03 May 2011
ByAppeared in BioNews 605
Korean scientists have uncovered another gene, GIT1, linked to Attention Deficit Hyperactivity Disorder (ADHD). The study, published in Nature Medicine, provides further evidence that this behavioural condition has a genetic component. It is sometimes attributed to poor parenting.
One SNP (single nucleotide polymorphism) or single variant in the GIT1 gene trebled the chances that a child suffered from ADHD, according to the research. Additionally, mice that lacked the GIT1 gene showed ADHD-like symptoms, including hyperactivity and impaired learning and memory.
The team looked at humans and mice. First, they scanned ADHD-associated genes identified in previous genome-wide analyses, specifically focusing on DNA linked to brain function. One potential candidate was GIT1.
Comparison of the sequence of the GIT1 gene in 192 Korean children with ADHD and a group of 196 age-matched children without the condition found a SNP called rs550818 was more common in children with ADHD than in the control group.
Next, they genetically engineered mice to lack the GIT1 gene. Approximately half of the mice died soon after birth. Surviving mice lacking GIT1 weighed significantly less than normal mice of the same age (minus 60-70 percent), but otherwise looked normal.
The genetically-modified mice also responded to drugs used to treat human ADHD, including Ritalin. This reduced their ADHD-like activity back to the normal levels seen in control animals. Lead author Dr Eunjin Kim writes in the paper: 'By extension, these results suggest that the reduced expression of GIT1 can lead to ADHD in humans'.
ADHD is one of the commonest behavioural disorders in the UK, according to NHS figures. It is estimated to affect 3-9 percent of school-aged children and young people. The main symptoms include inattention, hyperactivity and impulsivity.