Connexin 30 (Cx30), which forms gap junctions between astrocytes, regulates cell adhesion and migration, and modulates glutamate transport. Cx30 is upregulated on activated astroglia in central nervous system inflammatory lesions, including spinal cord lesions in mutant superoxide dismutase 1 (mSOD1) transgenic amyotrophic lateral sclerosis (ALS) model mice. Here, we investigated the role of Cx30 in mSOD1 mice. Cx30 was highly expressed in the pre-onset stage in mSOD1 mice. mSOD1 mice with knockout (KO) of the Cx30 gene (Cx30KO-mSOD1 mice) showed delayed disease onset and tended to have an extended survival period (log-rank, p = 0.09). At the progressive and end stages of the disease, anterior horn cells were significantly preserved in Cx30KO-mSOD1 mice. In lesions of these mice, glial fibrillary acidic protein/C3-positive inflammatory astroglia were decreased. Additionally, the activation of astrocytes in Cx30KO-mSOD1 mice was reduced compared with mSOD1 mice by gene expression microarray. Furthermore, expression of connexin 43 at the pre-onset stage was downregulated in Cx30KO-mSOD1 mice. These findings suggest that reduced expression of astroglial Cx30 at the early disease stage in ALS model mice protects neurons by attenuating astroglial inflammation.

Multiple system atrophy (MSA) is a progressive and fatal α-synucleinopathy characterized by α-synuclein-positive (α-syn⁺) glial cytoplasmic inclusions in oligodendrocytes. The cerebellar variant (MSA-C) primarily affects olivopontocerebellar fibers, resulting in extensive demyelination and glial activation. To model this pathology, we developed a Tet-Off-based MSA-C mouse model with oligodendrocyte-specific overexpression of human A53T α-syn. Upon doxycycline withdrawal at 8 weeks of age, mice developed progressive cerebellar ataxia by 26 weeks and succumbed by 30 weeks. These mice exhibited severe demyelination and marked activation of microglia and astroglia in the brainstem and cerebellum, along with widespread propagation of α-syn oligomers and phosphorylated α-syn (p-α-syn) aggregates in oligodendrocytes, astrocytes, and neurons. Single-cell RNA sequencing of CD11b⁺ cells from the brain and spinal cord identified a distinct microglial cluster expressing Toll-like receptor 2 (Tlr2), transglutaminase 2 (Tgm2), arginase-1, macrophage scavenger receptor-1 (Msr1), inflammatory genes (such as Nfkbia, Nfkbiz, and Il1b), and chemokines (including Ccl3, Ccl4, and Ccl12). These microglia were located adjacent to p-α-syn aggregates and were distinct from previously described protective disease-associated microglia and border-associated macrophages. TLR2- and TGM2⁺Iba1⁺ microglia were particularly enriched in demyelinating lesions. Prophylactic administration of the CSF1R inhibitor BLZ945 exacerbated motor deficits and demyelination, significantly increasing this microglial population. Similarly, MSR1⁺ and CD68⁺ microglia/macrophages were observed in early pontocerebellar lesions of six human MSA-C autopsy cases. These findings suggest that this pro-inflammatory microglia subset plays a central role in disease progression and may represent a promising therapeutic target for modifying the course of MSA-C and related synucleinopathies.