THE CNS-SPECIFIC HYALURONAN-BINDING PROTEIN BEHAB IS EXPRESSED IN VENTRICULAR ZONES COINCIDENT WITH GLIOGENESIS

Hyaluronan (HA) is a ubiquitous component of extracellular matrices, a nd in several systems it plays a central role in regulating cellular p roliferation and differentiation. Cell, or tissue, -specific functions of HA are likely to be mediated by cell, or tissue,-specific HA-bindi ng proteins. We previously reported the cloning of BEHAB, a CNS-specif ic, secreted, hyaluronan-binding protein from rat and cat (Jaworski et al., 1994). In view of the potential role of HA in neural differentia tion, we examined the expression ol BEHAB during late embryonic and ea rly postnatal development of the rat. BEHAB is expressed at very high levels in ventricular zones throughout the neuraxis. Expression is fir st detected at embryonic day 15 (E15) in the spinal cord, and is detec ted at progressively more rostral levels at later ages. BEHAB expressi on, like other features of neural development, follows both caudal-to- rostral and ventral-to-dorsal gradients. The timing of BEHAB expressio n parallels the timing of the generation of glial cells. In all areas of the CNS examined, BEHAB expression begins after the peak of neuroge nesis and coincident with gliogenesis. The regulation of proliferation and differentiation by HA in other tissues, together with the express ion of BEHAB in zones of mitotic activity coincident with the generati on of glia, suggests that the extracellular matrix protein encoded by BEHAB could play a role in the generation or differentiation of CNS gl ia.