Dissection of the embryonic brain using photoactivated gene expression.

The Drosophila brain is generated by a complex series of morphogenetic movements. To better understand brain development and to provide a guide for experimental manipulation of brain progenitors, we created a fate map using photoactivated gene expression to mark cells originating within specific mitotic domains and time-lapse microscopy to dynamically monitor their progeny. We show that mitotic domains 1, 5, 9, 20 and B give rise to discrete cell populations within specific regions of the brain. Mitotic domains 1, 5, 9 and 20 give rise to brain neurons; mitotic domain B produced glial cells. Mitotic domains 5 and 9 produce the antennal and visual sensory systems, respectively, where each sensory system is composed of several disparate cell clusters. Time-lapse analysis of marked cells showed complex mitotic and migratory patterns for cells derived from these mitotic domains.