DEVELOPMENTAL RESCUE OF DROSOPHILA CEPHALIC DEFECTS BY THE HUMAN OTX GENES

The molecular mechanisms of head development are a central question in vertebrate and invertebrate developmental biology, The anteriorly exp ressed homeobox gene otd in Drosophila and its homolog Otx in mouse ar e required for the early development of the most anterior part of the body, suggesting that a fundamental genetic program of cephalic develo pment might be conserved between vertebrates and invertebrates, We hav e examined this hypothesis by introducing the human Otx genes into fli es, By inducing expression of the human Otx homologs with a heat shock promoter, we found that both Otx1 and Otx2 functionally complement th e cephalic defects of a fly otd mutant through specific activation and inactivation of downstream genes, Combined with previous morphologica l studies, these results are consistent with the view that a common mo lecular ground plan of cephalization was invented before the diversifi cation of the protostome and the deuterostome in the course of metazoa n evolution.