Regionally restricted modulation of Sam68 expression and Arhgef9 alternative splicing in the hippocampus of a murine model of multiple sclerosis

Annalisa Adinolfi; Gabriele Di Sante; Luca Rivignani Vaccari; Maria Tredicine; Francesco Ria; Davide Bonvissuto; Valentina Corvino; Claudio Sette; Maria Concetta Geloso

doi:10.3389/fnmol.2022.1073627

Regionally restricted modulation of Sam68 expression and Arhgef9 alternative splicing in the hippocampus of a murine model of multiple sclerosis

Front Mol Neurosci. 2023 Jan 12:15:1073627. doi: 10.3389/fnmol.2022.1073627. eCollection 2022.

Authors

Annalisa Adinolfi¹, Gabriele Di Sante², Luca Rivignani Vaccari¹, Maria Tredicine³, Francesco Ria³, Davide Bonvissuto¹, Valentina Corvino¹, Claudio Sette^{1

4}, Maria Concetta Geloso¹

Affiliations

¹ Section of Human Anatomy, Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy.
² Section of Human, Clinic and Forensic Anatomy, Department of Medicine and Surgery, University of Perugia, Perugia, Italy.
³ Section of General Pathology, Department of Translational Medicine and Surgery, Università Cattolica del Sacro Cuore, Rome, Italy.
⁴ GSTEP-Organoids Core Facility, Fondazione Policlinico Agostino Gemelli IRCCS, Rome, Italy.

Abstract

Multiple sclerosis (MS) and its preclinical models are characterized by marked changes in neuroplasticity, including excitatory/inhibitory imbalance and synaptic dysfunction that are believed to underlie the progressive cognitive impairment (CI), which represents a significant clinical hallmark of the disease. In this study, we investigated several parameters of neuroplasticity in the hippocampus of the experimental autoimmune encephalomyelitis (EAE) SJL/J mouse model, characterized by rostral inflammatory and demyelinating lesions similar to Relapsing-Remitting MS. By combining morphological and molecular analyses, we found that the hippocampus undergoes extensive inflammation in EAE-mice, more pronounced in the CA3 and dentate gyrus (DG) subfields than in the CA1, associated with changes in GABAergic circuitry, as indicated by the increased expression of the interneuron marker Parvalbumin selectively in CA3. By laser-microdissection, we investigated the impact of EAE on the alternative splicing of Arhgef9, a gene encoding a post-synaptic protein playing an essential role in GABAergic synapses and whose mutations have been related to CI and epilepsy. Our results indicate that EAE induces a specific increase in inclusion of the alternative exon 11a only in the CA3 and DG subfields, in line with the higher local levels of inflammation. Consistently, we found a region-specific downregulation of Sam68, a splicing-factor that represses this splicing event. Collectively, our findings confirm a regionalized distribution of inflammation in the hippocampus of EAE-mice. Moreover, since neuronal circuit rearrangement and dynamic remodeling of structural components of the synapse are key processes that contribute to neuroplasticity, our study suggests potential new molecular players involved in EAE-induced hippocampal dysfunction.

Keywords: Arhgef9; Sam68; alternative splicing; experimental autoimmune encephalomyelitis; hippocampus; multiple sclerosis; neuroinflammation; parvalbumin.