Autism spectrum disorder (ASD) is a neurodevelopmental disease that is frequently characterized by movement disorders, including stereotyped repetitive hand movements, difficulties with gait, balance, and coordination, and delays in motor learning. Although all motor behaviors rely on the orderly recruitment of neurons in the brainstem and spinal cord, no studies have investigated the potential contributions of spinal motor circuit defects to ASD motor phenotypes. In this pilot project, Jeremy Dasen and colleagues at New York University propose to use cell type-restricted genetic manipulations and transcriptomic, circuit, and behavioral assays to explore the role of ASD risk genes in the development and function of spinal motor circuits. Their pilot study will focus on two genes that cause ASD phenotypes or ASD-related motor symptoms – Chd8 and Mecp2. Both genes encode nuclear proteins essential for the regulation of gene expression and are abundantly expressed in developing spinal neurons. In Aim 1, the team will assess the function of Chd8 and Mecp2 in establishing the transcriptional signatures of spinal neuron classes during murine embryonic development, postnatal stages, and in the mature nervous system. Examination of changes in gene expression and genomic accessibility will be explored using RNAseq, ATACseq, and 10X Multi-omics. In parallel, Aim 2 will investigate the behavioral consequences and changes in the synaptic inputs to motor neurons after deletion of ASD-associated genes. A battery of motor behavioral tests will be performed on early postnatal (e.g. ambulation, surface righting, negative geotaxis, limb suspension, cliff aversion) and in adult animals (e.g. rotarod, grip strength, beam crossing). Quantitative analyses of limb muscle strength during locomotion will also be examined by electromyography (EMG). Circuit-level changes will be investigated by examining the distribution and number of premotor synaptic inputs onto spinal MNs. Collectively, this pilot study seeks to provide foundational data to examine the function of ASD-risk genes in the development and function of spinal motor circuits.