Isoforms of terminal selector Mamo control axon guidance during adult Drosophila memory center construction via Semaphorin-1a.

In animals undergoing metamorphosis, the appearance of the nervous system is coincidently transformed by the morphogenesis of neurons. Such morphogenic alterations are exemplified in three types of intrinsic neurons in the Drosophila memory center. In contrast to the well-characterized remodeling of γ neurons, the morphogenesis of α/β and α'/β' neurons has not been adequately explored. Here, we show that mamo, a BTB-zinc finger transcription factor that acts as a terminal selector for α'/β' neurons, controls the formation of the correct axonal pattern of α'/β' neurons. Intriguingly, specific Mamo isoforms are preferentially expressed in α'/β' neurons to regulate the expression of axon guidance molecule Semaphorin-1a. This action directs proper axon guidance in α'/β' neurons, which is also crucial for wiring of α'/β' neurons with downstream neurons. Taken together, our results provide molecular insights into how neurons establish correct axonal patterns in circuitry assembly during adult memory center construction.