Autism is a complex disorder that is believed to be caused by a combination of genetic and environmental factors. Recent research has shed light on how unaffected parents can transmit autism to their children, and how genetic testing can help expectant parents determine their risk of having a child with autism. A team of researchers recently conducted a study to investigate the role of rare variants in the transmission of autism from parents to children. They found that children with autism inherit about twice as many rare variants from their parents than would be expected by chance.
On the contrary, rare variants inherited from mothers make a minimal contribution to autism, they found. The team found that mothers transmitted only half of their structural variants to their autistic children, a frequency that would be expected only by chance, suggesting that variants inherited from mothers are not associated with autism. But, surprisingly, parents transmitted substantially more than 50% of its variants. This suggests that autistic children may have inherited risk variants in regulatory regions from their parents, but not from their mothers. In general, autism cannot be attributed to a Mendelian mutation (a single gene) or to single-chromosome abnormalities, such as fragile X syndrome or 22q13 deletion syndrome.
Studies have linked the risk of autism to de novo mutations or DNA changes that arise spontaneously in sperm as the germline cell or embryo develops after fertilization. The authors of the study concluded that maternal effects do not create a risk of autism, however researchers studying these effects say that this is a complicated issue. If a country tends to diagnose autism less frequently, perhaps because of cultural differences or how and when providers evaluate autism, heritability is likely to show as a lower number as well. Over time, genetic testing could also tell expectant parents if they are at increased risk of having a child with autism. Currently, about 165 genetic mutations have been linked to autism, and an in-depth analysis of a potential father's sperm for some of these aberrations could let you know if you are at greater or lower risk of fathering a child who may be affected by autism. Another 2004 study examined whether symptoms characteristic of autism (altered social interaction, communication deficits, and repetitive behaviors) show less variation in symptoms among monozygotic twins compared to siblings in a sample of 16 families.
This study involved 10 DZ twins and 11 MZ twins in which at least one twin from each pair showed childhood autism. In conclusion, it is clear that autism is caused by a combination of genetic and environmental factors. While it is true that fathers can transmit rare variants associated with autism to their children, it is important to note that this does not necessarily mean that they are solely responsible for the disorder. It is important for expectant parents to understand the risks associated with having a child with autism and to seek out genetic testing if they feel it is necessary.
