THE ROLE OF GENETICS IN CHILDHOOD BEHAVIOUR
How do genes affect your child's behaviour?
MTHFR
Gokcen et al (2011) examined the relationship between (MTHFR) polymorphisms and Attention Deficit Hyperactivity Disorder (ADHD) in a sample of Turkish children. Of the two main mutations studied, the A1298C allele was found to be linked with ADD/ADHD. This study therefore suggests a link between MTHFR and ADHD.
The MTHFR enzyme is essential for DNA synthesis, with a mutation of the gene known to vastly increase an individual’s chance of expressing or developing a disease state. This meta-analysis by Pu et al (2013) examined the link between MTHFR and Autism Spectrum Disorders (ASD). Results from all studies showed the C677T mutation to be associated with an increased risk of ASD in countries without folic acid food fortification.
Weng et al (2014) conducted research on young mice to examine how extensively DNA methylation within the brain is regulated by nutrition early in life. The thalamus and hippocampus of malnourished mice were compared to the brains of normal mice, with the two regions showing differences in their levels of DNA methylation. 500 variations of gene methylation were found in the thalamus, with 60% of these variations relating to development of nerve cells and psychiatric disease. This shows the DNA methylation status of parts of the brain can differ, and is affected by malnutrition from a young age. This also highlights malnutrition from a young age may increase the risk of psychiatric disorders.
A study examining the presence of mutated MTHFR and methylation-related genes in mothers of children with Down’s Syndrome (DS) was undertaken by Liao et al (2010). The authors found the homozygous 677TT mutation to be more prevalent in mothers of children with DS when compared to a group of mothers with healthy controls. This mutation was found to give mothers a 3.51 increased risk of giving birth to a DS child compared to controls. The MTRR A66G mutation was also independently associated with a 3.16 fold increase in DS risk.
The presence of the MTHFR C677T mutation was studied in a group of mothers with Down’s Syndrome children. Results found the 677TT genotype to be present in 1.8% of the case group, with none of the women in the control group found to be carrying this genotype. The frequency of a T allele in cases was 0.13, compared with 0.11 in controls. Therefore, neither of these findings were found to be positively linked with the increased risk of developing Down’s Syndrome in offspring.
