NIMH project "A systematic test of the relation of ASD heterogeneity to synaptic function"

This project represents a broad systematic attempt to address a major challenge and opportunity arising from recent studies on the human genetics of autism spectrum disorders (ASDs). Although ASDs are highly heritable, ASDs are heterogeneous, and no single genetic cause contributes to ASDs in a large proportion of patients. Instead, heterogeneous genetic changes, including many single gene mutations and copy-number variations (CNVs) are found in ASDs. Thus, a key question is whether different genetic changes contribute to ASDs via multiple, independent, pathogenic pathways, or whether the various genetic changes in ASDs converge onto a single pathogenic pathway.

Several independent mutations in genes encoding synaptic proteins, such as neurexin-1, neuroligins, and SHANK3, suggested that ASDs may generally involve an impairment of synaptic communication between neurons. However, most of the other genetic changes observed in ASDs have no known effect on synapses in fact, have no known effect on any brain function.

Thus, the major goal of the present proposal is to conduct a large scale, systematic analysis of the synaptic effects of genetic changes in ASDs. The approach will be to overexpress (to mimic gene duplications) or knock down (to mimic gene inactivations) mRNAs corresponding to nearly 100 ASD candidate genes, and to test the effect of these manipulations on synapses using standardized assays. Cell viability, neuronal development, synapse density and synapse function will be assessed in cultured mouse neurons using optical and electrophysiological assays that are well established in the PI's laboratories. Genes that were found to affect neuronal development, synapse formation, or synapse function in cultured neurons will be studied by the same manipulations in vivo after stereotaxic injection of lentiviruses into the mouse hippocampus. Changes in synapse function and plasticity will then be examined in acute slices from these mice using standard electrophysiological techniques well established in the PI's laboratories. The results of this project will provide a standardized reference point for the function of ASD candidate genes, and provide an initial test of the hypothesis that despite their clinical and genetic heterogenity, ASDs involve a common, if diverse, pathway acting on synaptic communication in the brain.

The project started in November, 2009. We will describe the results from the project, as they are being generated, in three continually updated tables. Table 1 provides a list of candidate genes and their prioritization; Table 2 provides a list of shRNA sequences and their measured effectiveness; and Table 3 provides a list of phenotyping results obtained with effective shRNAs. Table 3 will be launched in the second half of 2010 when the initial phenotyping results are obtained.

Principal investigators

Thomas C. Südhof,
Stanford University School of Medicine
Avram Goldstein Professor in the School of Medicine and Professor, by courtesy, of Neurological Sciences and Psychiatry and Behavioral Sciences
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Robert C. Malenka,
Stanford University School of Medicine
Nancy Friend Pritzker Professor in Psychiatry and Behavioral Sciences
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