title: Evidence for two distinct waves of epidermal ionocyte differentiation during medaka embryonic development.
abstract: BACKGROUND
  The fish epidermis contains specific cells, or ionocytes, that are specialized in ion transport and contribute to the osmoregulatory function. Besides the zebrafish model, the medaka (Oryzias latipes) has recently emerged as an important model for osmoregulation studies because it possesses a particularly high adaptability to salinity changes. However, hindering the progress of research on embryonic ionocytes is the lack of a comprehensive view of their developmental dynamic.
  
  
  RESULTS
  Using EdU integrations and the foxi3 and NKA markers, we characterized the proliferating progenitors of ionocytes (here called ionoblastes) and we quantified them, along with ionocytes, during embryogenesis. While progenitors of the vitellin zone promptly differentiate in a synchronous manner, progenitors of the lateral zone differentiate progressively and asynchronously. Furthermore, we evidenced that nhe3 is expressed in differentiated ionocytes of both zones, whereas ecac, ncc, and gcm2 are strictly specific of the lateral zone. We also evidenced that the two zones are differentially regulated in distilled water and seawater.
  
  
  CONCLUSIONS
  Our data led us to propose a model timeline, which provides evidence for the expansion of two successive and distinct populations of ionocytes. This model opens the way for new studies related to epidermal development, plasticity and osmoregulation ontogeny.
authors.affiliation: INRA, UR1037 LPGP Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Trayer
authors.affiliation: INRA, UR1037 LPGP Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France.
authors.forename: Nina
authors.initials: N
authors.lastname: Séjourné
authors.affiliation: INRA, UR1037 LPGP Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Gay
authors.affiliation: INRA, UR1037 LPGP Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France.
authors.forename: Violette
authors.initials: V
authors.lastname: Thermes
mesh_terms: D000818:Animals; D000078404:Epidermal Cells; D004817:Epidermis / Q000196:embryology*; D029941:Fish Proteins / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D009990:Oryzias / Q000196:embryology*; D064587:Osmoregulation / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*
chemical_list: D029941:Fish Proteins; D051858:Forkhead Transcription Factors; D017923:Sodium-Hydrogen Exchangers
keywords: ecac; embryo; gcm2; ionocyte; lateral zone; mitochondria-rich cell; ncc; nhe3; vitellin zone; yolk sac epithelium