Neuronal Subtype Specification within a Lineage by Opposing Temporal Feed-Forward Loops

Neural progenitors generate distinct cell types at different stages, but the mechanisms controlling these temporal transitions are poorly understood. In the Drosophila CNS, a cascade of transcription factors, the ‘temporal gene cascade’, has been identified, that acts to alter progenitor competence over time. However, many CNS lineages display broad temporal windows, and it is unclear how broad windows progress into sub-windows that generate unique cell types. We have addressed this issue in an identifiable Drosophila CNS lineage, and find that a broad castor temporal window is sub-divided by two different feed-forward loops, both of which are triggered by castor itself. The first loop acts to specify a unique cell fate, while the second loop suppresses the first loop, thereby allowing for the generation of alternate cell fates. This mechanism of temporal and ‘sub-temporal’ genes acting in opposing feed-forward loops may be used by many stem cell lineages to generate diversity.Original Publication: Magnus Baumgardt, Daniel Karlsson, Javier Terriente, Fernando J. Díaz-Benjumea and Stefan Thor, Neuronal Subtype Specification within a Lineage by Opposing Temporal Feed-Forward Loops, 2009, Cell, (139), 5, 969-982. http://dx.doi.org/10.1016/j.cell.2009.10.032 Copyright: Elsevier Science B.V., Amsterdam. http://www.cell.com/cellpress