Abstract
Dorsal closure during Drosophila embryogenesis provides a robust genetic platform to study the basic cellular mechanisms that govern epithelial wound healing and morphogenesis. As dorsal closure proceeds, the lateral epithelial tissue (LE) adjacent to the dorsal opening advance contra-laterally, with a simultaneous retraction of the amnioserosa. The process involves a fair degree of coordinated cell shape changes in the dorsal most epithelial (DME) cells as well as a few penultimate rows of lateral epithelial (LE) cells (collectively referred here as Dorsolateral Epithelial (DLE) cells), lining the periphery of the amnioserosa, which in due course of time extend contra-laterally and ultimately fuse over the dorsal hole, giving rise to a dorsal epithelial continuum. The JNK-Dpp signaling in the dorsolateral epidermis, plays an instrumental role in guiding their fate during this process. A large array of genes have been reported to be involved in the regulation of this core signaling pathway, yet the mechanisms by which they do so is hitherto unclear, which forms the objective of our present study. Here we show a probable mechanism via which lgl, a conserved tumour suppressor gene, regulates the JNK-Dpp pathway during dorsal closure and epithelial morphogenesis. A conditional/targeted knock-down of lgl in the dorsolateral epithelium of embryos results in failure of dorsal closure. Interestingly, we also observed a similar phenotype in a Rab11 knockdown condition. Our experiment suggests Rab11 to be interacting with lgl as they seem to synergize in order to regulate the core JNK-Dpp signaling pathway during dorsal closure and also during adult thorax closure process.
