Figure 3

GRIK2 3' haplotypes in HD patients with earlier than expected onset. Haplotypes determined for microsatellite and SNP (labeled as in Figure 1) markers from GRIK2 exon 11 through the 3'UTR are shown for the four HD patients with earlier than expected onset, three possessing a 16 TAA allele at D6S1028 and one possessing a rare 17 TAA allele. The 16 TAA allele chromosomes are distinguishable by other polymorphisms except in the fully sequenced 2.3 kb region between rs12198351 and rs28383484 (denoted by a red bar above this region of the haplotype) suggesting that the TAA allele is responsible for the modifier effect.