Knockout mice: is it just genetics? Effect of enriched housing on fibulin-4(+/-) mice

Location- and sex-specific differences in weight and motor coordination in two commonly used mouse strains

Several studies have shown that environmental factors can affect the outcome of behavioral experiments, shedding doubts on the inter-laboratory reproducibility of behavioral test results. When our laboratory moved from the University of Rochester, Rochester, NY, to Sanford Research in Sioux Falls, SD, our mouse colony was also transferred and the new environment caused strain-dependent changes in the weight, motor coordination and motor learning capability of mice. Here we report the observed changes for two wild type mouse strains commonly used in transgenic studies, C57BL/6J and 129S6/SvEv, and show that the type of rodent diet is partially responsible for the geographical location-specific differences. We also found sex-specific differences in weight and motor coordination in both mouse strains. Our results show that environmental factors specific to a geographical location can change the body weight, motor coordination and motor learning capability of wild type mice commonly used as controls in transgenic studies.

Idealization in evolutionary developmental investigation: a tension between phenotypic plasticity and normal stages

Idealization is a reasoning strategy that biologists use to describe, model and explain that purposefully departs from features known to be present in nature. Similar to other strategies of scientific reasoning, idealization combines distinctive strengths alongside of latent weaknesses. The study of ontogeny in model organisms is usually executed by establishing a set of normal stages for embryonic development, which enables researchers in different laboratory contexts to have standardized comparisons of experimental results. Normal stages are a form of idealization because they intentionally ignore known variation in development, including variation associated with phenotypic plasticity (e.g. via strict control of environmental variables). This is a tension between the phenomenon of plasticity and the practice of staging that has consequences for evolutionary developmental investigation because variation is conceptually removed as a part of rendering model organisms experimentally tractable. Two compensatory tactics for mitigating these consequences are discussed: employing a diversity of model organisms and adopting alternative periodizations.

Environmental standardization: cure or cause of poor reproducibility in animal experiments?

It is widely believed that environmental standardization is the best way to guarantee reproducible results in animal experiments. However, mounting evidence indicates that even subtle differences in laboratory or test conditions can lead to conflicting test outcomes. Because experimental treatments may interact with environmental conditions, experiments conducted under highly standardized conditions may reveal local 'truths' with little external validity. We review this hypothesis here and present a proof of principle based on data from a multilaboratory study on behavioral differences between inbred mouse strains. Our findings suggest that environmental standardization is a cause of, rather than a cure for, poor reproducibility of experimental outcomes. Environmental standardization can contribute to spurious and conflicting findings in the literature and unnecessary animal use. This conclusion calls for research into practicable and effective ways of systematic environmental heterogenization to attenuate these scientific, economic and ethical costs.