Patterning the Drosophila Embryonic Central Nervous System: Establishing Neuroblast-Specific Gene Expression and Identity

Abstract

The Drosophila embryonic central nervous system (CNS) develops from the ventral neuroectoderm, which produces a stereotyped array of neural precursor cells, called neuroblasts. Neuroblasts are unique, based on their position in the embryo, the genes they express, and the number and type of neuronal progeny they produce. A fundamental problem in the development of any animal is how to generate cell diversity. Studying the mechanisms of neuroblast differentiation will help to understand cellular differentiation at a broad level. In this thesis, I present new information on how neuroectoderm position translates into neuroblast-specific gene expression. Along the antero-posterior axis, a group of segment polarity genes---hedgehog, wingless, engrailed, and gooseberry---act in the neuroectoderm and in neuroblasts to regulate the spatial pattern of huckebein, a gene required for the proper development of identified neurons and glia. Along the dorso-ventral axis, the ventral nervous system defective gene is expressed in ventral neuroectoderm and neuroblasts bordering the midline and specifies the identity of these cells. Thus, neuroblast identity is specified in the neuroectoderm by the combined action of antero-posterior and dorso-ventral patterning genes.