Saturday, December 11, 2010

Autism Genetics: Eschew Nihilism

A recent article in Brain Research by C. Betancur, a distinguished French geneticist, points out that many genes have been associated with autism in some individuals.  The title of the article says it all, “Etiological heterogeneity in autism spectrum disorders: More than 100 genetic and genomic disorders and still counting.”   Such an assertion is dispiriting, and smacks of nihilism to non-specialists who have been hoping geneticists would come up with one or a few genes that could be targeted for treatment and ultimately, prevention of some or most forms of autism.
The article’s title is, perhaps inadvertently, misleading. Dr. Betancur may be right, that in some cases it will be necessary to identify specific medication treatments that only work with a single gene defect that may only account for a fraction of autism cases, but that is not the only option. The article might be taken to imply that because different genes are involved means there are few common pathways by which most of those genes produce their results.  That is likely false.  It is far more likely that multiple genes can produce similar physiological, chemical and behavioral outcomes by slightly different mechanisms.
Case in point.  Approximately three years ago a group of scientists and clinicians at Harvard University headed by Christopher Walsh, Eric Morrow and colleagues, and several sites in the Middle East identified autism within families where the two parents shared a common ancestor, such as a great grandfather.  That greatly increases the risk of genetic disorders. By studying those autism related genes they found several, some located on different chromosomes, but they all contributed to the same process, the formation of new brain connections during learning, called synaptogenesis.  Synapse formation occurs in two steps that involve specialized cell adhesion molecules. This implies that it may be possible to overcome physiological and behavioral outcomes in more than one way.  For example, we know that intensive early behavioral treatment markedly reduces or reverses symptoms of autism in over half of treated children. The experience provided must be able to reduce the defect in synapse formation.  But perhaps there are other ways, for example, treating with medications that promote synapse formation during certain developmental periods.  Or perhaps the two approaches can be combined, as is being done by Dr. Diane Chugani at Wayne State University.
The long and short of it is, don’t despair. The “100 and still counting” in the title is designed to promote funding for genetics research, not help families understand the cause of their child’s autism spectrum disorder. 

Betancur C. Brain Res. 2010 Nov 30. [Epub ahead of print]
Morrow, EM et. al. Science 11 July 2008:
Vol. 321. no. 5886, pp. 218 - 223

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