Hypoxia tolerance in the Norrin-deficient retina and the chronically hypoxic brain studied at single-cell resolution

Proc Natl Acad Sci U S A. 2019 Apr 30;116(18):9103-9114. doi: 10.1073/pnas.1821122116. Epub 2019 Apr 15.

Abstract

The mammalian CNS is capable of tolerating chronic hypoxia, but cell type-specific responses to this stress have not been systematically characterized. In the Norrin KO (Ndp KO ) mouse, a model of familial exudative vitreoretinopathy (FEVR), developmental hypovascularization of the retina produces chronic hypoxia of inner nuclear-layer (INL) neurons and Muller glia. We used single-cell RNA sequencing, untargeted metabolomics, and metabolite labeling from 13C-glucose to compare WT and Ndp KO retinas. In Ndp KO retinas, we observe gene expression responses consistent with hypoxia in Muller glia and retinal neurons, and we find a metabolic shift that combines reduced flux through the TCA cycle with increased synthesis of serine, glycine, and glutathione. We also used single-cell RNA sequencing to compare the responses of individual cell types in Ndp KO retinas with those in the hypoxic cerebral cortex of mice that were housed for 1 week in a reduced oxygen environment (7.5% oxygen). In the hypoxic cerebral cortex, glial transcriptome responses most closely resemble the response of Muller glia in the Ndp KO retina. In both retina and brain, vascular endothelial cells activate a previously dormant tip cell gene expression program, which likely underlies the adaptive neoangiogenic response to chronic hypoxia. These analyses of retina and brain transcriptomes at single-cell resolution reveal both shared and cell type-specific changes in gene expression in response to chronic hypoxia, implying both shared and distinct cell type-specific physiologic responses.

Keywords: Norrie disease; familial exudative vitreoretinopathy; metabolomics; serine synthesis; single-cell RNA-seq.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Brain / metabolism
  • Disease Models, Animal
  • Endothelial Cells / metabolism
  • Familial Exudative Vitreoretinopathies / genetics
  • Familial Exudative Vitreoretinopathies / physiopathology
  • Female
  • Hypoxia / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Nerve Tissue Proteins / metabolism
  • Neuroglia / metabolism*
  • Neurons / metabolism*
  • Retina / metabolism
  • Retina / physiology
  • Retinal Neurons / metabolism
  • Retinal Vessels / metabolism
  • Sequence Analysis, RNA / methods
  • Single-Cell Analysis / methods

Substances

  • Nerve Tissue Proteins