Background
Conventional meta-analysis based on genetic markers may be less powerful for heterogeneous samples. In the present study, we introduced a new meta-analysis for four genome-wide association studies on alcohol dependence that integrated the information of putative causal variants.
Methods
A total of 12,481 subjects in four independent cohorts were analyzed, including one European-American cohort (1,409 cases with alcohol dependence and 1,518 controls), one European-Australian cohort (a total of 6,438 family subjects with 1,645 probands), one African-American cohort from SAGE+COGA (681 cases and 508 controls) and one African-American cohort from Yale (1429 cases and 498 controls). The genome-wide association analysis was conducted for each cohort, and then a new meta-analysis was performed to derive the combined p values. cis-eQTL analysis of each risk variant in human tissues and RNA expression analysis of each risk gene in rat brain served as functional validation.
Results
In meta-analysis of European-American and European-Australian cohorts, we found 10 top-ranked SNPs (p<10−6) that were associated with alcohol dependence. They included 6 at SERINC2 (3.1×10−8≤p≤9.6×10−8), 1 at STK40 (p=1.3×10−7), 2 at KIAA0040 (3.3×10−7≤p≤5.2×10−7) and 1 at IPO11 (p=6.9×10−7). In meta-analysis of two African-American cohorts, we found 2 top-ranked SNPs including 1 at SLC6A11 (p=2.7×10−7) and 1 at CBLN2 (p=7.4×10−7). In meta-analysis of all four cohorts, we found 2 top-ranked SNPs in PTP4A1-PHF3 locus (6.0×10−7≤p≤7.2×10−7). In an African-American cohort only, we found 1 top-ranked SNP at PLD1 (p=8.3×10−7; OR=1.56). Many risk SNPs had positive cis-eQTL signals and all these risk genes except KIAA0040 were found to express in both rat and mouse brains.
Conclusions
We found multiple genes that were significantly or suggestively associated with alcohol dependence. They are among the most appropriate for follow-up as contributors to risk for alcohol dependence.