GSE125708
Hypoxia tolerance in the Norrin-deficient retina and the chronically hypoxic brain stuied at single-cell resolution
The mammalian central nervous system (CNS) is capable of tolerating chronic hypoxia, but cell type-specific responses to this stress have not been systematically characterized.  In the Norrin-knockout (NdpKO) 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 have used single-cell RNA sequencing, untargeted metabolomics, and metabolite labeling from 13C-glucose to compare wild type and NdpKO retinas.  In NdpKO 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 tricarboxylic acid 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 NdpKO retinas to those in the hypoxic cerebral cortex of mice that were housed for one 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 NdpKO retina.  In both retina and brain, vascular endothelial cells activate a previously dormant tip cell gene expression program, which likely underlies the adaptive neo-angiogenic 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. Overall design: Single-cell RNAseq of NdpKO and WT retinas as well as normoxic and hypoxic cerebral cortices; Ribotag RNA-seq of NdpKO and WT retinas; RNA-seq of normoxic and hypoxic whole brains.