Our study was aimed at conducting a genome-wide association study (GWAS) to identify genetic variants that may play a role in heroin dependence and, with the aid of bioinformatics tools, to assess their expression patterns as well as functional pathways involved. The GWAS was performed using an ethnically homogeneous sample of Han Chinese origin; examination for presence of possible population substructure confirmed homogeneity of our sample of cases and controls. Case-control association analysis with 370 cases and 134 control individuals did not identify any genetic markers reaching genome-wide significance, as may be expected considering the relatively small sample size. Nonetheless, our gene based association analysis with VEGAS2, which involves fewer tests, also supported the putative role of CCDC42, consistent with the SNP based genome-wide analysis. Following imputation, three distinct regions were highlighted, on chromosomes 17, 11 and 8; the four most associated genes in these regions were CCDC42, BRSK2, CHIT1 and ARHGEF10. The top ranked gene was CCDC42 but little is known about the functional role of CCDC42, other than that it interacts with the transcriptional repressor ZBTB1 (zinc finger
