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Autism affects 1 in 59 children. Researchers link it to both genetics and environmental factors. However there was no clear visibility as to where and when the mutations occur. Nonetheless, one factor in particular has long intrigued scientists – DNA mutations originating from the father’s sperm.
A new study by Augustine Kong at deCODE Genetics in Iceland, points to father’s sperm as an important source of these mutations. In comparison to mothers, older fathers are responsible for nearly all of a child’s random genetic mutations. The study shows the father’s age at conception accounts for 97% of the new gene mutations in his offspring.
Autism Risk and DNA Changes
Studies show a co-relation between autism risk and changes in DNA. In fact, DNA changes occur either spontaneously in sperm as the germline cell develops, or in the embryo after fertilization. Scientists estimate that such mutations account for 10% – 30% of autism cases. It is important to note that the older a father is, the higher the chance his sperm will result in mutations. Thus age is a contributory factor to autism spectrum disorder.
According to statistics, with every decade of life, the number of gene mutations in sperm doubles.
Mosaicism and Autism
An anomaly takes place when a person has 2 or more genetically different sets of cells. As we know, each cell has 46 chromosomes grouped in 23 pairs. When cells divide, mistakes or genetic mutations can still happen, giving rise to an abnormality, mosaicism.
In a person with mosaicism, some cells have 46 chromosomes, whilst other cells have 47 chromosomes or even 45 chromosomes. This abnormality in the genetic make-up can cause health problems. For example, it can be the cause behind certain cancers, epilepsy, growth disorders and conditions such as Down Syndrome.
Researchers led by a team at the University of California, San Diego (UCSD) set out to determine if they could match specific disease-causing genetic mutations in the DNA of children with autism to the same mutations in their father’s sperm.
The UCSD research team analyzed DNA from eight fathers, parents of autistic spectrum disorder children. In the study, they looked for the mosaicism phenomenon among the children. The genetic mutation changes in the children with autism were later matched to those found in their fathers’ sperms. The findings confirmed that the mutations did play a role in contributing to autism in the children. As the genetic mutations occur only in the sperm, it did not affect the father but show up in the child instead.
Furthermore, the team of researchers determined that disease-causing mutations were present in up to 15 percent of the fathers’ sperm cells, information that could not be determined through other means, such as blood samples. This in return could potentially lead to a test that can help fathers of children with autism to know how likely they are to have another child affected by the condition.
Genetic Test Risk on Autism – A Possibility
Research is ongoing if the mutation test could be a means to predict more accurately the risk of autism recurrence in future children. This test would also be useful to help couples that haven’t had children yet, to assess their risk in families.
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by Yashwini Ravindranath
Born & raised in Malaysia, Yashwini earned her M.D. studying in Moscow's Russian National Research Medical University. With an affiliation towards research, all things coffee and the startup ecosystem, she now contributes articles to GetDocSays View all articles by Yashwini Ravindranath.
