Doctor K: Three studies offer news on autism
DEAR DOCTOR K: I’ve heard that scientists have discovered genes that cause autism. Could this lead to a cure?
DEAR READER: Three studies were recently published in the scientific journal Nature. Cell samples from 549 families were included. In each family, one child was autistic, but the parents and siblings were not.
Each study determined the sequence of every gene in every individual. Think of a gene as a string of pearls. Each “pearl” is one of four different nucleic acids, which are the building blocks of genes. The sequence of those nucleic acids determines what the effect of the gene will be.
All three research groups found very strong evidence that the autistic children had suffered serious mutations, or alterations, in at least three specific genes. The studies also found strong evidence of a role for another group of genes.
The mutations were not found in the parents or nonautistic siblings. So the mutations must have occurred in the DNA of the egg or the sperm that created the child with autism.
The studies also indicated that mutations in the father’s genes (in the sperm) are more likely to lead to autism than mutations in the mother’s genes (in the egg). Furthermore, mutations in the father’s genes are more likely as the father gets older.
More important, virtually all of the genes that were mutated in the children with autism were genes that are important to brain development. So it made sense that mutations in these genes could lead to autism.
Like most diseases, autism is likely caused not just by genes but also by factors in the environment. Not every child in these studies with these gene mutations was autistic. It often takes environmental factors to reveal genetic vulnerability.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.