Article

# Sloppy Models, Parameter Uncertainty, and the Role of Experimental Design

Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
(Impact Factor: 3.21). 10/2010; 6(10):1890-900. DOI: 10.1039/b918098b
Source: PubMed

ABSTRACT

Computational models are increasingly used to understand and predict complex biological phenomena. These models contain many unknown parameters, at least some of which are difficult to measure directly, and instead are estimated by fitting to time-course data. Previous work has suggested that even with precise data sets, many parameters are unknowable by trajectory measurements. We examined this question in the context of a pathway model of epidermal growth factor (EGF) and neuronal growth factor (NGF) signaling. Computationally, we examined a palette of experimental perturbations that included different doses of EGF and NGF as well as single and multiple gene knockdowns and overexpressions. While no single experiment could accurately estimate all of the parameters, experimental design methodology identified a set of five complementary experiments that could. These results suggest optimism for the prospects for calibrating even large models, that the success of parameter estimation is intimately linked to the experimental perturbations used, and that experimental design methodology is important for parameter fitting of biological models and likely for the accuracy that can be expected from them.

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Available from: Joshua Apgar, Nov 24, 2015
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• "). We point out that this is the premise invoked also in the context of Sloppy Models [35] [36] [37], whose behavior depends only on a few stiff combinations of parameters (accounted here by W and y), with many sloppy parameter directions largely unimportant for model predictions (accounted here by η z ). We also note here the fundamental difference with PCA decompositions which attain the same form as Equation(9). "
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• "Experiments are used to test hypotheses, and the more complex a hypothesis, the more complicated and numerous the necessary experimental tests are likely to be. Models can potentially be used to carefully design experimental tests that would be optimal for supporting or disproving a hypothesis [37] [38] [39]. Second, models can also be used to reconcile surprising or conflicting data. "
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• "In the case of an integral approach, experimental design can give data coverage for many parameter directions and maximize predictive accuracy (Apgar et al. 2010), because large uncertainty parameter directions in an experiment can correspond to less uncertainty parameter direction in other experiments (Apgar et al. 2010). The effect of the multi-fitting complementary design is the constriction of parameters (Gutenkunst et al. 2007b) in sloppy multi-parameter models with few stiff parameters and many sloppy parameter directions (Daniels et al. 2008). "
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