odd-paired: a zinc finger pair-rule protein required for the timely activation of engrailed and wingless in Drosophila embryos.

The pair-rule gene, odd-paired (opa), is essential for parasegmental subdivision of the Drosophila embryo. In addition to its previously defined role in the activation of wingless (wg) in odd parasegments, we find that opa is required for the timely activation of wg in the remaining parasegments and for the timely activation of engrailed (en) in all parasegments. opa encodes a zinc finger protein with fingers homologous to those of the Drosophila segment polarity gene ciD, the human glioblastoma gene GLI and the Caenorhabditis elegans sex determination gene tra-1. Previous work showed that opa activity was essential for the establishment of alternate parasegments, suggesting opa expression or activity would be spatially restricted like other pair-rule genes. Instead, opa mRNA and protein are found throughout all segment primordia. Thus, opa does not act in a spatially restricted manner to establish the position of en and wg expression. Rather, opa must cooperate with other spatially restricted proteins to achieve proper subdivision of the Drosophila embryo.