Spinocerebellar ataxia (SCA1) in two large Italian kindreds: evidence in favour of a locus position distal to GLO1 and the HLA cluster

Two large Italian pedigrees with HLA‐linked spinocerebellar ataxia (SCA1) were typed for HLA‐A, ‐B and ‐DR as well as for markers either distal (F13A, D6S8) or proximal (D6S29, GLOl) to HLA. Pairwise linkage analyses of SCA1 vs. HLA‐A, ‐B and ‐DR showed peak lodscores of 5‐3, 5‐6 and 3‐3 respectively at 7 % recombination. Negative lodscores significantly excluded linkage with F13A at less than 5% and with GLOl at less than 10%. The lodscores with D6S8 and D6S29 had only low peaks. Recombination events in the two pedigrees and the estimated genetic distances of SCAl from GLOl and HLA favour the hypothesis of a SCA1 location distal to both of them. An order cen‐GLOl‐HLA‐SCAl‐tel appears therefore most likely with present data. These results are discussed in relation to previous reports placing SCA1 distal to HLA in two families and proximal in another.