Genotype–environment interactions in mouse behavior: A way out of the problem

Abstract

In behavior genetics, behavioral patterns of mouse genotypes, such as inbred strains, crosses, and knockouts, are characterized and compared to associate them with particular gene loci. Such genotype differences, however, are usually established in singlelaboratory experiments, and questions have been raised regarding the replicability of the results in other laboratories. A recent multilaboratory experiment found significant laboratory effects and genotype ؋ laboratory interactions even after rigorous standardization, raising the concern that results are idiosyncratic to a particular laboratory. This finding may be regarded by some critics as a serious shortcoming in behavior genetics. A different strategy is offered here: (i) recognize that even after investing much effort in identifying and eliminating causes for laboratory differences, genotype ؋ laboratory interaction is an unavoidable fact of life. (ii) Incorporate this understanding into the statistical analysis of multilaboratory experiments using the mixed model. Such a statistical approach sets a higher benchmark for finding significant genotype differences. (iii) Develop behavioral assays and endpoints that are able to discriminate genetic differences even over the background of the interaction. (iv) Use the publicly available multilaboratory results in single-laboratory experiments. We use software-based strategy for exploring exploration (SEE) to analyze the open-field behavior in eight genotypes across three laboratories. Our results demonstrate that replicable behavioral measures can be practically established. Even though we address the replicability problem in behavioral genetics, our strategy is also applicable in other areas where concern about replicability has been raised.across-laboratory replicability ͉ mixed-model ANOVA ͉ open-field behavior I n behavior genetics, behavior patterns of standardized mouse genotypes, such as inbred strains or knockouts, are characterized to associate them with particular gene loci. The need for such characterization, referred to as behavioral phenotyping, has prompted the design of behavioral test batteries for mice (1-3). A practical problem well known to most experimenters in the field, however, is that it can be difficult to replicate behavioral phenotyping results in a different laboratory. This replicability problem was largely ignored until brought to light in 1999 by Crabbe, Wahlsten, and Dudek (3). In this pioneering study they conducted an experiment concurrently in three laboratories, comparing eight genotypes by using seven standard behavioral characteristics (endpoints) in a well coordinated study closely following identical protocols. Their main positive finding was that large genotype differences were demonstrated in all studied endpoints. On the negative side they found significant differences between laboratories across all genotypes in many endpoints. Although the difficulties raised by such significant laboratory effects can be overcome by running a common genotype as a local control, they ...

Quantifying the buildup in extent and complexity of free exploration in mice

“…The demand for replicability of the strain difference in the number of incursions per session across laboratories (captured by the mixed-model analysis in ref. 34) revealed that the strain difference was no longer significant (P > 0.08; upper left in Fig. S8), which deemed this measure of little value.…”

“…We previously added yet another demand for a good quantitative description (3,34): that of replicability across laboratories. This is an expectation that the measure will remain discriminative when the behavior is measured in different laboratories.…”

“…Following the estimation of growth rate for all types of sequences, it would be interesting to study the correlation structure between them within individuals and across strains. In a study along such lines of forced open-field behavior that used 25 different measures in eight inbred strains of mice across three laboratories, and involving standardized housing and experimental conditions (34), it was found that the two traditional measures discussed above, distance traveled and center time, accounted for only 7% of the variance (3). Can the measures of buildup of the different processes be captured by a few parameters, indicating thereby that the growth of arena occupancy is controlled by very few mediating mechanisms, or are the measures of growth controlled by multiple mediating mechanisms?…”

Genotype-Dependent Activity of Tryptophan Hydroxylase-2 Determines the Response to Citalopram in a Mouse Model of Depression

“…However, Lucki et al (2001) showed that fluoxetine reduced immobility time in DBA/2J and BALB/c mice, had no effect in C57BL/6J, and increased immobility in 129/SvemJ mice. Although this apparently argues against a role for allelic differences in TPH-2 in the effect of SSRIs, the genotype-environment interaction may cause differences in behavioral phenotype across laboratories (Crabbe et al, 1999;Wahlsten et al, 2003;Kafkafi et al, 2005). Differences in the SSRIs, substrain, and procedures used may also contribute.…”

The power of automated high-resolution behavior analysis revealed by its application to mouse models of Huntington's and prion diseases

“…Variability in standard behavioral tests hinders comparative studies (3)(4)(5) and most sample ''snapshots'' of behavior. Anxiety caused by being handled by the researcher complicates interpretation and obscures subtle phenotypes.…”