CD44-Positive Cells Are Candidates for Astrocyte Precursor Cells in Developing Mouse Cerebellum
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Neural stem cells are generally considered to be committed to becoming precursor cells before terminally differentiating into either neurons or glial cells during neural development. Neuronal and oligodendrocyte precursor cells have been identified in several areas in the murine central nervous system. The presence of astrocyte precursor cells (APCs) is not so well understood. The present study provides several lines of evidence that CD44-positive cells are APCs in the early postnatal mouse cerebellum. In developing mouse cerebellum, CD44-positive cells, mostly located in the white matter, were positive for the markers of the astrocyte lineage, but negative for the markers of mature astrocytes. CD44-positive cells were purified from postnatal cerebellum by fluorescence-activated cell sorting and characterized in vitro. In the absence of any signaling molecule, many cells died by apoptosis. The surviving cells gradually expressed glial fibrillary acidic protein, a marker for mature astrocytes, indicating that differentiation into mature astrocytes is the default program for these cells. The cells produced no neurospheres nor neurons nor oligodendrocytes under any condition examined, indicating these cells are not neural stem cells. Leukemia inhibitory factor greatly promoted astrocytic differentiation of CD44-positive cells, whereas bone morphogenetic protein 4 (BMP4) did not. Fibroblast growth factor-2 was a potent mitogen for these cells, but was insufficient for survival. BMP4 inhibited activation of caspase-3 and greatly promoted survival, suggesting a novel role for BMP4 in the control of development of astrocytes in cerebellum. We isolated and characterized only CD44 strongly positive large cells and discarded small and/or CD44 weakly positive cells in this study. Further studies are necessary to characterize these cells to help determine whether CD44 is a selective and specific marker for APCs in the developing mouse cerebellum. In conclusion, we succeeded in preparing APC candidates from developing mouse cerebellum, characterized them in vitro, and found that BMPs are survival factors for these cells.
KeywordsAstrocyte Precursor CD44 Survival FGF-2 BMP
This work was supported by a grant from the Uehara Memorial Foundation, Tokyo, Japan (to Y.I.), by a grant from Takeda Science Foundation, Tokyo, Japan (to Y.I.), by a grant from Grants-in-Aid for Scientific Research (Project No. 21200012 to K.S.) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and by Support Program for Improving Graduate School Education from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) to Gunma University (to N.C.). The 40E-C and Pax6 hybridomas were obtained from the Developmental Studies Hybridoma Bank, developed under the auspices of the National Institute of Child Health and Human Development, and maintained by the Department of Biological Sciences at the University of Iowa, Iowa City.
Conflict of Interest
The authors declare that they have no conflict of interest.
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