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    Autism- A Matter Of The Brain’s Connections
    By Jennifer Wong | June 1st 2010 03:21 PM | 4 comments | Print | E-mail | Track Comments
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    My column covers the latest primary research discoveries in the life-science discipline. Much of what is reported here are considered discoveries...

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    Mental retardation in autism is known to arise from a plethora of rare de novo mutations of key protein components in the synapse- the basic neuronal connection in the brain’s hardware. In a recent study published in Nature Genetics, Berkel and colleagues identified yet another de novo mutation associated with autism, which essentially consist of a series of loss of function mutations of the protein Shank2- a member of the postsynaptic scaffolding proteins located in the receiving end of synaptic connections known as the post-synaptic terminal (Berkel et al., 2010).

    Scaffolding proteins function to localize key synaptic proteins and signalling molecules to the postsynaptic terminals, and are required not only for effective neurotransmission, but also spontaneous strengthening and/or pruning of synaptic connections (known as synaptic plasticity) necessary for normal cognitive development in the brain. In autism, the displacement of these crucial synaptic proteins and signalling molecules results in profound synaptic defects, and thus contribute to the delayed cognitive development and mental retardation observed in autism patients (Betancur et al., 2009).

    In light of existing evidence that synaptic scaffolding proteins are mutated in cognitive disorders such as autism, the discovery of Shank2 mutations is just yet another mutation under the large list of de novo mutations associated with autism. However, unlike previous studies, Berkel and colleagues were first to use DNA microarray and sequencing technology to correlate the variations of Shank2 mutations with varying degrees or severity of mental retardation in autistic patients.

    The synapse is really a hub of proteins and signalling pathways for which scientists have very little understanding. The present study by Berkel provides the first molecular scalpel to take apart and understand the workings of the brain’s synaptic hardware. Moreover, Berkel’s approach enables one to explore the elusive synaptic mechanism underlying cognitive function, literally right down to the single nucleotide level. As autism is a multi-defective disorder in various cognitive functions including language, social skills and intelligence, Berkel’s novel molecular approach paves the way to understand how these distinct cognitive functions could be linked to the complex protein components in the synapse.

    References:

    Berkel, S. et al. (2010). Nature Genetics. 42, 489-491.
    Betancur, C. et al. (2009). Trends in Neuroscience. 32, 402-412.

    Comments

    Larry Arnold
    I doubt it, I suspect ulterior pharmaceutical motives behind the research, but then maybe my neurones cognitively dispose me towards such suspicion :)
    jenwong
    You're probably right. DNA sequence is likely not the answer to everything, although big shot molecular technology always sounds "sexy"  these days :). Not too sure about pharma motives though...you'll need to ask the authors.
    kmmuffy
    I think that we actually know a lot about the synapse, but thankfully not everything or I'd be out of a job.

    BTW, for anyone interested in learning more about the synapse I am helping to organize a summer symposium about the synapse that will have a live&interactive webcast so that anyone can join the symposium. 

    MiNDS Summer Symposium 2010, Big Questions in Neuroscience: The Synapse

    http://bit.ly/dnpW3S
    jenwong
    I'm a minimalist, so I tend to view the things in nature (including the synapses in our brain) to be infinitely complex.  I do realize from a neuroscientist's point of view that we know a lot about synapses, which is completely understandable given the decades of research that has gone into understanding how synapses actually work. But in my view, I think scientists have only scratched the surface of understanding synapses. Yes- scientists have uncovered a great deal of molecules in the synapse- and have come up with nice (sometimes animated) models that they could present in conferences. But whether these cute little models (based on studies from invertebrates and rodents) could represent the real thing is another story. That's why more research needs to be done. And as you say, this presents a great research niche for neuroscientists like you and I.