2026-02-27 | Mutant PLP1 impairs COPII vesicle formation via ER calcium depletion in Pelizaeus-Merzbacher disease.
Pelizaeus-Merzbacher disease (PMD) is a devastating, X-linked hypomyelinating leukodystrophy caused by mutations in a myelin gene, PLP1. While overwhelming endoplasmic reticulum (ER) stress caused by the accumulation of mutant PLP1 is widely recognized, blockade of the apoptotic arm of the unfolded protein response (UPR) failed to rescue the phenotypes in murine disease models, suggesting the involvement of additional, critical cellular mechanisms in oligodendrocyte dysfunction. Herein, we identified ER Ca2+ depletion and disrupted ER-Golgi trafficking as key cellular pathologies in PMD. Mutant PLP1 impairs COPII vesicle formation by destabilizing its key components, including Sec31A at ER exit sites due to the Ca2+ transport dysregulation and deconstruction of the ALG-2/Sec31A/AnxA11 interaction. Pharmacological restoration of ER Ca2+ levels rescued COPII formation. These findings highlight how PLP1 mutations affect the intracellular trafficking of membrane and secretory proteins through the ER Ca2+ depletion, which may be associated with the clinical consequences of PMD and other inherited myelin disorders.
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2026-02-25 | Spatially concentrated adenine base editors efficiently correct PLP1 mutations in oligodendrocytes.
Oligodendrocytes (OLs), the myelinating cells of the central nervous system, are particularly prone to pathogenic G-to-A mutations, such as PLP1A243V, which causes Pelizaeus-Merzbacher disease (PMD), a lethal hypomyelinating disorder lacking effective therapy. Although adenine base editors (ABEs) can in principle correct such mutations, their application in OLs is limited by inefficient on-target editing. Here, we develop a spatially concentrated ABE (cABE) strategy that enhances editing by promoting nuclear translocation of tRNA adenosine deaminase (TadA*) from the cytoplasm. Using a SunTag-based multivalent recruitment system, TadA* is locally enriched at genomic targets (cABE-1.0), achieving robust editing in vitro. To enable in vivo delivery while preserving high efficiency and fidelity, SpCas9 is replaced with compact eNme2-C Cas9, generating an AAV-compatible variant (cABE-2.0). Notably, cABE-2.0 forms dynamic nuclear puncta with properties of liquid-liquid phase separation, enhancing on-target editing while substantially reducing transcriptome-wide RNA off-target effects. Functionally, cABE-2.0 efficiently corrects the PLP1A243V mutation in OLs, restores Plp subcellular localization, and rescues myelination-related phenotypes. These findings demonstrate that spatial reorganization, rather than increasing intrinsic catalytic activity of TadA*, provides a distinct principle for improving base editing in difficult-to-edit cell types, such as OLs, offering a mechanistic and technical framework for gene therapy of PMD and related myelin disorders.
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2025-12-27 | Integrated stress response inhibition prolongs the lifespan of a Pelizaeus-Merzbacher disease mouse model by increasing oligodendrocyte survival.
The leukodystrophy Pelizaeus-Merzbacher disease (PMD) is caused by myelin protein proteolipid protein gene (PLP1) mutations. PMD is characterized by oligodendrocyte death and CNS hypomyelination; thus, increasing oligodendrocyte survival and enhancing myelination could provide therapeutic benefit. Here, we use the PMD mouse model Jimpy to determine the impact of the integrated stress response (ISR) on the oligodendrocyte response to mutant PLP expression. Male Jimpy animals in which the ISR-triggering eukaryotic initiation factor (eIF) 2α kinase, protein kinase-like endoplasmic reticulum kinase (PERK), is inactivated have an extended lifespan that correlates with increased oligodendrocyte survival and enhanced CNS myelination. Inactivation of downstream components of the ISR pathway, in contrast, does not rescue oligodendrocytes or myelin. Phosphorylated eIF2α inhibits the exchange factor eIF2B, resulting in diminished protein synthesis. Treatment with small molecule eIF2B activators 2BAct and ISRIB increases oligodendrocyte survival, CNS myelination, and doubled the Jimpy lifespan. These results suggest that ISR modulation could provide therapeutic benefit to PMD patients.
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