Rearing environment persistently modulates the phenotype of mice

The phenotype of an organism results from its genotype and the influence of the environment throughout development. Even when using animals of the exact same genotype, independent studies may test animals of different phenotypes, resulting in poor replicability due to genotype-by-environment interactions . Thus, genetically defined strains of mice may respond differently to experimental treatments depending on their rearing environment 4. However, the extent of such phenotypic plasticity and its implications for the replicability of research findings have remained unknown. Here, we examined the extent to which common environmental differences between rearing facilities modulate the phenotype of genetically homogeneous (inbred) mice. We conducted a comprehensive multi-center study, where genetically identical mice from the same breeding stock were reared in five different facilities throughout early life and adolescence, before being transported to a single test laboratory.