DEVELOPMENTAL-CHANGES REVEALED BY IMMUNOHISTOCHEMICAL MARKERS IN HUMAN CEREBRAL-CORTEX

The developing human cerebral cortex is distinguished by a particularl y wide subplate, a transient zone in which crucial cell-cell interacti ons occur. To further understand the role of the subplate in human bra in development, we have studied the immunohistochemical expression of certain neuronal (GAP-43, MAP-2, parvalbumin) and astroglial (vimentin , GFAP) markers in the developing visual cortex from gestational ages of 14 weeks to 9 months post-term. At 14-22 weeks, immunoreactivity to GAP-43, a protein involved in axonal outgrowth, was most prominent in the subplate and marginal zone neuropil and in the fibers of the radi ations running near the ventricular zone; at 22-42 weeks, GAP-43 immun oreactive fibers were observed in the maturing cortical plate. Immunor eactivity for the microtubule-associated protein MAP-2 was present in the differentiating cortical plate at 14 weeks, but at 22-42 weeks was most prominent in the somata and dendrites of differentiated neurons, particularly the Cajal-Retzius neurons of the marginal zone, in neuro ns of the subplate and in those forming cortical layer 5. Parvalbumin immunoreactivity did not appear until 26 weeks, when stained neurons w ere in a sparse band of cells in layer 6 and upper subplate. Vimentin and GFAP did not stain differentiated neuronal cells. Vimentin immunor eactivity appeared early in neuroepithelial and radial glial cells, de creasing after 35 weeks, with a concomitant increase in GFAP immunorea ctivity in radial glial and maturing astrocytic cells. Our results sho w that despite the greater complexity of the developing human neocorte x, molecular markers are expressed in spatial and temporal patterns si milar to those observed in non-human primates, carnivores and rodents. These protein markers should prove useful in developmental staging, a nd in providing a framework in which to examine congenital disorders o f cerebral development.