Abstract
Connexin43 (Cx43) is the predominant testicular gap junction protein and in cases of impaired spermatogenesis, Cx43 expression has been shown to be altered in several mammals. Amongst other functions, Cx43 is supposed to regulate junction formation of the blood-testis barrier (BTB). The aim of the present study was to investigate the expression pattern of different tight junction (TJ) proteins of the murine BTB using SC-specific Cx43 knockout mice (SCCx43KO). Adult homozygous male SCCx43KO mice (SCCx43KO-/-) predominantly show an arrest of spermatogenesis and SC-only tubules that might have been caused by an altered BTB assembly, composition or regulation. TJ molecules claudin-3, -5 and -11 were examined in adult wild type (WT) and SCCx43KO-/- mice using immunohistochemistry (IHC) and quantitative real-time PCR (qRT-PCR). In this context, investigation of single tubules with residual spermatogenesis in SCCx43KO-/- mice was particularly interesting to identify a potential Cx43-independent influence of germ cells (GC) on BTB composition and dynamics. In tubules without residual spermatogenesis, a diffuse cytoplasmic distribution pattern for claudin-11 protein could be demonstrated in mutant mice. Nevertheless, claudin-11 seems to form functional TJ. Claudin-3 and -5 could not be detected immunohistochemically in the seminiferous epithelium of those tubules. Correspondingly, claudin-3 and -5 mRNA expression was decreased, providing evidence of generally impaired BTB dynamics in adult KO mice. Observations of tubules with residual spermatogenesis suggested a Cx43-independent regulation of TJ proteins by GC populations. To determine initial BTB formation in peripubertal SCCx43KO-/- mice, immunohistochemical staining and qRT-PCR of claudin-11 were carried out in adolescent SCCx43KO-/- and WT mice. Additionally, BTB integrity was functionally analysed using a hypertonic glucose fixative. These analyses revealed that SCCx43KO-/- mice formed an intact BTB during puberty in the same time period as WT mice, which however seemed to be accelerated.
Highlights
Connexin43 (Cx43) is the predominant testicular gap junction (GJ) protein
Occludin was firstly identified as a component of tight junctions (TJ), claudin-11 seems to have a higher impact on the blood-testis barrier (BTB) integrity in mice
In addition to claudin-11, claudin-3 and -5 are associated with murine BTB formation and due to different distribution patterns different functions can be assumed for these three TJ proteins [63]
Summary
Connexin (Cx43) is the predominant testicular gap junction (GJ) protein. Within the seminiferous epithelium, it connects adjacent Sertoli cells (SC) as well as SC and germ cells (GC). Cx43 influences normal testis development and is necessary for initiation and physiological progression of spermatogenesis [1,2,3,4,5,6,7,8,9,10]. A functional BTB is crucial for GC survival and normal progression of spermatogenesis. The BTB is not rigid but represents a very dynamic structure as preleptotene/leptotene GC must cross the BTB to reach the adluminal compartment without compromising the integrity of this barrier. This occurs during stages VIII-IX of the murine seminiferous epithelial cycle. The BTB is more than just the junctions as this anatomical (physical) component has to interact with physiological and immunological components to create a barrier of maximal competence [33, 34]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
