ASD/OCD-Linked Protocadherin-10 Regulates Synapse, But Not Axon, Development in the Amygdala and Contributes to Fear- and Anxiety-Related Behaviors

Abstract

The Protocadherin-10 (PCDH10) gene is associated with autism spectrum disorder (ASD), obsessive-compulsive disorder (OCD), and major depression (MD). The PCDH10 protein is a homophilic cell adhesion molecule that belongs to the d2-protocadherin family. PCDH10 is highly expressed in the developing brain, especially in the basolateral nucleus of the amygdala (BLA). However, the role of PCDH10 in vivo has been debatable: one paper reported that a Pcdh10 mutant mouse line showed changes in axonal projections; however, another Pcdh10 mutant mouse line was reported to have failed to detect axonal phenotypes. Therefore, the actual roles of PCDH10 in the brain remain to be elucidated. We established a new Pcdh10 KO mouse line using the CRISPR/Cas9 system, without inserting gene cassettes to avoid nonspecific effects, examined the roles of PCDH10 in the brain, and studied the behavioral consequences of Pcdh10 inactivation. Here, we show that Pcdh10 KO mice do not show defects in axonal development. Instead, we find that Pcdh10 KO mice exhibit impaired development of excitatory synapses in the dorsal BLA. We further demonstrate that male Pcdh10 KO mice exhibit reduced anxiety-related behaviors, impaired fear conditioning, decreased stress-coping responses, and mildly impaired social recognition and communication. These results indicate that PCDH10 plays a critical role in excitatory synapse development, but not axon development, in the dorsal BLA and that PCDH10 regulates anxiety-related, fear-related, and stress-related behaviors. Our results reveal the roles of PCDH10 in the brain and its relationship to relevant psychiatric disorders such as ASD, OCD, and MD.

Altered Socio-Affective Communication and Amygdala Development in mice with Protocadherin10-deficient Interneurons

“…An inverted U-shaped developmental call emission pattern could be identified for both the KO and the cKO, as previously described in mice (16)(17)(18). (34,36). However, in our study both full body as well as conditional heterozygous models also exhibited heightened USV emission rates, most prominent during the peak call emission period (P3 -P6).…”

“…PCDH10 levels are already high at E13.5 and continue to rise during embryonic and early postnatal development, pointing towards an increasingly important role during neurogenesis, neuronal migration, axonal outgrowth and synapse formation and elimination. Expression of Pcdh10 within synapses of the amygdala at juvenile and adult stages was previously reported (34,36), and Pcdh10 was linked to synapse elimination in hippocampal cell cultures (94). Our data shows that Pcdh10 is already strongly expressed in the BLC of the amygdala during embryonic development (E17.5), but that the preferential expression within the BLA becomes stronger after birth.…”

“…Throughout development Pcdh10 is expressed in brain regions linked to ASD and social behavior Involvement of members of the non-clustered Protocadherin family in proliferation, sorting and spatial patterning of the brain has become evident over recent years (79)(80)(81)(82). Non-clustered protocadherins are associated with neural circuit formation (83), and Pcdh10 has been directly implicated in wiring of olfactory and amygdalar circuitry (34,36,84,85). The combinatorial expression of cadherin superfamily members, including protocadherins, delineates amygdala subdivisions, and this was suggested to underlie the functional organization of the amygdala (86).…”

“…Hoshina et al (2022) has reported decreased USV emission in homozygous Pcdh10 KO as compared to wild-type pups(34). They postulated that the increased USV previously observed bySchoch et al (2017) in the heterozygous knockout mice might be caused by non-specific effects of the LacZ cassette…”

“…Despite the disparities, Pcdh10 deficiency was associated with altered behaviors reminiscent of the core symptoms of ASD in both mouse models. This included decreased social approach and alterations in socio-affective communication through USV, together with changes in anxiety levels, impaired fear learning and reduced stress coping (34)(35)(36).…”