RESUMO
BACKGROUND: Alcohol and tobacco use are heritable phenotypes. However, only a small number of common genetic variants have been identified, and common variants account for a modest proportion of the heritability. Therefore, this study aims to investigate the role of low-frequency and rare variants in alcohol and tobacco use. METHODS: We meta-analyzed ExomeChip association results from eight discovery cohorts and included 12,466 subjects and 7432 smokers in the analysis of alcohol consumption and tobacco use, respectively. The ExomeChip interrogates low-frequency and rare exonic variants, and in addition a small pool of common variants. We investigated top variants in an independent sample in which ICD-9 diagnoses of "alcoholism" (Nâ¯=â¯25,508) and "tobacco use disorder" (Nâ¯=â¯27,068) had been assessed. In addition to the single variant analysis, we performed gene-based, polygenic risk score (PRS), and pathway analyses. RESULTS: The meta-analysis did not yield exome-wide significant results. When we jointly analyzed our top results with the independent sample, no low-frequency or rare variants reached significance for alcohol consumption or tobacco use. However, two common variants that were present on the ExomeChip, rs16969968 (pâ¯=â¯2.39â¯×â¯10-7) and rs8034191 (pâ¯=â¯6.31â¯×â¯10-7) located in CHRNA5 and AGPHD1 at 15q25.1, showed evidence for association with tobacco use. DISCUSSION: Low-frequency and rare exonic variants with large effects do not play a major role in alcohol and tobacco use, nor does the aggregate effect of ExomeChip variants. However, our results confirmed the role of the CHRNA5-CHRNA3-CHRNB4 cluster of nicotinic acetylcholine receptor subunit genes in tobacco use.
Assuntos
Consumo de Bebidas Alcoólicas/genética , Éxons/genética , Predisposição Genética para Doença/genética , Variação Genética/genética , Uso de Tabaco/genética , Consumo de Bebidas Alcoólicas/epidemiologia , Alcoolismo/diagnóstico , Alcoolismo/epidemiologia , Alcoolismo/genética , Estudos de Coortes , Feminino , Predisposição Genética para Doença/epidemiologia , Humanos , Masculino , Proteínas do Tecido Nervoso/genética , Polimorfismo de Nucleotídeo Único/genética , Receptores Nicotínicos/genética , Fatores de Risco , Uso de Tabaco/epidemiologia , Tabagismo/diagnóstico , Tabagismo/genéticaRESUMO
Recent studies show that different aspects of smoking behavior are associated with the α-5 subunit of the nicotinic acetylcholine receptor (CHRNA5) gene and the gene coding for brain-derived neurotrophic factor (BDNF). This raises the question whether the amount of cigarettes smoked per day has a different genetic background than smoking initiation and what other smoking phenotypes may be relevant. The aim of this study was to replicate these associations in a large population-based sample. We investigated the association with smoking initiation and the number of cigarettes used per day and additional smoking phenotypes in a population-based sample of 2166 participants of Dutch origin. Rs6265 in BDNF was not associated with smoking initiation. This single nucleotide polymorphism was associated with smoking cessation. Rs16969968 in CHRNA5 was associated with the amount of nicotine used and in particular smoking 25 cigarettes or more per day. Overall, the results confirm the involvement of the CHRNA5 gene in the amount of nicotine use and further suggest involvement of the BDNF gene in smoking behavior.