title: The inner lining of the reptilian brain: a heterogeneous cellular mosaic.
abstract: The ependymal layer is a preserved structure across vertebrates but its functional significance remains poorly understood. Modern studies emphasize the role played by radial glia (RG) as neurogenic progenitors. We speculated that the cells lining the prosencephalon ventricles of freshwater turtles may have retained key features of RG. To test this idea, we applied an approach that combined cellular, molecular, fine structural, and electrophysiological techniques. In the prosencephalon of juvenile turtles, we found cells with typical radial morphology that expressed four RG proteins: glial fibrillary acidic protein (GFAP), vimentin, S100/S100β and brain lipid-binding protein (BLBP). Most of these cells expressed the transcription factor Sox2 but few co-expressed Pax6. One type of RG had their somata close to the ventricle lumen and bear multiple cilia. A second class with cell bodies far from the lumen was usually uniciliated. RGs had low input resistances, passive properties and were coupled via Cx43 at the level of the cell bodies and radial processes. A third kind of cell was uncoupled, expressed neuronal proteins (HuC/D and NeuN) and fired spikes. The differential expression of HuC/D and NeuN together with their electrophysiological properties suggested various maturational stages. The occurrence of ependymal patches with a high density of 5-bromo-2-deoxyuridine (BrdU) labeled cells provides evidence of the proliferative capability of ependymal RG. Our data support the view that RG have retained key properties of neuroepithelial cells. The maintenance of proliferating RG could be also related with the outstanding endogenous ability of lower vertebrates for self-repair after injury.
authors: Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP11600, Montevideo, Uruguay.
authors: Omar
authors: O
authors: Trujillo-Cenóz
authors: Nicolás
authors: N
authors: Marichal
authors: María Inés
authors: MI
authors: Rehermann
authors: Raúl E
authors: RE
authors: Russo
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002552:Cerebral Ventricles / Q000378:metabolism; D004805:Ependyma / Q000166:cytology / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D014426:Turtles
chemical_list: D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; D055748:SOXB1 Transcription Factors
keywords: BLBP; Cx43; GFAP; Radial glia; cell coupling; ependymal layer; turtle; vimentin