Clonal analysis of olfaction in Drosophila: generation of flies with mosaic labeling.

Clonal analysis with the MARCM (mosaic analysis with a repressible cell marker) system can be used for studying cell lineage, development, and anatomy in the Drosophila olfactory system and other parts of the fly brain. This protocol gives a method for generating flies with mosaic labeling. It describes how to establish a mating cage for MARCM in PNs (projection neurons) of the fly antennal lobe and then select appropriate flies for dissection and staining using immunohistochemistry. The protocol can be adapted to determine the birth order of neuroblast lineages or individual cells. Alternatively, it can be used to dissect a complicated Gal4 line into its component neuroblast lineages to help elucidate projection patterns and connectivity. Collecting newly hatched larvae during a short time window allows for precise control of the stage during development at which the heat shock is applied.