Here it appears that MAOA controls dopamine extracellular concentration in the striatum. Since Fragile X syndrome seems associated with higher dopamine tone in the striatum (this related to increased sterotypical locomotion behaviors), lower MAOA may be a marker for Fragile X syndrome.
We have evaluated low MAOA as a correlate of Aggressiveness. While individuals with Fragile X are not typically aggressive and don't appear to be of NPA types NA, PA, A, or NPA, we do know that 5HTT l/l genotype (a non-Perfectionism candidate gene) is associated in individuals with Fragile X with Aggressive and Obsessive Compulsive behaviors. So, there may be some Aggression trait involved in Fragile X phenotype that is unmasked in individuals with non-Perfectionism. Some studies show that MAOA is not different in individuals with Fragile X syndrome but that high MAOA is associated with higher prevalence of taking anti-depressant and anti-anxiety medications. So, there may still be reason to think that low MAOA is associated with Fragile X syndrome, a very specific genetic syndrome at a gene on the X chromosome called FMR1.
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