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Editor,—We were particularly interested to read the paper of Hampe et al(OpenUrlCrossRefPubMedWeb of Science) which provides some supportive evidence for the presence of a gene involved in susceptibility to inflammatory bowel disease on chromosome 3p. As Hampeet al describe, this region of interest was initially identified in a study of 186 affected sibling pairs, all resident in and indigenous to the UK.1 Since that initial observation, subsequent genome wide scans in European and North American populations have produced inconsistent data for the chromosome 3p region. There are a number of possible explanations for the inconsistent data, all well summarised by Hampe et al.
We suggest that the issue of heterogeneity between populations may be pertinent to the study of the chromosome 3 locus. We noted with interest that the dataset of 353 sibling pairs studied by Hampeet al includes a high proportion (48%) of UK sibling pairs, together with sibling pairs from Germany (46%) and the Netherlands (6%). In view of the fact that there appears to be heterogeneity between the UK dataset and other populations in Europe concerning the chromosome 16 and 12 loci,2 ,3 we would be particularly interested to know whether the data implicating chromosome 3p in Hampe's study are in fact stronger in the subset of families from the UK than those from Germany and the Netherlands. It would be of benefit in future studies to ascertain whether the chromosome 3p region does have a relatively stronger effect in the UK population than in other populations.
Editor,—The point raised in the letter by Satsangi and Vermeire is very valid. There has been significant variation in the presence of linkage in different populations.1-1-1-4 From a preliminary re-analysis of the data presented in our paper (OpenUrlCrossRefPubMedWeb of Science), the hypothesis raised through Satsangi and Vermeire appears to be true: there is a stronger contribution of linkage in the UK families than in the German families to the chromosome 3p linkage with a peak multipoint LOD score of 1.0 in the UK and 0.8 in the German families (not all markers analysed). It should be noted that each subsample is somewhat subcritical for a proper linkage analysis and thus these data have to be viewed with caution.
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