Showing papers on "Radial glial cell published in 2004"

Cortical neurons arise in symmetric and asymmetric division zones and migrate through specific phases

Abstract: Precise patterns of cell division and migration are crucial to transform the neuroepithelium of the embryonic forebrain into the adult cerebral cortex. Using time-lapse imaging of clonal cells in rat cortex over several generations, we show here that neurons are generated in two proliferative zones by distinct patterns of division. Neurons arise directly from radial glial cells in the ventricular zone (VZ) and indirectly from intermediate progenitor cells in the subventricular zone (SVZ). Furthermore, newborn neurons do not migrate directly to the cortex; instead, most exhibit four distinct phases of migration, including a phase of retrograde movement toward the ventricle before migration to the cortical plate. These findings provide a comprehensive and new view of the dynamics of cortical neurogenesis and migration.

Epidermal, Neuronal and Glial Cell Fate Choice in the Embryo

Abstract: Development of the embryonic nervous system is characterized by a cascade of complex events. The classical experiments of Spemann and Mangold (1924) using the urodele amphibian model system have established that the initial step in this cascade is an inductive interaction between the dorsal mesoderm and the ectoderm that leads to a diversion of the epidermal lineage towards the neural fate. During this process, called neural induction (Gilbert and Saxen 1993), the ectoderm of the embryo becomes regionalized to form the highly specialized and interconnected regions found later in the adult nervous system (Hamburger 1988). Soon after the neural fate of the ectoderm has been established, cells of the neural anlage differentiate into many different types of neurons and glia. These distinct cells develop in defined temporal and spatial patterns as a result of several classes of signaling molecules and precise local control of gene expression. Thus, immature ectoderm cells are faced with a series of binary choices, first to become an epidermal or a neural cell, then, once the neural fate is established, becoming a neuronal or a glial cell type. In all cases, the underlying mechanism involves reception and integration of extrinsic signals together with early gene activation and repression.

P15: Radial glial cell origins and their transformation into astrocytes in the developing rat spinal cord

Abstract: Gliogenesis in the spinal cord has been studied extensively, but questions remain relating to radial glial cell origins and lineage. We have investigated radial glia by the in vivo analysis of nestin, vimentin, GLAST, BLBP, 3CB2 and GFAP expression. BrdU incorporation was used to identify proliferating glia and Western blot analysis revealed in vivo protein levels of GFAP, vimentin and GAP-43 in cord homogenates during development. At E12, nestin-immunoreactive (-IR) radial cells radiating from the central canal to the pial surface, are the first cell phenotype distinguishable from the nestin-IR neuroepithelium. The glial specific markers GLAST, BLBP, GFAP or 3CB2 are not detected at E12. This, together with the high degree of neuroepithelial cytogenesis at E12 as shown by BrdU incorporation, indicates that these radial cells most likely self-renew or generate neurons. From E14, GLAST and BLBP-IR radial glial cells become evident only ventrally, always colabelling with nestin and vimentin. As neurogenesis has ceased in the ventral cord, and cytogenesis is mostly restricted to the dorsal cord, these radial glia are most likely restricted to an astroglial cell lineage, while the GLAST/BLBP-negative, vimentin/nestin-IR radial cells dorsally may still be contributing to neurogenesis. By E16, GLAST/BLBP/3CB2-IR cells are found both ventrally and dorsally, co-labelling with nestin and vimentin in radial glia and the multipotential exclusively nestin/vimentin-IR radial cell phenotype is not longer evident. As neurogenesis is terminating in all regions of the cord these radial glia are presumably astrocyte precursors. At E16 the astrocyte specific marker GFAP is first detected in the peripheral white matter (WM). From E17, transitional radial glia containing co-localized GFAP and nestin or vimentin are evident, reflecting a direct transition to astrocytes. By E20, vimentin and nestin are down-regulated with GFAP and 3CB2 the dominant intermediate filaments in the WM, indicating the radial glial cell-astrocyte transformation is under completion. Postnatally, GLAST, 3CB2 and BLBP, having earlier labelled radial glia now label astrocytes in the grey and white matter, with 3CB2 labelling only WM astrocytes. The spatio-temporal distribution of markers used here has elucidated a neuroepithelium to radial cell, to radial glial cell, to transitional radial glial cell to astroglial cell lineage in the developing spinal cord.