"Spontaneous" Mutations of Genes Linked to Autism

Autism has many causes. According to a recent study, however, one of the most common causes of autism, usually begins before birth through "spontaneous" mutations.

Dr. Jonathan Sebat , a genetist at the Cold Spring Harbor Lab in New York, has recently performed groundbreaking research that could unlock some of the mysteries of autism. Sebat studied the genes of 264 families. Some of the families in this group had a member with autism, some of the families did not have a member with autism. By comparing the genes of the parents to the children, Sebat was able to identify mutations in the children's genes. He found that children with autism were much more likely to have "spontaneous" mutations of their genes than those who did not have autism. Some genes present on DNA replicate themselves so that there is a copy of the original gene. Sebat found that in many of the autistic children, these genes were missing their copy.

As an example, Dr. Sebat explained that one of the children that he studied had a duplicate missing of the gene for oxytocin. Oxytocin is a hormone that, among other things, is linked to human bonding and creation of social ties. Sebat suggests that by missing this duplicate, less oxytocin may be secreted by the brain, thus creating the "distant" behavior that so many of children with autism exhibit. Many other children in the study were missing similar duplicates of genes.

Doctors have previously determined that there may be as many as 30 genes that are responsible for inherited autism. However, with the "spontaneous" mutation cause of autism, Sebat has stated that there are over 100 genes that could cause a problem. In an interview Sebat states, "There may in fact be many genes -- I would speculate 100 or more -- that play some role in cognitive development, and when they are altered, could cause autism." Most of these alterations in the genetic code occur preconception or in the embryonic stages of development.

This study suggests that exposures to environmental factors and vaccines after birth are most likely not a major cause of autism. The study does suggest, however, that environmental factors that could cause mutations of the sperm and egg, need a closer look.

Ezra Susser, an epidemiologist at the Mailman School of Public Health at Columbia University, has determined last year, that older fathers are more likely to have autistic children due to the higher likelihood of mutations in the sperm. A child born to a father over the age of 40 is 5.75 times more likely to have/develop autism. He says that Sebat's work suggests that scientists also need to determine if chemical exposure in the parents can also trigger these "spontaneous" mutations in the egg, sperm, or embryo.

Sebat says that much more research is needed into these "spontaneous" mutations to determine a cause. He states, however, that there is a practical application for his study. Parents that have one autistic child can perform genetic testing on the child to determine if there are "spontaneous" mutations of the genes. Autism caused by "spontaneous" mutations is less likely to reoccur in future children than inherited autism.