title: Molecular scaffolds underpinning macroglial polarization: an analysis of retinal Müller cells and brain astrocytes in mouse.
abstract: Key roles of macroglia are inextricably coupled to specialized membrane domains. The perivascular endfoot membrane has drawn particular attention, as this domain contains a unique complement of aquaporin-4 (AQP4) and other channel proteins that distinguishes it from perisynaptic membranes. Recent studies indicate that the polarization of macroglia is lost in a number of diseases, including temporal lobe epilepsy and Alzheimer's disease. A better understanding is required of the molecular underpinning of astroglial polarization, particularly when it comes to the significance of the dystrophin associated protein complex (DAPC). Here, we employ immunofluorescence and immunogold cytochemistry to analyze the molecular scaffolding in perivascular endfeet in macroglia of retina and three regions of brain (cortex, dentate gyrus, and cerebellum), using AQP4 as a marker. Compared with brain astrocytes, Müller cells (a class of retinal macroglia) exhibit lower densities of the scaffold proteins dystrophin and α-syntrophin (a DAPC protein), but higher levels of AQP4. In agreement, depletion of dystrophin or α-syntrophin--while causing a dramatic loss of AQP4 from endfoot membranes of brain astrocytes--had only modest or insignificant effect, respectively, on the AQP4 pool in endfoot membranes of Müller cells. In addition, while polarization of brain macroglia was less affected by dystrophin depletion than by targeted deletion of α-syntrophin, the reverse was true for retinal macroglia. These data indicate that the molecular scaffolding in perivascular endfeet is more complex than previously assumed and that macroglia are heterogeneous with respect to the mechanisms that dictate their polarization.
authors.affiliation: Centre for Molecular Biology and Neuroscience, Institute of Basic Medical Sciences, University of Oslo, Norway.
authors.forename: Rune
authors.initials: R
authors.lastname: Enger
authors.forename: Georg Andreas
authors.initials: GA
authors.lastname: Gundersen
authors.forename: Nadia Nabil
authors.initials: NN
authors.lastname: Haj-Yasein
authors.forename: Martine
authors.initials: M
authors.lastname: Eilert-Olsen
authors.forename: Anna Elisabeth
authors.initials: AE
authors.lastname: Thoren
authors.forename: Gry Fluge
authors.initials: GF
authors.lastname: Vindedal
authors.forename: Pétur Henry
authors.initials: PH
authors.lastname: Petersen
authors.forename: Øivind
authors.initials: Ø
authors.lastname: Skare
authors.forename: Maiken
authors.initials: M
authors.lastname: Nedergaard
authors.forename: Ole Petter
authors.initials: OP
authors.lastname: Ottersen
authors.forename: Erlend A
authors.initials: EA
authors.lastname: Nagelhus
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism; D001253:Astrocytes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D001923:Brain Chemistry / Q000235:genetics*; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D016764:Cell Polarity / Q000235:genetics*; D016189:Dystrophin / Q000378:metabolism; D049029:Dystrophin-Associated Proteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009124:Muscle Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D009457:Neuroglia / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D012160:Retina / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D002135:Calcium-Binding Proteins; D016189:Dystrophin; D049029:Dystrophin-Associated Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C091824:syntrophin; C091825:syntrophin alpha1