A team from Canada and the USA investigated a new powerful method for fine-structure localization of disease genes.
The technique, known as linkage disequilibrium (LD) mapping, had not previously been widely applied to common diseases.
The researchers designed a systematic approach for LD mapping, and applied it to the localization of IBD5, a gene that confers susceptibility to Crohn's disease.
| IBD5 resides within chromosome 5q31.
This is the second gene to be implicated in Crohn's disease. In March of this year, the first, Nod2, was identified.
In previous studies, the researchers identified a large region on chromosome 5 that was associated with Crohn's disease and contained the IBD5 gene.
Then, using dense genetic maps of microsatellite markers and single-nucleotide polymorphisms (SNPs) across the entire region, they found strong evidence of LD.
Subsequently, the authors discovered that the IBD5 gene resides within an area of 5q31, surrounded by a cytokine gene cluster.
John D. Rioux, of the Massachusetts Institute of Technology, Massachusetts, USA, concluded on behalf of his group, "These results have important implications for Crohn's disease in particular, and LD mapping in general."