Cell migration in the rat embryonic neocortex

Abstract

Three-dimensional reconstructions of the normal rat embryonic (E) neocortex on days E15, E17, E19, and E21, using Skandha (software designed by J. Prothero, University of Washington, Seattle), show that the neocortical ventricular zone shrinks rapidly in the medial direction during cortical morphogenesis. [3H]thymidine autoradiography indicates that the shrinkage of the ventricular zone occurs before neurons in lateral and ventrolateral parts of layers IV-II are generated. Consequently, most of these neurons originate 400-1000 microns medial to their settling sites in the cortical plate. Embryos killed at daily intervals up to E21 after a single injection of [3H]thymidine on either E17 or E18 revealed the presence of a prominent migratory path, the lateral cortical stream, used by neurons migrating to the lateral and ventrolateral cortical plate; neurons migrating to the dorsal cortical plate follow a direct radial path. Arrival times of neurons in the cortical plate depend on the migratory path and are proportional to the overall distance travelled. Neurons that migrate only radially arrive in the dorsal cortical plate in two days (shortest route). Neurons that migrate laterally arrive in the lateral cortical plate in 3 days (longer route) and in the ventrolateral cortical plate in 4 days (longest route). [3H]thymidine autoradiography also shows that cells generated in the neocortical ventricular zone migrate in the lateral cortical stream for 5 or more days and accumulate in a reservoir. Cells leave the reservoir to enter the piriform cortex and destinations (as yet undetermined) in the basal telencephalon. The lateral cortical stream is found wherever the neocortical primordium surrounds the basal ganglia and is absent behind the basal ganglia. A computer analysis of nuclear orientation in anterior and posterior parts of the intermediate zone in the dorsal neocortex between days E17 and E22 shows that horizontally oriented nuclei are more common anteriorly where many cells are migrating laterally than posteriorly where most cells are migrating radially.

Selective Expression of Dopamine D3Receptor mRNA in Proliferative Zones during Embryonic Development of the Rat Brain

“…The neuroepithelium of olfactory bulb also was labeled. At this stage labeling appeared as a band becoming thinner than previously, because the cortical ventricular zone of the neuroepithelium also had become thinner (Bayer and Altman, 1991). Labeling in Purkinje cell plate also appeared stronger and more extended.…”

“…Labeled cells appeared as clusters in a 100-m-thick band lining the ventricle (Fig. 4 E), corresponding to the synthetic and mitotic zones of the neuroepithelium, as evidenced by Bayer and Altman (1991) with the use of [ 3 H]thymidine labeling, whereas the differentiating field was labeled only very scarcely. This shows that D 3 R-expressing cells are proliferative and not postmitotic differentiating cells.…”

Expression of neuron-specific tubulin defines a novel population in the proliferative layers of the developing telencephalon

“…This angle is believed to mark the border between the ventricular zones of the developing neocortex and the striatum (Smart and Sturrock, 1979). It has been shown that neurons generated along the dorsal bank of the caudatopallial angle migrate ventrolaterally toward the lateral isocortex following the guidance ofthe radial glial fibers (Smart and Sturrock, 1979;Bayer et al, 1991;Misson et al, 1991a). Nevertheless, what is revealed by the TuJl immunostaining within the proliferative zones surrounding the angle are not cells directed ventrolaterally, but dorsomedially, perpendicular to the directions of the radial glial processes of this area (Misson et al,199 la).…”

Neurogenesis and Neuroprotection Induced by Peripheral Immunomodulatory Treatment of Experimental Autoimmune Encephalomyelitis

“…The combination of two detection markers allowed us to evaluate both the amount of new neurons generated 10 -14 d before the animal was killed, by the overall expression of the immature neuronal marker DCX (Bayer et al, 1991), as well as the number of neuroprogenitors emerging during the concurrent BrdU/GA injection period (those that differentiated into the neuronal lineage and thus presented BrdU/DCX dual staining). Both systems gave comparable results as to the effect of the pathological process of EAE and that of GA treatment.…”