Six3 and Six6 Are Jointly Required for the Maintenance of Multipotent Retinal Progenitors through Both Positive and Negative Regulation

Cell Rep. 2018 Nov 27;25(9):2510-2523.e4. doi: 10.1016/j.celrep.2018.10.106.


Gene regulation of multipotent neuroretinal progenitors is partially understood. Through characterizing Six3 and Six6 double knockout retinas (DKOs), we demonstrate Six3 and Six6 are jointly required for the maintenance of multipotent neuroretinal progenitors. Phenotypes in DKOs were not found in either Six3 nulls or Six6 nulls. At the far periphery, ciliary margin (CM) markers Otx1 and Cdon together with Wnt3a and Fzd1 were ectopically upregulated, whereas neuroretinal progenitor markers Sox2, Notch1, and Otx2 were absent or reduced. At the mid periphery, multi-lineage differentiation was defective. The gene set jointly regulated by Six3 and Six6 significantly overlapped with the gene networks regulated by WNT3A, CTNNB1, POU4F2, or SOX2. Stimulation of Wnt/β-catenin signaling by either Wnt-3a or a GS3Kβ inhibitor promoted CM progenitors at the cost of neuroretinal identity at the periphery of eyecups. Therefore, Six3 and Six6 together directly or indirectly suppress Wnt/β-catenin signaling but promote retinogenic factors for the maintenance of multipotent neuroretinal progenitors.

Keywords: Six3; Six6; Wnt/β-catenin signaling; cell differentiation; cell fate specification; ciliary margin progenitor; multipotent neuroretinal progenitor.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Astrocytes / metabolism
  • Biomarkers / metabolism
  • Cell Differentiation
  • Cell Lineage
  • Cilia / metabolism
  • Embryo, Mammalian / cytology
  • Eye Proteins / metabolism*
  • Gene Expression Regulation*
  • Gene Regulatory Networks
  • Glycogen Synthase Kinase 3 beta / metabolism
  • Homeodomain Proteins / metabolism*
  • Humans
  • Mice, Knockout
  • Multipotent Stem Cells / metabolism*
  • Nerve Tissue Proteins / metabolism*
  • Retina / metabolism*
  • Retina / pathology
  • Trans-Activators / metabolism*
  • Up-Regulation
  • Wnt Signaling Pathway
  • Wnt3A Protein / metabolism


  • Biomarkers
  • Eye Proteins
  • Homeodomain Proteins
  • Nerve Tissue Proteins
  • Sine oculis homeobox homolog 3 protein
  • Six6 protein, mouse
  • Trans-Activators
  • Wnt3A Protein
  • Glycogen Synthase Kinase 3 beta