Fig. 5.

Dose-responsiveness and specificity of BMP and activin A signaling sentinels. (A) ES cell signaling sentinel lines with response elements for BMP (IBRE-4-CFP) or activin A (AR8-TA-mCherry) inserted at the −60 and −228 sites of the endogenous Rosa26 locus. All cells exhibited responses to the respective agonists and not their antagonists (100 nM LDN193189 and 10 μM SB431542, respectively). Assays were for 48 hours. (B) Dose-response tests of the BMP and activin A (ActA) sentinels substituted at −60 and −228, demonstrating high sensitivity of both constructs for each reporter type. Individual FACS profiles are shown in supplementary material Fig. S4. (C) Specificity tests demonstrate high specificity of responsiveness, particularly illustrating that the BMP reporter responds to BMP4 and not activin A, whereas the activin A reporter responds to activin A and not BMP (doses as for Fig. 3). One-tailed t-tests of drug-treated samples compared with DMSO controls; **P<0.01.