Juvenile manifestation of ultrasound communication deficits in the neuroligin-4 null mutant mouse model of autism

•Nlgn4−/− mice are a construct valid autism model, now confirmed in pups and juveniles.•USV in pups on brief maternal separation revealed remarkable gender and mild genotype effects.•USV in juveniles on exposure to an anesthetized female was reduced in Nlgn4−/− mice.•Neonatal development from PND4 to 21 did not yield further differences between genotypes. Neuroligin-4 (Nlgn4) is a member of the neuroligin family of postsynaptic cell adhesion molecules. Loss-of-function mutations of NLGN4 are among the most frequent, known genetic causes of heritable autism. Adult Nlgn4 null mutant (Nlgn4−/−) mice are a construct valid model of human autism, with both genders displaying a remarkable autistic phenotype, including deficits in social interaction and communication as well as restricted and repetitive behaviors. In contrast to adults, autism-related abnormalities in neonatal and juvenile Nlgn4−/− mice have not been reported yet. The present study has been designed to systematically investigate in male and female Nlgn4−/− pups versus wildtype littermates (WT, Nlgn4+/+) developmental milestones and stimulus-induced ultrasound vocalization (USV). Neonatal development, followed daily from postnatal days (PND) 4 to 21, including physical development, neurological reflexes and neuromotor coordination, did not yield any differences between Nlgn4−/− and their WT littermates. USV in pups (PND8–9) in response to brief separation from their mothers revealed remarkable gender effects, and a genotype influence in females regarding latency to first call. In juveniles (PND22–23), USV monitoring upon exposure to an anesthetized female intruder mouse uncovered a clear genotype effect with reduced USV in Nlgn4−/− mice, and again a more prominent phenotype in females. Together, these data support an early manifestation of communication deficits in Nlgn4−/− mice that appear more pronounced in immature females with their overall stronger USV as compared to males.