Control of antennal versus leg development in Drosophila.
During the evolution of insects from a millipede-like ancestor, the Hox genes are thought to have promoted the diversification of originally identical body structures. In Drosophila melanogaster, antennae and legs are homologous structures that differ from each other as a result of the Hox gene Antennapedia (Antp), which promotes leg identities by repressing unknown antennal-determining genes. Here we present four lines of evidence that identify extradenticle (exd) and homothorax (hth) as antennal-determining genes. First, removing the function of exd or hth, which is required for the nuclear localization of Exd protein, transforms the antenna into leg; such transformations occur without activation of Antp. Second, hth is expressed and Exd is nuclear in most antennal cells, whereas both are restricted to proximal cells of the leg. Third, Antp is a repressor of hth. Fourth, ectopic expression of Meis1, a murine hth homologue, can trigger antennal development elsewhere in the fly. Taken together, these data indicate that hth is an antennal selector gene, and that Antp promotes leg development by repressing hth and consequently nuclear Exd.
Casares
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F
Department of Biochemistry and Molecular Biophysics, Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Mann
R S
RS
D000818:Animals; D051943:Antennapedia Homeodomain Protein; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D017344:Genes, Insect; D018398:Homeodomain Proteins / Q000235:genetics*; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics; D009687:Nuclear Proteins; D012679:Sense Organs / Q000196:embryology*; D014157:Transcription Factors / Q000235:genetics*
D051943:Antennapedia Homeodomain Protein; C497974:Antp protein, Drosophila; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C083405:exd protein, Drosophila; C108704:hth protein, Drosophila