Experiential contributions to social dominance in a rat model of fragile-X syndrome

Proc Biol Sci. 2018 Jun 13;285(1880):20180294. doi: 10.1098/rspb.2018.0294.


Social withdrawal is one phenotypic feature of the monogenic neurodevelopmental disorder fragile-X. Using a 'knockout' rat model of fragile-X, we examined whether deletion of the Fmr1 gene that causes this condition would affect the ability to form and express a social hierarchy as measured in a tube test. Male fragile-X 'knockout' rats living together could successfully form a social dominance hierarchy, but were significantly subordinate to wild-type animals in mixed group cages. Over 10 days of repeated testing, the fragile-X mutant rats gradually showed greater variance and instability of rank during their tube-test encounters. This affected the outcome of future encounters with stranger animals from other cages, with the initial phenotype of wild-type dominance lost to a more complex picture that reflected, regardless of genotype, the prior experience of winning or losing. Our findings offer a novel insight into the complex dynamics of social interactions between laboratory living groups of fragile-X and wild-type rats. Even though this is a monogenic condition, experience has an impact upon future interactions with other animals. Gene/environment interactions should therefore be considered in the development of therapeutics.

Keywords: Fmr1; autism-spectrum disorders; fragile-X; gene–environment interactions; hierarchy; social dominance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Disease Models, Animal
  • Fragile X Syndrome / psychology*
  • Male
  • Rats
  • Rats, Long-Evans
  • Social Dominance*

Associated data

  • Dryad/10.5061/dryad.mh352th