Investigating the Role of Slc4a4 in Multiple Sclerosis - ABSTRACT Multiple Sclerosis (MS) is one of the most common autoimmune diseases affecting the central nervous system, impacting approximately 2.5 million people worldwide. It is characterized by immune cell-driven inflammatory demyelination and axonal degeneration, leading to a spectrum of motor, sensory, and cognitive deficits. A key pathological hallmark of MS is increased blood-brain barrier (BBB) permeability. The BBB, composed of multiple cell types, including astrocytes, is critical for maintaining CNS homeostasis. Astrocytic dysfunction has been implicated in BBB impairment across several CNS disorders. Recent evidence suggests that Slc4a4, an astrocyte-enriched gene, plays an essential role in regulating BBB integrity during brain injury. However, its involvement in MS pathology and progression remains unexplored. To address this, we combined a novel astrocyte-specific Slc4a4 conditional knockout (Slc4a4-cKO) mouse model with the experimental autoimmune encephalomyelitis (EAE) model, a well-established MS model that recapitulates key clinical and pathological features of the disease. Our preliminary data reveal that Slc4a4-cKO mice exhibit more severe EAE clinical symptoms, including heightened blood-protein leakage, reduced expression of endothelial tight junction markers, and increased demyelination. Furthermore, bulk RNA sequencing of Slc4a4-cKO mice post-EAE induction highlights an enrichment of genes associated with endothelial cell dysfunction, although the underlying mechanisms remain unclear. To bridge this knowledge gap, I propose three aims to investigate the role of astrocytic Slc4a4 in MS progression. First, I will characterize Slc4a4 expression in human MS tissue and assess EAE pathology across different disease stages in Slc4a4-cKO mice. Next, I will explore whether overexpression of astrocytic Slc4a4 confers therapeutic benefits in EAE. Finally, I will examine the role of Edn1, a candidate gene upregulated in Slc4a4-cKO mice, along with its associated receptors, in human MS and during EAE in Slc4a4-cKO mice. Additionally, I will test whether pharmacological or genetic inhibition of the Edn1 pathway can rescue the exacerbated EAE phenotypes in Slc4a4-cKO mice. Altogether, these studies aim to uncover the Slc4a4 pathway as a potential mechanism underlying astrocyte-driven BBB dysfunction and MS pathogenesis, potentially identifying new therapeutic targets for this disease.
