An international study led by University of Montreal scientists suggests family history may not be a good predictor of the presence of mutations predisposing to autism or schizophrenia. The findings show how new or de novo gene mutations – alterations of the cell’s DNA – play a role in these devastating conditions. Published in the American Journal of Human Genetics, this study has implications for disease prevalence and severity.
Dr. Guy Rouleau
“Harmful de novo mutations, as observed in this study, may in part explain the high global incidences of autism and schizophrenia,” adds Dr. Rouleau, who is also director of the Sainte-Justine University Hospital Research Center and a scientist at the University of Montreal Hospital Research Centre.
Investigating human mutation rate:
The team analyzed 400 genes that are turned on in nerve cells from patients with autism or schizophrenia spectrum disorders. Their results showed that there is an excess of de novo gene mutations associated with the two diseases.
Dr. Philip Awadalla
“In the process of confirming our findings, we were also able to provide one of the first direct estimates of the human mutation rate,” continues Dr. Awadalla. “The number of mutations per generation is extremely small but on the order of what was previously indirectly inferred for human-chimpanzee comparisons. We also discovered that mutations can be introduced when cell lines are produced, which creates false-positive results. This artefact can significantly bias results and therefore great care needs to taken when analyzing these samples.”
About de novo mutations:
Mutations are alterations of the cell’s DNA that can occur because of errors in the DNA replication, which happen prior to cell division. Once DNA is changed, this mutation is passed down to a next generation. A mutation that is newly formed and therefore not inherited from either parent is called a de novo mutation.
Material adapted from University of Montreal.
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