SPECIFICATION OF ANTEROPOSTERIOR CELL FATES IN CAENORHABDITIS-ELEGANSBY DROSOPHILA HOX PROTEINS

ANTENNAPEDIA class homeobox (Hox) genes specify cell fates in successi ve anteroposterior body domains in vertebrates, insects and nematodes( 1-3). The DNA-binding homeodomain sequences are very similar between v ertebrate and Drosophila Hox proteins, and this similarity allows vert ebrate Hox proteins to function in Drosophila(4-7). In contrast, the C aenorhabditis elegans homeodomains are substantially divertent(8). Fur ther, C. elegans differs from both insects and vertebrates in having a non-segmented body as well as a distinctive mode of development that involves asymmetric early cleavages and invariant cell lineages. Here we report that, despite these differences, Drosophila Hox proteins exp ressed in C. elegans can substitute for C. elegans Hox proteins in the control of three different cell-fate decisions: the regulation of cel l migration, the specification of serotonergic neurons, and the specif ication of a sensory structure. We also show that the specificity of o ne C. elegans Hox protein is partly determined by two amino acids that have been implicated in sequence-specific DNA binding. Together these findings suggest that factors important for target recognition by spe cific Hox proteins have been conserved throughout much of the animal k ingdom.