Expression of the cCdx-B homeobox gene in chick embryo suggests its participation in rostrocaudal axial patterning.
cCdx-B (formerly cHox-cad 2) is a chick homeobox-containing gene related to the Drosophila caudal. Compared with other caudal homologues, its similarity is highest with the murine Cdx-4. In the present study, we characterize the localization of cCdx-B transcripts to the caudal region of the embryo by using reverse transcription-polymerase chain reaction (RT-PCR) and, in detail, by using in situ hybridization. Chick embryos from gastrulation to early organogenesis were hybridized with digoxigenin-labeled riboprobes, and the pattern of expression of cCdx-B mRNA was analyzed in wholemount embryos and in tissue sections. In the early gastrula, transcripts were localized in a gradient through the caudal half of the embryo, in the epiblast and the mesoderm cells, but not including Hensen's node. During neurulation, cCdx-B transcripts were found more rostrally, with high levels localized in Hensen's node and the posterior neural plate. Expression was also high in paraxial mesoderm, with a rostral limit in the most recently formed somite. There was no expression in definitive endoderm. During late neurulation and tail bud formation, cCdx-B mRNA expression regressed posteriorly and was finally confined to the tail bud region. This pattern of expression of cCdx-B, regulated in time and space, is different from that of the other known chick caudal homologue, cCdx-A. Both genes may play a coordinated role in the posterior axial patterning of the chick embryo, whereas cCdx-B may specify further the identity of the tail region.
Morales
A V
AV
Department of Cell and Developmental Biology, CSIC, Madrid, Spain.
de la Rosa
E J
EJ
de Pablo
F
F
D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins; D001483:Base Sequence; D002642:Chick Embryo; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data
D030161:Avian Proteins; D018398:Homeodomain Proteins