A genetic cause for a rare form of epilepsy-associated autism has been identified by UC San Diego and Yale scientists.

Moreover, symptoms of the newly discovered form have been reversed in mouse models by altering diet. This gives rise to the possibility that similar treatment might help people, the researchers said.The study was published online Thursday in the journal Science.

Researchers led by Gaia Novarino and Joseph G. Gleeson of UCSD studied two families, one of Egyptian descent and another of Turkish origin. They examined the genome of patients and healthy relatives for exons, gene sequences that code for proteins. The researchers found that patients shared an exon mutation on a gene called BCKDK. The mutant gene is recessive, meaning that it must be inherited from both mother and father to manifest.

Moreover, the researchers found that the mutation caused patients to produce abnormally low levels of certain types of amino acids, the building blocks of proteins. They were able to boost levels of these amino acids to normal with a nutritional supplement from a health food store. Research is now ongoing as to whether this supplementation will reduce symptoms of epilepsy and autism in these patients.

Those who might be helped are only a small fraction of people with autism, Novarino said in an Tuesday interview. Those without the metabolic defect wouldn’t benefit from the supplementation.

The study illustrates how scientists have become more sophisticated in using knowledge of the human genome to crack the puzzle of previously intractable diseases.The genome is the complete set of hereditary information encoded in DNA.

Narrowing the search

The vast majority of DNA does not code for proteins, the body’s workhorse molecules. This “non-coding” DNA was ignored in the new method of DNA analysis, called “whole exome” sequencing, which looks only at the exons. An advantage of whole exome sequencing is that it focuses exclusively on proteins, which are altered or missing in genetic diseases.

Whole exome sequencing can find previously undiscovered genetic diseases, according to another study performed by some of the same UCSD researchers. They examined 118 patients diagnosed with neurological disorders who had no known genetic disease causes. In addition to the newly discovered genetic causes, in about 10 percent of cases the researchers even found a known disease-causing gene that had previously escaped detection.

That study was published in June in Science Translational Medicine, a journal devoted to getting research discoveries into the hands of doctors more quickly.

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SCI-TECH: Autism gene found by UCSD researchers

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