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Oligodendrocyte progenitors balance growth with self-repulsion to achieve homeostasis in the adult brain

Nature Neuroscience volume 16, pages 668676 (2013) | Download Citation

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Abstract

The adult CNS contains an abundant population of oligodendrocyte precursor cells (NG2+ cells) that generate oligodendrocytes and repair myelin, but how these ubiquitous progenitors maintain their density is unknown. We generated NG2-mEGFP mice and used in vivo two-photon imaging to study their dynamics in the adult brain. Time-lapse imaging revealed that NG2+ cells in the cortex were highly dynamic; they surveyed their local environment with motile filopodia, extended growth cones and continuously migrated. They maintained unique territories though self-avoidance, and NG2+ cell loss though death, differentiation or ablation triggered rapid migration and proliferation of adjacent cells to restore their density. NG2+ cells recruited to sites of focal CNS injury were similarly replaced by a proliferative burst surrounding the injury site. Thus, homeostatic control of NG2+ cell density through a balance of active growth and self-repulsion ensures that these progenitors are available to replace oligodendrocytes and participate in tissue repair.

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  • 06 May 2013

    In the version of this article initially published, ϕ  was substituted for θ in equation (2) in the Online Methods. The error has been corrected for the PDF and HTML versions of this article.

References

  1. 1.

    , & Maintaining tissue homeostasis: dynamic control of somatic stem cell activity. Cell Stem Cell 9, 402–411 (2011).

  2. 2.

    & Strategies for homeostatic stem cell self-renewal in adult tissues. Cell 145, 851–862 (2011).

  3. 3.

    , & Mechanisms and functional implications of adult neurogenesis. Cell 132, 645–660 (2008).

  4. 4.

    , & Local recruitment of remyelinating cells in the repair of demyelination in the central nervous system. J. Neurosci. Res. 50, 337–344 (1997).

  5. 5.

    , , , & Local self-renewal can sustain CNS microglia maintenance and function throughout adult life. Nat. Neurosci. 10, 1538–1543 (2007).

  6. 6.

    , , & NG2-expressing glial progenitor cells: an abundant and widespread population of cycling cells in the adult rat CNS. Mol. Cell Neurosci. 24, 476–488 (2003).

  7. 7.

    , , , & NG2+ CNS glial progenitors remain committed to the oligodendrocyte lineage in postnatal life and following neurodegeneration. Neuron 68, 668–681 (2010).

  8. 8.

    et al. Competing waves of oligodendrocytes in the forebrain and postnatal elimination of an embryonic lineage. Nat. Neurosci. 9, 173–179 (2006).

  9. 9.

    et al. In vivo time-lapse imaging shows dynamic oligodendrocyte progenitor behavior during zebrafish development. Nat. Neurosci. 9, 1506–1511 (2006).

  10. 10.

    , , & Polydendrocytes (NG2 cells): multifunctional cells with lineage plasticity. Nat. Rev. Neurosci. 10, 9–22 (2009).

  11. 11.

    et al. PDGFRA/NG2 glia generate myelinating oligodendrocytes and piriform projection neurons in adult mice. Nat. Neurosci. 11, 1392–1401 (2008).

  12. 12.

    , , , & Progeny of Olig2-expressing progenitors in the gray and white matter of the adult mouse cerebral cortex. J. Neurosci. 28, 10434–10442 (2008).

  13. 13.

    et al. Oligodendrocyte dynamics in the healthy adult CNS: evidence for myelin remodeling. Neuron 77, 873–885 (2013).

  14. 14.

    , , , & NG2 glia generate new oligodendrocytes, but few astrocytes, in a murine experimental autoimmune encephalomyelitis model of demyelinating disease. J. Neurosci. 30, 16383–16390 (2010).

  15. 15.

    & Activation and proliferation of endogenous oligodendrocyte precursor cells during ethidium bromide-induced demyelination. Exp. Neurol. 160, 333–347 (1999).

  16. 16.

    , , & Subtype-specific oligodendrocyte dynamics in organotypic culture. Glia 57, 1000–1013 (2009).

  17. 17.

    et al. Gray matter NG2 cells display multiple Ca2+-signaling pathways and highly motile processes. PLoS ONE 6, e17575 (2011).

  18. 18.

    , & Proliferation of NG2-positive cells and altered oligodendrocyte numbers in the contused rat spinal cord. J. Neurosci. 21, 3392–3400 (2001).

  19. 19.

    et al. Adult glial precursor proliferation in mutant SOD1G93A mice. Glia 56, 200–208 (2008).

  20. 20.

    et al. Asymmetry-defective oligodendrocyte progenitors are glioma precursors. Cancer Cell 20, 328–340 (2011).

  21. 21.

    , & Constitutive EGFR signaling in oligodendrocyte progenitors leads to diffuse hyperplasia in postnatal white matter. J. Neurosci. 28, 914–922 (2008).

  22. 22.

    et al. Mosaic analysis with double markers reveals tumor cell of origin in glioma. Cell 146, 209–221 (2011).

  23. 23.

    et al. Non-stem cell origin for oligodendroglioma. Cancer Cell 18, 669–682 (2010).

  24. 24.

    , , & Ballistic labeling and dynamic imaging of astrocytes in organotypic hippocampal slice cultures. J. Neurosci. Methods 141, 41–53 (2005).

  25. 25.

    et al. ATP mediates rapid microglial response to local brain injury in vivo. Nat. Neurosci. 8, 752–758 (2005).

  26. 26.

    , & Resting microglial cells are highly dynamic surveillants of brain parenchyma in vivo. Science 308, 1314–1318 (2005).

  27. 27.

    , & MEGF10 and MEGF11 mediate homotypic interactions required for mosaic spacing of retinal neurons. Nature 483, 465–469 (2012).

  28. 28.

    , , , & Protocadherins mediate dendritic self-avoidance in the mammalian nervous system. Nature 488, 517–521 (2012).

  29. 29.

    , , & Choice of cranial window type for in vivo imaging affects dendritic spine turnover in the cortex. Nat. Neurosci. 10, 549–551 (2007).

  30. 30.

    , , , & Thinned-skull cranial window technique for long-term imaging of the cortex in live mice. Nat. Protoc. 5, 201–208 (2010).

  31. 31.

    et al. Directional guidance of oligodendroglial migration by class 3 semaphorins and netrin-1. J. Neurosci. 22, 5992–6004 (2002).

  32. 32.

    et al. Origin of oligodendrocytes in the subventricular zone of the adult brain. J. Neurosci. 26, 7907–7918 (2006).

  33. 33.

    , , & Cell cycle dynamics of NG2 cells in the postnatal and ageing brain. Neuron Glia Biol. 5, 57–67 (2009).

  34. 34.

    & The glial nature of embryonic and adult neural stem cells. Annu. Rev. Neurosci. 32, 149–184 (2009).

  35. 35.

    & The role of extracellular matrix in CNS regeneration. Curr. Opin. Neurobiol. 17, 120–127 (2007).

  36. 36.

    et al. A pericyte origin of spinal cord scar tissue. Science 333, 238–242 (2011).

  37. 37.

    , , & NG2 is a major chondroitin sulfate proteoglycan produced after spinal cord injury and is expressed by macrophages and oligodendrocyte progenitors. J. Neurosci. 22, 2792–2803 (2002).

  38. 38.

    , , & Neurite arborization and mosaic spacing in the mouse retina require DSCAM. Nature 451, 470–474 (2008).

  39. 39.

    et al. Oligodendrocyte population dynamics and the role of PDGF in vivo. Neuron 20, 869–882 (1998).

  40. 40.

    et al. PDGF stimulates the massive expansion of glial progenitors in the neonatal forebrain. Glia 57, 1835–1847 (2009).

  41. 41.

    & Density-dependent feedback inhibition of oligodendrocyte precursor expansion. J. Neurosci. 16, 6886–6895 (1996).

  42. 42.

    , , , & NG2-positive oligodendrocyte progenitor cells in adult human brain and multiple sclerosis lesions. J. Neurosci. 20, 6404–6412 (2000).

  43. 43.

    , & NG2-positive cells in the mouse white and grey matter display distinct physiological properties. J. Physiol. (Lond.) 561, 109–122 (2004).

  44. 44.

    , , & Glutamatergic synapses on oligodendrocyte precursor cells in the hippocampus. Nature 405, 187–191 (2000).

  45. 45.

    , & Excitability and synaptic communication within the oligodendrocyte lineage. J. Neurosci. 30, 3600–3611 (2010).

  46. 46.

    et al. Cell type–specific structural plasticity of axonal branches and boutons in the adult neocortex. Neuron 49, 861–875 (2006).

  47. 47.

    et al. Oligodendrocyte progenitor cell proliferation and lineage progression are regulated by glutamate receptor–mediated K+ channel block. J. Neurosci. 16, 2659–2670 (1996).

  48. 48.

    et al. Extensive piano practicing has regionally specific effects on white matter development. Nat. Neurosci. 8, 1148–1150 (2005).

  49. 49.

    Increased expression of the NG2 chondroitin-sulfate proteoglycan after brain injury. J. Neurosci. 14, 4716–4730 (1994).

  50. 50.

    , , , & Matrix metalloproteinase-9 facilitates remyelination in part by processing the inhibitory NG2 proteoglycan. J. Neurosci. 23, 11127–11135 (2003).

  51. 51.

    , & Homologous recombination based modification in Escherichia coli and germline transmission in transgenic mice of a bacterial artificial chromosome. Nat. Biotechnol. 15, 859–865 (1997).

  52. 52.

    et al. Long-term, high-resolution imaging in the mouse neocortex through a chronic cranial window. Nat. Protoc. 4, 1128–1144 (2009).

  53. 53.

    & Femtosecond laser ablation of neurons in C. elegans for behavioral studies. Appl. Phys. A Mater. Sci. Process. 96, 335–341 (2009).

  54. 54.

    et al. Fiji: an open-source platform for biological-image analysis. Nat. Methods 9, 676–682 (2012).

  55. 55.

    , , & Differentiation and death of premyelinating oligodendrocytes in developing rodent brain. J. Cell Biol. 137, 459–468 (1997).

  56. 56.

    A modification of the Rayleigh test for vector data. Biometrika 67, 175–180 (1980).

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Acknowledgements

We thank M. Pucak, N. Ye and T. Lee for technical assistance, B. Cudmore (Johns Hopkins University) and S. Wang (Princeton University) for advice on cranial window implantation, W.-B. Gan (New York University) for advice on preparing thinned skull windows, and members of the Bergles laboratory for discussions. E.G.H. was supported by a Kirschstein National Research Service Award grant from the US National Institutes of Health (F32NS076098). Funding was provided by grants from the US National Institutes of Health (NS051509, NS050274) and the Brain Science Institute at Johns Hopkins University.

Author information

Author notes

    • Shin H Kang
    •  & Masahiro Fukaya

    Present addresses: Center for Neural Repair and Rehabilitation, Temple University School of Medicine, Philadelphia, Pennsylvania, USA (S.H.K.) and Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Japan (M.F).

    • Ethan G Hughes
    • , Shin H Kang
    •  & Masahiro Fukaya

    These authors contributed equally to this work.

Affiliations

  1. The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

    • Ethan G Hughes
    • , Shin H Kang
    • , Masahiro Fukaya
    •  & Dwight E Bergles

Authors

  1. Search for Ethan G Hughes in:

  2. Search for Shin H Kang in:

  3. Search for Masahiro Fukaya in:

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Contributions

E.G.H., M.F., S.H.K. and D.E.B. designed the experiments. E.G.H. designed, executed and analyzed the experiments described in the figures, movies and text. M.F. made seminal observations of NG2+ cell dynamics and their response to laser-induced lesions in thinned skull preparations, and generated data for Supplementary Figure 8. S.H.K. generated and characterized the NG2-mEGFP-H and NG2-mEGFP-L mouse lines and created Supplementary Figure 1. E.G.H. and D.E.B. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Dwight E Bergles.

Supplementary information

PDF files

  1. 1.

    Supplementary Text and Figures

    Supplementary Figures 1–9 and Supplementary Tables 1 and 2

Videos

  1. 1.

    Supplementary Video 1

    Density and distribution of NG2+ cells in the somatosensory cortex visualized through in vivo two-photon imaging. In vivo two-photon images of EGFP-expressing cells at increasing depths in the somatosensory cortex of an adult NG2-mEGFP-H mouse implanted with a chronic cranial window. NG2+ cells are evenly distributed throughout the upper layers of the cortex and occupy non-overlapping domains. A subset of perivascular cells that enwrap blood vessels also express EGFP, providing landmarks for locating the same regions during repetitive time-lapse imaging. The autofluoresence at the surface arises from the meninges. (Image width: 300 μm; frame rate: 7 frames per second).

  2. 2.

    Supplementary Video 2

    Numerous motile filopodia extend from NG2+ cells. In vivo time-lapse imaging of an individual NG2+ cell located 90–135 μm from the brain surface. Images were acquired every 1.5 minutes for 1 hour. Many thin filopodia can be seen extending and retracting along the processes of this cell on a time scale of minutes (e.g. green arrow). Process tips extend many dynamic filopodia while advancing (magenta arrow). Filopodia retract after making contact with a neighboring NG2+ cell process (yellow arrow). Note the EGFP+ pericyte enwrapping a blood vessel (lower left), which pulsates due to vessel constriction and dilation. (Image width: 112 μm; frame rate: 7 frames per second).

  3. 3.

    Supplementary Video 3

    Contact mediated repulsion between NG2+ cell processes. In vivo time-lapse images showing examples of homotypic interactions between processes of an NG2+ cell. Motile filopodia that contact neighboring processes halt their extension and retract. Images were collected 128–132 μm from the cortical surface, and acquired every 3 seconds for 18.5 minutes. (Image width: 14 μm; fame rate: 50 frames per second).

  4. 4.

    Supplementary Video 4

    NG2+ cell processes with motile filopodia imaged in a thinned-skull preparation. In vivo time-lapse images from a mouse imaged through a thinned-skull window, showing the presence of motile filopodia along a NG2+ cell process. Images were collected 30–40 μm from the brain surface, and acquired every 1.5 minutes for 15 minutes. Filopodia along the NG2+ cell processes extend and retract on a time scale of minutes, similar to the dynamic behavior of filopodia seen along NG2+ cell processes in mice implanted with chronic cranial windows. (Image width: 118 μm; frame rate: 5 frames per second).

  5. 5.

    Supplementary Video 5

    Dynamic reorganization of NG2+ cells within the cortex. In vivo time-lapse images of NG2+ cells located 60–90 μm from the cortical surface. Images were acquired every 2 days for 40 days. NG2+ cells continually reorient their processes, migrate, and change their position within the cortex. An individual NG2+ cell (pseudo-colored green) is highlighted in the movie. It is located below the field of view at the start of the imaging period, and over 40 days migrates into the field of view and divides. Two blood vessels wrapped by EGFP expressing perivascular cells (pseudo-colored magenta) serve as landmarks. (Image width: 326 μm; frame rate: 5 frames per second).

  6. 6.

    Supplementary Video 6

    NG2+ cells migrate through the cortex by somatic translocation. In vivo time-lapse images of a NG2+ cell (pseudo-colored green) and a perivascular cell (pseudo-colored red) located 45–114 μm from the cortical surface. During the two week imaging period this NG2+ cell migrated by translocation of the soma after process extension, while the position of the perivascular cell remained stable. Images were acquired every 2 days for 12 days. (Image width: 157 μm; frame rate: 2 frames per second).

  7. 7.

    Supplementary Video 7

    NG2+ cells extend processes and encapsulate regions of tissue injury. In vivo time-lapse images of NG2+ cells located 150–165 μm from the cortical surface. Following induction of a laser-induced lesion at 0 hrs, NG2+ cells adjacent to the lesion reorient their processes, extend towards the lesion, encapsulating the site of injury within 24 hours. Images were acquired every 1 hour for 12 hours, and 1 day later. (Image width: 208 μm; frame rate: 3 frames per second).

  8. 8.

    Supplementary Video 8

    Tissue injury triggers homeostatic replacement of NG2+ cells. In vivo time-lapse images of NG2+ cells located 100–147 μm from the cortical surface. Following induction of a laser-induced injury (pseudo-colored yellow), NG2+ cells migrate toward the lesion over subsequent days. An individual NG2+ cell (pseudo-colored green) migrated towards the lesion site and proliferated. Note that the movie pauses to highlight reorientation of the processes of this cell and the time of cell proliferation. Images were acquired approximately every 2 days for 41 days. (Image width: 220 μm; frame rate: 3 frames per second).

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https://doi.org/10.1038/nn.3390

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