The role of Cbln1 on Purkinje cell synapse formation.

•Cbln1 induces excitatory synapse formation between parallel fibers and Purkinje cells.•Cbln1 forms a tripartite protein complex with neurexin and delta 2 glutamate receptors.•Parallel fibers undergo dynamic structural changes during Cbln1-induced synaptogenesis.•Cbln1 down-regulates formation and function of inhibitory synapses on Purkinje cells.