Three genomic loci exceeded genome-wide significance in the ever smoking analysis (Table 1b). The top signal was yielded by the noncoding antisense RNA transcript BDNF-AS (P=6.25E-07) on 11p14. Note also that the CDC27 gene, harbouring the rs16941640 SNP with the lowest p-value in the initial TAG analysis (P=2.2E-07), achieved significance in our gene-based analysis (P=3.04E-06). Two genes were significantly associated with smoking cessation (see Table 1c), with the SLC25A21 gene on 14q13 yielding the lowest p-value (P=2.09E-08). The gene-based tests revealed the non-coding RNA MIR1323-MIR512-1-MIR512-2 locus on 19q13.42 as significantly associated with age at initiation (P=1.33E-06; Table 1d). Note that no individual SNP reached significance in the original TAG analysis of age at initiation. We refer to the Supplementary Table S1 for details on gene functions and to the Tables S2-S5 for details on SNPs assigned to genes.
