The first common variant associated with autism has been identified and validated, according to a new study scheduled to appear online today in Nature. The paper, one of several autism genetic studies published online this week, supports the idea that autism involves altered connections between neurons or brain cells."Environmental factors in the womb causing a pre-disposition caused by several distinct genes to be triggered". Now where have I heard that before? Oh yes, it's our current "best guess" as to what is causal for Transsexuality, and for that matter, why phocomelia is triggered by Thalidomide in some cases and not in others.
A team of researchers from across the US genotyped more than 10,000 individuals in an attempt to uncover genetic variants and copy number changes linked to autism and autism spectrum disorders. Their search turned up half a dozen common SNPs in a region on chromosome 5 between CDH9 and CDH10, cadherin genes coding for proteins that help glue cells together. One of these reached genome-wide significance and appears to account for roughly 15 percent of the population risk of autism.
An independent study led by University of Miami Institute for Human Genomics Director Margaret Pericak-Vance and published in the Annals of Human Genetics appears to confirm the connection between the CDH9/10 region and autism, suggesting neural cell adhesion plays a role in autism.
"Until now, no common genetic variant has been identified with such overwhelming evidence to support its role in autism spectrum disorders," Pericak-Vance said in a statement. "The identification of a common variant for autism is a monumental achievement. Researchers have been looking for clues about the genetic architecture of autism for decades."
"In most cases, it's likely that each gene contributes a small amount of risk, and interacts with other genes and environmental factors to trigger the onset of disease," Hakonarson said in a statement.
Meanwhile, in another autism genetics paper scheduled to appear in Molecular Psychiatry, a European research team did a high-density association analysis of regions on chromosomes 7 and 2 that were previously implicated in autism by the International Molecular Genetic Study of Autism Consortium in a few hundred families. That work suggests at least two genes on chromosome 7 — IMMP2L and DOCK4 — contribute to autism.
Androgen Receptor Repeat Length Polymorphism Associated with Male-to-Female Transsexualism by Hare at al Biological Psychiatry Volume 65, Issue 1, Pages 93-96 (1 January 2009)
A polymorphism of the CYP17 gene related to sex steroid metabolism is associated with female-to-male but not male-to-female transsexualism by Bentz et al Fertility and Sterility , Volume 90 , Issue 1 , Pages 56 - 59
Again, the correlation is subtle, only a 5 or 10% increase in chance. But in the same ballpark.
There is no "autism gene" or "transsexual gene" or "phocomelia gene". There are genes that increase the chances significantly, allowing anomalous environmental factors (such as administration of Thalidomide or DES) to trigger the syndrome. And sometimes, it just happens, with no obvious environmental stimulus. If I was doing the research, I'd start looking for anomalous foetal environmental factors in cases of autism too. I think we have here a "meta-pattern", a pattern that patterns of development of different congenital syndromes follow.