Cortical type 2 astrocytes are not dye coupled nor do they express the major gap junction genes found in the central nervous system.
The O-2A progenitor cell first described from the rat optic nerve is a bipotential precursor of oligodendrocytes and type 2 astrocytes. Each cell expresses specific markers that distinguish them as unique cell types. O-2A progenitors cultured in high serum preferentially differentiate into type 2 astrocytes and when exposed to defined medium or low serum develop along the oligodendrocyte lineage. We analyzed the gap junction gene expression of type 2 astrocytes to determine if they are coupled to form a syncytium, like their type 1 astrocyte counterparts. Dye coupling experiments demonstrated that cortical type 2 astrocytes are not coupled, while type 1 astrocytes in the same culture dish are highly coupled. Immunocytochemistry revealed the presence of Cx43 in type 1 astrocytes but we could not detect Cx26, 32, or 43 protein in type 2 astrocytes. In situ hybridization did not detect mRNA for any of the three connexin genes in type 2 astrocytes. These data demonstrate that type 2 astrocytes do not express the major gap junction genes found in the central nervous system. The precise function of type 2 astrocytes is not known but the lack of gap junction genes expression suggests that their functions are different from the spatial buffering capacity of type 1 astrocytes.
Department of Anatomy, University of Western Ontario, London, Canada.
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D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology*; D015152:Blotting, Northern; D002450:Cell Communication; D002478:Cells, Cultured; D002490:Central Nervous System / Q000378:metabolism*; D002540:Cerebral Cortex / Q000166:cytology* / Q000378:metabolism; D004396:Coloring Agents; D017630:Connexins / Q000096:biosynthesis; D017629:Gap Junctions / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology
D004396:Coloring Agents; D017630:Connexins; D012333:RNA, Messenger