OBJECTIVE OF THE EXPERIMENT The objective of these experiments is to understand some of the major principles underlying neural development by applying classic and modern genetic experimental techniques to this problem. In this chapter we will study (1) the neural and ectodermal phenotypes of different mutations, (2) the use of classic loss-of-function and conditional alleles with modern gain-of-function techniques, and (3) genetic interactions that allow the determination of epistatic relationships among genes.

DEGREE OF DIFFICULTY Moderate. The experiments require some experience in the handling of flies and in the preparation of microscope slides for cuticle preparations and whole-mount antibody staining.

INTRODUCTION

The precisely regulated formation of neurons and glial cells is of obvious importance during development of higher metazoan organisms. Work over the last few decades has led to the initially surprising finding that invertebrates and vertebrates utilize very similar molecular mechanisms to elaborate a functional nervous system.

In all animals, neural tissue develops from the ectoderm. This raises the question of how ectodermal cells are initially routed towards the neural fate and how the correct number of neural founder cells is established in a stereotyped pattern. Pioneering work on Drosophila neurogenesis has set the stage for efficient molecular dissection of neural development.

THE PROCESS

During the blastoderm stage, positional information is translated to define the neurogenic ectoderm that resides between the mesodermal anlage and the future dorsal ectoderm (Figure 1a). In addition, a domain that will give rise to the brain is set aside as the procephalic ectoderm.