title: Dynamic mRNA Transport and Local Translation in Radial Glial Progenitors of the Developing Brain.
abstract: In the developing brain, neurons are produced from neural stem cells termed radial glia [1, 2]. Radial glial progenitors span the neuroepithelium, extending long basal processes to form endfeet hundreds of micrometers away from the soma. Basal structures influence neuronal migration, tissue integrity, and proliferation [3-7]. Yet, despite the significance of these distal structures, their cell biology remains poorly characterized, impeding our understanding of how basal processes and endfeet influence neurogenesis. Here we use live imaging of embryonic brain tissue to visualize, for the first time, rapid mRNA transport in radial glia, revealing that the basal process is a highway for directed molecular transport. RNA- and mRNA-binding proteins, including the syndromic autism protein FMRP, move in basal processes at velocities consistent with microtubule-based transport, accumulating in endfeet. We develop an ex vivo tissue preparation to mechanically isolate radial glia endfeet from the soma, and we use photoconvertible proteins to demonstrate that mRNA is locally translated. Using RNA immunoprecipitation and microarray analyses of endfeet, we discover FMRP-bound transcripts, which encode signaling and cytoskeletal regulators, including many implicated in autism and neurogenesis. We show FMRP controls transport and localization of one target, Kif26a. These discoveries reveal a rich, regulated local transcriptome in radial glia, far from the soma, and establish a tractable mammalian model for studying mRNA transport and local translation in vivo. We conclude that cytoskeletal and signaling events at endfeet may be controlled through translation of specific mRNAs transported from the soma, exposing new mechanistic layers within stem cells of the developing brain.
authors.affiliation: Department of Molecular Genetics and Microbiology, Research Drive, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Louis-Jan
authors.initials: LJ
authors.lastname: Pilaz
authors.affiliation: Department of Molecular Genetics and Microbiology, Research Drive, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Ashley L
authors.initials: AL
authors.lastname: Lennox
authors.affiliation: Department of Molecular Genetics and Microbiology, Research Drive, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Rouanet
authors.affiliation: Department of Molecular Genetics and Microbiology, Research Drive, Duke University Medical Center, Durham, NC 27710, USA; Department of Cell Biology, Research Drive, Duke University Medical Center, Durham, NC 27710, USA; Department of Neurobiology, Research Drive, Duke University Medical Center, Durham, NC 27710, USA; Duke Institute for Brain Sciences, Research Drive, Duke University Medical Center, Durham, NC 27710, USA. Electronic address: debra.silver@duke.edu.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Silver
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D001921:Brain / Q000196:embryology*; D063928:Ependymoglial Cells / Q000378:metabolism*; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D051379:Mice; D011485:Protein Binding; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D059467:Transcriptome
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; D012333:RNA, Messenger; C497684:Fmr1 protein, mouse
keywords: FMRP; RNA immunoprecipitation; RNA localization; corticogenesis; embryonic brain; live imaging; local translation; neural stem cell; neurogenesis; radial glia