Genome-wide linkage analysis of heroin dependence in Han Chinese: results from Wave Two of a multi-stage study

Previously we reported the results of Wave One of a genome-wide search for heroin dependence susceptibility loci in Han Chinese families from Yunnan Province, China, near Asia's "Golden Triangle". Our initial analysis of 194 independent affected sibling-pairs from 192 families identified two regions with nonparametric linkage (NPL) Z-scores greater than 2.0, which were suggestive of linkage. Presently we have supplemented our sample with additional individuals and families, bringing the total number of genotyped individuals to 1513 and the number of independent sibling-pairs to 397. Upon repeating our analyses with this larger sample, we found that the evidence for linkage at our most strongly implicated locus from Wave One (marker D17S1880; 53.4cM on 17q11.2; NPL Z=2.36; uncorrected p=0.009) was completely abolished (Z=-1.13; p=0.900). In contrast, the evidence for linkage at the second-most strongly implicated locus from Wave One (D4S1644; 143.3cM on 4q31.21; NPL Z=2.19; uncorrected p=0.014) increased in its magnitude and significance (Z=2.64; uncorrected p=0.004), becoming the most strongly implicated locus overall in our full sample. Other loci on chromosomes 1, 2, 4, 12, 16, and X also displayed nominally significant evidence for linkage (p< or =0.05). These loci appear to be entirely distinct from opioid-linked loci reported by other groups; however, meta-analyses of all available linkage data may reveal common sites of interest and promising candidate genes that can be further evaluated as risk factors for the illness.