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Scientists in the US have found what they believe to be a genetic basis for attention deficit hyperactivity disorder (ADHD).The researchers found specific types of mutations, known as copy number variations, in a gene called GMR5, in children who had ADHD.GMR5 is involved in glutamate receptors, which play a crucial role in connecting neurons.Lead researcher Hakon Hakonarson, director of the Center for Applied Genomics at Children's Hospital in Philadelphia, said that members of the GMR gene family, along with genes they interacted with, affected nerve transmission, the formation of neurons, and interconnections in the brain.He said the fact that children with ADHD were more likely to have alterations in those genes reinforced previous evidence that the GMR pathway was important in ADHD.For the study, the researchers made use of modern gene sequencing technology to study the entire genetic code of 1,000 children who had ADHD.As a plain text file, a single human genome takes up about 725 megabytes on a computer.Using the genomes of 4,100 children who did not have ADHD, the researchers were able to find the places where those ADHD genomes seemed to differ.On average, no human differs from any other by more than 1%.Copy number variation, the type of genetic mutation found in 10% of the children who had been diagnosed with ADHD, involves the occurrence of deleted or duplicated DNA sequences.Hakonarson said that the finding seemed to hint at the cause of ADHD symptoms for a subset of children who had the disease.Andrew Adesman, chief of developmental and behavioral paediatrics at Steven & Alexandra Cohen Children's Medical Center of New York, who was not involved in the study, said he believed the research was important not only in that it had identified gene variants that were associated with ADHD in approximately 10% of cases, but in that it identified novel treatment strategies related to the neurotransmitter glutamate.He said that researchers could now try to develop drugs for individuals with the newly identified gene variants.ADHD tends to run in families, and researchers believe that the syndrome may involve the interactions of several genes.Adesman said that the study provided further evidence not only that ADHD had a genetic basis in a distinct subset of children with ADHD but that the neurotransmitter glutamate seemed to play a big role in some cases. He said that having a genetic understanding of ADHD would eventually help researchers identify safe and effective treatment strategies for the subset of children with ADHD who had variations in their glutamate-related genes....
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