Novel deployment of temporal fating factors in a diverse neuronal lineage of the Drosophila central brain

摘要

The anterodorsal projection neuron (adPN) lineage of Drosophila melanogaster produces 40 neuronal types in a stereotypic order. Here we take advantage of this complete lineage sequence to examine the role of known temporal fating factors, including Chinmo and the Hb/Kr/Pdm/Cas transcriptional cascade, within this diverse central brain lineage. Kr mutation affects the temporal fate of the neuroblast (NB) itself causing a single fate to be skipped, whereas Chinmo null only elicits fate transformation of NB progeny without altering cell counts. Notably, Chinmo operates in two windows separated by a single fate with fate transformation within each window towards the directly following fate. By contrast, Hb/Pdm/Cas play no detectable role, indicating that Kr either acts outside of the cascade identified in the ventral nerve cord or that redundancy exists at the level of fating factors. Therefore hierarchical fating mechanisms operate within the lineage to generate neuronal diversity in an unprecedented fashion.