Advertisement
Beyond neuronal degeneration: oligodendroglial dysfunction as a driver of spinocerebellar ataxia type 1 pathogenesis
Puneet Opal, Associate Editor
Address correspondence to: Puneet Opal, Denning Ataxia Center, Department of Neurology, Northwestern Feinberg School of Medicine, Ward 10-332, 303 East Chicago Avenue, Chicago, Illinois 69611, USA. Phone: 312.503.4699; Email: p-opal@northwestern.edu.
Find articles by Opal, P. in: PubMed | Google Scholar
Published June 15, 2026 - More info
J Clin Invest. 2026;136(12):e209207. https://doi.org/10.1172/JCI209207.
© 2026 The American Society for Clinical Investigation
Related article:
Abstract
Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disease marked by progressive motor deficits and Purkinje cell (PC) degeneration, driven by polyglutamine expansion in ataxin-1. While oligodendroglial dysfunction precedes PC loss, its direct contribution toward SCA1 pathogenesis remains unclear. Here, using an oligodendroglia-specific SCA1 conditional knockin mouse model, we demonstrate that mutant ataxin-1 in oligodendrocytes is sufficient to drive aspects of SCA1-related pathology, including dysregulated myelination, PC axonal shrinkage, and torpedo formation, ultimately impairing motor coordination. Transcriptomic analysis uncovers cerebellar oligodendrocyte subtypes with distinct gene expression signatures and aberrant abundance that contribute to demyelination. This, compounded by a progressive decline in the neuroprotective functions of a cerebellum-specific oligodendrocyte subtype, establishes a critical link between demyelination, axo-myelinic dysfunction, and axonal pathology in SCA1. Upstream transcriptional regulator analysis in oligodendroglia identifies transcription factor 7-like 2 (TCF7L2) and huntingtin (HTT) as key mediators of oligodendroglial dysfunction in SCA1, suggesting shared pathogenic mechanisms with other polyglutamine diseases. Collectively, these findings establish oligodendroglia as key mediators of SCA1 pathogenesis and underscore their critical role in preserving PC axonal integrity.
Authors
Changwoo Lee, Rosalie M. Grijalva, Leon Tejwani, Eunwoo Bae, Alison Chase, Hannah Ro, Hannah Kim, Victor Olmos, James P. Orengo, Janghoo Lim
Neurodegenerative diseases have historically been viewed as disorders of neuronal dysfunction and cell loss, with glial alterations often considered secondary or reactive phenomena despite their frequent presence in affected tissue. In spinocerebellar ataxia type 1 (SCA1), disease pathogenesis has similarly centered on degeneration of Purkinje cells, the principal projection neurons of the cerebellar cortex coordinating cerebellar output and motor function. These neurons exhibit profound vulnerability to the pathogenic polyglutamine expansion in ataxin-1 underlying SCA1. However, emerging evidence suggests glial abnormalities, including astrocytic and microglial activation, arise early during disease progression and may contribute more directly to SCA1 pathogenesis than previously appreciated (1, 2). In this issue of the JCI, Lee and colleagues provide compelling evidence that oligodendroglial dysfunction is itself an important driver of key pathological features of SCA1 (3).
Using an oligodendroglia-specific conditional knockin mouse model, the investigators selectively expressed mutant, polyglutamine-expanded ataxin-1 throughout the oligodendrocyte lineage. Strikingly, oligodendroglial expression alone induced progressive motor dysfunction, Purkinje cell axonal shrinkage, torpedo formation, and myelin abnormalities, despite the absence of overt Purkinje cell loss. These findings implicate oligodendroglia as active contributors to cerebellar circuit dysfunction rather than passive responders to neuronal degeneration.
A strength of this study is its integration of behavioral, histological, and single-nucleus transcriptomic approaches to define mechanisms linking oligodendroglial dysfunction to neuronal pathology. The authors identified distinct cerebellar oligodendrocyte subpopulations with differential vulnerability and functional specialization during disease progression. In particular, the authors identify a depletion of myelin-associated oligodendrocyte subtype, consistent with impaired myelin maintenance, alongside a transient expansion of a cerebellum-enriched oligodendrocyte subtype characterized by genes involved in axonal support and synaptic organization. These findings suggest an early compensatory response within the oligodendroglial compartment that progressively fails with disease evolution.
Upstream pathway analyses have implicated transcriptional programs associated with transcription factor 7-like 2 and huntingtin in oligodendroglial dysfunction, the latter raising the possibility that impaired axo-myelinic interactions represent a shared pathogenic mechanism across other polyglutamine-driven disorders (4). Intriguingly, recent studies have implicated ataxin-1 loss of function in multiple sclerosis, another disease associated with oligodendroglial and myelin dysfunction, raising the possibility that ataxin-1 may have broad roles in oligodendroglial biology (5).
Overall, this work substantially expands current models of SCA1 pathogenesis by positioning oligodendroglia as important mediators of disease progression. The study further highlights axo-myelinic integrity as a critical determinant of cerebellar function and suggests that therapeutic strategies aimed at restoring oligodendroglial support pathways may hold promise for not only SCA1 but also other neurodegenerative diseases characterized by white matter dysfunction. More broadly, these findings add to evidence that cerebellar degeneration is a network disease implicating various neurons and glia, not just Purkinje cells, in disease pathogenesis (6, 7). As a corollary, the findings further suggest that effective gene-targeted therapies likely need to extend beyond selectively targeting Purkinje cells or oligodendroglia alone.
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)