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

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

Author information

1
Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
2
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
3
McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
4
Moran Eye Center, University of Utah, Salt Lake City, UT 84132.
5
Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205; jnathans@jhmi.edu.
6
Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
7
Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205.

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

PMID:
30988181
PMCID:
PMC6500147
[Available on 2019-10-15]
DOI:
10.1073/pnas.1821122116

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