Most unexplained mental retardation is caused by acquired mutations, researchers in the Netherlands report in the journal Nature Genetics.
Gene copy number differences are a known cause of schizophrenia, autism and mental retardation. Much less is known about the influence of single, newly acquired point mutations (concerning one of the principles – the letters of the DNA alphabet) on the development of these disorders.
Joris Veltman and Han Brunner, along with a team from Radboud University, Nijmegen Medical Center, studied the DNA sequences (encoding proteins) of 10 people with unexplained mental retardation and compared these DNA sequences with the genetic material of their healthy parents.
In 6 subjects, the presence of new mutations in DNA sequences encoding proteins was found – these mutations were not present in the genetic material of any of the healthy parents. And these were most likely the changes responsible for mental retardation.
According to the authors of the study, the results indicate that new point mutations combined with differences in gene copy number are responsible for the majority of cases of mental retardation in the entire population. (PAP)