Expression of the novel basic-helix-loop-helix transcription factor cMespo in presomitic mesoderm of chicken embryos.

We have identified a novel chicken gene, cMespo, which encodes a basic-helix-loop-helix (bHLH) protein with sequence homology to a subgroup of bHLH transcription factors that have been implicated in somitogenesis. cMespo transcripts are first found in the primitive streak of gastrulating chick embryos (HH stage 4) and continue to accumulate in presomitic mesoderm (PSM) until somite formation has been concluded. cMespo, however, is not expressed within somites or in tailbud mesoderm. The expression domain of cMespo in PSM largely overlaps with delta-1 but spares a region of several prospective somites at the rostral end of PSM in which c-Meso and Cek-8 are expressed.