1. Astroglial-targeted expression of the fragile X CGG repeat premutation in mice yields RAN translation, motor deficits and possible evidence for cell-to-cell propagation of FXTAS pathology
- Author
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Kyoungmi Kim, Michael R. Hunsaker, Lies Anne Severijnen, Saif N Haify, Rob Willemsen, Albert R. La Spada, H. Jürgen Wenzel, Paul J. Hagerman, Christopher Raske, Bryce L. Sopher, Robert F. Berman, Karl D Murray, Renate K. Hukema, Jared J. Schwartzer, and Clinical Genetics
- Subjects
0301 basic medicine ,Male ,Pathology ,Gene Expression ,Cell Communication ,Neurodegenerative ,Inbred C57BL ,Transgenic ,lcsh:RC346-429 ,Fragile X Mental Retardation Protein ,Mice ,0302 clinical medicine ,Tremor ,Non-cell-autonomous ,Neocortex ,biology ,Neurodegeneration ,Fragile X premutation ,Motor Skills Disorders ,medicine.anatomical_structure ,Neurological ,FMRpolyG ,medicine.symptom ,Astrocyte ,medicine.medical_specialty ,Ataxia ,Intellectual and Developmental Disabilities (IDD) ,Clinical Sciences ,Mice, Transgenic ,Neuropathology ,Pathology and Forensic Medicine ,Mouse model ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Rare Diseases ,RAN translation ,Glia ,Genetics ,medicine ,Animals ,lcsh:Neurology. Diseases of the nervous system ,Electron microscopy of inclusions ,Base Sequence ,Research ,Neurosciences ,medicine.disease ,FMR1 ,Brain Disorders ,Mice, Inbred C57BL ,030104 developmental biology ,nervous system ,Astrocytes ,Fragile X Syndrome ,biology.protein ,Biochemistry and Cell Biology ,Neurology (clinical) ,FXTAS ,NeuN ,Trinucleotide repeat expansion ,Trinucleotide Repeat Expansion ,030217 neurology & neurosurgery - Abstract
The fragile X premutation is a CGG trinucleotide repeat expansion between 55 and 200 repeats in the 5′-untranslated region of the fragile X mental retardation 1 (FMR1) gene. Human carriers of the premutation allele are at risk of developing the late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). Characteristic neuropathology associated with FXTAS includes intranuclear inclusions in neurons and astroglia. Previous studies recapitulated these histopathological features in neurons in a knock-in mouse model, but without significant astroglial pathology. To determine the role of astroglia in FXTAS, we generated a transgenic mouse line (Gfa2-CGG99-eGFP) that selectively expresses a 99-CGG repeat expansion linked to an enhanced green fluorescent protein (eGFP) reporter in astroglia throughout the brain, including cerebellar Bergmann glia. Behaviorally these mice displayed impaired motor performance on the ladder-rung test, but paradoxically better performance on the rotarod. Immunocytochemical analysis revealed that CGG99-eGFP co-localized with GFAP and S-100ß, but not with NeuN, Iba1, or MBP, indicating that CGG99-eGFP expression is specific to astroglia. Ubiquitin-positive intranuclear inclusions were found in eGFP-expressing glia throughout the brain. In addition, intracytoplasmic ubiquitin-positive inclusions were found outside the nucleus in distal astrocyte processes. Intriguingly, intranuclear inclusions, in the absence of eGFP mRNA and eGFP fluorescence, were present in neurons of the hypothalamus and neocortex. Furthermore, intranuclear inclusions in both neurons and astrocytes displayed immunofluorescent labeling for the polyglycine peptide FMRpolyG, implicating FMRpolyG in the pathology found in Gfa2-CGG99 mice. Considered together, these results show that Gfa2-CGG99 expression in mice is sufficient to induce key features of FXTAS pathology, including formation of intranuclear inclusions, translation of FMRpolyG, and deficits in motor function. Electronic supplementary material The online version of this article (10.1186/s40478-019-0677-7) contains supplementary material, which is available to authorized users.
- Published
- 2019