Résumé :
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Correct diversification of cell types during development is controlled by combinatorial code of transcription factor activities, the identity gene code. The role of identity genes in specifying cell fates has been demonstrated in a broad range of developing tissues and metazoan organisms. However, our understanding of the global gene expression program that operates downstream of the identity gene code and leads to the acquisition of a given cell fate remains very limited. Particularly well suited to studying cell fate acquisition are Drosophila somatic muscles for which virtually all cell types can be identified by specific molecular markers. Recently, we have used microarray and ChIP on chip approaches (Junion et al., 2007) to identify downstream targets of Ladybird homeodomain factors known to be required for the identity of a small subset of Drosophila muscle precursors. Unsuspectedly, our data revealed that ladybird acts over a long time period and at multiple levels by regulating directly not only other identity genes, as previously thought, but also late acting genes encoding modulators of actin cytoskeleton involved in determining the morphological, dynamic and functional properties of muscle fibers (Junion et al, 2007). Junion, G., Bataillé, L., Jagla, T., Da Ponte, J.P., Tapin, R. and Jagla, K. (2007). Genome-wide view of cell fate specification: ladybird acts at multiple levels during diversification of muscle and heart precursors. Genes & Dev 21, 3163-80.
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