Candidate tumor suppressor gene. May contribute to specialized endoplasmic reticulum functions in neurons. In cerebellar predominantly localized to the endoplasmic reticulum. Expressed exclusively in the brain, predominantly in neurons. Wide expression in the gray matter of the brain with high levels in the olfactory bulb, anterior olfactory nuclei, hippocampal formation and cerebellar cortex. Detected diffusely and weakly in the white matter, such as the corpus callosum and cerebellar medulla. In the cerebellar cortex, intensely expressed in Purkinje cells and granule cells. Detected also in interneurons in the molecular layer. Mice lacking Sez6, Sez6l1, Sez6l2 exhibit motor discordination, and PCs are ofen innervated by multiple climbing fibers with different neuronal origins in the cerebellum. Belongs to the SEZ6 family.