Attempts to isolate the Huntington disease (HD) gene based on its position have been frustrated by apparently contradictory recombination events in HD pedigrees that have predicted two non-overlapping candidate regions: 100 kb at the telomere of the short arm of chromosome 4, and a 2.2 Mb region located internally at 4p16.3. The proximal location is also supported by the detection of a linkage disequilibrium between HD and some restriction fragment length polymorphisms (RFLPs) at the D4S95, D4S98, and D4S127 loci. In the present study, a proximal marker D4S95 showed tight linkage to the disease locus in Japanese pedigrees (Zmax = 3.31, theta max = 0.00), while distal markers D4S115 and D4S111 did not. Particularly, a two point linkage analysis between D4S111 and HD yielded a lod score -2.01 for theta = 0.015. This result leads to the exclusion, as a possible region of localization of the HD gene, of more than 3 cM of the genome around D4S111 locus. At the same time our results favor aforementioned proximal location as a candidate location for the HD gene.
Adult Alleles