Circulating neuronal proteins are elevated in severe autism and associated with patient-specific neuronal dysfunction and behavioral deficits.

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with a multifactorial etiology involving both genetic and environmental factors. Although previous studies have identified altered levels of circulating proteins in individuals with ASD, the functional significance of these peripheral biomarkers remains largely unclear. In this study, we recruited a well-characterized cohort of young Arab children with ASD (n = 100) and matched controls (n = 60), aged 2-4 years, in Qatar. We used a multimodal approach, integrating data from proteomics, transcriptomics, induced pluripotent stem cell (iPSC)-derived cortical neurons, cellular imaging, functional assays using microelectrode recordings, and behavioral assays in Drosophila models. High-throughput screening of plasma samples revealed considerable heterogeneity in circulating proteomic profiles across different Arab subpopulations; therefore, we focused our subsequent analyses on Qatari children. We identified elevated levels of several neuronal proteins in the peripheral circulation of individuals with severe, but not mild, ASD symptoms. Furthermore, we found that neurons derived from the severe ASD group showed increased MAP2