Impaired Aggrephagy, Interrupted Vesicular Trafficking, and Cellular Stress, Lead to Protein Aggregation, and Synaptic Dysfunction in Cerebellum of Children and Adults with Idiopathic Autism

Autism spectrum disorder (ASD) is a debilitating neurodevelopmental disorder with genetic and environmental etiologies involving several brain areas exhibiting abnormalities of cognition and social behavior. Previous work showed involvement of synaptic abnormalities in dorsolateral prefrontal cortex [1]. We hypothesized whether similar synaptic proteins were involved in pathology of cerebellar vermis of children and adults with ASD. Subcellular fractions of synaptosomes from cerebellar vermal cortices of age-, brain area-, and postmortem-interval-matched samples from children and adults with idiopathic ASD vs. controls were subjected to HPLC-tandem mass spectrometry. Analysis of proteomic data in cerebellar vermis of children with ASD showed enrichment of significantly downregulated pathways and proteins (FDR-adjusted p < 0.05) involved in protein folding, Rho GTPase cycle, aggrephagy, macroautophagy, anterograde and retrograde transport, proteinopathy, protein stability, and cell response to stress. Enrichment of significantly upregulated pathways and proteins (FDR-adjusted p < 0.05) involved processes of glycolysis, gluconeogenesis, metabolism of amino acids, and degradation of lysine, fatty acids, valine, leucine, and isoleucine. Analysis of proteomic data in cerebellar vermis of adults with ASD showed enrichment of significantly downregulated pathways and proteins (FDR-adjusted p < 0.05) involved in aggrephagy, COPI-mediated anterograde transport and COPI-independent Golgi-to-ER retrograde transport, endocytosis, presynaptic, postsynaptic, and PSD related vesicle mediated activities, serotonin and dopamine neurotransmitter release, and neurodegeneration-related diseases. Enrichment of significantly upregulated pathways and proteins (FDR-adjusted p < 0.05) in adults with ASD included peptide cross-linking, amyloidosis, intermediate filament organization, citrullination, methylation, and proteolysis. Overall, the proteomic data support the concept that cerebellar abnormalities in synaptic structure and function begin during fetal cerebellar development [2], culminate in early childhood, and evolve into adulthood, consistent with pathologic involvement of genes subserving the cognitive domains in ASD.