Project Summary/Abstract Autism Spectrum Disorders (ASDs) are associated with dysfunctional corticostriatal networks. Molecular control over development of these connections remains to be defined. Rare microdeletions in the gene encoding the transsynaptic adhesion protein cadherin-8 (Cdh8) are implicated in ASDs. Cdh8 is expressed in prefrontal cortex and striatum during early postnatal corticostriatal synaptogenesis. We hypothesize that deficits in Cdh8-dependent control of developing corticostriatal synaptic circuitry contributes to autism-related behaviors. To test this, we generated conditional Cdh8 knockout (cKO) mice where I will selectively delete Cdh8 from striatal and/or cortical neurons early in postnatal development. In Aim 1, the effects of Cdh8 ablation on neuronal connectivity and synaptic plasticity of pre-and post-synaptic corticostriatal neuronal populations will be studied by combining axonal tracing, whole-cell recording approaches and morphometric analyses. In Aim 2, young adult Cdh8 cKO and control mice will be tested on behavioral tasks that model deficits in cognitive flexibility, social contact and perseverative/obsessive behaviors observed in autism. We expect significant deficits in corticostriatal connectivity and synaptic function leading to impairments in striatally-based behaviors. Together, this project will reveal new details about normal corticostriatal development, as well as identify potential molecular mechanisms that could become targets for therapeutic treatment in ASDs.