The results of these analyses suggest that partitioning the total AD sample reduced genetic heterogeneity. Figure 1 summarizes the location of the four genes in the NTAD gene cluster, the distribution of the 43 SNPs, and the identified susceptibility regions. For AD-all, risk regions were consistent in both samples, with the exception of NCAM1 exon 12 (which was identified as associated only in the family sample). In particular, TTC12 exon 3 was significant in both global and individual haplotypic associations and in both samples. A broader region from ANKK1 exon 2 to DRD2 intron 1 was significant in the global association analyses in both samples, and was narrowed to ANKK1 exons 2 and 5 in the individual specific haplotypes for the case-control sample.
