title: Induced expression of expanded CGG RNA causes mitochondrial dysfunction in vivo.
abstract: Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder affecting carriers of premutation forms of the FMR1 gene, resulting in a progressive development of tremor, ataxia and neuropsychological problems. The disease is caused by an expanded CGG repeat in the FMR1 gene, leading to an RNA gain-of-function toxicity mechanism. In order to study the pathogenesis of FXTAS, new inducible transgenic mouse models have been developed that expresses either 11CGGs or 90CGGs at the RNA level under control of a Tet-On promoter. When bred to an hnRNP-rtTA driver line, doxycycline (dox) induced expression of the transgene could be found in almost all tissues. Dox exposure resulted in loss of weight and death within 5 d for the 90CGG RNA expressing mice. Immunohistochemical examination of tissues of these mice revealed steatosis and apoptosis in the liver. Decreased expression of GPX1 and increased expression of cytochrome C is found. These effects were not seen in mice expressing a normal sized 11CGG repeat. In conclusion, we were able to show in vivo that expression of an expanded CGG-repeat rather than overexpression of a normal CGG-repeat causes pathology. In addition, we have shown that expanded CGG RNA expression can cause mitochondrial dysfunction by regulating expression levels of several markers. Although FTXAS patients do not display liver abnormalities, our findings contribute to understanding of the molecular mechanisms underlying toxicity of CGG repeat RNA expression in an animal model. In addition, the dox inducible mouse lines offer new opportunities to study therapeutic interventions for FXTAS.
authors.affiliation: a Department of Clinical Genetics ; Erasmus MC ; Rotterdam , The Netherlands.
authors.forename: Renate K
authors.initials: RK
authors.lastname: Hukema
authors.forename: Ronald A M
authors.initials: RA
authors.lastname: Buijsen
authors.forename: Chris
authors.initials: C
authors.lastname: Raske
authors.forename: Lies Anne
authors.initials: LA
authors.lastname: Severijnen
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Nieuwenhuizen-Bakker
authors.forename: Michelle
authors.initials: M
authors.lastname: Minneboo
authors.forename: Alex
authors.initials: A
authors.lastname: Maas
authors.forename: Rini
authors.initials: R
authors.lastname: de Crom
authors.forename: Johan M
authors.initials: JM
authors.lastname: Kros
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Hagerman
authors.forename: Robert F
authors.initials: RF
authors.lastname: Berman
authors.forename: Rob
authors.initials: R
authors.lastname: Willemsen
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001259:Ataxia / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004318:Doxycycline / Q000378:metabolism; D005234:Fatty Liver / Q000473:pathology; D005600:Fragile X Syndrome / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D014202:Tremor / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D017382:Reactive Oxygen Species; D012313:RNA; D004318:Doxycycline
keywords: CGG repeat; FXTAS; FXTAS, Fragile X-associated tremor/ataxia syndrome; RNA gain-of-function; TRE, Tet Responsive Element; Tet-On; apoptosis; caspase 3; cytochrome C; dox, doxycycline; eGFP, enhanced green fluorescent protein; gpx, gluthation peroxidase; gpx-1; inducible mouse model; mitochondria; rtTA, reverse tetracycline transactivator