Endocrine Abstracts

Coxsackievirus and adenovirus receptor (CXADR) is localized at the blood-testis barrier (BTB) and at the interface between Sertoli cells (SC) and germ cells (GC). Earlier studies indicated that CXADR plays role in BTB function and germ cell migration. However, conventional knockout of CXADR leads to embryonic lethality, making the study of CXADR in the testis impossible. We aim to generate SC-specific CXADR knockout (KO) mice to evaluate the SC-specific function of CXADR on spermatogenesis in vivo. RNA sequencing and bioinformatics analyses were employed to identify and unravel the regulatory mechanisms that may involve in reproductive impairment. The SC-specific deletion of CXADR under the control of Amh promoter was confirmed by PCR and immunohistochemistry. Adult SC-Cxadr^−/− mice exhibited significant reductions in fertility efficacy (>40% reduction) and testes/body weight ratio due to GC loss. Compromised BTB function coupled with down-regulation or mislocalization of the BTB components including occludin/ZO-1 complex and β-catenin have been observed in SC-Cxadr^−/− testes. Transcriptomic and proteomic analyses of SC-Cxadr^−/− testes revealed that the enriched gene ontology (GO) terms are highly related to male reproduction. Rap1/Wnt/Hippo signaling network and its core mediators such as β-catenin and Cdc42 were predicted in pertinent to fertility impairment in SC-Cxadr^−/− testes via genome-wide data analyses. Besides, Wnt/Hippo targets including Wnt5a, Wnt6, Wnt9a, Myc and Snai2 were also significantly altered in SC-Cxadr^−/− testes. Activation of β-catenin and inhibition of Cdc42 with disorganized F-actin at the apical ES were observed in SC-Cxadr^−/− testis and cultured Cxadr^−/− SCs (Cxadr^−/− MSC-1 cells). Overexpression of constitutively active Cdc42 in Cxadr^−/− MSC-1 cells could partially recover the CXADR-mediated inhibition of non-phosphorylated β-catenin and F-actin filaments. Apparently, apart from being a structural protein at the BTB, CXADR functions as a crucial signaling mediator to trigger the downstream effects on junction disruption and actin reorganization via non-phosphorylation of β-catenin and Cdc42 inhibition. Taken together, CXADR in SCs affects the BTB function and F-actin organization via crosstalk of CXADR/β-catenin/Cdc42. SC-CXADR plays an indispensable role in spermatogenesis.