Expression profiling by high throughput sequencing
Single-cell RNA-seq of a mouse model of MS uncovers new oligodendrocyte populations, putative disease markers and suggests new mechanisms underlying the pathogenesis of disease. In Multiple Sclerosis (MS), oligodendrocytes (OLs) are damaged during an immune system attack targeting myelin. It remains unclear how different OL lineage cells respond to inflammatory autoimmune demyelination in MS. We performed single-cell transcriptomics analysis of OL lineage cells from the spinal cord of mice induced with experimental autoimmune encephalomyelitis (EAE), which mimics certain aspects of MS. We found unique OLs and OL precursor cells (OPCs) in EAE, including populations expressing genes involved in antigen processing and presentation via major histocompatibility complex (MHC) Class I and II, but also in immunoprotection. We further uncovered several genes specifically alternatively spliced in OL lineage cells in EAE, including Mbp, Mobp and Pdgfa. Strikingly, we identified a substantial number of genes known to be susceptibility genes for MS, so far mainly associated with immune cells in the context of this disease, to be expressed in the OL lineage cells. Finally, we found that disease-specific oligodendroglia are present in human MS brains. Our results suggest that OL and OPCs are not passive targets but instead active immunomodulators in MS. The disease-specific OL lineage cells, for which we identify several biomarkers, may represent novel direct targets for immunomodulatory therapeutic approaches in MS.
Mouse lines used in this study included C57BL/6NJ wild type mice, Pdgfra-Cre-LoxP- GFP and Pdgfra-H2B-GFP knock-in mice. Experimental Autoimmune Encephalomyelitis mice were generated by subcutaneous injection with an emulsion in MOG35-55 in complete Freud’s adjuvant (CFA) (EK-2110 kit from Hooke Laboratories) followed by the administration of pertussis toxin in PBS (0,2μg per animal), for two consecutive days (all according to manufacture’s instructions). Spinal cords and cerebellum were collected at the chronic stage of the disease with clinical score=3 representing limp tail and complete paralysis of hind legs. Animals that did not reach this clinical score were not analysed in this study. Additional animals were injected subcutaneously with a CFA emulsion (CK-2110 kit from Hooke Laboratories) and used as controls.