A GABAergic Maf-expressing interneuron subset regulates the speed of locomotion inDrosophila

Interneurons (INs) coordinate motoneurons activity to generate adequate patterns of muscle contractions, providing animals with the ability to adjust their body posture and to move over a range of speeds. In the Drosophila larvae several IN subtypes have been morphologically described and their function well documented. However, the general lack of molecular characterization of those INs prevents the identification of evolutionary counterparts in other model animals, limiting our understanding of widespread principles ruling neuronal circuits organization and functioning. Here we characterize a highly restricted neuronal subset expressing the Maf transcription factor Traffic Jam (TJ). We found that TJ + neurons are highly diverse and their activation using intersectional genetics disrupted larval body posture and locomotion speed. We also showed that a small subset of TJ + GABAergic INs, singled out by the unique expression of Per , Fkh , Grain and Hlh3b , a molecular signature reminiscent to V 2b INs in vertebrate, impacted the larvae crawling speed.