PTEN is a phosphatidylinositol phosphatase that antagonizes signaling downstream of growth factor receptors. Mutations in PTEN have repeatedly been identified in patients with autism spectrum disorder (ASD) and macrocephaly. Further, experimental deletion of Pten in the mouse brain causes macrocephaly and deficits in social behavior, suggesting a causative role in the development of ASD. In neurons, Pten knockout results in aberrant growth and increased excitatory synapse function. Thus, studying Pten fits with our long- term goal of understanding how synaptic connectivity and activity contribute to cognitive and emotional processes. My central hypothesis is that Pten dysfunction causes aberrant neuronal growth and excitability leading to altered synaptic circuit formation during development. Guided by this hypothesis, the specific aims of this proposal will strengthen our understanding of the molecular and neurophysiological basis of ASD. There is a lack of pharmacological therapies for ASDs because we are just beginning to identify the molecular mechanisms underlying these disorders. We have defined a set of robust and reproducible cellular phenotypes elicited by Pten knockout in developing neurons. Understanding the molecular mechanisms underlying cellular phenotypes could lead to new treatments for ASDs.
Our first aim will test the hypothesis that cellular phenotypes are caused by deregulation of translation and cytoskeletal organization to alter the developmental elaboration of neurons. Defining cell-autonomous changes in neuronal development is a first step into understanding the emergent impact on network formation and function.
Our second aim will test our central hypothesis by determining whether Pten knockout results in similar cellular phenotypes across neuronal types and contexts. Different genetic models of ASDs display disparate cellular changes. Some models display synaptic hyperconnectivity while others display hypoconnecectivity and there is variability in excitation/inhibition ratios. Activity-dependent sculpting of synaptic connectivity during development fundamentally shapes network activity allowing for appropriate responses to our environment. A common feature shared by models of ASD may be pathological activity-dependent sculpting of synaptic connectivity during development. For the third aim, we will test the hypothesis that Pten dysfunction alters the activity-dependent sculpting of neuronal connectivity during development. This proposal will use innovative genetic approaches to manipulate gene expression and control neuronal activity in vivo. We will test the consequences of these genetic manipulations through detailed neuronal morphological and electrophysiological analyses. The broad goal of this research is to define the molecular basis of how Pten dysfunction contributes to aberrant neuronal development and network function.
This research proposal is relevant to public health because it addresses the molecular and cellular mechanisms through which the ASD-associated gene Pten alters neuronal function. Thus it is directly relevant to the part of NIH's mission outlined in PA-13-216- Research on Autism Spectrum Disorders or PAR-14-309? Molecular and Cellular Substrates of Complex Brain Disorders.
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