There are several chromosomal regions where asthma-associated genes are known to be located. These include a region on the long arm of chromosome 3 that is linked with other immune system related diseases such as Crohn's or systemic lupus erythematosus.
In research published in the January issue of European Respiratory Journal, Koichiro Asano and colleagues from Keio University School of Medicine, Tokyo, examined the DNA sequence of a gene in this region of chromosome 3 that encodes a chemokine receptor CCR3. They have identified a mutation in the CCR3 gene that is more common in patients with asthma (Eur Respir J. 2001, 17: in press). But this mutation changes only the DNA sequence of CCR3 and not the amino-acid sequence of its product, so the authors speculate there is likely to be another mutation that causes asthma in the neighbourhood of CCR3.