HARNESSING ASCL1- AND NEUROG2-INDUCED GLIAL REPROGRAMMING TO TREAT MACHADO–JOSEPH DISEASE

Machado–Joseph Disease (MJD) is an autosomal dominant neurodegenerative disorder caused by CAG repeat expansion in the MJD1 gene, resulting in toxic polyglutamine accumulation and progressive neuronal dysfunction. Currently, no effective treatments exist to halt disease progression. This study evaluated astrocyte-to-neuron direct reprogramming as a potential therapeutic strategy for MJD.
Astrocyte reprogramming was induced using the transcription factors Achaete-scute homolog 1 (Ascl1) and Neurogenin 2 (Ngn2), which promote glutamatergic and/or GABAergic neuronal identities. Lentiviral (LV) and AAV5 vectors combined with a Cre-Flex system (GFAP::Cre with FLEx-CAG::TF-P2A-mCherry) were employed to selectively target astrocytes and enable lineage tracing. TFs were delivered to the striatum of wild-type mice and to the deep cerebellar nuclei of severely symptomatic SCA3 transgenic mice (69Q, 6–8 weeks old).
In wild-type mice, LV-mediated TF delivery produced robust mCherry expression, confirming efficient Cre-Flex recombination and increased NeuN expression. TF-treated conditions showed elevated Iba1 and GFAP expression, consistent with a TF-specific glial response, without evidence of toxicity or DARPP-32–positive neuronal loss, suggesting glial proliferation. In MJD mice, viral genome quantification confirmed AAV5 delivery, although transgene expression was low. We observed gait parameters improvement, whereas neuronal marker expression remained unchanged. Co-localization of NeuN and mCherry nevertheless confirmed astrocyte-to-neuron reprogramming.
These findings demonstrate that Ascl1 and Ngn2 can induce glia-to-neuron conversion in vivo. However, further optimization of dosing and therapeutic timing will be performed to enhance reprogramming efficiency and therapeutic impact in MJD. Moreover, efficiency of TF delivery using LNPs-encapsulated mRNAs and viral vectors will be compared.