May function as a growth and differentiation factor involved in neuritogenesis and more particularly in neurite extension. Binds TNC and TNR. The 80 kDa form but not the 140 kDa form can bind TNC and TNR when expressed at the cell surface. Expressed in astroglial and neuronal surfaces in different parts of the embryonic brain. Expressed in adult brain and retina (at protein level). The 80 kDa and 200 kDa forms were detected only during embryonic development. The 80 kDa form reaches a maximum of expression at E14/E15 and then decreases gradually. The 140 kDa form is already detected at E7. The 130 and 140 kDa forms reach their maximal expression at E20 (at protein level). Different forms exist: the 140 kDa form (also reported as 130 kDa), which probably consists of the entire protein, and the 38 and 80 kDa forms, which are probably cleaved in their N-terminus. Increase in synaptic activity, results in shedding of the extracellular domain and expression at the cell surface of a 38 kDa form. A form of 200 kDa has also been reported, which is probably hyperglycosylated. N-glycosylated. O-glycosylated; contains chondroitin sulfate glycans. Part-time proteoglycan, the 200 kDa form is the only one containing chondroitin sulfate glycans.