Experiments done in Black-6 mice: what does it mean?

Abstract

Low replicability of animal experiments is perceived as a major hurdle in the field of biomedicine. Attempts to enhance the replicability and to reduce the variability in basic research has led to a recommendation to use isogenic mice. The C57BL/6 strain has evolved as a gold standard strain for this purpose. However, the C57BL/6 mice are maintained as sub-strains by multiple vendors. Evidence exists that the subtle differences between these mouse lines have not been systematically investigated and are often ignored. In the present study, we characterized the female mice of two closely related sub-strains (C57BL/6J and C57BL/6N) from three vendors in Europe (Charles River Laboratories, Envigo, Janvier Labs) in a battery of behavioral tests. Our data show and confirm substantial behavioral differences between the C57BL/6J and C57BL/6N mice. Importantly, the sub-strain differences were largely affected by the origin of animals, as a significant effect of vendor or interaction between the sub-strain and vendor occurred in all tests. This work highlights the importance of adhering to precise international nomenclature in all publications reporting the animal experiments. Moreover, the generalization of research findings from a single mouse sub-strain can be seriously limited due to genetic drift and environmental variables at different vendors. However, generalizability can be enhanced by heterogenization of samples by including the animals of different substrains. These issues need to be seriously considered for improving reproducibility, replicability and translational potential of the mouse models.

Boldness in Male and Female Zebrafish (Danio rerio) Is Dependent on Strain and Test

“…The AB strain is among the most common lab strains used. Since AB fish often are bred at different facilities, differences between fish from different facilities can be expected to the same extent as those described in rodents from different vendors (Palm et al, 2011a,b, 2012; Goepfrich et al, 2013; Momeni et al, 2015; Åhlgren and Voikar, 2019). Considering the different tests used, fewer differences were revealed using the scototaxis test.…”

High‐throughput analysis of vocalizations reveals sex‐specific changes in Fmr1 mutant pups

“…A multitude of studies have shown significant effects of background strain on specific behaviors, such as tests of baseline activity level and even complex learning tasks. 23 As such, it is conceivable that the lack of findings in the previous paper may not generalize to the strain used in the present study (ie, FVB). 22 Moreover, even substrains of the same background strain (ie, C57BL/6J and C57BL/6N) show significant differences on a battery of tests.…”

“…22 Moreover, even substrains of the same background strain (ie, C57BL/6J and C57BL/6N) show significant differences on a battery of tests. 23 As such, it is conceivable that the lack of findings in the previous paper may not generalize to the strain used in the present study (ie, FVB). Moreover, it is important to consider other variables of vocalization production, such as call-type utilization profiles, or spectral parameters like fundamental frequency and amplitude.…”

Improving reproducibility in animal research by splitting the study population into several ‘mini-experiments’

“…Therefore, even subtle and inevitable changing experimental conditions may lead to completely contradicting conclusions about the treatment under investigation (in our case strain differences). This might even occur when an experiment is replicated in the same laboratory, but for example the animals are purchased by another vendor 47 , tested by another experimenter 48 or at another time of the day 34 . In line with these examples, 50% of interviewed scientists stated they have experienced failures in replicating their own experiments 5 .…”