Rictor is involved in Ctnnd2 deletion-induced impairment of spatial learning and memory but not autism-like behaviors.

Background: The CTNND2 gene which encodes a δ-catenin protein (CTNND2) is associated with multiple severe neurological disorders. However, the specific role of CTNND2 in spatial cognition and related mechanisms remains obscure. Methods: In this study, we generated a new line of Ctnnd2-Knock out (KO) mice with its exon2 deleted, and then characterized their behavioral phenotypes and explore the Biological mechanism. Results: Ctnnd2-KO mice were with typical autism-like behaviors as evidenced by reduced social interaction in three-chamber sociability test, more frequent stereotypic behaviors (self-grooming), and deficits in spatial learning and memory tested by the Morris water maze. Furthermore, the expression of Rictor protein, a core component of the mTORC2 complex, was significantly decreased in the hippocampus of mutant mice. ShRNA-induced knockdown of Rictor protein in the hippocampus of both Ctnnd2-KO mice and wild-type mice exacerbated spatial learning and memory deficits but did not affect their autism-like behaviors. Mechanistically, the hippocampal CA1 neurons of Ctnnd2-KO mice showed decreased actin polymerization, postsynaptic spine density. Down-regulation of Rictor resulted in altered expression of post-synaptic proteins such as GluR1 and ELKS, but not presynaptic protein Synapsin1, implying abnormal synaptic changes in KO mice. Conclusion: The CTNND2 gene is involved in spatial learning and memory via Rictor-mediated actin polymerization and synaptic plasticity. Our study provides a novel insight into the role and mechanisms of the Ctnnd2 gene in cognition at the molecular and synaptic levels.