Sex-dependent parameters of social behavior show marked variations between distinct laboratory mouse strains and their mixed offspring

Background: The survival of individuals of gregarious species depends on their ability to properly form social interactions. In humans, atypical social behavior is a hallmark of several psychopathological conditions, such as depression and autism spectrum disorder, many of which have sex-specific manifestations. Various strains of laboratory mice are used to reveal the mechanisms mediating typical and atypical social behavior in mammals. Methods: Here we used three social discrimination tests (social preference, social novelty preference, and sex preference) to characterize social behavior in males and females of three widely used laboratory mouse strains (C57BL/6J, BALB/c, and ICR). Results: We found marked sex- and strain-specific differences in the preference exhibited by subjects in a test-dependent manner. Interestingly, we found some characteristics that were strain-dependent, while others were sex-dependent. Moreover, even in the social preference test, where both sexes of all strains prefer social over object stimuli, we revealed sex- and strain-specific differences in the behavioral dynamics. We then cross-bred C57BL/6J and BALB/c mice and demonstrated that the offspring of such cross-breeding exhibit a profile of social behavior which is different from both parental strains and depends on the specific combination of parental strains. Conclusions: We conclude that social behavior of laboratory mice is highly sex- and strain-specific and strongly depends on genetic factors.