Figure 4

Social behaviours in wild-type (WT) and Crmp4-KO mice. (a and b) The three-chamber test performed at 6-weeks [(a), male WT, n = 11; male Crmp4-KO, n = 10; female WT, n = 11; and female Crmp4-KO, n = 12] and 10-weeks [(b), male WT, n = 10; male Crmp4-KO, n = 8; female WT, n = 9; and female Crmp4-KO, n = 11]. The testing apparatus comprised two sides and one centre chamber (19 × 40 × 22 cm, each) divided by two doors (11.5 cm wide). An age-matched unfamiliar C57BL/6N WT mouse of the same sex (stranger) enclosed in a wire cage (φ82 × 93.1 mm) was placed behind the partition in one side chamber (stranger side chamber) and an empty wire cage (novel object) was placed behind the partition in the other side chamber (object side chamber) of the three-chambered apparatus. Time spent in each chamber (1) and time spent sniffing stranger and novel object (2). (c) Social interaction test to assess active interaction time in 10 min. Male WT, n = 15; male Crmp4-KO, n = 17; female WT, n = 12; and female Crmp4-KO, n = 17. (d) The tube test to show the difference in social dominance between WT and Crmp4-KO mice. An age-matched pair of unfamiliar mice (one WT and one Crmp4-KO) of the same sex and similar body weight (within 5% difference) was placed into opposite ends of a clear acrylic tube and simultaneously released. The test ended when one mouse completely retreated from the tube, who was assigned a score of zero (loser). The remaining mouse was assigned a score of one (winner). Male WT, n = 6; male Crmp4-KO, n = 6; female WT, n = 8; and female Crmp4-KO, n = 8. Values are expressed as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 (three-way ANOVA followed by Fisher’s PLSD post-hoc tests).