A pilot study on the relationship between a variable number tandem repeat polymorphism and monoamine oxidase A...

Monoamine oxidase A (MAOA) catalyzes the oxidative deamination of amine neurotransmitters and xenobiotics. The MAOA gene is located on the X chromosome and has a functional variable number tandem repeat (VNTR) polymorphism of 30 bp repeats in the promoter region (MAOA-uVNTR). The MAOA-uVNTR polymorphism has been associated with transcriptional activity. We herein examined the frequencies of MAOA-uVNTR alleles in 21 cases in which amphetamines or psychotropic drugs were not detected in blood or urine samples (ND cases). We also investigated MAOA protein expression levels in the brains of these cases. In ND cases, brain MAOA expression levels were significantly higher in males with 4-repeat alleles and females who were homozygous for 4-repeat alleles (4 + 4/4 genotype group) than in males with 3-repeat alleles and females who were homozygous for 3-repeat alleles (3 + 3/3 genotype group) (p = 0.0395). Collectively, these results indicate that the MAOA-uVNTR polymorphism affects the brain expression level of MAOA in ND cases.