Linkage analysis of multiple sclerosis with candidate region markers in Sardinian and Continental Italian families

Previous genome screens in multiple sclerosis have shown some evidence of linkage in scattered chromosomal regions. Although in no case the evidence of each single study was compelling and although in general the linkage 'peaks' of the different studies did not coincide, some regions can be considered likely candidates for the presence of MS risk genes because of the clustering of MLS scores and homology with eae loci. We performed a linkage analysis of markers in these regions and of intragenic markers of some individual candidate genes (HLA-DRB1, CTLA-4, IL9, APOE, BCL2, TNFR2). For the first time, Southern European populations were targeted, namely Continental Italians and Sardinians. A total of 69 multiplex families were typed for 67 markers by a semi-automatic fluorescence-based assay. Results were analysed for linkage by two non-parametric tests: GENEHUNTER and SimIBD. In general, the linkage scores obtained were low, confirming the conclusion that no gene is playing a major role in the disease. However, some markers, in 2p11, 3q21.1, 7p15.2 and 22q13.1 stood out as promising since they showed higher scores with one or the other test. This stimulates further association analysis of a large number of simplex families from the same populations.