Monday, February 19, 2007

Neurexin: one of 6 autism genes?

The Autism Genome project has released one gene candidate involved in "autism" on chromosome 2, they suspect they'll find at least five more including one on chromosome 11.
Scientific American: Largest Ever Autism Study Identifies Two Genetic Culprits

The largest genome scan ever conducted to get to the bottom of autism has pinpointed two locations in the human genetic makeup that may trigger the mysterious mental condition. The Autism Genome Project, a collaboration of 120 scientists representing 19 countries and 50 institutions, compared the genomes of 1,168 families with at least two autism sufferers in them to try to track down the regions. The consortium reports its findings in this week's issue of Nature Genetics.

... In the two-fold analysis, the researchers implicated the gene neurexin 1, located on chromosome 2, as well as a swath of sequence on chromosome 11.

Neurexin 1 is part of a three-member family of genes coding for proteins involved in communication between neurons. It is associated with glutamate, the neurotransmitter known to elevate neuronal activity and play a role in early wiring the brain. Glutamate g has been implicated in other syndromes involving mental retardation of which autism is often a symptom, such as Fragile X and tuberous sclerosis. Neurexin 1 is specifically believed to be involved in building glutamate synapses, the links through which glutamate neurons send and receive electrical signals.

... "As for the chromosome 11 location, we think there is another susceptibility gene there and we are actively pursuing it. We are in the neighborhood and have a plan to find it." The section of chromosome 11 identified in the study has been linked to proteins that ferry glutamate across synapses.

... Among the variations found in the Autism Genome Project subjects was the deletion of the neurexin gene. Much of the autism research community believes there may be roughly six major genes involved in autism, and maybe 30 others that may confer some risk. A combination of mutations in any of these genes could contribute to the likelihood of being born with autism.

As we identify the genes we'll be able to divide autism into subtypes based on gene mutations and combinations of mutations and adaptations. That will help with developing prognostic measures and subtype specific medications and interventions. We'll be able to detect at risk persons earlier, and see if there are interventions that will mitigate disability. One day, perhaps, we may even be able to identify medications and therapies that might facilitate healing of the injured brain -- though that is likely at least 10 years away.

I would not be surprised to learn that there are adaptive advantages to some of these mutations in some persons ...

Update 2/20/07: Thinking it over, it's probably worth pointing out that the major implications of identifying these genes will be eugenic. A significant portion of people carrying the autism-associated variants may opt for sperm egg/selection, selective abortion, etc. I wonder if Isaac Newton would have been born under these circumstances ...

1 comment:

Anonymous said...

yes..on one hand,it is so exciting to see them narrow in on something major,perhaps. but it also makes my throat tight and my heart heavy when i think of beautiful babies with autism being murdered before ever having a chance..a chance they would have more than ever with the ability to find out about it from the start and thus have the most early intervention possible.