The IL9R region contribution in asthma is supported by genetic associationin an isolated population

Interleukin 9 (IL9) is involved in mast cell maturation and the enhancement of IgE production by B cells. Furthermore, linkage data in human and mice have suggested that IL9 may contribute to asthma. Since our genetic analysi s of the 5q cytokine cluster did not support a genetic role for the IL9 gen e, we became interested in the IL9 receptor gene (IL9R) in the pseudoautoso mal region. We genotyped markers sDF2 and sDF1 close to the IL9R gene among 289 affected and 368 family-based controls. The results were studied by us ing linkage, transmission disequilibrium, association and homozygosity anal yses. Linkage analyses remained negative, presumably because of our low pow er for linkage study. However, all the other analyses yielded evidence that the IL9R gene region may have a role in the development of asthma. The sDF 2*10 allele was more frequently transmitted than untransmitted to asthmatic offspring (34 vs 16, P chi(2) less than or equal to 0.01), and it was foun d homozygotic among asthma patients more often than expected (P-simul2 = 0. 009), Also, a specific X chromosomal haplotype, sDF2*10-sDF1*6 associated w ith asthma (40 vs 7, P chi(2) < 0.005, P-simul1 = 0.04).