title: The N17 domain mitigates nuclear toxicity in a novel zebrafish Huntington's disease model.
abstract: BACKGROUND
  Although the genetic cause for Huntington's disease (HD) has been known for over 20 years, the mechanisms that cause the neurotoxicity and behavioral symptoms of this disease are not well understood. One hypothesis is that N-terminal fragments of the HTT protein are the causative agents in HD and that peptide sequences adjacent to the poly-glutamine (Q) repeats modify its toxicity. Here we test the function of the N-terminal 17 amino acids (N17) in the context of the exon 1 fragment of HTT in a novel, inducible zebrafish model of HD.
  
  
  RESULTS
  Deletion of N17 coupled with 97Q expansion (mHTT-ΔN17-exon1) resulted in a robust, rapidly progressing movement deficit, while fish with intact N17 and 97Q expansion (mHTT-exon1) have more delayed-onset movement deficits with slower progression. The level of mHTT-ΔN17-exon1 protein was significantly higher than mHTT-exon1, although the mRNA level of each transgene was marginally different, suggesting that N17 may regulate HTT protein stability in vivo. In addition, cell lineage specific induction of the mHTT-ΔN17-exon1 transgene in neurons was sufficient to recapitulate the consequences of ubiquitous transgene expression. Within neurons, accelerated nuclear accumulation of the toxic HTT fragment was observed in mHTT-ΔN17-exon1 fish, demonstrating that N17 also plays an important role in sub-cellular localization in vivo.
  
  
  CONCLUSIONS
  We have developed a novel, inducible zebrafish model of HD. These animals exhibit a progressive movement deficit reminiscent of that seen in other animal models and human patients. Deletion of the N17 terminal amino acids of the huntingtin fragment results in an accelerated HD-like phenotype that may be due to enhanced protein stability and nuclear accumulation of HTT. These transgenic lines will provide a valuable new tool to study mechanisms of HD at the behavioral, cellular, and molecular levels. Future experiments will be focused on identifying genetic modifiers, mechanisms and therapeutics that alleviate polyQ aggregation in the nucleus of neurons.
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Veldman
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
authors.forename: Yesenia
authors.initials: Y
authors.lastname: Rios-Galdamez
authors.affiliation: Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, Los Angeles, USA.|Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, Los Angeles, USA.|Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Lu
authors.affiliation: Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, Los Angeles, USA.|Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, Los Angeles, USA.|Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Gu
authors.affiliation: Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Qin
authors.affiliation: Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
authors.forename: Song
authors.initials: S
authors.lastname: Li
authors.affiliation: Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, Los Angeles, USA.|Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, Los Angeles, USA.|Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
authors.forename: X William
authors.initials: XW
authors.lastname: Yang
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA. shuolin@ucla.edu.|Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China. shuolin@ucla.edu.
authors.forename: Shuo
authors.initials: S
authors.lastname: Lin
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics; D001522:Behavior, Animal / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D004195:Disease Models, Animal; D005091:Exons / Q000235:genetics; D006816:Huntington Disease / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics; D015027:Zebrafish
chemical_list: D009687:Nuclear Proteins