CAPS2 deficiency affects environmental enrichment-induced adult neurogenesis and differentiation/survival of newborn neurons in the hippocampal dentate gyrus.

Hippocampal adult neurogenesis is observed in the subgranular zone of the dentate gyrus (DG), and is associated with hippocampal memory formation and several psychiatric disorders including autism spectrum disorder (ASD). Calcium-dependent activator protein for secretion 2 (CAPS2) is a candidate gene related to ASD, and is highly expressed in the hippocampal DG region, with Caps2 knockout (KO) mice exhibiting ASD-like behavior. Accordingly, CAPS2 is potentially associated with hippocampal adult neurogenesis, the relationship between CAPS2 and adult neurogenesis has not yet been investigated. Here, we determined whether deficit of the Caps2 gene affects hippocampal adult neurogenesis and maturation of newborn neurons. To induce adult neurogenesis, we used the environmental enrichment (EE) condition. Both wild-type (WT) and Caps2 KO mice were housed in control or EE conditions for 3 or 14days. Hippocampal levels of brain-derived neurotrophic factor (BDNF) can be used as a physiological EE conditioned marker, and were increased at 14days in the EE condition in both WT and KO mice. Newborn cells during control and EE conditions were labeled by BrdU, and the labeled cells co-immunostained with the immature and mature neuron markers, calretinin (CR) and NeuN. The ratio of CR/BrdU and NeuN/BrdU double positive cells to all of BrdU positive cells were significantly increased in WT mice housed in the EE condition for 14days compared with the control condition. Whereas KO mice in the EE condition showed no significant increase of newborn neurons. These findings suggest that CAPS2 deficiency strongly impairs hippocampal adult neurogenesis and maturation of newborn neurons.