DNA sequence analysis of monoamine oxidase B gene coding and promoter regions in Parkinson's disease cases and unrelated controls.

The allele G of the intron 13 G/A polymorphism of the monoamine oxidase B gene (MAO-B) has been associated with Parkinson's disease (PD) in several studies. Apart from a potential direct effect on splicing processes, the association of this intronic polymorphism with PD is due possibly to linkage disequilibrium with other mutations in the coding or promoter regions of the gene. We addressed this latter hypothesis by determining the DNA sequence of the entire MAO-B coding region comprising 15 exons and partial intronic sequences flanking each exon, in 33 cases with idiopathic PD and 38 unrelated controls. The promoter region of MAO-B gene up to base -1,369 from ATG (start point of mRNA translation) was also sequenced to identify variants with potential functional effects on gene transcription. In the promoter region, a new polymorphism consisting of a C to T single base change was detected in position -1,114 from ATG, with an allelic frequency of 3.5%, but it was not associated with PD risk. No commonly occurring (>10%) polymorphisms were found in the exons or the intronic sequences flanking the exons, although several rare variants were detected in the coding and promoter regions.