Most occurrences of unexplained mental retardation may be caused by new mutations, reports a study published online this week in Nature Genetics.
New large-scale copy number variation is a known cause of schizophrenia, autism and mental retardation, but much less is known about the frequency and impact of new point mutations in these common diseases. To explore this, Joris Veltman, Han Brunner and colleagues examined the complete protein-coding sequences of 10 individuals with unexplained mental retardation and compared these sequences to those of their unaffected parents. In six of the individuals, the team found a new mutation in a protein-coding sequence that was absent from both of their parents and that was most likely responsible for their intellectual disability.
These findings suggest that new point mutations, together with new large-scale copy number variation, could explain a majority of all mental retardation cases in the population.