HSF-1 interconnects insulin/IGF-1 and TGF-β signaling. A, Inactivation of HSF-1 causes upregulation of daf-7 in daf-2(e1370) mutant dauer larvae (this interaction is fully penetrant; N=462). In the hsf-1(sy441) mutant background, a strong ectopic expression of daf-7 is evident in neurons related to the ventral nerve cord (GFP-positive cells at the ventral side of the body). Up: differential interference contrast images, down: the corresponding fluorescent images. B, Activity of the IGF-1 receptor DAF-2 causes daf-7 upregulation via inhibiting HSF-1. The daf-2 mutation e1370 leads to downregulation of daf-7 at the L1 stage, as compared with the wild-type background. Note that decrease in daf-7 expression in daf-2(−) mutants is less robust than in daf-11(−) mutants. The hsf-1(sy441) mutation suppresses downregulation of daf-7 in daf-2(e1370) mutant L1 larvae. 91% of double mutant animals exhibited strong (wild-type levels) daf-7 expression (N=220). In panels A and B, the corresponding fluorescent images were captured with the same exposure time. C, Quantification of daf-7::gfp expression intensity in the ASIs. * indicates: p<0.0001; Student’s t-test. D, Epistatic relationships among DAF-2/IGF-1, HSF-1 and DAF-7/TGF-β. Arrows indicate activations, bars represent inhibitions.
Barna et al. BMC Developmental Biology 2012 12:32 doi:10.1186/1471-213X-12-32