A Drosophila model of Pontocerebellar Hypoplasia reveals a critical role for the RNA exosome in neurons

• Type of Material: Article
• Authors: Derrick J. Morton, Emory University; Binta Jalloh, Emory University; Lily Kim, Emory University; Isaac Kremsky, Emory University; Rishi J. Nair, Emory University; Khuong B. Nguyen, Emory University; J. Christopher Rounds, Emory University; Maria C. Sterrett, Emory University; Brianna Brown, Emory University; Thalia Le, Emory University; Maya C. Karkare, Emory University; Kathryn D. McGaughey, Emory University; Shaoyi Sheng, Emory University; Sara Leung, Emory University; Milo Fasken, Emory University; Kenneth Moberg, Emory University; Anita Corbett, Emory University
• Language: English
• Date: 2020-07-09
• Publisher: Public Library of Science (PLoS)
• Publication Version: Final Published Version
• Copyright Statement: © 2020 Morton et al
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pgen.1008901
• Title of Journal or Parent Work: PLoS Genetics
• Volume: 16
• Issue: 7
• Grant/Funding Information: This work was supported by both a National Institutes of Health F32 grant (GM125350) and a Postdoctoral Enrichment Award from the Burroughs Wellcome Fund to D.J.M, National Institutes of Health F31 grants to B.J. (NS103595) and J.C.R (HD088043), a National Institutes of Health R01 grant (MH107305) to A.H.C. and K.H.M, and a National Institutes of Health R01 grant (GM130147) to A.H.C. D.J.M. was also supported by the Emory University National Institutes of Health Institutional Research and Academic Career Development Award (IRACDA) (GM000680) Fellowships in Research and Science Teaching (FIRST) Postdoctoral Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
• Keywords: exosome; degradation; tissue-specific disease; PCH1b; EXOSC3; ribonuclease complex; encoding structure; gene; RNA
• Research Categories: Biology, Cell; Biology, Genetics

Abstract

The RNA exosome is an evolutionarily-conserved ribonuclease complex critically important for precise processing and/or complete degradation of a variety of cellular RNAs. The recent discovery that mutations in genes encoding structural RNA exosome subunits cause tissue-specific diseases makes defining the role of this complex within specific tissues critically important. Mutations in the RNA exosome component 3 (EXOSC3) gene cause Pontocerebellar Hypoplasia Type 1b (PCH1b), an autosomal recessive neurologic disorder. The majority of disease-linked mutations are missense mutations that alter evolutionarily-conserved regions of EXOSC3. The tissue-specific defects caused by these amino acid changes in EXOSC3 are challenging to understand based on current models of RNA exosome function with only limited analysis of the complex in any multicellular model in vivo. The goal of this study is to provide insight into how mutations in EXOSC3 impact the function of the RNA exosome. To assess the tissue-specific roles and requirements for the Drosophila ortholog of EXOSC3 termed Rrp40, we utilized tissue-specific RNAi drivers. Depletion of Rrp40 in different tissues reveals a general requirement for Rrp40 in the development of many tissues including the brain, but also highlight an age-dependent requirement for Rrp40 in neurons. To assess the functional consequences of the specific amino acid substitutions in EXOSC3 that cause PCH1b, we used CRISPR/Cas9 gene editing technology to generate flies that model this RNA exosome-linked disease. These flies show reduced viability; however, the surviving animals exhibit a spectrum of behavioral and morphological phenotypes. RNA-seq analysis of these Drosophila Rrp40 mutants reveals increases in the steady-state levels of specific mRNAs and ncRNAs, some of which are central to neuronal function. In particular, Arc1 mRNA, which encodes a key regulator of synaptic plasticity, is increased in the Drosophila Rrp40 mutants. Taken together, this study defines a requirement for the RNA exosome in specific tissues/cell types and provides insight into how defects in RNA exosome function caused by specific amino acid substitutions that occur in PCH1b can contribute to neuronal dysfunction.