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 and BTB domain containing 1), which in turn is functionally important for chromatin remodeling [43] (www.ncbi.nlm.nih.gov); this relationship suggests that CCDC42 might be involved in epigenetic processes. A more intriguing functional relationship would be its involvement in immunological processes, as suggested by the association of CCDC42 with Behcet’s disease [44]. Characterized by recurrent inflammatory attacks, Behcet’s disease affects orogenital mucosa, eyes, joints as well as the nervous system and the gastrointestinal tract [45]. A number of immunoregulatory pathways have implicated in Behcet’s disease; if CCDC42 belonged to any of these pathways, it might explain its role in both Behcet’s disease and heroin addiction, as heroin use is often associated with increased presence of infectious diseases. Our gene-based analysis also yielded significant results with CCDC42 as well as the neighboring gene, SPDYE4 (Speedy/RINGO cell cycle regulator family member E4) of which little is known in terms of function.
