Social Interaction

Our social interaction test is used to measure how mice respond to a social partner during a 5-min test following group or isolation housing. Since isolation housing potentiates expression of innate territorial defensive responses like intermale attack behavior in this test, it is ideally suited to assess gene by environment effects on mouse behavior.

We use counts of intermale attack behavior as a primary phenotype because it requires little subjective interpretation.We also have developed a social behavior coding system that encompasses all aspects of mouse social behavior as a secondary phenotype. We use Noldus Observer behavior coding software to code behaviors from digital videos that can be sped up and slowed down in order to accurately code mouse social behavior responses. The video illustrates typical strain specific social behaviors observed in this test as well as intermale attack behavior. Note that the all social interaction test are always monitored live and terminated if the participant mice show any signs of injury.

A/J mice show high levels of passive avoidance (avoid social interaction by not moving), whereas WSB mice show high levels of active avoidance (avoid social interaction by rapidly moving away from the social partner).

PWK mice exhibit high levels of social approach, but are also the only Collaborative Cross founder strain that consistently exhibits inter-male attack behavior (vigorous biting of the social partnerís hindquarters rarely resulting in injury).

Among the Collaborative Cross mice we have examined in this test following isolation housing, 30% attack. The video mouse of the Collaborative Cross with mouse ID OR2558m54 contains 6 attacks. Our results indicate that transgressive segregation is a major feature of the genetic architecture of the social interaction phenotypes in the CC.

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