title: The Hunchback temporal transcription factor establishes, but is not required to maintain, early-born neuronal identity.
abstract: BACKGROUND
  Drosophila and mammalian neural progenitors typically generate a diverse family of neurons in a stereotyped order. Neuronal diversity can be generated by the sequential expression of temporal transcription factors. In Drosophila, neural progenitors (neuroblasts) sequentially express the temporal transcription factors Hunchback (Hb), Kruppel, Pdm, and Castor. Hb is necessary and sufficient to specify early-born neuronal identity in multiple lineages, and is maintained in the post-mitotic neurons produced during each neuroblast expression window. Surprisingly, nothing is currently known about whether Hb acts in neuroblasts or post-mitotic neurons (or both) to specify first-born neuronal identity.
  
  
  METHODS
  Here we selectively remove Hb from post-mitotic neurons, and assay the well-characterized NB7-1 and NB1-1 lineages for defects in neuronal identity and function.
  
  
  RESULTS
  We find that loss of Hb from embryonic and larval post-mitotic neurons does not affect neuronal identity. Furthermore, removing Hb from post-mitotic neurons throughout the entire CNS has no effect on larval locomotor velocity, a sensitive assay for motor neuron and pre-motor neuron function.
  
  
  CONCLUSIONS
  We conclude that Hb functions in progenitors (neuroblasts/GMCs) to establish heritable neuronal identity that is maintained by a Hb-independent mechanism. We suggest that Hb acts in neuroblasts to establish an epigenetic state that is permanently maintained in early-born neurons.
authors.affiliation: Howard Hughes Medical Institute, Eugene, 97403, USA.|Institute of Molecular Biology, Eugene, 97403, USA.|Institute of Neuroscience, University of Oregon, Eugene, 97403, USA.
authors.forename: Keiko
authors.initials: K
authors.lastname: Hirono
authors.affiliation: Department of Neuroscience, Columbia University Medical Center, New York, NY, 10032, USA.
authors.forename: Minoree
authors.initials: M
authors.lastname: Kohwi
authors.affiliation: Howard Hughes Medical Institute, Eugene, 97403, USA.|Institute of Molecular Biology, Eugene, 97403, USA.|Institute of Neuroscience, University of Oregon, Eugene, 97403, USA.
authors.forename: Matt Q
authors.initials: MQ
authors.lastname: Clark
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, 60637, USA.
authors.forename: Ellie S
authors.initials: ES
authors.lastname: Heckscher
authors.affiliation: Howard Hughes Medical Institute, Eugene, 97403, USA. cdoe@uoregon.edu.|Institute of Molecular Biology, Eugene, 97403, USA. cdoe@uoregon.edu.|Institute of Neuroscience, University of Oregon, Eugene, 97403, USA. cdoe@uoregon.edu.
authors.forename: Chris Q
authors.initials: CQ
authors.lastname: Doe
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D004331:Drosophila melanogaster; D018507:Gene Expression Regulation, Developmental; D008124:Locomotion; D008938:Mitosis; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D014157:Transcription Factors; C061245:hb protein, Drosophila