PROJECT SUMMARY Autism spectrum disorder (ASD) accounts for a large individual, familial, and societal burden. The lives of patients and their families are also significantly impacted, as the biopsychosocial effects generally impair functioning in multiple settings. Currently, treatment approaches focus on behavioral therapy since developing biological treatments has been challenging due to the variability in causative mechanisms and lack of reliable biomarkers. To address this challenge, it is crucial to uncover common pathogenic mechanisms underlying multiple ASD risk factors, as such understanding could eventually help develop therapeutic strategies for larger groups of patients. One candidate pathway that has been studied in a subset of ASD patients is the PI3K-AKT- mTOR pathway. Evidence suggests that this pathway can become dysregulated in response to both genetic and environmental influences, though the mechanistic link to ASD remains unclear. This proposal seeks to examine one environmental (exposure to maternal inflammation in utero) and one genetic (heterozygous mutations in PTEN) regulator of mTOR and probe neurobiological phenomena using state-of-the-art techniques. Specifically, the persistence and reversibility of abnormal repetitive behavior in adult mice exposed to maternal inflammation in utero will be assessed in the MIR mouse model developed in the Kornblum Lab, using single-cell informatics approaches to determine how mTOR acutely regulates neuronal activity and behavior. Further, possible developmental links to ASD will be studied using ASD patient-derived cortical organoids along with genome engineering, structural assays, and single-cell informatics to identify the cellular and molecular mediators of mTOR-related abnormal developmental phenotypes. These findings will yield insight into the mechanisms through which aberrant mTOR signaling can alter both adult behavior and early neurodevelopment. The proposal also aims to determine whether the two factors interact by examining patient- derived organoids exposed to media containing inflammatory mediators. This potential gene-environment interaction converging on mTOR signaling could reveal significant mechanistic overlap that may guide future studies seeking to understand human ASD biology in the contexts of environmental and genetic perturbations related to the mTOR pathway. These studies will take place at the University of California, Los Angeles. Relevant research centers include the Intellectual and Developmental Disabilities Research Center (IDDRC), the Jonsson Comprehensive Cancer Center (JCCC), and the Eli & Edythe Broad Center of Regenerative Medicine and Stem Cell Research (BSCRC). The applicant is enrolled in the UCLA Medical Scientist Training Program (MSTP) and will proceed to finish clinical training after defending his PhD thesis.