Adeno-Associated Virus-Based Gene Therapy for Lafora Disease in Epm2b-Deficient Mice

Lafora disease is a fatal neurodegenerative disorder caused by loss-of-function mutations in the EPM2A or EPM2B genes, which encode laforin and malin, respectively. These mutations lead to the accumulation of intracellular inclusions of abnormal glycogen, known as Lafora bodies, the hallmark of the disease. Symptoms typically begin in early adolescence with seizures and rapidly progress to cognitive and motor decline, ultimately resulting in dementia and death within a decade of onset. Disruption of Epm2a or Epm2b in mice causes neuronal degeneration and Lafora body accumulation in the brain and other tissues. Epm2a^-/- and Epm2b^-/- mice exhibit motor and memory impairments, epileptic activity, and molecular and histological abnormalities. We previously demonstrated that intracerebroventricular delivery of a recombinant adeno-associated virus carrying EPM2A significantly improved pathology in Epm2a^-/- mice. In this study, we tested recombinant adeno-associated virus-mediated delivery of the human EPM2B gene in Epm2b^-/- mice. The treatment partially improved neurological, molecular, and histopathological outcomes, although some pathological features persisted. Importantly, our findings reveal differences between EPM2A- and EPM2B-based gene therapies, highlighting the need to better understand their distinct mechanisms. Despite limitations, our study provides new insights into the complexity of targeting EPM2B mutations in Lafora disease.