Homeo box genes and animal development

Abstract

Homeotic and segmentation genes of Drosophila effect crucial patterning decisions in the morphogenesis of the fruit fly body plan. Many of these genes are members of a highly diverged multi-gene family. The signal homology for this family is the homeo box, a protein coding sequence of approximately 180 base pairs. The mouse and human genomes also contain multi-gene families with homeo boxes very similar to those found in Drosophila. A tenable hypothesis is that the various members of this gene family perform similar morphogenetic programming functions in both fly and mouse development. Thus far, there are two lines of experimental evidence that support this hypothesis. The first is that comparison of specific Drosophila and mouse gene homeo box gene sequences shows that some of the individual genes in the two species are truly homologues in terms of structure, i.e., individual homeo box genes had evolved conserved and separate functions before the evolutionary divergence that eventually gave rise to arthropods and mammals. The second line of evidence is that the patterns of expression of mouse homeo box genes during embryonic development show remarkable similarities to the patterns of expression exhibited by their Drosophila counterparts.