Homeotic Complex (Hox) gene regulation and homeosis in the mesoderm of theDrosophila melanogaster embryo: the roles of signal transduction and cell autonomous regulation

In this paper we evaluate homeosis and Homeotic Complex (Hox) regulatory hi erarchies in the somatic and visceral mesoderm. We demonstrate that both Ho x control of signal transduction and cell autonomous regulation are critica l for establishing normal Hox expression patterns and the specification of segmental identity and morphology. We present data identifying novel regula tory interactions associated with the segmental register shift in Hox expre ssion domains between the epidermis/somatic mesoderm and visceral mesoderm. A proposed mechanism for the gap between the expression domains of Sex com bs reduced (Scr) and Antennapedia (Antp) in the visceral mesoderm is provid ed. Previously, Hox gene interactions: have been shown to occur on multiple levels: direct cross-regulation, competition for binding sites at downstre am targets and through indirect feedback involving signal transduction. We find that extrinsic specification of cell fate by signaling can be overridd en by Hox protein expression in mesodermal cells and propose the term auton omic dominance for this phenomenon. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.