The caudal genes in vertebrates as in invertebrates assume a posterior position along the anterior-posterior axis and they appear to regulate the expression of the Hox genes. The third chicken caudal gene, Cdx-C, was cloned. Extensive comparisons of the sequence of this protein to the other known members of this homeobox family has lead to the suggestion that vertebrate genomes contain three members of the caudal homeobox family. A comparative study of the chicken Cdx-A and Cdx-C genes during gastrulation and neurulation revealed the differences between the genes. The caudal genes exhibit sequential activation in the newly formed neural plate and sequential extinction in axial midline structures during the primitive streak regression along the anterior-posterior axis. This pattern of expression suggests that the number and identity of caudal genes expressed along the anterior- posterior axis changes dynamically.
Bibliographical noteFunding Information:
We wish to thank Y. Gruenbaum for the advice during the course of the work, O. Khaner, A. Frumkin and G. Pillemer for critically reading the manuscript, P. Gruss for the Cdx-1 probe, W. Gehring for the Drosophila caudal probe and K. Cho for the Xcad-1 and Xcad-2 probes. This work was funded in part by a grant from The Council of Tobacco Research Inc. USA to A.F.
- Axial specification
- Embryonic development
- Primitive streak