Journal Article

Expression of an expanded CGG-repeat RNA in a single pair of primary sensory neurons impairs olfactory adaptation in <i>Caenorhabditis elegans</i>

Bi-Tzen Juang, Anna L. Ludwig, Kelli L. Benedetti, Chen Gu, Kimberly Collins, Christopher Morales, Aarati Asundi, Torsten Wittmann, Noelle L'Etoile and Paul J. Hagerman

in Human Molecular Genetics

Volume 23, issue 18, pages 4945-4959
Published in print September 2014 | ISSN: 0964-6906
Published online May 2014 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddu210

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Fragile X-associated tremor/ataxia syndrome (FXTAS) is a severe neurodegenerative disorder that affects carriers of premutation CGG-repeat expansion alleles of the fragile X mental retardation 1 (FMR1) gene; current evidence supports a causal role of the expanded CGG repeat within the FMR1 mRNA in the pathogenesis of FXTAS. Though the mRNA has been observed to induce cellular toxicity in FXTAS, the mechanisms are unclear. One common neurophysiological characteristic of FXTAS patients is their inability to properly attenuate their response to an auditory stimulus upon receipt of a small pre-stimulus. Therefore, to gain genetic and cell biological insight into FXTAS, we examined the effect of expanded CGG repeats on the plasticity of the olfactory response of the genetically tractable nematode, Caenorhabditis elegans (C. elegans). While C. elegans is innately attracted to odors, this response can be downregulated if the odor is paired with starvation. We found that expressing expanded CGG repeats in olfactory neurons interfered with this plasticity without affecting either the innate odor-seeking response or the olfactory neuronal morphology. Interrogation of three RNA regulatory pathways indicated that the expanded CGG repeats act via the C. elegans microRNA (miRNA)-specific Argonaute ALG-2 to diminish olfactory plasticity. This observation suggests that the miRNA-Argonaute pathway may play a pathogenic role in subverting neuronal function in FXTAS.

Journal Article.  9381 words.  Illustrated.

Subjects: Genetics and Genomics

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