Cuticle differentiation in the embryo of the fruit fly Drososphila melanogaster

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The cuticle is a widespread extracellular structure shared by most animal species classified as arthropods and related taxa, and is an evolutionary successful concept to protect its possessor against dehydration, predators and pathogens, to support the body shape and to serve at the same time as an exoskeleton. To fulfil its multiple functions, the cuticle is subdivided into three horizontal layers with distinct compositions. The molecular mechanisms that implement the cuticle architecture had not been investigated yet. Our strategy to understand cuticle differentiation is to study this process during Drosophila embryogenesis profiting from the wealth of advantages this classic model organism offers. In the last few years, we have been able to identify several essential cuticle factors allowing the discovery and partial dissection of mechanisms of cuticle differentiation. In summary, the work on these factors underlines the importance of the apical plasma membrane and the need for controlled secretion for a stereotypic organisation of the cuticle. These data enable us now to tackle the problem of how different functional units of the cuticle differentiate simultaneously. We are focussing our efforts on transcriptional regulation and secretion control to answer this question, while we continue our genetic approach to isolate and characterise additional components acting during cuticle differentiation. In particular, we are interested in registering the effective transcriptome of cuticle differentiation by the identification of the target genes of the transcription factors Grainyhead, βFtzF1 and CrebA that are known to govern differentiation processes during late embryogenesis. In parallel, we seek to unravel the secretion mechanisms directing coordinated construction of the extracellular matrix that will become the cuticle. These systematic ventures will be accompanied by an RNAi-based genetic search for more effectors of cuticle differentiation, the characterisation of which will enable us to further dissect the underlying molecular mechanisms. With this project strengthened by our solid knowledge in histology, we expect to launch cuticle differentiation as a pathfinder of the research field of organ differentiation.