Hox genes regulate segmentation in the terminal regions of Drosophila through the activation of apoptosis. I. Endl , W. McGinnis. Dept Biol, Univ California , San Diego, San Diego, CA.

   To understand the morphogenesis of segments along the anterior-posterior (A/P) body axis of animals, it is crucial to identify cell biological processes directly regulated by Hox genes. In the head of Drosophila embryos the Hox gene Deformed (Dfd) is necessary for maintaining the boundary between the maxillary and mandibular segments. We show that Dfd accomplishes this function by inducing apoptosis through the direct activation of the cell death gene reaper (rpr). The unsuspected role of Dfd in acting as a segmentation gene by activating apoptosis is also true for at least one other Hox gene, since abdominal-B (abd-B) uses the same mechanism. Thus, in Drosophila Hox genes seem to play a role in the sculpting of segments by inducing cell death at the segment boundaries.