Fig. 1: Behavioral and cognitive phenotypes of adult mice expressing HERV-W ENV.

All data were obtained from adult male transgenic CAG^HERV-Wenv mice (TG) and wild-type (WT) littermates. A Total distance moved, distance moved in the center zone (CZ) and time spent in the CZ during the open field test. B Number of buried marbles and distance moved during the marble burying test. **p < 0.01, based on independent t-test (t₍₅₂₎ = 2.97, 2-tailed). C Phase 1 (D = dummy object, M = unfamiliar mouse) and phase 2 (F = familiar mouse; N = novel mouse) of the social interaction test, which assessed sociability and social memory, respectively. The line plots show the time spent with the unfamiliar mouse or dummy object in phase 1 of the test, or with the novel or familiar mouse in phase 2 of the test. The scatter plots depict the social preference index (values > 0 represent a preference toward the unfamiliar mouse) in phase 1 and the social memory index (values > 0 represent a preference toward the novel mouse) in phase 2 of the test. ^§p < 0.001, reflecting the significant main effect of object (F_(1,52) = 57.13) in repeated-measures ANOVA; ^#p < 0.001, reflecting the significant difference between novel and familiar mouse exploration in WT mice, based on Šidák post-hoc test after the presence of a significant 2-way interaction between genotype and object (F_(1,52) = 13.68, p < 0.001) in repeated-measures ANOVA; ***p < 0.001, based on independent t-test (t₍₅₂₎ = 4.09, 2-tailed). D Object recognition memory in the novel object recognition test, in which the animals were required to discriminate a novel object from a previously familiarized object. The line plot shows the time spent with the novel or familiar object during the test phase, whereas the scatter plot depicts the novel object recognition index (values > 0 represent a preference toward the novel object). ^#p < 0.001, reflecting the significant difference between novel and familiar object exploration in WT mice, based on Šidák multiple post-hoc test following a significant 2-way interaction between genotype and object (F_(1,52) = 10.52, p < 0.001) in repeated-measures ANOVA; **p < 0.001, based on independent t-test (t₍₅₂₎ = 3.06; 2-tailed). E Prepulse inhibition (PPI) test of sensorimotor gating using 3 prepulse intensities (71, 77 and 83 dB_A) and 3 pulse intensities (P-100, P-110 and P-120, which correspond to 100, 110 and 120 dB_A). The line plots show % PPI as a function of prepulse and pulse intensities, whereas the scatter plot depicts the mean % PPI across all prepulse and pulse intensities. ***p < 0.001, reflecting the significant main effect of genotype (F_(1,52) = 19.55) in repeated-measures ANOVA. F Acoustic startle reactivity (in arbitrary units, AU) to 100-, 110- and 120-dB_A pulse stimuli. All scatter plots show individual mice with overlaid group means ± s.e.m; all line plots show group means ± s.e.m. All data are based on n = 27 mice in each genotype per test.