Machado-Joseph disease/spinocerebellar ataxia type 3 (MJD/SCA3) is a genetic neurodegenerative disorder associated with expansion of the CAGs number within the coding region of MJD1 gene, which translates into an expanded polyglutamine tract within ataxin-3 (ATXN3) protein, leading to the formation of a mutated form (mutATXN3). MJD patients have severe clinical manifestations and premature death and there is no treatment available. Transcriptional dysregulation has been shown to contribute to MJD pathogenesis. More recently, microRNAs (miRNA) dysregulation in other neurodegenerative disorders was suggestive of a potential role in MJD, however knowledge on this subject is very scarce. In a previous study where we evaluated miRNA let-7 role in MJD, we demonstrated that delivery of let-7 to the striatum of a lentiviral (LV) mouse model of MJD was sufficient to reduce neuronal protein aggregation in the context of significantly upregulated LC3-II levels, thus indicating that let-7-mediated autophagy activation is beneficial to MJD. In addition, very recently our group identified mir-9, mir-181a and mir- 494 predicted to target ATXN3 3?UTR. Overexpression of these miRNAs effectively reduced mutATXN3 levels and ameliorated the associated MJD neuropathology. These achievements demonstrate that it is of crucial importance to pursue the investigation of miRNAs expression profiling in MJD. Preliminary data suggest that a set of miRNAs are dysregulated in a LV mouse model of MJD. Particularly, miR-10b appears dysregulated and reinstatement of miR-10b normal levels ameliorated MJD phenotype. Moreover, transthyretin was identified as a direct miR- 10b target. Therefore, the aim of this project is to identify dysregulated miRNAs that contribute decisively to MJD pathology, taking advantage of modulation of miRNA levels to develop a miRNA-based therapeutic strategy, and simultaneously to identify their associated target transcriptome. In the first task, we will pursue with miRNA profiling in LV and transgenic (Tg) mouse models of the disease and in fibroblasts and human induced pluripotent stem cells (hiPSCs) derived neurons obtained from MJD patients to identify dysregulated miRNAs. In the second task, LV vectors encoding the most relevant miRNAs or miRNAs inhibitors, depending on miRNA levels in a disease context, will be used as an in vivo gene therapy strategy that will be evaluated both in striatal LV and Tg mouse models of MJD. Finally, in the third task having identified miRNAs with the highest therapeutic effect, we will explore the miRNA targets involved in the miRNA mediated-neuroprotective effect, which may also be used as novel therapeutic strategies. These studies will contribute to characterize the miRNAs expression profiling in different models of MJD, to validate selected miRNAs and develop a miRNA-based therapy to MJD, and simultaneously to identify the associated miRNA target players, which may also be used as novel therapeutic strategies.
The aim of this project is to identify dysregulated miRNAs that contribute decisively to MJD pathology, taking advantage of miRNA modulation to correct miRNA levels in this way developing a miRNA-based therapeutic strategy, and simultaneously to identify their associated target transcriptome.
PTDC/MED-NEU/32309/2017 | POCI-01-0145-FEDER-032309