CELL LINEAGE ANALYSIS OF THE DROSOPHILA PERIPHERAL NERVOUS-SYSTEM

The peripheral nervous system (PNS) of Drosophila provides a very well -characterized model system for studying the genes involved in basic p rocesses of neurogenesis. Because of its simplicity and stereotyped pa ttern, each cell of the PNS can be individually identified and the phe notypic consequences of mutations can be studied in detail. Thus, some of the genetic mechanisms leading to the formation of type I sensory organs, the external, bristle-type sensory organs (es), and the intern al, stretch-receptive chordotonal organs (ch) have been elucidated. Ea ch sensory organ seems to be generated by a stereotyped pattern of cel l division of individual ectodermal precursor cells. Recent advances i n cell lineage analysis of the PNS have provided a detailed picture of almost all the lineages in the PNS, including those giving rise to th e type II sensory neurons, also known as multiple dendritic (md) neuro ns. This knowledge will be instrumental in the precise characterizatio n of the phenotypes associated with mutations in known and new genes a nd their interactions which determine cell fate decisions during neuro genesis. Here, we describe and compare th ree recently developed metho ds by which cell lineages have been assessed: single cell transplantat ion, bromodeoxyuridine (BrdU) incorporation studies, and the flp/FRT r ecombinase system from yeast. In the light of a more complete knowledg e of the PNS lineages, we will discuss the effects of known mutations that alter neuronal cell fates. (C) 1996 Wiley-Liss, Inc.