A Radical Behaviorist

Observations and comments about autism, behavior, and learning.

CNVs: The True Cause of Autism?

It seems as if it really isn't the vaccines that cause autism.

A very important paper was published this week in Nature (Pinto et al., 2010; http://www.nature.com/nature/journal/vaop/ncurrent/full/nature09146.html).  In this paper it was reported that persons with an ASD diagnosis were found to "carry a higher global burden of ...CNVs..."  So what are those CNVs?  They must be some substance carried in vaccines!  Finally we found the environmental toxin that Big Pharma has used to cause the autism epidemic.  Well, not so much.  CNVs are copy number variants and this refers to pieces of DNA in which there are duplications or deletions of segments of a chromosome.  We typically have two copies of every gene sequence but sometimes there are more (or fewer). So duplication of a gene can be inherited and additional duplication can occur during the unzipping/rezipping of the DNA that occurs during replication.  Deletions and translocations of gene segments can occur as well.

CNVs specifically refer to when there is a difference in the number of gene sequences across persons/populations.  In this study, the investigators found that persons with a diagnosis of an ASD were more likely to have CNVs than the matched control group.  The study also looked at the genetic material of the parents of the persons with ASDs and found that some of the CNVs were inherited while some of them were novel events presumably occuring during replication.  The total number of CNVs identified was just under 450 with the type of CNV somewhat equally split across these mechanisms.  Though this number is quite large and continues to support the notion that the genetics of autism is quite complex, this study also sought to determine what each of these genes were involved in.

The functions of the identified genes when mapped out provided some interesting information.  First, a large number of the CNVs are known to be involved in central nervous system development.  Secondly, the CNVs were concentrated in areas thought to be involved in cellular development and cellular communication.  It is not much of a stretch to presume that problems such as these that occur during development could readily translate into the learning difficulties or atypical learning.

While one study, even though it included the genetic material from nearly 1,000 persons with ASDs, their families, and matched controls, in isolation is not that definitive on its own.  However, this is not the first study to implicate CNVs as being involved in the development of autism.  Sebat and colleagues (2007) reported in Science that there was a strong association between novel CNVs and autism.  Additionally, a number of the affected genes identified in the current study correspond with genes identified as suspect in many other investigation.  It's the convergence of findings that provides good confidence in the relevance of this study.

 

 

Bill Ahearn is Director of Research at the New England Center for Children, a private nonprofit educational facility for children with autism.

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