Oligodendrocytes in mouse corpus callosum are coupled via gap junction channels formed by connexin47 and connexin32

Abstract

According to previously published ultrastructural studies, oligodendrocytes in white matter exhibit gap junctions with astrocytes, but not among each other, while in vitro oligodendrocytes form functional gap junctions. We have studied functional coupling among oligodendrocytes in acute slices of postnatal mouse corpus callosum. By whole-cell patch clamp we dialyzed oligodendrocytes with biocytin, a gap junction-permeable tracer. On average 61 cells were positive for biocytin detected by labeling with streptavidin-Cy3. About 77% of the coupled cells stained positively for the oligodendrocyte marker protein CNPase, 9% for the astrocyte marker GFAP and 14% were negative for both CNPase and GFAP. In the latter population, the majority expressed Olig2 and some NG2, markers for oligodendrocyte precursors. Oligodendrocytes are known to express Cx47, Cx32 and Cx29, astrocytes Cx43 and Cx30. In Cx47-deficient mice, the number of coupled cells was reduced by 80%. Deletion of Cx32 or Cx29 alone did not significantly reduce the number of coupled cells, but coupling was absent in Cx32/Cx47-double-deficient mice. Cx47-ablation completely abolished coupling of oligodendrocytes to astrocytes. In Cx43-deficient animals, oligodendrocyte-astrocyte coupling was still present, but coupling to oligodendrocyte precursors was not observed. In Cx43/Cx30-double deficient mice, oligodendrocyte-to-astrocyte coupling was almost absent. Uncoupled oligodendrocytes showed a higher input resistance. We conclude that oligodendrocytes in white matter form a functional syncytium predominantly among each other dependent on Cx47 and Cx32 expression, while astrocytic connexins expression can promote the size of this network.

Classic 18.5- and 21.5-kDa Myelin Basic Protein Isoforms Associate with Cytoskeletal and SH3-Domain Proteins in the Immortalized N19-Oligodendroglial Cell Line Stimulated by Phorbol Ester and IGF-1

“…Tight junctions are important selective barriers that regulate the paracellular pathway for the movement of ions and solutes between cells [90,91]. Gap junctions form between OLGs, and between OLGs and astrocytes, and allow electrical coupling between the cells [92]. Interactions of these junctions with the cytoskeleton may regulate cytoskeletal dynamics, and conversely, the cytoskeleton may regulate junctional activity [93].…”

Estimating functional connectivity in an electrically coupled interneuron network

“…In either case the distinction between GJ-associated capacitive currents and intrinsic capacitive currents may be compromised. Finally, in the extreme case of a GJ-linked syncytium (36), as formed by glial cells, proper voltage control of the recorded cell becomes impossible. The input impedance being dominated by the series resistance of the recording pipette, the amplitude of capacitive currents is severely reduced (36), making the capacitive current analysis impractical.…”

Panglial Gap Junctional Communication is Essential for Maintenance of Myelin in the CNS

“…Oligodendrocytes were approached with a patch-clamp pipette in acute sagittal slices of cerebellar white matter or in acute coronal slices of corpus callosum obtained from P10 -P15 mice, before the action tremor was evident. By whole-cell patch-clamp recording, single oligodendrocytes were dialyzed via the patch pipette with the gap junction permeable tracer biocytin as described previously (Maglione et al, 2010). For a detailed numeric representation, see Tables 2 and 3.…”

“…Astrocytes express Cx43 and Cx30, and some of them Cx26, whereas Cx47, Cx32, and Cx29 are expressed by oligodendrocytes (Nagy et al, 2001;Kleopa et al, 2004). Gap junction channels are formed among astrocytes (A/A), among oligodendrocytes (O/ O), and between oligodendrocytes and astrocytes (O/A), which results in formation of panglial networks (Wallraff et al, 2006;Maglione et al, 2010;Wasseff and Scherer, 2011). Since Cx29 does not form functional gap junction channels in cell culture experiments and Cx26 expression is limited to few gray matter astrocytes, panglial networks are mainly formed by astrocytic Cx43 and Cx30 and oligodendrocytic Cx47 and Cx32 (Ahn et al, 2008;Giaume and Theis, 2010;Nagy et al, 2011).…”

“…In contrast, deficiency of both oligodendrocytic connexins, Cx32 and Cx47, leads to loss of O/O and O/A coupling, severe myelin abnormalities, and death at ϳ6 weeks after birth (Odermatt et al, 2003;Menichella et al, 2003;Maglione et al, 2010). However, mice deficient for both astrocytic connexins, Cx43 and Cx30, display only mild myelin defects tinuously depolarized and hyperpolarized between Ϫ170 and ϩ50 mV from a holding potential of Ϫ70 mV (10 mV steps, 50 ms).…”