RORC and cyst: These data indicate that the InR/PI3K cascade is not a major activator of the Tor kinase during GSC differentiation, in agreement with the previous observation that the null InR mutant had a much less severe cyst growth delay than the null Tor mutant.21 A second established upstream pathway regulating Tor depends on amino acid sensing, which can activate the Tor kinase through the Rag GTPases RagAB and RagCD (Figure 2A).