Characterization of Xenopus Phox2a and Phox2b defines expression domains within the embryonic nervous system and early heart field

Gene Expr Patterns. 2004 Sep;4(5):601-7. doi: 10.1016/j.modgep.2004.01.012.


The closely related homeodomain containing genes, Phox2a and Phox2b, are essential for neuronal specification and differentiation within discrete subsets of neurons during vertebrate embryogenesis. We have isolated Xenopus Phox2 homologs, termed Xphox2a and Xphox2b, and characterized their expression during early development. In addition, we have characterized a Phox2a splice variant, termed Xphox2a.2, which lacks homeo- and C-terminal protein coding domains. Xphox2a, Xphox2a.2 and Xphox2b transcripts are expressed in dynamic temporal and regional patterns during nervous system development. The expression of Xphox2a and Xphox2b is only partially overlapping and includes cranial motor and interneuron populations as well as peripheral sympathetic and cranial ganglion neurons, sites linked to Phox2 expression in other species. In addition, we have identified an early domain of Xphox2a and subsequent Xphox2b expression in ventral regions of the embryo, within the developing heart field. XPhox2 expression within this domain is preceded by the gastrula-stage expression of the proneural basic helix-loop-helix transcription factor, Xash1, pointing to a new region of action for this group transcription factors during vertebrate development.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Basic Helix-Loop-Helix Transcription Factors
  • Gene Expression Regulation, Developmental
  • Gene Expression*
  • Heart / embryology
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • In Situ Hybridization
  • Molecular Sequence Data
  • Nerve Tissue Proteins / metabolism
  • Nervous System / embryology
  • Nervous System / metabolism*
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Xenopus / embryology*
  • Xenopus / metabolism
  • Xenopus Proteins / metabolism


  • Basic Helix-Loop-Helix Transcription Factors
  • Homeodomain Proteins
  • NBPhox protein
  • Nerve Tissue Proteins
  • Transcription Factors
  • Xenopus Proteins
  • ascl1 protein, Xenopus