IMMUNOCYTOCHEMICAL LOCALIZATION OF GROWTH-ASSOCIATED PROTEIN GAP-43 IN EARLY HUMAN-DEVELOPMENT

Fibers labelled with antibody to the growth associated protein (GAP-43 ) were observed as early as 4 gestational weeks (g.w.) in the nervous system of human embryos. At 6 g.w, these fibers could be traced throug hout the brainstem and the diencephalon. None of the immunolabelled fi bers entered the telencephalic wall at that point, but 2 weeks later a t 8 g.w., GAP-43 positive fibers were observed bellow the newly formed cortical plate of the cerebral cortex. GAP-43 positive fiber bundles had the same distribution as those previously labeled with tyrosine hy droxylase antibodies at the same age. These results strongly suggest t hat this growth associated protein is localized in the early growing d opaminergic fibers.