2 TYPES OF BRAIN CHONDROITIN SULFATE PROTEOGLYCAN - THEIR DISTRIBUTION AND POSSIBLE FUNCTIONS IN THE RAT EMBRYO

The distribution of neurocan-like and 6B4 proteoglycan-like immunoreac tivities in the rat embryo was investigated from gestational days 10.5 -15.5 with monoclonal antibody 1G2 or 6B4 that immunoreacted with neur ocan and 6B4 proteoglycan, respectively. In the brain region, the lept omeningeal layer in the myelencephalon, metencephalon, diencephalon or telencephalon was first stained with monoclonal antibody 1G2 at embry onic day 12.5. In the spinal cord, monoclonal antibody 1G2 stained the regions corresponding to the boundary caps (designated the boundary c aps) after embryonic day 11.5 and the roof plate after embryonic day 1 2.5. The intensity of staining in the boundary caps reached a maximum at embryonic day 13.5, at around the time when the axons from the dors al root ganglia reach this region. However, the points of contact of t he axons with the boundary caps were hardly stained. By contrast, the roof plate was most strongly and widely stained at embryonic day 14.5, at around the time when the axons enter the spinal cord. Western blot ting of preparations from the spinal cord that included the boundary c aps revealed the presence of neurocan in this region. Thus, it is like ly that neurocan serves as a barrier molecule to regulate the directio n of axonal growth from the dorsal root ganglia. By contrast, in addit ion to staining of the future brain and spinal cord, monoclonal antibo dy 6B4 stained the trigeminal and sympathetic ganglia in the rat embry o on and after embryonic day 12.5, as well as the vestibular, facial a nd dorsal root ganglia after embryonic day 12.5. In studies in tissue culture, monoclonal antibody 6B4 prevented the inhibitory effects of 6 B4 proteoglycan on the proliferation of PC12D cells. No immunostaining with monoclonal antibody 6B4 was observed in cells that had incorpora ted bromodeoxyuridine in vivo. Possible functions of 6B4 proteoglycan in the rat embryo are discussed. (C) 1998 Elsevier Science Ireland Ltd . All rights reserved.