Zebrafish Klf4 maintains the ionocyte progenitor population by regulating epidermal stem cell proliferation and lateral inhibition

Chen, Y.C., Liao, B.K., Lu, Y.F., Liu, Y.H., Hsieh, F.C., Hwang, P.P., Hwang, S.L.
PLoS Genetics   15: e1008058 (Journal)
Registered Authors
Hwang, Pung Pung, Hwang, Sheng-Ping L.
MeSH Terms
  • Amino Acid Sequence
  • Animals
  • Animals, Genetically Modified
  • Body Patterning
  • Cell Differentiation
  • Cell Proliferation
  • Cyclin-Dependent Kinase Inhibitor p21/genetics
  • Cyclin-Dependent Kinase Inhibitor p21/metabolism
  • Ectoderm/cytology
  • Ectoderm/embryology
  • Ectoderm/metabolism
  • Embryonic Stem Cells/cytology*
  • Embryonic Stem Cells/metabolism*
  • Epidermal Cells/cytology*
  • Epidermal Cells/metabolism*
  • Gene Expression Regulation, Developmental
  • Gills/cytology
  • Gills/embryology
  • Gills/metabolism
  • Intracellular Signaling Peptides and Proteins/genetics
  • Intracellular Signaling Peptides and Proteins/metabolism
  • Ion Transport
  • Kruppel-Like Transcription Factors/deficiency
  • Kruppel-Like Transcription Factors/genetics
  • Kruppel-Like Transcription Factors/metabolism*
  • Membrane Proteins/genetics
  • Membrane Proteins/metabolism
  • Phosphoproteins/genetics
  • Phosphoproteins/metabolism
  • Promoter Regions, Genetic
  • Receptors, Notch/genetics
  • Receptors, Notch/metabolism
  • Trans-Activators/genetics
  • Trans-Activators/metabolism
  • Tumor Suppressor Protein p53/genetics
  • Tumor Suppressor Protein p53/metabolism
  • Zebrafish/embryology*
  • Zebrafish/genetics
  • Zebrafish/metabolism*
  • Zebrafish Proteins/deficiency
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
30933982 Full text @ PLoS Genet.
In the skin and gill epidermis of fish, ionocytes develop alongside keratinocytes and maintain body fluid ionic homeostasis that is essential for adaptation to environmental fluctuations. It is known that ionocyte progenitors in zebrafish embryos are specified from p63+ epidermal stem cells through a patterning process involving DeltaC (Dlc)-Notch-mediated lateral inhibition, which selects scattered dlc+ cells into the ionocyte progenitor fate. However, mechanisms by which the ionocyte progenitor population is modulated remain unclear. Krüppel-like factor 4 (Klf4) transcription factor was previously implicated in the terminal differentiation of mammalian skin epidermis and is known for its bifunctional regulation of cell proliferation in a tissue context-dependent manner. Here, we report novel roles for zebrafish Klf4 in the ventral ectoderm during embryonic skin development. We found that Klf4 was expressed in p63+ epidermal stem cells of the ventral ectoderm from 90% epiboly onward. Knockdown or knockout of klf4 expression reduced the proliferation rate of p63+ stem cells, resulting in decreased numbers of p63+ stem cells, dlc-p63+ keratinocyte progenitors and dlc+ p63+ ionocyte progenitor cells. These reductions subsequently led to diminished keratinocyte and ionocyte densities and resulted from upregulation of the well-known cell cycle regulators, p53 and cdkn1a/p21. Moreover, mutation analyses of the KLF motif in the dlc promoter, combined with VP16-klf4 or engrailed-klf4 mRNA overexpression analyses, showed that Klf4 can bind the dlc promoter and modulate lateral inhibition by directly repressing dlc expression. This idea was further supported by observing the lateral inhibition outcomes in klf4-overexpressing or knockdown embryos. Overall, our experiments delineate novel roles for zebrafish Klf4 in regulating the ionocyte progenitor population throughout early stem cell stage to initiation of terminal differentiation, which is dependent on Dlc-Notch-mediated lateral inhibition.
Genes / Markers
Figure Gallery
Mutation and Transgenics
Human Disease / Model Data
Sequence Targeting Reagents
Engineered Foreign Genes
Errata and Notes