The effects of regulatory perturbations on stripe 2 expression are predicted by altering regulator concentrations but keeping all the model coefficients unchanged; for TF deletion or binding site mutants, this involves setting the relevant regulator’s concentrations to 0. Predictions are made for perturbations using the linear and quadratic models. Comparisons to experiments provide robust, independent validations of model predictions. Loss of (A) gt or (B) Kr causes eve expression to extend towards the anterior and posterior of the embryo respectively, in excellent agreement with experimental evidence. (C) For the bcd mutant, the linear model predicts expression at the anterior of the embryo, something that is not observed in experiments. In contrast, the quadratic model does not suffer from this. (D) Perturbing hb leads to complete loss of eve stripe 2 for both models. The better agreement between predictions and experimental evidence suggests that the quadratic is a more plausible model of eve 2 regulation.
In situ images in panels 1, 2, and 6 are reproduced from Figure 4B–C and 6C, Small et al. (1992), The EMBO Journal; Nature Publishing Group has granted permission to reproduce these images under the terms of the Creative Commons Attribution 3.0 Unported License (CC BY 3.0).
© 1991, Cold Spring Harbor Laboratory Press, All Rights Reserved. The in situ image in panel 3 is reprinted with permission from Figure 2D, Small et al. (1991), Genes & Development.
© 1991, American Association for the Advancement of Science, All Rights Reserved. In situ images in panels 4 and 5 are reprinted with permission from Figure 3A and 3C, Stanojevic et al. (1991), Science.
© 1996, The Company of Biologists, All Rights Reserved. The in situ image in panel 7 is reproduced with permission from Figure 6B, Arnosti et al. (1996), Development.