Investigators F. Lucy Raymond (Cambridge Institute of Medical Research, University of Cambridge, Cambridge, UK) and Patrick S. Tarpey (Wellcome Trust Sanger Institute, Hixton, UK) describe the ZDHHC9 gene found in those with severe retardation as being mutated to the point of entirely losing function.
"ZDHHC9 is a novel gene," explains Dr. Raymond. "This gene would not have been predicted to play a role in mental retardation based on the previous genetics work. It was found only because we were systematically looking at all the genes on the X chromosome irrespective of what they do."
X-linked mental retardation is severe. Some patients require total care and may not have language ability. The condition runs in families and only affects the male offspring. So far only a few of these genes have been identified.
Working through a large, international collaboration, the researchers collected genetic samples from 250 families in which at least two boys have mental retardation to help identify novel genes that cause X-linked mental retardation. The investigators systematically analyzed the X chromosome for gene mutations.
Dr. Raymond says that the families are receiving information from the study and using it to make decisions in their lives. "We cannot currently make their children better, but knowing that we found a genetic abnormality gives them an explanation for what has happened," she explains. "We had one family that said this knowledge was the best news they had ever been given."
"We have identified the cause of problems in certain families and are able to tell whether or not women are carriers of the condition," Dr. Raymond c
Source:University of Chicago Press Journals