Expression of JNK target genes during dorsal closure of the Drosophila embryo

Tissue morphogenesis relies on proper differentiation of morphogenetic domains, adopting specific cell behaviours. Yet, how signalling pathways interact to determine and coordinate these domains remains poorly understood. Dorsal closure (DC) of the Drosophila embryo represents a powerful model to study epithelial cell sheet sealing. In this process, JNK (JUN N-terminal Kinase) signalling controls leading edge (LE) differentiation generating local forces and cell shape changes essential for DC. The LE represents a key morphogenetic domain in which, in addition to JNK, a number of signalling pathways converges and interacts (anterior/posterior -AP- determination; segmentation genes, such as Wnt/Wingless; TGFβ/Decapentaplegic). To better characterize properties of the LE morphogenetic domain, we used microarrays to identify genes whose expression is regulated by the JNK pathway during dorsal closure of the Drosophila embryo. Three genetic conditions were compared: wild-type (WT), gain of function (GOF) and loss of function (LOF). For the GOF embryos, the JNK pathway was strongly activated by expressing HepACT in the ectoderm using the UAS-GAL4 system (69B-GAL4). For the LOF embryos, we used a combination of 2 alleles, heprev75 and hep1. Carefully staged embryos, corresponding to stages 13 and 14, were collected and for each condition, three independent RNA samples were prepared to be hybridized on the microarrays.