Molecular Biology: A Very Short Introduction by Aysha Divan & Janice Royds

Author:Aysha Divan & Janice Royds
Language: eng
Format: epub
ISBN: 9780191035814
Publisher: OUP Oxford
Published: 2016-06-22T04:00:00+00:00

Gene–environment interactions

The role of enhancers and epigenetics in mediating changes in gene expression and hence vulnerability to disorders is widely accepted but how these interact with the environment is now becoming of great importance and also controversy. The first gene to be linked with social behaviour is a particular variation of the X chromosome gene MAOA that produces the enzyme monoamine oxidase A. This enzyme degrades the neurotransmitters dopamine, norepinephrine, and serotonin in the brain affecting their levels and therefore our moods. Inhibitors of MAOA activity are common drugs used in treatment of clinical depression and anxiety. Mutations in MAOA cause the Brunner Syndrome, characterized by violent and impulsive behaviour. The lack of activity of the mutant enzyme gives rise to an excess of monoamine neurotransmitters, causing the behaviour seen in this syndrome. Levels of expression of the wild type gene can also cause behavioural differences. The MAOA gene has two types of enhancer sequence upstream of the promoter. The shorter form is associated with low enzyme expression and has been named the ‘Warrior gene’ as it enhances the qualities associated with successful fighters. However this low expression variant gene in combination with maltreatment during childhood may result in an increased risk of antisocial and aggressive behaviour. Studies have linked methylation of the MAOA gene and low expression with nicotine and alcohol dependence in women but not in men. Interestingly epigenetic methylation of this gene is very low in men.

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