title: Subtypes of hypoxia-responsive cells differentiate into neurons in spinal cord of zebrafish embryos after hypoxic stress.
abstract: BACKGROUND
  Neuron stem/progenitor cells (NSPCs) of zebrafish central nervous system (CNS) are known to thrive during oxygen recovery after hypoxia, but not all cell types have been fully characterised due to their heterogeneities. In addition, an in vivo model system is not available that can help us to identify what type-specific cell populations that are involved in neural regeneration and to track their cell fate after regeneration. To solve these issues, we employed a zebrafish transgenic line, huORFZ, which harbours an inhibitory upstream open reading frame of human chop mRNA fused downstream with GFP reporter and driven by cytomegalovirus promoter. When huORFZ embryos were exposure to hypoxic stress, followed by oxygen recovery, GFP was exclusively expressed in some particular cells of CNS. Unlike GFP-negative cells, all GFP-expressing cells were not apoptotic, indicating that cell populations that are able to survive after hypoxia can be identified through this approach.
  
  
  RESULTS
  When GFP-expressing cells of spinal cord were studied, we found mostly NSPCs and radial glia cells (RGs), along with a few oligodendrocyte progenitor cells and oligodendrocytes, all termed as hypoxia-responsive recovering cells (HrRCs). After hypoxic stress, these GFP-positive HrRCs did not undergo apoptosis, but GFP-negative neurons did. Prolonged recovery time after hypoxia was correlated with higher proportions of GFP(+)-NSPCs and GFP(+)-RGs, in contrast to lower proportions of proliferating/differentiating GFP(-)-NSPCs and GFP(-)-RGs. Among HrRCs subtypes, only GFP(+)-NSPCs and GFP(+)-RGs proliferated, migrated and differentiated into functional neurons during oxygen recovery. When some HrRCs were ablated in the spinal cord of hypoxia-exposed huORFZ embryos, swimming performance was impaired, suggesting that HrRCs are involved in neuronal regeneration.
  
  
  CONCLUSIONS
  We demonstrated type-specific cell populations able to respond sensitively to hypoxic stress in the spinal cord of zebrafish embryos and that these type-specific populations play a role in neural regeneration.
  
  
  CONCLUSIONS
  Among heterogeneous cell types that exist in the spinal cord of zebrafish embryos after hypoxia, the particular cells that are resistant to hypoxia and also involved in neuronal regeneration can be clearly identified and dynamically traced using a transgenic model fish.
authors.affiliation: Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Zeng
authors.affiliation: National Institute for Basic Biology, Okazaki, 444-8585, Aichi, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kamei
authors.affiliation: Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Chih-Tien
authors.initials: CT
authors.lastname: Wang
authors.affiliation: Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, 10617, Taiwan.|Institute of Biomedical Science, Mackay Medical College, New Taipei City, 252, Taiwan.
authors.forename: Huai-Jen
authors.initials: HJ
authors.lastname: Tsai
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000196:embryology / Q000235:genetics; D015687:Cell Hypoxia; D002460:Cell Line; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D058953:Neural Stem Cells / Q000166:cytology* / Q000378:metabolism; D055495:Neurogenesis; D016366:Open Reading Frames; D012333:RNA, Messenger / Q000235:genetics; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology*; D051742:Transcription Factor CHOP / Q000235:genetics; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics
chemical_list: C497249:DDIT3 protein, human; D012333:RNA, Messenger; D051742:Transcription Factor CHOP; D049452:Green Fluorescent Proteins
keywords: Hypoxic stress; Neuronal regeneration; Spinal cord injury; Zebrafish embryos