Nitric oxide (NO) gas concentrations are higher in expired air in asthmatic
s, NO is synthesized by three isoforms of NO synthase (NOS) encoded by thre
e distinct genes, NOS1, NOS2, and NOS3. Genome-wide searches have identifie
d linkages to asthma on chromosomes 7, 12, and 17 where these three genes a
re localized. No association study, however, has been reported to date. To
test whether variants of NOS1, NOS2, and NOS3 relate to asthma, a genetic a
ssociation study was conducted in a British population (n 300). Intragenic
microsatellite variants of NOS1 were significantly associated with asthma [
odds ratio (OR) = 2.08, 95% CI: 1.20-3.57 (95% CI), P = 0.008 (Pc = 0.048)]
, but not with IgE levels, Neither NOS2 nor NOS3 variants showed any associ
ation with asthma nor IgE levels. These findings suggest that NOS1 variants
may be a significant contributor to asthma in a British population. (C) 20
00 Academic Press.