Abstract
In Drosophila melanogaster, the neuroblasts (neural progenitor cells) develop from a special region of the ectoderm, called the neuroectoderm. During early embryonic development, the neuroblasts separate from the remaining cells of the neuroectoderm, which develop as epidermoblasts (epidermal progenitor cells). The separation of these two cell types is the result of cellular interactions. The available data indicate that a signal chain formed by the products of several identified genes regulates the cell's decision to enter either neurogenesis or epidermogenesis. Various kinds of data, in particular from cell transplantation studies and from genetic and molecular analyses, suggest that the proteins encoded by the genes Notch and Delta interact at the membrane of the neuroectodermal cells to provide a regulatory signal. This signal is thought to lead, on the one hand, to epidermal development through the action of the genes of the Enhancer of split complex, a gene complex that encodes several functions related to the transduction and further processing of the signal, including the genetic regulation in the receiving cell; on the other hand, the signal is thought to lead to neural development through the participation of the genes of the achaete-scute complex and daughterless, which are members of a family of DNA-binding regulatory proteins and of the gene vnd whose molecular nature is still unknown.
