THE CHICKEN CAUDAL GENES ESTABLISH AN ANTERIOR-POSTERIOR GRADIENT BY PARTIALLY OVERLAPPING TEMPORAL AND SPATIAL PATTERNS OF EXPRESSION

The caudal genes in vertebrates as in invertebrates assume a posterior position along the anterior-posterior axis and they appear to regulat e the expression of the Hox genes. The third chicken caudal gene, Cdx- C, was cloned. Extensive comparisons of the sequence of this protein t o the other known members of this homeobox family has lead to the sugg estion that vertebrate genomes contain three members of the caudal hom eobox 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 struct ures during the primitive streak regression along the anterior-posteri or axis. This pattern of expression suggests that the number and ident ity of caudal genes expressed along the anterior-posterior axis change s dynamically. (C) 1997 Elsevier Science Ireland Ltd.