Detection and analysis of four polymorphic markers at the human monoamine oxidase (MAO) gene in Japanese controls and patients with Parkinson's disease.

Monoamine oxidase (MAO), which exists in two forms (MAOA and MAOB), plays an important role in the oxidative metabolism of neurotransmitters such as dopamine, and has been implicated in the etiology of Parkinson's disease (PD). Individual variations in the activity of these enzymes appear to be genetically determined, and these genetic variations appear to be predominantly mediated by the MAO locus. Here, we detected and analyzed four polymorphic markers in the MAO gene using a polymerase chain reaction method in 228 Japanese controls (102 males and 126 females) and 68 patients with PD (30 males and 38 females). Although the analysis of the MAOA marker demonstrated no overall association between its alleles and PD, a significant difference in the frequency of one particular MAOA allele between controls and patients with PD was found. Moreover, in a comparison of the distribution of the full haplotypes at the MAOA locus, there was a significant difference in the frequency of one particular haplotype between male controls and patients with PD. In the MAOB polymorphism, there was no difference in the distribution of alleles between them. These findings support the hypothesis that the MAOA gene may affect the susceptibility of individuals to PD among MAOA polymorphic loci.