Characterization of a murine homeo box gene, Hox-2.6, related to the Drosophila Deformed gene.

The Hox-2 locus on chromosome 11 represents one of the major clusters of homeo-box-containing genes in the mouse. We have identified two new members (Hox-2.6 and Hox-2.7), which form part of this cluster of seven linked genes, and it appears that the Hox-2 locus is related by duplication and divergence to at least one other mouse homeo box cluster, Hox-1. The Hox-2.6 gene encodes a predicted protein of 250 amino acids, which displays extensive similarity in multiple regions to certain mouse, human, Xenopus, and zebra fish homeo domain proteins. The Drosophila Deformed (Dfd) gene also shares these same regions of similarity, and based on this sequence conservation, we suggest that Hox-2.6 forms part of a vertebrate 'Dfd-like' family. Hox-2.6 is expressed in fetal and adult tissues and is modulated during the differentiation of F9 teratocarcinoma stem cells. In situ hybridization analysis of mouse embryos shows that the Hox-2.6 is expressed in ectodermal derivatives: spinal cord, hindbrain, dorsal root ganglia, and the Xth cranial ganglia. In the central nervous system, expression is observed in the most posterior parts of the spinal cord, with the anterior limit residing in a region of the hindbrain and no expression in the mid- or forebrain. In mesodermal structures, Hox-2.6 is expressed in the kidney, the mesenchyme of the stomach and lung, and the longitudinal muscle layer of the gut. Expression has not been observed in derivatives of embryonic endoderm. The patterns of Hox-2.6 expression in both mesoderm and ectoderm are spatially restricted and may reflect a role for the gene in the response to or establishment of positional cues in the embryo.