The causes of autism spectrum disorder or ASD are not fully understood; researchers believe both genetics and environment play a role.
In some cases, the disorder is linked to de novo mutations that appear only in the child and are not inherited from either parent’s DNA.
In a new study, researchers report a method to measure disease-causing mutations found only in the sperm of the father, providing a more accurate assessment of ASD risk in future children.
The research was led by the University of California San Diego School of Medicine.
Autism afflicts 1 in 59 children and we know that a significant portion is caused by these de novo DNA mutations, yet scientists are still blind to when and where these mutations will occur.
Recent studies suggest gene-damaging de novo mutations are involved in at least 10 to 30 percent of ASD cases, with the number of mutations rising with the father’s age at the time of conception.
De novo mutations occur spontaneously in parents’ sperm or eggs or during fertilization. The mutation is then present in each cell as the fertilized egg divides.
Studies now point to male sperm as a particularly important source of these mutations, with the chance of the mutation recurring within the same family generally estimated at 1 to 3 percent.
In the study, the team analyzed the sperm of eight fathers who were already parents of children with ASD.
The goal was to look for the presence of multiple, genetically different material in cells in the same person, a phenomenon called mosaicism.
Using deep whole-genome sequencing, they found variants in offspring that were matched only in the fathers’ sperm.
The researchers determined that disease-causing mutations were present in up to 15% of the fathers’ sperm cells, information that could not be determined through other means, such as blood samples.
If developed into a clinical test, the researchers say fathers could have their sperm studied to determine their precise risk of recurrence in future children.
The methods might also be applied to men that haven’t had children yet, but who want to know the risk of having a child with a disease.
The author of the study is Jonathan Sebat, Ph.D., a professor and chief of the Beyster Center for Molecular Genomics of Neuropsychiatric Diseases.
The study is published in Nature Medicine.
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