title: Steroid hormone induction of temporal gene expression inDrosophilabrain neuroblasts generates neuronal and glial diversity.
abstract: An important question in neuroscience is how stem cells generate neuronal diversity. During Drosophila embryonic development, neural stem cells (neuroblasts) sequentially express transcription factors that generate neuronal diversity; regulation of the embryonic temporal transcription factor cascade is lineage-intrinsic. In contrast, larval neuroblasts generate longer ~50 division lineages, and currently only one mid-larval molecular transition is known: Chinmo/Imp/Lin-28+ neuroblasts transition to Syncrip+ neuroblasts. Here we show that the hormone ecdysone is required to down-regulate Chinmo/Imp and activate Syncrip, plus two late neuroblast factors, Broad and E93. We show that Seven-up triggers Chinmo/Imp to Syncrip/Broad/E93 transition by inducing expression of the Ecdysone receptor in mid-larval neuroblasts, rendering them competent to respond to the systemic hormone ecdysone. Importantly, late temporal gene expression is essential for proper neuronal and glial cell type specification. This is the first example of hormonal regulation of temporal factor expression in Drosophila embryonic or larval neural progenitors.
authors.affiliation: Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.
authors.forename: Mubarak Hussain
authors.identifier: http://orcid.org/0000-0003-2424-175X
authors.initials: MH
authors.lastname: Syed
authors.affiliation: Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.
authors.forename: Brandon
authors.initials: B
authors.lastname: Mark
authors.affiliation: Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.
authors.forename: Chris Q
authors.identifier: http://orcid.org/0000-0001-5980-8029
authors.initials: CQ
authors.lastname: Doe
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000196:embryology*; D002454:Cell Differentiation / Q000187:drug effects*; D004330:Drosophila; D004440:Ecdysone / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D058953:Neural Stem Cells / Q000187:drug effects / Q000502:physiology*
chemical_list: D004440:Ecdysone
keywords: D. melanogaster; hormone; neural progenitor; neuroblast; neurogenesis; neuroscience; temporal identity; transcription factors