AXONAL ORIGIN AND PURITY OF GROWTH CONES ISOLATED FROM FETAL-RAT BRAIN

The investigation of the molecular properties of nerve growth cones de pends to a significant degree on their isolation from fetal brain in t he form of 'growth cone particles' (GCPs). The availability of markers for developing axons and dendrites, as well as glial cells, has made it possible to characterize the GCP fraction in much greater detail th an before and to optimize its yield. Marker analyses show that a membe r of the N-CAM family (5B4-CAM), synaptophysin, and especially GAP-43 and non-phosphorylated tau, are enriched in the GCP fraction. In contr ast, MAP2 and, particularly, glial fibrillary acidic protein and vimen tin are fractionated away from GCPs, Furthermore, GCP yield can be dou bled relative to the original procedure, without compromising purity, by raising the sucrose concentration of the fractionation gradient's u ppermost layer. The results indicate that GCPs are highly purified gro wth cone fragments with very little glial contamination, and that they are primarily of axonal origin.