More on CNTNAP2, an Autism Susceptibility Gene, and Parent of Origin Bias
January 12, 2008 by Kristina Chew, PhD
Filed under Classics, Genetics, History, Neuroscience
CNTNAP2 (contactin-associated proteinlike 2) is a gene that indicates susceptibility for autism, as noted in a new study by Alarcón et al., in the January 10th American Journal of Human Genetics. Another article in the same journal by Aravinda Chakravarti et al. of the Johns Hopkins University School of Medicine has found that a variation in CNTNAP2 raises the risk of having autism, especially when the gene with that variation is inherited from the mother. CNTNAP2 is a member of the neurexin superfamily and is, as noted in the January 11th Science Daily, “makes a protein that enables brain cells to communicate with each other through chemical signals and appears to play a role in brain cell development.”
The researches studied two groups of first participants. The first was comprised of 145 children with autism and their parents, from families that had two or more children with autism. The researchers found that a chromosome, 7q35, seemed to be linked to autism and, on looking further at the chromosome, identified CNTNAP2 and a variant relevant to autism: “Where a single segment of the genetic code could contain either the chemical base adenine or thymine, children with autism tended to have inherited the thymine variant.” On studying the second group—-containing 1,295 children with autism and their parents—-the researchers found that autistic children had “higher rates of the thymine variant in the CNTNAP2 gene than would be expected to occur by chance.” When the data from both studies were combined, it was found that autistic children were 20 percent more likely to have inherited the thymine variant from their mothers than from their fathers.
Chakravarti notes that this is a “‘common variant’” and that the “parent of origin bias” is “‘intriguing, but needs to replicated.’”
The question has been raised about why so much research about autism is about genetics; a January 11th post at Gene Expression explains why genes matter in history (the post is not about neurological disorders but about the Etruscans—-I am getting ready to teach Roman history this semester and this discussion adds some new dimensions to my own studies). The subject of genetic testing has also come up in regard to studies of autism genetics: There is currently no prenatal genetic test for autism, but it does not seem unlikely that some test might result from research into the genetics of autism. The January 10th Eye on DNA comments thoughtfully on an article in the New England Journal of Medicine that gives direct to consumer genome scans a thumbs down (or, to end on a Classical note, pollice verso).
Jeff Stimpson
Jill Cornfield
Elaine Warburton over at Genetics and Health posts more information about CNTNAP2 and includes an informative graphic.
I do think genetic studies are good. Probably because we had our daughter genetically tested and found some answers. I can understand the fears involved with further study too.
“Parent of origin” makes me both curious and nervous. My child’s blindness is genetic with both parents as carriers of a recessive trait. So far, research indicates that his Aspergers may also be related. But both parents or one? I have a cousin with autism, too. It’s more likely my genes that made this happen.
So was ol’ Kanner right then? It’s all the mother’s fault!
(Sorry couldn’t resist :-P)
To Daisy:
It turns out that blindness itself makes a child predisposed to autism, so in this respect autism is definitely genetic. However, there is still sparse evidence that a gene specific to autism exists. In other words, autism seems to be secondary to blindness, Rett Syndrome and Fragile X syndrome which are all genetic; but so far autism itself hasn’t been pinpointed genetically.
You know, Freud thought that all mental illness involves some degree of endowment. It’s fine to look for predispositions, just so long as autistic children don’t get dehumanized by searches for mechanical malfunctions rather than emotional ones. Psychology is always involved in some way.
Here is a link to the research on blindness and autism:
http://www.ssc.education.ed.ac.uk/resources/vi&multi/hcass96.html
Larry
To feebee:
LOL! You know, Kanner never had the balls to come right out and say that. He saw what happened to Bettelheim for even suggesting it.