LINKAGE ANALYSIS WITH CHROMOSOME-9 MARKERS IN HEREDITARY ESSENTIAL TREMOR

Hereditary essential tremor (ET) is an autosomal dominant disorder wit h variable expression and redUCed penetrance. A tremor indistinguishab le from ET may be observed in patients with autosomal dominant idiopat hic torsion dystonia (ITD), in which the disease locus has been mapped to 9q32-34 in some kindreds, tightly linked to the argininosuccinate synthetase (ASS) locus. We performed linkage analysis in 15 families w ith ET containing 60 definitely affected individuals, using dinucleoti de repeat polymorphisms at the ASS locus and the Abelson locus (ABL). Cumulative lod scores were -19.5 for ASS and -10.8 for ABL at a recomb ination fraction of 0.01, and tight linkage to ASS was excluded indivi dually in 11 of the families. These data indicate that the ET gene is not allelic to that causing ITD.