Suppressed USVs in pups, but normal social interaction, communication, and repetitive behaviors in adult Lrfn2^−/− mice. A, Normal social approach and social novelty recognition in Lrfn2^−/− mice (3–4 months) in the 3-chamber test, as shown by time spent in the chamber and sniffing. n = 14 mice for WT and 17 mice for KO. *p < 0.05, **p < 0.01, ***p < 0.001, paired t test and Wilcoxon test. B, Normal social interaction in Lrfn2^−/− mice (3–4 months) in the direct social interaction test. n = 7 WT mouse pairs and 8 KO mouse pairs. NS, Student's t test. C, Normal USVs of male Lrfn2^−/− mice (4–5 months) induced by encounter with a female. n = 13 mice for WT and 16 mice for KO. NS, Student's t test. D, Normal pup retrieval in female Lrfn2^−/− mice (3–5 months) induced by WT pups (P1) separated from their mothers, as shown by the time taken to retrieve first, second, and third pups. n = 23 mice for WT and 21 mice for KO. NS, Mann–Whitney U test. E, Suppressed USVs in Lrfn2^−/− pups (P4, P6, P8, and P10) separated from their mothers, as shown by number of calls and individual call duration. For P4, n = 16 mice for WT and 22 mice for KO; for P6, n = 17 for WT and 21 for KO; for P8, n = 11 for WT and 21 for KO; for P10, n = 14 for WT and 21 for KO. *p < 0.05, **p < 0.01, NS, Student's t test and Mann–Whitney U test. F, G, Normal repetitive behaviors of Lrfn2^−/− mice (3–4 months), as shown by self-grooming, digging, and marble burying. For digging and grooming, n = 14 mice for WT and 17 mice for KO; for marble burying, n = 13 for WT and 16 for KO. NS, Student's t test and Mann–Whitney U test. H, Normal motor coordination of Lrfn2^−/− mice (4–5 months) in the rotarod test. n = 14 mice for WT and 17 mice for KO. NS, repeated-measures two-way ANOVA.