Allelic Diversity of VNTR Polymorphism in Monoamine Oxidase A (MAOA) Gene in Young Women and Men in Mashhad, Iran

Monoamine oxidase A (MAOA) enzyme activity is changed in mood disorders, as well as lower activity associated with criminal and aggressive behaviors. The MAOA gene, which plays a vital role in degradation of neurotransmitters such as serotonin, norepinephrine, and dopamine, </em>contains a polymorphism in its promoter region that affects transcriptional efficiency. Moreover, MAOA-VNTR genotype has been related with both physical activity level and psychological measures. The aim of the current study was to determine the genetic variation and allelic frequency of the MAOA-VNTR in young population, and to compare the result with similar data from other populations.

Salvia samples were obtained from 124 volunteers in Mashhad, Iran (age: 24.3 ± 5.7 years, 55 men and 67 women). DNA was extracted from the cheek cell, and the MAOA genotype was identified using polymerase chain reaction (PCR) with gene specific primers. The polymorphism was detected by PCR using primers: Forward: 5′ACAGCCTGACCGTGGAGAAG-3′ and Revers: 5′GAACGTGACGCTCCATTCGGA-3′, and resulted in following products: 321 (3-repeat allele), 336 (3.5-repeat allele), 351 (4-repeat allele), and 381 (5-repeat allele).

From the sequencing results, 3.5R, 4.5R and 5.5R repeats were successfully identified instead of the 3R, 4R, 5R repeats which were identified by previous researchers. The result of the MAOA-VNTR genotyping revealed that the three common genotype were 4.5*4.5, 3.5*3.5, and 3.5*4.5 with frequency of 46.77%, 26.61%, and 20.96%, respectively, and the two common alleles were 4.5R and 3.5R with frequency of 37.50% and 58.06% respectively. The result of our study, compared with data of twelve populations, showed a significant difference between allele frequencies of Iranian samples with Iraqi, Afrikaner, New Zealand (European origin), German, Italian, Chinese and American populations (P < 0.05).

The frequency of MAOA allele is different between racial groups, and the frequency of the 4.5R allele is greater in the men and women populations of our study. As a result, as previously confirmed, individuals with the 4.5R allele have lower levels of physical activity, depression, and arousal due to high MAOA gene transcription activity.