AUTOSOMAL-DOMINANT DISTAL MYOPATHY - LINKAGE TO CHROMOSOME-14

We have studied a family segregating a form of autosomal dominant dist al myopathy (MIM 160500) and containing nine living affected individua ls. The myopathy in this family is closest in clinical phenotype to th at first described by Gowers in 1902. A search for linkage was conduct ed using microsatellite, VNTR, and RFLP markers. In total, 92 markers on all 22 autosomes were run. Positive linkage was obtained with 14 of 15 markers tested on chromosome 14, with little indication of linkage elsewhere in the genome. Maximum two-point LOD scores of 2.60 at reco mbination fraction .00 were obtained for the markers MYH7 and D14S64-t he family structure precludes a two-point LOD score greater than or eq ual to 3. Recombinations with D14S72 and D14S493 indicate that this di stal myopathy locus, MPD1, should lie between these markers. A multipo int analysis assuming 100% penetrance and using the markers D14S72, D1 4S50, MYH7, D14S64, D14S54, and D14S49 gave a LOD score of exactly 3 a t MYH7. Analysis at a penetrance of 80% gave a LOD score of 2.8 at thi s marker. This probable localization of a gene for distal myopathy, MP D1, on chromosome 14 should allow other investigators studying distal myopathy families to test this region for linkage in other types of th e disease, to confirm linkage or to demonstrate the likely genetic het erogeneity.