Postnatal nectin‐3 knockdown induces structural abnormalities of hippocampal principal neurons and memory deficits in adult mice

The early postnatal stage is a critical period of hippocampal neurodevelopment and also a period of high vulnerability to adverse life experiences. Recent evidence suggests that nectin‐3, a cell adhesion molecule, mediates memory dysfunction and dendritic alterations in the adult hippocampus induced by postnatal stress. But it is unknown whether postnatal nectin‐3 reduction alone is sufficient to alter hippocampal structure and function in adulthood. Here, we down regulated hippocampal expression of nectin‐3 and its heterophilic adhesion partner nectin‐1, respectively, from early postnatal stage by injecting adeno‐associated virus (AAV) into the cerebral lateral ventricles of neonatal mice (postnatal day 2). We found that suppression of nectin‐3, but not nectin‐1, expression from the early postnatal stage impaired hippocampus‐dependent novel object recognition and spatial object recognition in adult mice. Moreover, AAV‐mediated nectin‐3 knockdown significantly reduced dendritic complexity and spine density of pyramidal neurons throughout the hippocampus, whereas nectin‐1 knockdown only induced the loss of stubby spines in CA3. Our data provide direct evidence that nectins, especially nectin‐3, are necessary for postnatal hippocampal development of memory functions and structural integrity.