Human embryonic stem cells in culture possess primary cilia with hedgehog signaling machinery

J Cell Biol. 2008 Mar 10;180(5):897-904. doi: 10.1083/jcb.200706028.


Human embryonic stem cells (hESCs) are potential therapeutic tools and models of human development. With a growing interest in primary cilia in signal transduction pathways that are crucial for embryological development and tissue differentiation and interest in mechanisms regulating human hESC differentiation, demonstrating the existence of primary cilia and the localization of signaling components in undifferentiated hESCs establishes a mechanistic basis for the regulation of hESC differentiation. Using electron microscopy (EM), immunofluorescence, and confocal microscopies, we show that primary cilia are present in three undifferentiated hESC lines. EM reveals the characteristic 9 + 0 axoneme. The number and length of cilia increase after serum starvation. Important components of the hedgehog (Hh) pathway, including smoothened, patched 1 (Ptc1), and Gli1 and 2, are present in the cilia. Stimulation of the pathway results in the concerted movement of Ptc1 out of, and smoothened into, the primary cilium as well as up-regulation of GLI1 and PTC1. These findings show that hESCs contain primary cilia associated with working Hh machinery.

Publication types

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

MeSH terms

  • Axoneme / genetics
  • Axoneme / metabolism
  • Axoneme / ultrastructure
  • Cell Differentiation / genetics*
  • Cell Line
  • Cell Lineage / genetics
  • Cilia / genetics
  • Cilia / metabolism
  • Cilia / ultrastructure*
  • Culture Media, Serum-Free / pharmacology
  • Embryonic Stem Cells / metabolism
  • Embryonic Stem Cells / ultrastructure*
  • Female
  • Fluorescent Antibody Technique
  • Hedgehog Proteins / genetics
  • Hedgehog Proteins / metabolism*
  • Humans
  • Kruppel-Like Transcription Factors / genetics
  • Kruppel-Like Transcription Factors / metabolism
  • Male
  • Microscopy, Confocal
  • Microscopy, Electron, Transmission
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Patched Receptors
  • Patched-1 Receptor
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism
  • Signal Transduction / genetics*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Zinc Finger Protein GLI1
  • Zinc Finger Protein Gli2


  • Culture Media, Serum-Free
  • GLI1 protein, human
  • GLI2 protein, human
  • Hedgehog Proteins
  • Kruppel-Like Transcription Factors
  • Nuclear Proteins
  • PTCH protein, human
  • Patched Receptors
  • Patched-1 Receptor
  • Receptors, Cell Surface
  • SHH protein, human
  • Transcription Factors
  • Zinc Finger Protein GLI1
  • Zinc Finger Protein Gli2