title: GFAP-expressing cells in the postnatal subventricular zone display a unique glial phenotype intermediate between radial glia and astrocytes.
abstract: Neural stem cells in the adult subventricular zone (SVZ) derive from radial glia and express the astroglial marker glial fibrillary acidic protein (GFAP). Thus, they have been termed astrocytes. However, it remains unknown whether these GFAP-expressing cells express the functional features common to astrocytes. Using immunostaining and patch clamp recordings in acute slices from transgenic mice expressing green fluorescent protein (GFP) driven by the promoter of human GFAP, we show that GFAP-expressing cells in the postnatal SVZ display typical glial properties shared by astrocytes and prenatal radial glia such as lack of action potentials, hyperpolarized resting potentials, gap junction coupling, connexin 43 expression, hemichannels, a passive current profile, and functional glutamate transporters. GFAP-expressing cells express both GLAST and GLT-1 glutamate transporters but lack AMPA-type glutamate receptors as reported for dye-coupled astrocytes. However, they lack 100 microM Ba2+-sensitive inwardly rectifying K+ (K(IR)) currents expressed by astrocytes, but display delayed rectifying K+ currents and 1 mM Ba2+-sensitive K+ currents. These currents contribute to K+ transport at rest and maintain hyperpolarized resting potentials. GFAP-expressing cells stained positive for both K(IR)2.1 and K(IR)4.1 channels, two major K(IR) channels in astrocytes. Ependymal cells, which also derive from radial glia and express GFAP, display typical glial properties and K(IR) currents consistent with their postmitotic nature. Our results suggest that GFAP-expressing cells in concert with ependymal cells can perform typical astrocytic functions such as K+ and glutamate buffering in the postnatal SVZ but display a unique set of functional characteristics intermediate between astrocytes and radial glia.
authors.affiliation: Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520-8082, USA.
authors.forename: Xiuxin
authors.initials: X
authors.lastname: Liu
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Bolteus
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Balkin
authors.forename: Oliver
authors.initials: O
authors.lastname: Henschel
authors.forename: Angélique
authors.initials: A
authors.lastname: Bordey
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D048430:Cell Shape / Q000502:physiology; D017630:Connexins / Q000378:metabolism; D004805:Ependyma / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D010641:Phenotype; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D013687:Telencephalon / Q000166:cytology* / Q000254:growth & development* / Q000378:metabolism
chemical_list: D027322:Amino Acid Transport System X-AG; D015415:Biomarkers; D017630:Connexins; D005904:Glial Fibrillary Acidic Protein; D015221:Potassium Channels; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D018698:Glutamic Acid; D011188:Potassium