Monday, May 16, 2011

Progress and Challenges in the Genetics of Autism Spectrum

Disclaimer: Much of this Session went over my head, and I hope my notes make sense. 

Brett Abrahams, PhD  ( )

Genome - A big collection of 4 letters (AGCT) organized in chromosomes. 
-Sequencing genomes is a little bit like reading and recording 1500 times over. 
Genes- The portion of DNA that encodes proteins to make the cell work.
Allele-Different types of genes (ie., one letter difference).
-A single base pair change can have an effect on brain outcome.

What is being discovered about the genetics of autism, is there is a "Snowflake Hypothesis" - Every individual with autism is entirely unique.

-Common Alleles (polymorphism)
-Rare alleles (mutations)

-There are many kinds of autism genes, but most/many of these genes very subtly increase risk.  50% of us carry a particular gene.
-It takes many things to combine in a particular way that comprise the individuals with autism.
-Some variants within a specific gene can cause autism, but others do not cause disease but subtly affect aspects of language.
-Increased local connectivity.  Decreased long-term connectivity.

There are research banks to study blood of families affected by autism:

Genetics-How They Research

The variant that was studied by this researcher with mice was CNTNAP2 which is a neurexin homolog.  There were two groups of mice studied, the affected mice,"knockout mice" and "typical mice." 
-The knockout mice had restricted interest, (ie., increased grooming), suggestion of reduced flexibility, increased hyperactivity.  Some of these mice showed epilepsy as well.  Human disease was closely replicated by the mice.  Interestingly, risperidone was used to normalize the mice behavior, much in the same way it is used in many people with autism to normalize behavior.

Conclusion:  ASDs are common, but show variability.  There is not one single genetic variant that causes autism, but innumerable combinations of different genetic variants.

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