Gene therapy rescues brain edema and motor function in a mouse model of megalencephalic leukoencephalopathy with subcortical cysts

Abstract

Gene therapy; Megalencephalic leukoencephalopathy with subcortical cysts; White matter

Teràpia gènica; Leucoencefalopatia megalencefàlica amb quists subcorticals; Matèria blanca

Terapia génica; Leucoencefalopatía megalencefálica con quistes subcorticales; Materia blanca

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an ultrarare, infantile-onset leukodystrophy characterized by white matter edema for which there is no treatment. More than 75% of diagnosed cases result from biallelic loss-of-function mutations in the astrocyte-specific gene MLC1, leading to early-onset macrocephaly, cerebellar ataxia, epilepsy, and mild cognitive decline. To develop a gene therapy for MLC, we administered an adeno-associated viral vector capable of crossing the murine blood-brain barrier, delivering the human MLC1 cDNA under the control of a human astrocyte-specific promoter, to 10-month-old Mlc1−/− mice. We observed long-term astrocyte-driven expression of MLC1 up to 1 year after viral vector administration in all brain areas analyzed. Despite the late-stage intervention, in vivo magnetic resonance imaging revealed normalization of water accumulation. Notably, our therapy successfully reversed locomotor deficits in Mlc1−/− mice, as evidenced by improved performance in motor tests assessing cerebellar ataxia-like behaviors. Collectively, these findings not only demonstrate the sustained efficacy of our gene therapy but also highlight the reversibility of vacuolation and motor impairments in Mlc1−/− mice, suggesting that MLC patients could benefit from treatment even after symptom onset.

This study was funded by the European Leukodystrophies Association (ELA2018-005I2, ELA2022-004I2 to A.Bosch), the Spanish Network of Advanced Therapies (TERAV), NextGenerationEU – Recovery, Transformation and Resilience Plan (RD21/0017/0008 to M.C.), Generalitat de Catalunya (2021-SGR00529 to A.Bosch, 2024 FI-1 0080 to I.R.), the Spanish Ministry of Universities (FPU20/00187 to A.Brao), and the Spanish Ministry of Science and Innovation (PID2021-126246NB-I00 to R.E.). We thank Jorge Lunar (Institute of Neurosciences, Universitat Autònoma de Barcelona) for his valuable technical assistance. This article is dedicated to the memory of Virginia Nunes.