Essential for the proper localization of brevican (BCAN), mainly as a perineuronal nets (PNNs)-type deposition in the brainstem and cerebellum thereby playing a key role in the formation and structural organization of PNNs (By similarity). Contributes to the formation and transmission of inhibitory GABAergic synapses between Purkinje cells and deep cerebellar nuclei neurons (By similarity). . This is the function of HAPLN4 (hyaluronan and proteoglycan link protein 4, Ensembl gene identifier ENSG00000187664).