Androgen-dependent sertoli cell tight junction remodeling is mediated by multiple tight junction components

Area of Science:

• Reproductive Biology
• Cell Biology
• Endocrinology

Background:

• Sertoli cell tight junctions (SCTJs) form a blood-testis barrier, essential for male germ cell development.
• Androgen signaling in Sertoli cells regulates SCTJ integrity, but specific molecular targets remain incompletely understood.
• Claudin 3 (CLDN3) is an androgen-regulated tight junction protein implicated in SCTJ function.

Purpose of the Study:

• To investigate the role of Claudin 3 in SCTJ function and spermatogenesis.
• To identify other androgen-regulated genes critical for SCTJ remodeling in Sertoli cell androgen receptor knockout (SCARKO) mice.
• To elucidate the contribution of androgen signaling to both bicellular and tricellular junctions within the seminiferous epithelium.

Main Methods:

• Phenotypic analysis of Cldn3-null mice and a new SCARKO mouse model.
• Assessment of spermatogenesis, fertility, and SCTJ integrity using imaging and tracer studies.
• Quantitative analysis of tight junction gene expression and chromatin immunoprecipitation to identify androgen receptor binding sites.

Main Results:

• Cldn3-null mice exhibit normal fertility and spermatogenesis, indicating CLDN3 is not essential for SCTJ function.
• SCARKO mice show altered expression of other SCTJ components, including down-regulation of Claudin 13 (CLDN13) and TJP2iso3.
• Direct androgen receptor binding was confirmed for CLDN13 and TJP2iso3 gene loci.
• CLDN13 is a component of SCTJs, and TJP2iso3 localizes with tricellulin, highlighting androgen's role in regulating bicellular and tricellular junctions.

Conclusions:

• Claudin 3 is dispensable for Sertoli cell tight junction function and male fertility.
• Androgen signaling directly regulates key SCTJ components like CLDN13 and TJP2iso3, which are crucial for maintaining testicular microenvironment integrity.
• These findings reveal novel androgen-dependent mechanisms governing Sertoli cell tight junction dynamics and spermatogenesis.