Crohn's disease (CD) and ulcerative colitis (UC) are the major forms of idiopathic inflammatory bowel disease (IBD). CD and UC are heritable with complex genetics (1). Genome scans and other genetic linkage studies in IBD have identified several linkages that satisfy Lander and Kruglyak criteria for confirmed linkage (2), including confirmed linkage between CD and the pericentromeric region of chromosome 16 (the IBD1 locus) (3–12), confirmed linkage between IBD (especially UC) and a locus on chromosome 12q (the IBD2 locus) (8,10,13–17), confirmed linkage between IBD (especially CD) and a locus on chromosome 6p (the IBD3 locus) (10,18–22), confirmed linkage between CD and a locus on chromosome 14q (the IBD4 locus) (16,23–25), and confirmed linkage between IBD and a locus on chromosome 3p (13,21,26–28). Other linkages satisfy Lander and Kruglyak criteria for significant linkage but have not been replicated in independent studies with sufficient evidence to satisfy criteria for confirmed linkage (2). These include significant linkage between CD and a locus on chromosome 5q in families with at least one CD-affected with age at diagnosis ≤16 (the IBD5 locus) (21), significant linkage between IBD and a locus on chromosome 19p (the IBD6 locus) (21), and significant linkage between IBD and a locus on chromosome 1p (the IBD7 locus) (6,29,30). Three relatively uncommon polymorphisms in the CARD15/NOD2 gene, located within the IBD1 linkage interval, have been independently associated with CD (particularly ileal CD) but not UC (31–36). A common haplotype that spans the chromosome 5q31 cytokine gene cluster, located within the IBD5 locus, has also been associated with CD (37). The CARD15/NOD2 and chromosome 5q31 cytokine gene cluster associations do not fully explain the genetics of CD and have not been associated with UC, so other IBD genes remain to be found (37,38).
http://hmg.oxfordjournals.org/content/11/21/2599.full
http://hmg.oxfordjournals.org/content/11/21/2599.full
