MITOCHONDRIAL DYSFUNCTION SHAPES CEREBELLUM MECHANICS, NEUROINFLAMMATION, AND METABOLIC IMBALANCE: INSIGHTS FROM THE HARLEQUIN MOUSE

Mitochondrial diseases (MD) are rare genetic disorders caused by defects in the oxidative phosphorylation (OXPHOS) system, affecting high-energy-demanding tissues, such as the nervous system. The Harlequin (Hq) mouse, characterized by Apoptosis-Inducing Factor (AIF) deficiency and OXPHOS complex I dysfunction, is a well-established MD model that develops progressive cerebellar ataxia. While neuronal vulnerability has been extensively studied in the model, our work indicates that intrinsic glial dysfunction, neuroinflammation, and alterations in tissue mechanics may act as early drivers of neurodegeneration.
To further investigate the intrinsic nature of these defects, we analyzed primary cultures of cerebellar astrocytes and microglia. Hq-derived astrocytes exhibited cell-autonomous OXPHOS defect, with reduced oxygen consumption rates, increased endogenous H₂O₂ levels, and impaired antioxidant capacity. Likewise, Hq-derived microglia showed lower levels of OXPHOS complex I and IV subunits and a pro-inflammatory phenotype, marked by increased TNFα and IL-1β production under oxidative stress conditions.
In this study, we combined in vitro analyses with high-throughput transcriptomics and measurements of cerebellar mechanical properties. Preliminary single-nucleus RNA sequencing from 6-month-old Hq cerebellum revealed widespread transcriptional changes across multiple cell populations. Remarkably, we identified a link between metabolic and inflammatory disturbances in Hq cerebellum with alterations in tissue mechanics. Our findings suggest that neuroinflammation and edema reduce tissue stiffness in both granular and molecular layers of Hq cerebellum.
In conclusion, our results indicate that convergence of glial dysfunction, neuroinflammation, and altered mechanical properties creates a pathological microenvironment promoting cerebellar degeneration. Targeting glial activation and restoring mechanical properties may represent promising therapeutic strategies for MD.