SAN FRANCISCO, Dec. 13 (UPI) -- Autism investigators are collecting clues about genes that may be responsible for inherited traits which by themselves do not cause the disorder but may be associated with it.

A number of scientific teams have set their sights on these so-called "endophenotypes" -- which can be behavioral or biological -- in the kin of autistic children.

Once they recognize the telling traits in families with autistic members, they can sift through their gene pool for any changes, or "mutations," that might be responsible for said characteristics, researchers explained.

The endophenotypes for autism reported thus far include: a large head size in the child's kindred, the parents' abnormal brain processing of faces and relatives' diminished ability to read another person's mental state, among others, scientists said.

"As we identify endophenotypes and their related genes, such as for language delay, we will be homing in on genes for autism," said Dr. Daniel Geschwind, associate professor of neurology, director of the Neurogenetics Program and the Center for Autism Research and Treatment at the University of California, Los Angeles, School of Medicine, and author of "Microarrays for the Neurosciences" (MIT Press, 2002).

"This is one of the most exciting developments in the field of autism genetics today," he added.

Geschwind said his recent research illustrates the importance of such traits as guideposts for zeroing in on autism-related regions in the vastly complex landscape of the human genome.

Steered by behavioral symptoms of the autistic children in their study, the scientists headed to the area, on chromosome 17, thought to harbor the corresponding gene for the social impairment.

Chromosomes are threadlike structure at the heart of each cell composed of heredity-harboring deoxyribonucleic acid, or DNA

Geschwind and his team duplicated their initial effort in a separate population. They said the achievement marked the first time such a finding was made and replicated, a key step in the scientific process of discovery.

In an earlier investigation, the scientists were surprised to find the gene they were targeting contributes to autism only in boys, perhaps explaining why males face a dramatically higher risk of developing the disorder than do females, they said.

The researchers' next task is to settle on the precise site within the chromosomal region they have linked to the genetic alteration responsible for the social deficit.

"The first step is finding the region of the genome, what we call the locus. It's like you're in Kansas, and you need to find the haystack where the needle is," Geschwind explained. "We've found the haystack -- the location of the gene -- but not yet the needle -- the gene itself."

Geschwind thinks the way to autism's genetic core, and perchance its cure, is through its individual parts.

"Autism is caused by many genes acting together, we think, causing different aspects of the disorder," he said.

"If we divide it up and look (separately) at the aspect related to language and other features that are easier to measure, such as head size or social or repetitive behavior, that will move us closer to finding the genes," he added.

"Once the gene is located, the next step is to understand how that gene affects brain function," he concluded. "Once the gene's function is understood, then scientists can measure the impact of various environmental agents on that function."

As with studies examining the diverse ways different types of mercury course through the body, the findings provide a critical piece of the autism puzzle, but not telling enough to solve the jigsaw.

(Note: In this multi-part installment, based on dozens of reports, conferences and interviews, Ped Med is keeping an eye on autism, taking a backward glance at its history and surrounding controversies, facing facts revealed by research and looking forward to treatment enhancements and expansions. Wasowicz is the author of the forthcoming book, "Suffer the Child: How the Healthcare System Is Failing Our Future," to be published by Capital Books.)

Next: Autism as a multi-faceted disorder

--

UPI Consumer Health welcomes comments on this column. E-mail: lwasowicz@upi.com