Hox transcription factors have a well-documented role in morphogenesis along the anteroposterior axis. They are expressed colinearly along the body axis and regulate specific downstream targets via their conserved DNA-binding homeodomain. But only a small number of their transcriptional target genes have so far been identified. On p. 381, Hueber et al. report the identification of potentially hundreds of new Hox targets from a microarray analysis designed to identify the targets of six Drosophila Hox proteins. The authors validated many of these targets by in situ hybridisations in different genetic backgrounds, and interestingly reveal how most targets are regulated by a specific Hox protein. Many of the identified genes have known functions in processes such as apoptosis, cell migration and cell-cell adhesion. For example, skl, an apoptotic activator, is identified as a target of the Hox protein Deformed (Dfd), and has reduced expression in Dfd mutants, accompanied by reduced apoptosis. Many targets encode transcription factors, such that Hox factors appear to regulate morphogenesis indirectly.
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