Radial glial elements in the cerebral cortex of the lesser hedgehog tenrec
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We investigated astroglial cells in several areas of the telencephalic cortex of the lesser hedgehog tenrec (Echinops telfairi). Compared to other mammals, the cortex of the tenrec has a relatively large paleocortex and a low encephalization index. We stained sections from tenrec forebrains with structural and functional glia markers focusing on selected cortical areas, the paleocortex, rhinal cortex, neocortex and the dentate gyrus of the hippocampal formation. We found that in all parts of the tenrec forebrain cortex, radial processes exist which are positive for glial fibrillary acidic protein (GFAP) although with differential localization: in the rhinal cortex and neocortical region radial glial fibers are located in the subventricular regions, whereas in the dentate gyrus and paleocortex they appear to arise from the cells in the respective granular layers. The relatively high abundance of the radial fibers in layer III of the paleocortex was very conspicuous. Only few of these radial processes were also co-labeled with doublecortin (DCX), yet most of the DCX-positive cells were negative for GFAP. The GFAP-positive radial fibers were in turn neither positive for glutamine synthetase, nor did they show immunoreactivity for the astroglia-specific water channel aquaporin-4 (AQP4). Star-shaped astrocytes, however, displayed the typical perivascular and subpial expression patterns for AQP4. We conclude that the radial glia in the adult tenrec represents an immature form of astroglia that persists in these animals throughout life.
KeywordsAstrocytes Glia evolution Aquaporin-4 Afrotheria
The authors wish to thank Dr. Jens Grosche, Ms. Ute Bauer and Dr. Yulia Popkova (all from Leipzig University), and Karin Tiedemann (Tübingen) for excellent technical assistance.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. As outlined in the “Materials and methods” the brain tissue used in this study was derived from previous studies which were in line with the ethical guidelines of the laboratory animal care and use committee at the University of Munich and were approved by the administration of Upper Bavaria (License no. 55.2-1-54-2531-85-05). This article does not contain any studies with human participants performed by any of the authors.
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