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

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.

A novelPSMB8isoform associated with multiple sclerosis lesions induces P-body formation

“…This most frequently occurred in the chronic active lesion border, where inflammation is thought to persist. This corresponds with preclinical observations correlating alternative splicing with inflammation (Marchese et al, 2021, Adinolfi et al, 2023.…”

“…Proinflammatory cytokines induce alternative splicing in many genes in vitro , including in primary astrocytes derived from human MS patients (Werkman et al, 2020). Additionally, in animal models of MS, splicing is dysregulated in lesions and this aberrant splicing correlates with interleukin-1β expression (Marchese et al, 2021, Adinolfi et al, 2023). Additionally, the microglial splicing factor QKI-5 is downregulated in brain WMLs of MS patients (Lee et al, 2020).…”

A novel PSMB8 isoform associated with multiple sclerosis lesions induces P-body formation

“…This most frequently occurred in the chronic active lesion border, where inflammation is thought to persist. This corresponds with preclinical observations correlating alternative splicing with inflammation ( Marchese et al, 2021 , Adinolfi et al, 2023 ). Indeed, a recent study has highlighted a potential role for the splicing factor hnRNP A1 in neurodegeneration in MS lesions ( Salapa et al, 2024 ).…”

“…Proinflammatory cytokines induce alternative splicing in many genes in vitro , including in primary astrocytes derived from human MS patients ( Werkman et al, 2020 ). Additionally, in animal models of MS, splicing is dysregulated in lesions and this aberrant splicing correlates with interleukin-1β expression ( Marchese et al, 2021 ; Adinolfi et al, 2023 ). Further, the microglial splicing factor QKI-5 is downregulated in brain WMLs of MS patients ( Lee et al, 2020 ).…”

New Challenges for Anatomists in the Era of Omics

“…This knowledge has implications for understanding neurodevelopmental disorders, brain plasticity, and potential therapeutic interventions. For example, the combination of the growing amount of histochemical markers and proteins [ 157 , 158 , 159 , 160 , 161 ] such as neurofilament (NFL), microtubule-associated protein (MAP), Tau, synaptic proteins, growth cone (such as GAP-43) and neuronal nuclear markers (such as NeuN, doublecortin and Reelin), and glial fibrillary acidic protein (GFAP), allows pathologists and researchers to assess the health and maturity of neurons, dissect the anatomy of the peripheral nervous system [ 162 ] and identify pathological changes associated with various neurological disorders [ 163 ].…”