ISOLATION AND CHARACTERIZATION OF A 230 KDA PROTEIN (P230) SPECIFICALLY EXPRESSED IN FETAL BRAINS - ITS INVOLVEMENT IN NEURITE OUTGROWTH FROM RAT CEREBRAL-CORTEX NEURONS GROWN ON MONOLAYER OF ASTROCYTES

By screening with monoclonal antibodies (mAbs) raised against growth c one membrane fraction from fetal porcine brains, we have identified a 230 kDa antigen, termed p230, Western blot analysis of extracts from v arious tissues demonstrated that p230 is specifically expressed in bra ins, in which its expression is temporally restricted; it was especial ly prominent in the embryonic and the early postnatal stage, and decre ased to subdetectable levels in the adult brain. Further characterizat ion of p230 revealed that it, is a peripherally-membrane associated, c ell surface protein produced by astrocytes, Neurite outgrowth of E18 r at cerebral cortex neurons cultured on a monolayer of astrocytes was s ignificantly reduced in the presence of anti-p230 polyclonal antibody, Partial amino acid sequences of p230 purified from fetal porcine brai ns were highly homologous to an extracellular matrix protein, tenascin -C. These lines of evidence suggest that p230, a tenascin-C-like molec ule present in fetal porcine brains, plays important roles during earl y brain development, particularly in growth cone guidance.