Developmental dynamics of the postsynaptic proteome to understand synaptic maturation and dysmaturation

The postsynaptic density (PSD) is a protein condensate composed of ∼1,000 proteins beneath the postsynaptic membrane of excitatory synapses. The number, shape, and plasticity of synapses are altered during development. However, the dynamics of synaptic protein composition across development have not been fully understood. Here we show alterations of PSD protein composition in mouse and primate brains during development. Proteins involved in synapse regulation are enriched in the differentially expressed (288 decreased and 267 increased) proteins on mouse PSD after a 2-week-old. We find that the changes in PSD protein abundance in mouse brains correlate with gene expression levels in postnatal mice and perinatal primates. This alteration of PSD composition is likely to be defective in the brains of mouse models or patients with autism spectrum disorder (ASD). Finally, we demonstrate that the brain of the common marmoset ( Callithrix jacchus ) changes PSD composition after the juvenile period. The alteration of PSD composition after 2-month-old is distinct from that observed in mice. Our results provide a comprehensive architecture of the remodeling of PSD composition across development, which may explain the molecular basics of synapse maturation and the pathology of psychiatric disorders, such as ASD. ### Competing Interest Statement The authors have declared no competing interest.