Small RNA sequencing of differentiated astrocytoma exposed to NMOSD patient sera reveals perturbations in neurodegenerative signaling.

Abstract

The signaling pathways behind severe astrocytic lysis with Aquaporin4 auto-antibody (AQP4-IgG) seropositivity, and reactive astrocytosis with myelin oligodendrocyte glycoprotein auto-antibody (MOG-IgG) seropositivity, remain largely unexplored in Neuromyelitis optica spectrum disorder (NMOSD), while almost no molecular details being known about double-seronegative (DN) patients. Recent discovery of glial fibrillary acidic protein (GFAP) in DN NMOSD patients' cerebrospinal fluid, akin to AQP4-IgG + ve cases, suggests astrocytopathy. Here, we aim to study small non coding RNA (sncRNA) signature alterations in astrocytes exposed to AQP4-IgG + ve and MOG-IgG + ve patient sera, and their potential resemblance with DN-NMOSD. Next Generation Sequencing (NGS) revealed differential expression of several microRNAs with notable alterations in hsa-miR-6824-3p, hsa-miR-324-5p and hsa-miR-4466 respectively upon sera treatment. Results with DN-NMOSD patient sera are majorly similar to that of AQP4+ve sera. Strikingly, in all three treatments, hsa-miR-200b-3p was significantly upregulated. Functional enrichment analysis revealed that Hippo and FoxO signaling pathways were primarily impacted in AQP4-IgG + ve and double negative sera treated cells whereas, MOG-IgG + ve sera treatment perturbed the PI3K-Akt and MAPK signaling pathways. Furthermore, NGS also revealed differential expression of several piRNAs in cells upon treatment with AQP4-IgG + ve and MOG-IgG + ve sera and VEGF signaling was identified as the common target of differentially expressed piRNAs of both the groups. This study, for the first time, revealed that the molecular pathophysiology of double-seronegative NMOSD might involve astrocytopathy akin to AQP4+ve NMOSD, thus pointing towards the possible existence of unidentified astrocytic autoimmune targets and identified the major alterations in intracellular sncRNAs and the associated overall cellular signaling pathways that potentially contribute to the fate of astrocytes during the progression of the disease.