XCoe2, a transcription factor of the Col/Olf-1/EBF family involved in the specification of primary neurons in Xenopus

Curr Biol. 1998 Feb 12;8(4):199-209. doi: 10.1016/s0960-9822(98)70084-3.


Background: Primary neurogenesis in Xenopus is a model for studying the control of neural cell fate decisions. The specification of primary neurons appears to be driven by transcription factors containing a basic region and a helix-loop-helix (HLH) motif: expression of Xenopus neurogenin-related-1 (X-ngnr-1) defines the three prospective domains of primary neurogenesis, and expression of XNeuroD coincides with neuronal differentiation. The transition between neuronal competence and stable commitment to a neuronal fate remains poorly characterised, however.

Results: Drosophila Collier and rodent early B-cell factor/olfactory-1 define a family of HLH transcription factors containing a previously unknown type of DNA-binding domain. We isolated an orthologous gene from Xenopus, Xcoe2, which is expressed in precursors of primary neurons. Xcoe2 is transcribed after X-ngnr-1 and before XNeuroD. Overexpression of a dominant-negative mutant of XCoe2 prevented neuronal differentiation. Conversely, overexpressed wild-type Xcoe2 could promote ectopic differentiation of neurons, in both the neural plate and the epidermis. In contrast to studies with X-ngnr-1 or XNeuroD, the supernumerary neurons induced by Xcoe2 appeared in a 'salt-and-pepper' pattern, resulting from the activation of X-Delta1 expression and feedback regulation by lateral inhibition.

Conclusions: XCoe2 may play a pivotal role in the transcriptional cascade that specifies primary neurons in Xenopus embryos: by maintaining Delta-Notch signalling, XCoe2 stabilises the higher neural potential of selected progenitor cells that express X-ngnr-1, ensuring the transition between neural competence and irreversible commitment to a neural fate; and it promotes neuronal differentiation by activating XNeuroD expression, directly or indirectly.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Basic Helix-Loop-Helix Transcription Factors
  • DNA, Complementary
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Drosophila
  • Gene Expression Regulation, Developmental
  • Helix-Loop-Helix Motifs
  • Mice
  • Models, Biological
  • Molecular Sequence Data
  • Nerve Tissue Proteins / genetics
  • Nervous System / cytology
  • Nervous System / embryology
  • Neurons / cytology*
  • Signal Transduction
  • Trans-Activators / chemistry
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Tubulin / genetics
  • Xenopus
  • Xenopus Proteins*


  • Basic Helix-Loop-Helix Transcription Factors
  • DNA, Complementary
  • DNA-Binding Proteins
  • Ebf1 protein, mouse
  • Nerve Tissue Proteins
  • Trans-Activators
  • Transcription Factors
  • Tubulin
  • Xenopus Proteins
  • ebf2 protein, Xenopus
  • NeuroD protein