Linkage analysis and exclusion of regions of chromosomes 3 and 8 in Gilles de la Tourette syndrome following the identification of a balanced reciprocal translocation 46 XY, t(3

Abstract

Gilles de la Tourette syndrome (GTS) and related disorders such as chronic multiple tics and obsessive compulsive behaviour are likely to be genetically transmitted with a Mendelian autosomal dominant mode of transmission. Following our discovery of a patient with GTS who also carried a balanced translocation 46 XY, t(3:8) (p21.3 q24.1), a linkage study of several families was performed covering the areas on chromosomes 3 and 8 implicated by the cytogenetic abnormality in this unique GTS patient. A positive multipoint lod score of 2.9 was obtained on chromosome 3 with markers at the loci RAF1, THRB, and D3S11. Subsequently, the genetic map of this region was improved and new polymorphic markers close to our original three markers were identified. With the new map the maximum two-point lod with any marker was reduced to 1.77 at RAF1, and the FASTMAP approximate multipoint lod excluded the likely region of the breakpoint. After constructung a somatic cell hybrid, the original three markers were mapped relative to the break point of the translocation and to other new markers. It was confirmed that the original markers were at least 20 cM away from the position of the break point. In addition, we traced further family members of our translocation GTS proband, and identified affected individuals who did not possess the translocation. We concluded that the translocation was not responsible for the GTS symptoms in our affected proband.