Temporal control of differentiation by the insulin receptor/Tor pathway in Drosophila

Multicellular organisms must integrate growth and differentiation precisely to pattern complex tissues. Despite great progress in understanding how different cell fates are induced, it is poorly understood how differentiation decisions are temporally regulated. In a screen for patterning mutants, we isolated alleles of tsc1, a component of the insulin receptor (InR) growth control pathway. We find that loss of tsc1 disrupts patterning due to a loss of temporal control of differentiation. tsc1 controls the timing of differentiation downstream or in parallel to the RAS/MAPK pathway. Examination of InR, PI3K, PTEN, Tor, Rheb, and S6 kinase mutants demonstrates that increased InR signaling leads to precocious differentiation while decreased signaling leads to delays in differentiation. Importantly, cell fates are unchanged, but tissue organization is lost upon loss of developmental timing controls. These data suggest that intricate developmental decisions are coordinated with nutritional status and tissue growth by the InR signaling pathway.