Bunched specifically regulates α/β mushroom body neuronal cell proliferation during metamorphosis

In Drosophila, mushroom bodies are centers for higher order behavior. Mushroom body neurons consist of three distinct types of neuronal cells, α, α′/β′, and α/β, which are all generated by the same neuroblasts. The mechanism by which a single neuroblast generates three different types of mushroom body neurons is a compelling area of research. Here, we report that bunched (bun) is expressed only in α/β-type mushroom body neurons and that mutation of the bun gene only affects the development of α/β neurons. Reduced bun expression causes decreased and premature arrest of neuroblast cell division, which results in reduced numbers of α/β neurons and thin axon bundled formation. We propose that bun acts as a specific factor in regulating neuroblast mitotic activity during the development of α/β neurons.