Dec 23, 2019
TIME – There’s no question that autism can be traced to a combination of genetic and environmental factors. One genetic contributor in particular has in recent years intrigued scientists studying autism: DNA mutations originating in fathers’ sperm.
Studies have linked autism risk to de novo mutations, or changes in DNA that arise spontaneously in sperm as the germline cell develops, or in the embryo after fertilization.
Researchers estimate that such mutations might be involved in anywhere from 10% to 30% of autism cases, and that the older a father is at the time of conception, the higher the chance his sperm will result in de novo mutations that can contribute to autism spectrum disorder. In fact, with every decade of life, the number of de novo mutations in sperm doubles.
In a new study published in Nature Medicine, 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 fathers’ sperm.
The team analyzed DNA from eight sets of fathers and children. In the children, they looked for a phenomenon called mosaicism, which are genetic differences even among cells from the same person.
Each time a cell divides, the process can generate mutations, or genetic mistakes—some can be harmful (for example, some can lead to cancer), but most are not because they occur outside of important genes in what are known as “DNA deserts.”
The researchers then matched these changes found in the children to those found in their fathers’ sperm. That confirmed that the de novo mutations were indeed playing some role in contributing to autism.