The Irish Times - Tuesday, February 21, 2012

DICK AHLSTROM

AUTISM: RESEARCHERS AROUND the world continue to struggle with the complexity of autism. They now believe that genetic factors and brain changes triggered by man-made chemicals in the environment are equally to blame for the development of autism in young children.

Efforts to track the causes of autism were discussed yesterday in a session at the American Association for the Advancement of Science’s annual meeting in Vancouver.

“Autism is a very complicated disorder,” said Prof Scott Selleck of Pennsylvania State University. “We have come to know it has many, many genetic contributors.”

A number of genetic alterations have emerged as important in autistic disorders but persistent chemicals in the environment including flame retardants and polychlorinated biphenyls were also important, he said. “The balance of genetic and environmental contributors is about equal. It is 50/50.”

The panel, which included Prof Janine LaSalle and Prof Isaac Pessah, both of the University of California Davis, was completely dismissive of the now discredited theory that autism in its various forms was caused by “refrigerator parents” or “refrigerator moms”, parents who interacted only minimally with their children.

The phraseology arose in the 1950s. “The idea was that autism was caused because parents were distant. That idea has done a lot of damage,” Prof Selleck said and he ruled it out as nonsense.

He described his own research, cataloguing the number of “copy number variations” in the genomes of those with autism. These were either copied additions to the genome or deletions left out of the genome.

Prof LaSalle described her work on how exposure to persistent chemicals such as flame retardants could cause long-lived changes in how collections of genes were expressed, for example the genes associated with building neurological networks. This was referred to as “epigenetics”, she said, and the complex system involved could be perturbed by low-level environmental chemicals.

She exposed mouse models to the flame retardant PBE-47 and polychlorinated biphenyl MECP-2 at minute levels that matched human exposures.

It affected both sociability of these mice and also their learning behaviour.

There were now upwards of 80,000 non-natural chemicals in the environment produced by industrial processes and other sources, said Prof Pessah. Few had been tested for their neurotoxicity despite human exposures to these substances.

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Genetics and man-made chemicals equally to blame, say researchers

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