Replicated Risk Nicotinic Cholinergic Receptor Genes for Nicotine Dependence
GENES
Authors: Zuo, Lingjun; Garcia-Milian, Rolando; Guo, Xiaoyun; Zhong, Chunlong; Tan, Yunlong; Wang, Zhiren; Wang, Jijun; Wang, Xiaoping; Kang, Longli; Lu, Lu; Chen, Xiangning; Li, Chiang-Shan R.; Luo, Xingguang
Abstract
It has been hypothesized that the nicotinic acetylcholine receptors (nAChRs) play important roles in nicotine dependence (ND) and influence the number of cigarettes smoked per day (CPD) in smokers. We compiled the associations between nicotinic cholinergic receptor genes (CHRNs) and ND/CPD that were replicated across different studies, reviewed the expression of these risk genes in human/mouse brains, and verified their expression using independent samples of both human and mouse brains. The potential functions of the replicated risk variants were examined using cis-eQTL analysis or predicted using a series of bioinformatics analyses. We found replicated and significant associations for ND/CPD at 19 SNPs in six genes in three genomic regions (CHRNB3-A6, CHRNA5-A3-B4 and CHRNA4). These six risk genes are expressed in at least 18 distinct areas of the human/mouse brain, with verification in our independent human and mouse brain samples. The risk variants might influence the transcription, expression and splicing of the risk genes, alter RNA secondary or protein structure. We conclude that the replicated associations between CHRNB3-A6, CHRNA5-A3-B4,CHRNA4 and ND/CPD are very robust. More research is needed to examine how these genetic variants contribute to the risk for ND/CPD.
Genome-wide meta-analysis reveals common splice site acceptor variant in CHRNA4 associated with nicotine dependence
TRANSLATIONAL PSYCHIATRY
Authors: Hancock, D. B.; Reginsson, G. W.; Gaddis, N. C.; Chen, X.; Saccone, N. L.; Lutz, S. M.; Qaiser, B.; Sherva, R.; Steinberg, S.; Zink, F.; Stacey, S. N.; Glasheen, C.; Chen, J.; Gu, F.; Frederiksen, B. N.; Loukola, A.; Gudbjartsson, D. F.; Brueske, I.; Landi, M. T.; Bickeboeller, H.; Madden, P.; Farrer, L.; Kaprio, J.; Kranzler, H. R.; Gelernter, J.; Baker, T. B.; Kraft, P.; Amos, C. I.; Caporaso, N. E.; Hokanson, J. E.; Bierut, L. J.; Thorgeirsson, T. E.; Johnson, E. O.; Stefansson, K.
Abstract
We conducted a 1000 Genomes-imputed genome-wide association study (GWAS) meta-analysis for nicotine dependence, defined by the Fagerstrom Test for Nicotine Dependence in 17 074 ever smokers from five European-ancestry samples. We followed up novel variants in 7469 ever smokers from five independent European-ancestry samples. We identified genome-wide significant association in the alpha-4 nicotinic receptor subunit (CHRNA4) gene on chromosome 20q13: lowest P = 8.0 x 10(-9) across all the samples for rs2273500-C (frequency = 0.15; odds ratio = 1.12 and 95% confidence interval = 1.08-1.17 for severe vs mild dependence). rs2273500-C, a splice site acceptor variant resulting in an alternate CHRNA4 transcript predicted to be targeted for nonsense-mediated decay, was associated with decreased CHRNA4 expression in physiologically normal human brains (lowest P = 7.3 x 10(-4)). Importantly, rs2273500-C was associated with increased lung cancer risk (N = 28 998, odds ratio = 1.06 and 95% confidence interval = 1.00-1.12), likely through its effect on smoking, as rs2273500-C was no longer associated with lung cancer after adjustment for smoking. Using criteria for smoking behavior that encompass more than the single 'cigarettes per day' item, we identified a common CHRNA4 variant with important regulatory properties that contributes to nicotine dependence and smoking-related consequences.
COA
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