Genomic structure and embryonic expression of the Xenopus winged helix factors XFD-13/13'.

We have isolated the gene, its corresponding cDNA and a closely related cDNA encoding the Xenopus winged helix factors XFD-13' and XFD-13, respectively. XFD-13/13' are regarded as pseudo-alleles and, based upon a comparison of sequences and genomic structures, represent the Xenopus orthologues to mammalian FREAC-1/HFH-8. XFD-13/13' genes are not transcribed during oogenesis, zygotic transcription starts at late gastrula/early neurula and transcripts persist throughout embryogenesis. Expression is found within head derived neural crest cells and the dorsolateral plate (DLP). At later developmental stages, cell populations of the DLP migrate to the ventral region but exclude the most posterior part. Since they are subsequently found to accumulate in vessel like structures, we suggest that these cells represent hematopoietic/endothelial progenitor cells.