Dynamics of Expression of the Neuronal Markers MAP2 and N200 in Human Brain Tissue during Early Gestation

The article presents the results of investigation of the cerebral wall layer cytoarchitecture, overall cell density, and expression of neuronal markers N200 and MAP2 in human fetuses (n = 20) at early gestational stages (8-11 completed weeks). At 8 week of embryogenesis, the telencephalic wall consisted of the ventricular, intermediate, and marginal zones. By week 10, the subventricular zone, subplate, and cortical plate had formed; however, no distinct cortical layering was observed at this stage. The developing neural tissue demonstrated wave-like changes in cell density. Active proliferation, reflected by the highest density of DAPI-positive nuclei, was recorded at week 8, followed by regression with a decline in cell numbers by week 9 and a partial recovery of the cell pool by weeks 10-11. A similar trend was observed for the relative proportion of N200-positive cells, a marker of developing corticofugal neurons. The proportion of N200-positive cells was highest at 8 weeks of gestation, decreased significantly by week 10, and increased again by week 11. In contrast, no changes in the dynamics of synaptogenesis were revealed, as assessed by the area occupied by MAP2-positive structures, which remained stable at all studied time points, with no significant intergroup differences. The distribution of this marker in the intermediate zone and its absence in the ventricular and marginal zones from week 8 indicated an early onset of dendritic differentiation of neuroblasts during radial migration, before their final positioning in the cortical plate.