Although autism spectrum disorders (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 over express (to mimic gene duplications) or knock down (to mimic gene inactivations) mRNAs corresponding to 81 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 electro-physiological 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, or after in utero electroporation. 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. All results from this project will be posted on a dedicated public website, and all reagents generated will be made readily available to the scientific community. 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.
Autism spectrum disorders are known to be clinically and genetically heterogeneous, but it is unclear whether these two types of heterogeneity are related, and how specifically the various genetic changes affect brain function. This project will address these issues by studying the changes in neuron-to-neuron communication caused by the genes associated with autism.
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