%0 Journal Article %A R. Michelle Saré %A Merlin Levine %A Carolyn Beebe Smith %T Behavioral Phenotype of Fmr1 Knockout Mice During Active Phase in an Altered Light Dark Cycle %D 2016 %R 10.1523/ENEURO.0035-16.2016 %J eneuro %P ENEURO.0035-16.2016 %X Fragile X syndrome (FXS) is the most commonly inherited form of intellectual disability and is a disorder that is also highly associated with autism. FXS occurs as a result of an expanded CGG repeat sequence leading to transcriptional silencing. In an animal model of FXS in which Fmr1 is knocked out (Fmr1 KO), many physical, physiological, and behavioral characteristics of the human disease are recapitulated. Prior characterization of the mouse model was conducted during the day, the inactive phase of the circadian cycle. Circadian rhythms are an important contributor to behavior and may play a role in the study of disease phenotype. Moreover, changes in parameters of circadian rhythm are known to occur in FXS animal models. We conducted an investigation of key behavioral phenotypes in Fmr1 KO mice during their active phase. We report that phase did not alter the Fmr1 KO phenotype in open field activity, anxiety, and learning and memory. There was a slight effect of phase on social behavior as measured by time in chamber, but not by time spent sniffing. Our data strengthen the existing data characterizing the phenotype of Fmr1 KO mice, indicating that it is independent of circadian phase.Significance Statement: This study seeks to characterize the behavioral phenotype of Fmr1 KO mice during the active phase of the circadian rhythm. Given that for many behaviors the active phase is more physiologically relevant; our study is an important validation of Fmr1 KO mice as a model for FXS. We find that classical behavioral phenotypes; such as hyperactivity, reduced anxiety, and learning and memory impairments; reported in the Fmr1 KO mice are not influenced by circadian phase. %U https://www.eneuro.org/content/eneuro/early/2016/04/03/ENEURO.0035-16.2016.full.pdf