Intrinsic and extrinsic signals in the developing vertebrate and fly eyes: viewing vertebrate and invertebrate eyes in the same light.

The development of complex tissues, such as the nervous system, requires coordinated interactions between cells, and defining the molecular basis of these interactions is a primary goal of developmental neurobiology. Classic experimental embryological studies of the developmental potential of embryonic neural tissues have more recently been augmented by genetic and molecular approaches to yield a picture of the mechanisms by which such complex neural structures arise during development. Perhaps coincidentally, two of the most well-studied structures in this regard have been the eyes of Drosophila and vertebrates. In the past few years, a number of laboratories have focused on the development of the eye, of both Drosophila and vertebrates in order to understand the role of cell-cell interactions in the generation of organized neural structures. Recent evidence from both the vertebrate and Drosophila models suggests that common mechanisms apply in both systems, particularly in the role of tyrosine kinases in regulating phenotypic choices during histogenesis. Thus, although the eyes of flies and vertebrates have very different appearances, we examine the possibility that similar developmental processes are used to produce tissues with analogous functions.