Throughout development, the brain dynamically regulates the composition of its extracellular fluid compartments. Proteins secreted into these compartments, defined collectively as the brain secretome, have been shown to influence key neurodevelopmental processes from cell migration to synaptogenesis. Nonetheless, only a fraction of the brain secretome has been comprehensively characterized, leaving the developmental contribution of many disorder-associated secreted proteins unexplored. A growing body of literature highlights the dysregulation of extracellular fluids in the brain as a common feature of Autism Spectrum Disorder (ASD). In this study, our focus will be on a specific group of proteins previously linked to neurodevelopment through their involvement in ASD. Specifically, we aim to characterize the molecular and cellular processes regulated by the fraction of the brain secretome associated with ASD, termed the ASD secretome. Perturbations of human neurons with a comprehensive library of recombinant proteins will be examined via single nuclei RNA sequencing to identify the cellular processes modulated by the ASD secretome. By validating the insights obtained from this screen, we will discern the effects of these proteins on a wide array of neurodevelopmental processes, spanning from neurogenesis to synaptic function. Additionally, proximity labeling techniques, such as the TurboID system, will allow us to unravel the molecular mechanisms underlying the mode of action of these secreted proteins. Insights into extracellular molecular mechanisms governing neurodevelopmental processes will not only shed light on the developmental function of fluid compartments in the brain but also pave the way for targeted therapeutic interventions currently lacking for ASD.