ELECTRONIC LETTER Transmission disequilibrium test of stromelysin-1 gene variation in relation to Crohn’s disease

C rohn’s disease (MIM 266600) and ulcerative colitis (MIM 191390) are the major forms of inflammatory bowel disease (MIM 601458), the prevalence of Crohn’s disease being more than 1/1000 in the Western countries. Inflammatory bowel disease is characterised by chronic relapsing intestinal inflammation, and its pathogenesis probably involves microbial, immunological, environmental, and genetic factors. 3 Recent genetic association studies have shown that sequence variations in the Caspase Activating Recruitment Domain (CARD15) gene (MIM605956, formerly named NOD2) on chromosome 16q are a strong genetic factor for Crohn’s disease but not for ulcerative colitis. CARD15 represents the first major Crohn’s disease susceptibility gene identified, and its identification might facilitate the uncovering of other genetic factors for the disease. The matrix metalloproteinases (MMP) are a group of matrix degrading enzymes that play an important role in the pathogenesis of various inflammatory diseases including osteoarthritis, rheumatoid arthritis, atherosclerosis, cancers, and inflammatory bowel disease. We have shown that, of four MMPs studied (interstitial collagenase, gelatinase A and B, and stromelysin-1), stromelysin-1 in particular is directly involved in mucosal destruction following T cell activation in the human fetal gut. Furthermore, patients with Crohn’s disease have increased expression of stromelysin-1 in the mucosa at both the mRNA and protein levels. Microarray techniques have demonstrated that stromelysin-1 expression is increased 8.7-fold in the mucosa of patients with Crohn’s disease compared with healthy controls (Pender SLF, unpublished data), and have also shown that stromelysin-1 expression is 8.2-fold higher relative to controls in PWM stimulated human fetal gut explant culture. Thus, although the stromelysin-1 gene on chromosome 11q23 is not located within the particular chromosomal regions (19p13, 16q12, 16p, 14q11–q12, 12p13.2–q24.1, 6p, 5q31, and 1p36) that have been shown to be in linkage with inflammatory bowel disease (MIN 266600), it is a strong functional candidate gene that might have an influence on this multifactorial disorder. We have previously identified a functional polymorphism in the promoter of the stromelysin-1 gene. The polymorphism arises from insertion or deletion of an adenosine within a cluster of adenosines located at position 21612 and upwards, relative to the transcriptional start site of the gene, with one allele having a cluster of five adenosines (5A) and the other allele having six adenosines (6A). In vitro assays have shown that the 5A allele has a higher promoter activity than the 6A allele, with differential binding of a nuclear protein to the two allelic promoters. Given that increased stromelysin-1 expression plays an important role in the development of Crohn’s disease and that the 5A/6A polymorphism has an allele specific effect on stromelysin-1 expression, individuals carrying the 5A allele might have increased susceptibility to Crohn’s disease. We tested this hypothesis in the present study. METHODS Subjects The stromelysin-1 gene 5A/6A polymorphism was analysed in a collection of trios from Germany, each consisting of one patient with inflammatory bowel disease and their two unaffected parents (table 1). In addition, the polymorphism was analysed in a cohort of German families and a cohort of British families, each with multiple cases of inflammatory bowel disease (table 1). These samples were recruited by an international group of inflammatory bowel disease investigators at the Charité University Hospital (Berlin, Germany), the Christian-Albrechts-Universtität Hospital (Kiel, Germany), St Mark’s Hospital (London, UK), Guy’s Hospital (London, UK), King’s College Hospital (London, Key points