A haplotype‐specific linkage disequilibrium pattern of monoamine oxidase A gene associated with regular smoking in women

BACKGROUND: Cigarette smoking in women is raising a public health problem. The X-linked monoamine oxidase A (MAOA) was considered as a susceptibility gene to substance abuse of tobacco, but the evolutionary effect of MAOA may lead to a positive or negative association between genetic variations and smoking development among study regions. METHODS: Based on linkage disequilibrium (LD), we performed a haplotype-based association to explore the effect of MAOA gene on women's smoking risk in a case-control study. RESULTS: Genotyped single nucleotide polymorphisms (SNPs) of MAOA gene, rs5953210G>A, rs2283725A>G and rs1137070T>C, were significantly associated with current smoking risk in women, and the increased level of plasma MAO-A activity was raised with per copy increment of risk allele in current smokers (P .05 were constructed using the Expectation-Maximization algorithm, and the haplotype-specific A-G-C pattern raised the 2-fold risk to develop regular smoking (P = .0005). In the diplotype analysis based on X-inactivation mechanism relative to no and full dosage compensation, we showed that A-G-C haplotype not only increased regular smoking risk in a dose-dependent manner (Ptrend = .0011) but also contributed to smoking risk in the dosage compensation mechanism. Compared to non-smokers, the effect of A-G-C haplotype on random X-activation was associated with the raised MAO-A activity in women smokers (P < .05) although the lifetime cigarette consumption showed a difference that was not statistically significant. CONCLUSION: This study provides information on MAOA LD-based haplotype and diplotype patterns in women smoking.