Acts as a synaptic organizer in specific subsets of neurons in the brain (By similarity). Essential for the formation and maintenance of inhibitory GABAergic synapses (By similarity). Promotes the development of dendrite-targeting inhibitory GABAergic synapses made by somatostatin-positive interneurons (By similarity). May contribute to the function of ventral medial habenula region of the brain implicated in the regulation of anxiety-related behaviors (By similarity). May play a role in CBLN3 export from the endoplasmic reticulum and secretion (By similarity). . This is the function of ENSG00000054803 (CBLN4, cerebellin 4 precursor).