from parents to affected offspring (P=0.003). Individually, haplotype A_18 showed preferential transmission (82.6%) to affected offspring (P=0.001), thereby confirming the case-control results. In summary, this is the first study identifying the CC16 gene to be associated with asthma in the Indian population.