Search

Neuronal process remodeling occurs widely in the construction of both invertebrate and vertebrate nervous systems. During Drosophila metamorphosis, γ neurons of the mushroom bodies (MBs), the center for olfactory learning in insects, undergo pruning of larval-specific dendrites and axons followed by outgrowth of adult-specific processes. To elucidate the underlying molecular mechanisms, we conducted a genetic mosaic screen and identified one ultraspiracle ( usp ) allele defective in larval process pruning. Consistent with the notion that USP forms a heterodimer with the ecdysone receptor (EcR), we found that the EcR-B1 isoform is specifically expressed in the MB γ neurons, and is required for the pruning of larval processes. Surprisingly, most identified primary EcR/USP targets are dispensable for MB neuronal remodeling. Our study demonstrates cell-autonomous roles for EcR/USP in controlling neuronal remodeling, potentially through novel downstream targets.

During the development of the adult central nervous system (CNS) of the fruitfly Drosophila melanogaster, the A-isoform of the ecdysone receptor (EcR-A), a typical nuclear hormone receptor, is expressed at high levels in the Type II neurons, a set of neurons that die shortly after the emergence of the adult. To understand the role that transcriptional regulation of nuclear receptor genes plays in CNS development, we have dissected the region controlling the transcription of EcR-A by analyzing the ability of this region to drive the expression of reporter genes in transgenic animals. These analyses have demonstrated that the Type II neurons are a heterogeneous collection of neurons that utilize different regulatory elements to coordinate the expression of the same transcript.