Sertoli cell–specific coxsackievirus and adenovirus receptor regulates cell adhesion and gene transcriptionviaβ‐catenin inactivation and Cdc42 activation

Abstract

Blood‐testis barrier (BTB) and apical ectoplasmic specialization (ES) serve as structural supports for germ cell (GC) development. We demonstrated that the Sertoli cell (SC)‐specific coxsackievirus and adenovirus receptor (CXADR) knockout (SC‐CXADR−/−), but not the GC‐specific knockout, impaired spermatogenesis. An increase in GC apoptosis and premature loss of elongated spermatids were observed in SC‐CXADR−/− testes. The BTB function was compromised in SC‐CXADR−/− testes with dysregulation of oocludin and zonula occludens‐1 expression at the basal compartment of the seminiferous epithelium. An integrated omics analyses confirmed that altered gene ontology terms identified in SC‐CXADR−/− testes are highly associated with spermatid development and differentiation, spermatogenesis, and sperm motility and are considered as unique testicular function terms. Leptin, Nasp, Tektin3, Larp 7, and acrosin, which are highly associated with male fertility, were found to be down‐regulated in SC‐CXADR−/− testes. Based on the data from the omics analyses, we employed the CXADR‐deficient SC model to further investigate the molecular mechanisms involved. We unraveled that SC‐CXADRs are required for β‐catenin inactivation and cell division cycle protein 42 (Cdc42) activation, resulting in maintaining the integrity and function of the BTB and apical ES as well as inhibiting gene transcription, such as the Myc gene, in the testes. We demonstrated for the first time that CXADR is an important mediator governing β‐catenin and Cdc42 signaling that is essential for spermatogenesis. The molecular mechanisms identified herein may provide new insights to unravel the novel functions and signaling cascades of CXADR in other key CXADR‐expressing tissues.—Huang, K., Ru, B., Zhang, Y., Chan, W.‐L., Chow, S.‐C., Zhang, J., Lo, C., Lui, W.‐Y. Sertoli cell‐specific coxsackievirus and adenovirus receptor regulates cell adhesion and gene transcription via β‐catenin inactivation and Cdc42 activation. FASEB J. 33, 7588–7602 (2019). http://www.fasebj.org

BRG1 Is Dispensable for Sertoli Cell Development and Functions in Mice

“…It is thus possible that Amh-Cre (Jackson) is not transcriptionally active in a subset of Sertoli cells. Consistent with our findings on those Amh-Cre mouse models, Huang et al also observed the mosaic deletion within the Sertoli cell population when using Amh-Cre (Jackson) [43]. However, other studies used the same Amh-Cre (Jackson) strain, but did not find such an incomplete Cre recombinase activity [44][45][46].…”

Cdc42activity in Sertoli cells is essential for maintenance of spermatogenesis

“…It has been proposed that CDC42 (through its interactions with TGF- or other extracellular pathways) ultimately signals directly through JNK or indirectly through Ras/ERK and p38 to elicit cellular responses (Lui et al, 2003;Wong et al, 2005;Xia and Cheng, 2005). Recently, CDC42 was implicated in mediating mTORC1 signaling downstream of NC1 peptide-mediated BTB remodeling via actin and microtubule cytoskeletal reorganization (Su and Cheng, 2019), as well as being a downstream mediator of coxsackievirus and adenovirus receptor (CXADR) signaling to regulate BTB and apical ES integrity and function (Huang et al, 2019). In vitro studies using dominant-negative constructs demonstrated that Cdc42 is required for TGF--induced BTB breakdown (Wong et al, 2010), which normally occurs when preleptotene spermatocytes traverse the BTB, suggesting that this activity is mediated via the GTP-active form of CDC42.…”

CXADR: From an Essential Structural Component to a Vital Signaling Mediator in Spermatogenesis

“…Apart from the tamoxifen-inducible CXADR knockout models, two testicular cell type-specific CXADR mouse models named germ cell-specific and Sertoli cell (SC)-specific CXADR knockout have been generated [ 47 ]. Two loxP sites flanking exon 3 of the Cxadr gene are inserted to generate floxed mice.…”

“…Two loxP sites flanking exon 3 of the Cxadr gene are inserted to generate floxed mice. Floxed mice were then crossed with stimulated by retinoic acid 8 (Stra8)-Cre and anti-Mullerian hormone (Amh)-Cre mouse strains, respectively, to generate germ cell-specific knockout (GC-CXADR, Cxadr flox/flox ; Stra8-iCre) and Sertoli cell-specific CXADR knockout (SC-CXADR, Cxadr flox/flox ; Amh-iCre) mice [ 47 ]. GC-CXADR mice display no apparent abnormality in testicular size and tubular morphology compared to age-matched controls [ 47 ].…”