Involved in neuronal migration during development of the cerebral neocortex. May function in a cell autonomous and a non-cell autonomous manner and play a role in appropriate adhesion between migrating neurons and radial glial fibers. May also regulate growth and differentiation of dendrites (By similarity). Homodimer. Interacts with AP2M1; required for clathrin-mediated endocytosis (By similarity). Expressed in the frontal neocortex, glanglionic eminence, mesencephalon and cerebellum at 13.5 dpc. More prominently expressed in the developing cerebral neocortex and mesencephalon at 15.5 dpc and in the cortical plate and in the remnant of the ventricular zone at 18.5 dpc. N-glycosylated. O-glycosylated. Shedding of the extracellular domain and intramembrane cleavage produce several proteolytic products. The intramembrane cleavage releases a soluble cytoplasmic polypeptide that translocates to the nucleolus (By similarity). Extended N-terminus.