Molecular and cellular mechanisms of developmental synapse elimination inthe cerebellum: Involvement of autism spectrum disorder-related genes

neural circuits are initially created with excessive synapse formation untilaround birth and undergo massive reorganization until they mature. During postnatal develop-ment, necessary synapses strengthen and remain, whereas unnecessary ones are weakened andeventually eliminated. These events, collectively called "synapse elimination" or "synapse prun-ing", are thought to be fundamental for creating functionally mature neural circuits in adultanimals. In the cerebellum of neonatal rodents, Purkinje cells (PCs) receive synaptic inputsfrom multiple climbing fibers (CFs). Then, inputs from a single CF are strengthened and thosefrom the other CFs are eliminated, and most PCs become innervated by single CFs by the endof the third postnatal week. These events are regarded as a representative model of synapseelimination. This review examines the molecular and cellular mechanisms of CF synapse elim-ination in the developing cerebellum and argues how autism spectrum disorder (ASD)-relatedgenes are involved in CF synapse development. We introduce recent studies to update our knowl-edge, incorporate new data into the known scheme, and discuss the remaining issues and futuredirections