The Genetic Link

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Article by: Lisa Gamwell

Gene-by-environment interactions: When nature and nurture collide


Last month we posted our first blog article in the Genetics and Mental Health Series.  We discussed incorporating genetic analysis into research programs to uncover differences in traits and diseases, or to potentially improve the diagnosis and treatment of patients. This month we would like to expand on that idea by exploring how our traits and personality characteristics are controlled by two things: our environment and our genetics. A person’s genes and their environment interact to affect their mental health and behaviour, and this interaction, referred to aptly as the gene-by-environment interaction, is a very interesting, if challenging, area of research. 

One of the most widely studied gene-by-environment interactions involves genetic variations or polymorphisms in the monoamine oxidase (MAOA) gene. This gene encodes an enzyme that plays a role in regulating key neurotransmitters in the brain. Individuals that carry the MAOA-LPR high activity variant have a higher expression of the MAOA enzyme compared to those with the low activity variant. In a classic gene-by-environment interaction, the MAOA-LPR low activity variant (gene) has been reported to interact with the occurrence of childhood maltreatment (environment) to have an effect on childhood behavioural problems and adult anti-social behaviour.

In a recent article published in Genes, Brain and Behavior; Professor Jonathon Hill, a professor of Child and Adolescent Psychiatry at the University of Manchester, and his colleagues wondered if the MAOA-LPR genotype modifies the effect of stress experienced by the mother during fetal development on the irritability of her baby, 5 weeks after the baby is born [1]. Participants in this study, which included 209 infants and their mothers, were recruited from the Wirral Child Health and Development study. 

The environment

Professor Hill and his colleagues used a variety of measures to determine the level of stress the mothers experienced whilst they were pregnant; including socio-economic status, being a single parent, partner psychological abuse, depression, anxiety, marital satisfaction, and stressful life events. They also looked at the health of the pregnancy since an at-risk pregnancy is understandably very stressful for a pregnant mother.

The gene

To collect DNA from the 5-week old infants, Professor Hill used an Oragene saliva collection kit designed to collect samples from non-spitters. This non-invasive kit uses small sponges to collect high quality DNA from the infant’s saliva in a completely pain-free manner. The DNA in the samples was analysed to determine if the infants were carriers of the low or high activity variants of MAOA-LPR.

The main findings

The researchers found that, in the infants, the low activity variant of MAOA-LPR altered the effect of social adversity experienced by their mothers during pregnancy on early infant negative emotionality or irritability. In other words, the babies that were low activity variant carriers and were born to mothers that reported 4 or more stressful life events during their pregnancy (compared to none) were 3-times more likely to be fussy and irritable. If the baby was a high activity variant carrier there was no effect of stress experienced by mom during pregnancy on the newborn baby’s irritability and fussiness.

Similarly, the study also found that if the mom lived in a neighbourhood that was considered deprived, based on factors such as living conditions, crime, and average income, there was a similar alteration in the association between MAOA-LPR and infant irritability.  

Professor Hill’s research found two gene-by-environment interactions that linked the mother’s experiences while pregnant to the infant’s irritability. Finding not one, but two such interactions is very difficult. The team credited the large sample size, which was in part due to the fact that they used a non-invasive, easy to use and reliable DNA collection method like Oragene. The researchers hope that should this exciting finding be replicated, it

“would provide the basis for the development of prenatal stress prevention programs targeted at mothers with MAOA-LPR fetuses.” [1]

The importance of incorporating genetic analysis into research is very clear in this study: Had the researchers not looked at MAOA gene variants they would not have an explanation why maternal stress might have a greater effect on the temperament of some babies but not others.

This is just one of more than 500 publications that describe how non-invasive sample collection with Oragene is supporting brain and mind researchers in their discoveries. If you are thinking of using DNA from saliva for your next research project, click below to request evaluation kits.

Request free trial kits of any DNA Genotek saliva kit


[1] Hill j et al. Evidence for interplay between genes and maternal stress in utero: monoamine oxidase A polymorphism moderates effects of life events during pregnancy on infant negative emotionality at 5 weeks. Genes, Brain and Behavior. 12(4):388-96 (2013)

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