Torsion dystonia genes in two populations confined to a small region on chromosome 9q32-34.

Idiopathic torsion dystonia (ITD) is characterized by sustained, involuntary muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. Most familial forms of ITD display autosomal dominant inheritance with reduced penetrance. Linkage analysis has been previously used to localize a dystonia gene to the 9q32-34 region in a large non-Jewish family and in a group of Ashkenazi Jewish families. Utilizing GT repeat polymorphisms from this region, here we demonstrate that the gene causing dystonia in Ashkenazi Jews can be localized to the 11-cM interval between AK1 and D9S10. Linkage analysis in the non-Jewish family is also consistent with occurrence of the gene in this region, although positive lod scores extend over a greater than 20-cM interval in that family. These results set the stage for positional cloning of the dystonia gene. Currently there are no known candidate genes in this region.