Showing papers on "Radial glial cell published in 2011"

Regulating the balance between symmetric and asymmetric stem cell division in the developing brain

Abstract: Stem cells proliferate through symmetric division or self-renew through asymmetric division whilst generating differentiating cell types. The balance between symmetric and asymmetric division requires tight control to either expand a stem cell pool or to generate cell diversity. In the Drosophila optic lobe, symmetrically dividing neuroepithelial cells transform into asymmetrically dividing neuroblasts. The switch from neuroepithelial cells to neuroblasts is triggered by a proneural wave that sweeps across the neuroepithelium. Here we review recent findings showing that the orchestrated action of the Notch, EGFR, Fat-Hippo, and JAK/STAT signalling pathways controls the progression of the proneural wave and the sequential transition from symmetric to asymmetric division. The neuroepithelial to neuroblast transition in the optic lobe bears many similarities to the switch from neuroepithelial cell to radial glial cell in the developing mammalian cerebral cortex. The Notch signalling pathway has a similar role in the transition from proliferating to differentiating stem cell pools in the developing vertebrate retina and in the neural tube. Therefore, findings in the Drosophila optic lobe provide insights into the transitions between proliferative and differentiative division in the stem cell pools of higher organisms.

Neural Progenitors Are Direct Targets of Xenoestrogens in Zebrafish

Abstract: Because a large proportion of endocrine disruptor chemicals (EDC) end up in surface waters, aquatic species are particularly vulnerable to their potential effects. In this regard, fish populations must be carefully monitored for fishes are absolutely crucial in terms of biodiversity and protein resources, but also they are extremely valuable as sentinel species. In this chapter, we discuss EDCs effects on the brain of fish, in particular on radial glial cells, which in all vertebrate species are brain stem cells. Indeed, one of the most prominent effect of EDCs in zebrafish is their impact on the cyp19a1b gene that encodes aromatase B. Strikingly, aromatase B is only expressed in radial glial cells that behave as neuronal progenitors. Detailed molecular and whole animal studies in transgenic zebrafish demonstrated the extreme sensitivity of the cyp19a1b gene to estrogen mimics. In particular, doses as low as 1.5 ng/L of EE2 were consistently shown to turn on cyp19a1b gene expression in 2–5 days old zebrafish embryos. As recent studies indicate that estrogens modulate proliferative activity of radial glia progenitors, it is likely that estrogen mimics may have similar activity. The potential outcome of such effects requires thorough investigations, not only in fish but also in developing mammals. In addition, those studies have led to the development of a very sensitive in vivo assay that makes use of cyp19a1b-GFP transgenic embryos whose brain exhibits GFP expression if exposed to any estrogen mimic acting through estrogen receptors.

Human Motor Cortex First Lamina and Gray Matter Special Astrocytes: Development and Cytoarchitecture

Abstract: During the development of the mammalian cerebral cortex, the gliogenesis of the different glial cell types parallel the evolution of its various compartments. Each basic glial cell type evolves at specific time, occupies a specific compartment, and develops specific morphological and functional features. The following glial cell types are recognized in the developing mammalian cerebral cortex: radial glia cells, white matter fibrous astrocytes and oligodendrocytes, subependymal polymorphous astrocytes, first lamina special astrocytes, and the gray matter protoplasmic astrocytes. The developmental history of each type is characteristic and occurs at specific time. The developmental histories and morphologic features of most glial cells types have been well documented (Rakic 1972, 1988; Marin-Padilla 1995). However, the late developmental gliogenesis of both the first lamina astrocytes and the gray matter protoplasmic astrocytes are less well documented. First lamina special astrocytes are needed for the late maintenance of the cerebral cortex expanding external glial limiting membrane (EGLM) and the protoplasmic astrocytes are necessary for the late gray matter neuronal and vascular maturations (Marin-Padilla 1995).