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Glia- and neuron-specific functions of TrkB signalling during retinal degeneration and regeneration.

Harada C, Guo X, Namekata K, Kimura A, Nakamura K, Tanaka K, Parada LF, Harada T - Nat Commun (2011)

Bottom Line: Furthermore in TrkB(GFAP) knockout mice, BDNF did not prevent photoreceptor degeneration and failed to stimulate Müller glial cell proliferation and expression of neural markers in the degenerating retina.These results demonstrate that BDNF signalling in glia has important roles in neural protection and regeneration, particularly in conversion of Müller glia to photoreceptors.In addition, our genetic models provide a system in which glia- and neuron-specific gene functions can be tested in central nervous system tissues in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Neurobiology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.

ABSTRACT
Glia, the support cells of the central nervous system, have recently attracted considerable attention both as mediators of neural cell survival and as sources of neural regeneration. To further elucidate the role of glial and neural cells in neurodegeneration, we generated TrkB(GFAP) and TrkB(c-kit) knockout mice in which TrkB, a receptor for brain-derived neurotrophic factor (BDNF), is deleted in retinal glia or inner retinal neurons, respectively. Here, we show that the extent of glutamate-induced retinal degeneration was similar in these two mutant mice. Furthermore in TrkB(GFAP) knockout mice, BDNF did not prevent photoreceptor degeneration and failed to stimulate Müller glial cell proliferation and expression of neural markers in the degenerating retina. These results demonstrate that BDNF signalling in glia has important roles in neural protection and regeneration, particularly in conversion of Müller glia to photoreceptors. In addition, our genetic models provide a system in which glia- and neuron-specific gene functions can be tested in central nervous system tissues in vivo.

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Effect of BDNF on the proliferation of Müller glial cells during retinal degeneration.(a) Animal protocols. MNU (60 mg kg−1) was injected intraperitoneally (i.p.) to WT, TrkBGFAP KO and GFAP-Cre LacZ mice. BrdU (50 mg kg−1) was injected (i.p.) at day 0, 2, 4 and 6 after MNU treatment. PBS, BDNF (1 μg μl−1) and K252a (1 mM) were intraocularly injected at day 0, 2 and 4, and the animals were killed at day 5 or 7. (b) Sections of the retina treated with PBS, BDNF and K252a in WT and TrkBGFAP KO mice (day 5). BDNF increased BrdU-labelling in GLAST-positive cells in the INL (arrowheads) and some cells in the ONL in WT, but not in TrkBGFAP KO mice. K252a (a blocker for Trk receptors) inhibited BDNF-induced BrdU expression. (c) BrdU-labelled cells in the ONL were double labelled (arrowheads) with rhodopsin or recoverin in WT mice, and with β-gal in GFAP-Cre LacZ mice (day 7). (d) BrdU-labelled cells in the GCL were double labelled (arrowheads) with Brn3b or calretinin (day 7). Scale bar, 50 μm. GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer.
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f5: Effect of BDNF on the proliferation of Müller glial cells during retinal degeneration.(a) Animal protocols. MNU (60 mg kg−1) was injected intraperitoneally (i.p.) to WT, TrkBGFAP KO and GFAP-Cre LacZ mice. BrdU (50 mg kg−1) was injected (i.p.) at day 0, 2, 4 and 6 after MNU treatment. PBS, BDNF (1 μg μl−1) and K252a (1 mM) were intraocularly injected at day 0, 2 and 4, and the animals were killed at day 5 or 7. (b) Sections of the retina treated with PBS, BDNF and K252a in WT and TrkBGFAP KO mice (day 5). BDNF increased BrdU-labelling in GLAST-positive cells in the INL (arrowheads) and some cells in the ONL in WT, but not in TrkBGFAP KO mice. K252a (a blocker for Trk receptors) inhibited BDNF-induced BrdU expression. (c) BrdU-labelled cells in the ONL were double labelled (arrowheads) with rhodopsin or recoverin in WT mice, and with β-gal in GFAP-Cre LacZ mice (day 7). (d) BrdU-labelled cells in the GCL were double labelled (arrowheads) with Brn3b or calretinin (day 7). Scale bar, 50 μm. GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer.

Mentions: Recent studies have provided evidence that radial glia sustain neural regeneration even in the adult brain456. Müller glia are considered to be a type of radial glia that may function as retinal progenitor cells1011. We therefore examined the regenerative response of Müller cells to BDNF in the MNU-induced photoreceptor degeneration model (Fig. 5a). To observe dividing cells, we labelled WT and TrkBGFAP KO animals with 5-bromodeoxyuridin (BrdU). Although few BrdU-labelled cells were detected at day 5, intraocular injection of BDNF clearly increased BrdU-labelling in GLAST-IP cells in the inner retina (arrows) and in some cells in the ONL (Fig. 5b). In contrast, BDNF injection did not promote BrdU incorporation in TrkBGFAP KO mice or WT mice treated with K252a, an inhibitor of Trk receptors (Fig. 5b). At day 7, BDNF-induced BrdU-positive cells were detected predominantly in the remaining ONL, where they were co-labelled with rod photoreceptor markers, such as rhodopsin and recoverin (Fig. 5c). However, BDNF-induced BrdU incorporation was suppressed in TrkBGFAP KO mice (Supplementary Fig. S2). Furthermore, these BrdU-labelled cells were overlapped with β-gal staining in GFAP-Cre LacZ mice, providing evidence that they were derived from Müller glia (Fig. 5c). In addition, some BrdU-positive cells were detected in the inner retina and double labelled with Brn3b (another RGC marker) or calretinin (Fig. 5d). These results suggest the possibility that BDNF can convert the proliferating Müller glia to rod photoreceptors and, to a lesser extent, to other retinal neurons in the MNU model. Thus, TrkB deficiency achieved by Cre-mediated recombination results in the loss of regenerating Müller cells.


Glia- and neuron-specific functions of TrkB signalling during retinal degeneration and regeneration.

Harada C, Guo X, Namekata K, Kimura A, Nakamura K, Tanaka K, Parada LF, Harada T - Nat Commun (2011)

Effect of BDNF on the proliferation of Müller glial cells during retinal degeneration.(a) Animal protocols. MNU (60 mg kg−1) was injected intraperitoneally (i.p.) to WT, TrkBGFAP KO and GFAP-Cre LacZ mice. BrdU (50 mg kg−1) was injected (i.p.) at day 0, 2, 4 and 6 after MNU treatment. PBS, BDNF (1 μg μl−1) and K252a (1 mM) were intraocularly injected at day 0, 2 and 4, and the animals were killed at day 5 or 7. (b) Sections of the retina treated with PBS, BDNF and K252a in WT and TrkBGFAP KO mice (day 5). BDNF increased BrdU-labelling in GLAST-positive cells in the INL (arrowheads) and some cells in the ONL in WT, but not in TrkBGFAP KO mice. K252a (a blocker for Trk receptors) inhibited BDNF-induced BrdU expression. (c) BrdU-labelled cells in the ONL were double labelled (arrowheads) with rhodopsin or recoverin in WT mice, and with β-gal in GFAP-Cre LacZ mice (day 7). (d) BrdU-labelled cells in the GCL were double labelled (arrowheads) with Brn3b or calretinin (day 7). Scale bar, 50 μm. GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f5: Effect of BDNF on the proliferation of Müller glial cells during retinal degeneration.(a) Animal protocols. MNU (60 mg kg−1) was injected intraperitoneally (i.p.) to WT, TrkBGFAP KO and GFAP-Cre LacZ mice. BrdU (50 mg kg−1) was injected (i.p.) at day 0, 2, 4 and 6 after MNU treatment. PBS, BDNF (1 μg μl−1) and K252a (1 mM) were intraocularly injected at day 0, 2 and 4, and the animals were killed at day 5 or 7. (b) Sections of the retina treated with PBS, BDNF and K252a in WT and TrkBGFAP KO mice (day 5). BDNF increased BrdU-labelling in GLAST-positive cells in the INL (arrowheads) and some cells in the ONL in WT, but not in TrkBGFAP KO mice. K252a (a blocker for Trk receptors) inhibited BDNF-induced BrdU expression. (c) BrdU-labelled cells in the ONL were double labelled (arrowheads) with rhodopsin or recoverin in WT mice, and with β-gal in GFAP-Cre LacZ mice (day 7). (d) BrdU-labelled cells in the GCL were double labelled (arrowheads) with Brn3b or calretinin (day 7). Scale bar, 50 μm. GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer.
Mentions: Recent studies have provided evidence that radial glia sustain neural regeneration even in the adult brain456. Müller glia are considered to be a type of radial glia that may function as retinal progenitor cells1011. We therefore examined the regenerative response of Müller cells to BDNF in the MNU-induced photoreceptor degeneration model (Fig. 5a). To observe dividing cells, we labelled WT and TrkBGFAP KO animals with 5-bromodeoxyuridin (BrdU). Although few BrdU-labelled cells were detected at day 5, intraocular injection of BDNF clearly increased BrdU-labelling in GLAST-IP cells in the inner retina (arrows) and in some cells in the ONL (Fig. 5b). In contrast, BDNF injection did not promote BrdU incorporation in TrkBGFAP KO mice or WT mice treated with K252a, an inhibitor of Trk receptors (Fig. 5b). At day 7, BDNF-induced BrdU-positive cells were detected predominantly in the remaining ONL, where they were co-labelled with rod photoreceptor markers, such as rhodopsin and recoverin (Fig. 5c). However, BDNF-induced BrdU incorporation was suppressed in TrkBGFAP KO mice (Supplementary Fig. S2). Furthermore, these BrdU-labelled cells were overlapped with β-gal staining in GFAP-Cre LacZ mice, providing evidence that they were derived from Müller glia (Fig. 5c). In addition, some BrdU-positive cells were detected in the inner retina and double labelled with Brn3b (another RGC marker) or calretinin (Fig. 5d). These results suggest the possibility that BDNF can convert the proliferating Müller glia to rod photoreceptors and, to a lesser extent, to other retinal neurons in the MNU model. Thus, TrkB deficiency achieved by Cre-mediated recombination results in the loss of regenerating Müller cells.

Bottom Line: Furthermore in TrkB(GFAP) knockout mice, BDNF did not prevent photoreceptor degeneration and failed to stimulate Müller glial cell proliferation and expression of neural markers in the degenerating retina.These results demonstrate that BDNF signalling in glia has important roles in neural protection and regeneration, particularly in conversion of Müller glia to photoreceptors.In addition, our genetic models provide a system in which glia- and neuron-specific gene functions can be tested in central nervous system tissues in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Neurobiology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.

ABSTRACT
Glia, the support cells of the central nervous system, have recently attracted considerable attention both as mediators of neural cell survival and as sources of neural regeneration. To further elucidate the role of glial and neural cells in neurodegeneration, we generated TrkB(GFAP) and TrkB(c-kit) knockout mice in which TrkB, a receptor for brain-derived neurotrophic factor (BDNF), is deleted in retinal glia or inner retinal neurons, respectively. Here, we show that the extent of glutamate-induced retinal degeneration was similar in these two mutant mice. Furthermore in TrkB(GFAP) knockout mice, BDNF did not prevent photoreceptor degeneration and failed to stimulate Müller glial cell proliferation and expression of neural markers in the degenerating retina. These results demonstrate that BDNF signalling in glia has important roles in neural protection and regeneration, particularly in conversion of Müller glia to photoreceptors. In addition, our genetic models provide a system in which glia- and neuron-specific gene functions can be tested in central nervous system tissues in vivo.

Show MeSH
Related in: MedlinePlus