title: An miRNA-mediated therapy for SCA6 blocks IRES-driven translation of the CACNA1A second cistron.
abstract: Spinocerebellar ataxia type 6 (SCA6) is a dominantly inherited neurodegenerative disease characterized by slowly progressive ataxia and Purkinje cell degeneration. SCA6 is caused by a polyglutamine repeat expansion within a second CACNA1A gene product, α1ACT. α1ACT expression is under the control of an internal ribosomal entry site (IRES) present within the CACNA1A coding region. Whereas SCA6 allele knock-in mice show indistinguishable phenotypes from wild-type littermates, expression of SCA6-associated α1ACT (α1ACTSCA6) driven by a Purkinje cell-specific promoter in mice produces slowly progressive ataxia and cerebellar atrophy. We developed an early-onset SCA6 mouse model using an adeno-associated virus (AAV)-based gene delivery system to ectopically express CACNA1A IRES-driven α1ACTSCA6 to test the potential of CACNA1A IRES-targeting therapies. Mice expressing AAV9-mediated CACNA1A IRES-driven α1ACTSCA6 exhibited early-onset ataxia, motor deficits, and Purkinje cell degeneration. We identified miR-3191-5p as a microRNA (miRNA) that targeted CACNA1A IRES and preferentially inhibited the CACNA1A IRES-driven translation of α1ACT in an Argonaute 4 (Ago4)-dependent manner. We found that eukaryotic initiation factors (eIFs), eIF4AII and eIF4GII, interacted with the CACNA1A IRES to enhance α1ACT translation. Ago4-bound miR-3191-5p blocked the interaction of eIF4AII and eIF4GII with the CACNA1A IRES, attenuating IRES-driven α1ACT translation. Furthermore, AAV9-mediated delivery of miR-3191-5p protected mice from the ataxia, motor deficits, and Purkinje cell degeneration caused by CACNA1A IRES-driven α1ACTSCA6 We have established proof of principle that viral delivery of an miRNA can rescue a disease phenotype through modulation of cellular IRES activity in a mouse model.
authors.affiliation: Department of Neurology, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Miyazaki
authors.affiliation: Department of Neurology, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Du
authors.affiliation: Division of Neurology, Department of Medicine, Jichi Medical University, Tochigi 3290498, Japan. Center for Gene and Cell Therapy, Institute of Medical Science, University of Tokyo, Tokyo 1088639, Japan.
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Muramatsu
authors.affiliation: Department of Neurology, University of Chicago, Chicago, IL 60637, USA. cgomez@neurology.bsd.uchicago.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Gomez
mesh_terms: D000818:Animals; D015153:Blotting, Western; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005796:Genes / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D000067556:Internal Ribosome Entry Sites / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D011689:Purkinje Cells / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020754:Spinocerebellar Ataxias / Q000235:genetics / Q000378:metabolism* / Q000628:therapy*
chemical_list: D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D000067556:Internal Ribosome Entry Sites; D035683:MicroRNAs; D034741:RNA, Small Interfering; C105656:CACNA1A protein, human