Compared to the results of a GWA for smoking initiation and current smoking in the Dutch NESDA/NTR sample and 3 replication samples (Uhl et al., 2008a), some gene groups overlapped with the results of the present study (Figure 1), including the cell adhesion proteins DSCAM and CNTN4, transporters ABCA13 and ATP10A, and cytoskeleton proteins MYOM2 and DNAH11. In contrast, the study of Vink et al. (2009) showed a large group of glutamate signaling proteins which was not found in the present study (only GRIA1) whereas the group of genes involved in intracellular calcium signaling identified in the present study was not found by Vink et al. The overlapping groups (and genes) may reflect mechanisms involved in addictive behaviour in general, while the specific groups may reflect mechanisms specific for a phenotype, for example glutamate genes for smoking initiation and intracellular calcium signalling for nicotine dependence.
