Genetic Mutations Linked to Autistic Spectrum Disorders

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Genetic Mutations Linked to Autistic Spectrum Disorders

By Rick Nauert PhD Senior News Editor

Reviewed by M. Grohol, Psy.D. on May 17, 2011

A new research study discovers several sporadic genetic mutations in children

with autistic spectrum disorder.

University of Washington researchers used new molecular biology techniques to

discover the mutations. The research is published online in the journal Nature

Genetics.

Dr, O'Roak and colleagues analyzed the genetic makeup of 20 individuals

with autism spectrum disorder and their parents.

Autism spectrum disorders encompass a range of social impairments in language,

communicating and interacting with others, repetitive behaviors, and engrossing

fascinations. The condition can be mildly to severely disabling.

The researchers found 21 newly occurring mutations, 11 of which altered

proteins. Proteins altered by genetic mutations may hold clues to the biological

pathways involved in the development of the disease. The abnormal proteins or

the pathways they affect could draw interest as targets in the design of

preventive or treatment drugs.

In four of the 20 families studied, O'Roak and colleagues identified disruptive

new mutations that are potentially causative for autism. In examining the

clinical data on the child in each of the four families, they learned that these

children were among the most severely affected of the study group, both in

intellectual disability and in their autistic features.

The findings suggest that these new sporadic disruptive genetic mutations could

play a significant factor in the underlying mechanisms and severity of autism in

perhaps 20 percent of the cases in which no larger family history of autism

exists.

In some cases, the combination of newly appearing mutations and those inherited

from the parents may worsen the severity of the disorder.

In this study, many of the discovered mutations were located in genome areas

that were highly conserved during evolution. These parts of the genome likely

play a fundamental role in the biology of many animals, including humans.

Mutations in these regions tend to have significant repercussions.

" Consistent with the complexity of autism and its symptoms, the new mutations

were identified in several different genes, " lead author O'Roak said.

Moreover, many of these mutated genes have already been associated with other

brain disorders, including epilepsy, schizophrenia and intellectual disability —

reflecting a surprising genetic overlap.

Still, the researchers say that are not sure what the genetic overlap means. It

could point to common underlying mechanisms in the development of these

neurological diseases, or different manifestations stemming from similar genetic

lesions.

Another view is that the mutations may stem from other factors, such as

environmental triggers or other genes in a person's make-up that influence how

and when genes operate, whether or not a disease will appear in a genetically

susceptible individual, and what type of disease it will be.

How and why sporadic mutations such as these originate is as yet unknown.

However researchers are uncovering clues about risk factors.

In six of the affected children in this study, the scientists were able to trace

the original genes that were later mutated in the child back to the father's

half the child's genome, and in one case to the mother's half. This findings

support population studies showing that autism is more common among children of

older parents, especially older fathers.

Researchers say the identification of mutations is a positive step toward

understanding autism and the interaction of genetic and environmental factors.

Source: University of Washington