Defining the proximal border of the Huntington disease candidate region by multipoint recombination analyses

The candidate region for the Huntington disease (HD) gene has been narrowed down to a 2.2-Mb region between D4S10 and D4S98 on the short arm of chromosome 4. To map the HD gene within this candidate region 65 Dutch HD families were studied. In total 338 informative meioses were analyzed and 11 multiple informative crossovers were detected. Assuming a minimum number of recombinations and no double recombinations, our multiple informative crossovers are consistent with one specific genetic order for 12 loci: D4S10-(D4S81, D4S126)-D4S125-(D4S127,D4S95)-D4S43-(D4 S115, D4S96, D4S111, D4S90, D4S141). This is in agreement with the known data derived from similar and other methods. The loci between brackets could not be mapped relative to each other. In our family material, two informative three-point marker recombination events were detected in the proximal HD candidate region, which are also informative for HD. Both recombination events map the HD gene distal to D4S81 and most likely distal to D4S125, narrowing down the HD candidate region to a 1.7-Mb region between D4S125 and D4S98.