Overexpression of plastin 3 in Sertoli cells disrupts actin microfilament bundle homeostasis and perturbs the tight junction barrier

Abstract

Throughout the epithelial cycle of spermatogenesis, actin microfilaments arranged as bundles near the Sertoli cell plasma membrane at the Sertoli cell-cell interface that constitute the blood-testis barrier (BTB) undergo extensive re-organization by converting between bundled and unbundled/branched configuration to give plasticity to the F-actin network. This is crucial to accommodate the transport of preleptotene spermatocytes across the BTB. Herein, we sought to examine changes in the actin microfilament organization at the Sertoli cell BTB using an in vitro model since Sertoli cells cultured in vitro is known to establish a functional tight junction (TJ)-permeability barrier that mimics the BTB in vivo. Plastin 3, a known actin microfilament cross-linker and bundling protein, when overexpressed in Sertoli cells using a mammalian expression vector pCI-neo was found to perturb the Sertoli cell TJ-barrier function even though its overexpression increased the overall actin bundling activity in these cells. Furthermore, plastin 3 overexpression also perturbed the localization and distribution of BTB-associated proteins, such as occludin-ZO1 and N-cadherin-β-catenin, this thus destabilized the barrier function. Collectively, these data illustrate that a delicate balance of actin microfilaments between organized in bundles vs. an unbundled/branched configuration is crucial to confer the homeostasis of the BTB and its integrity.

Regulation of Blood-Testis Barrier (BTB) Dynamics, Role of Actin-, and Microtubule-Based Cytoskeletons

“…This coordinated effort is necessary to support the timely transport of step 19 spermatids across the epithelium in stage VII–VIII tubules to prepare for their release at spermiation in stage VIII tubules [19, 20]. But they are also necessary to facilitate the timely remodeling of the BTB to support the transport of preleptotene spermatocytes across the immunological barrier at stage VIII of the epithelial cycle [15, 16]. Studies have shown that these two cellular events that take place at the opposite ends of the seminiferous epithelium are coordinated at stage VIII of the epithelial cycle [9, 21, 22].…”

“…1d), Eps8 (an actin barbed end capping and bundling protein) [13, 17, 24], and palladin (an actin-bundling protein) [25]. In both animal models, namely, the adjudin and the formin 1 knockdown model, step 19 spermatids are persistently found in the seminiferous epithelium that are trapped near the base of the epithelium in stage IX–XII tubules until they are eliminated by the Sertoli cell through lysosomal degradation, sometimes through the appearance of multinucleated round and/or spermatocytes [13, 15, 16], as noted in other toxicant-induced aspermatogenesis models [26–29]. …”

Cry1 deficiency leads to testicular dysfunction and altered expression of genes involved in cell communication, chromatin reorganization, spermatogenesis, and immune response in mouse testis

“…The former is a multi‐step biological process that involves mitosis, meiosis, and spermiogenesis and yields mature spermatozoa capable of fertilization; the latter is critical for normal spermatogenesis (Neto, Bach, Najari, Li, & Goldstein, ; Ramaswamy & Weinbauer, ). These processes involve many genes whose dysregulation can lead to testicular dysfunction (Li, Lee, & Cheng, ; Skakkebaek et al, ). External stimuli such as toxicity, temperature change, and nutrient status have also been shown to influence spermatogenesis by altering the expression of genes in the testis (Cuypers et al, ; Egbowon, Harris, Arnott, Mills, & Hargreaves, ; Mocarelli et al, ; Skakkebaek et al, ; Spiazzi et al, ; Valles, Aveldano, & Furland, ).…”

Modern approaches to morphofunctional dynamics of spermatogenesis process

“…Fiind unul dintre elementele importante ale citoscheletului, rețeaua de microfilamente nu numai că oferă suport structural pentru morfologia și mișcarea celulelor, dar mai participă și la transportul moleculelor de miozină intracelulară [22,23]. Perturbarea citoscheletului pe bază de actină în timpul spermatogenezei poate afecta fertilitatea masculină [24,25]. Infertilitatea observată clinic poate fi cauzată de dinamica anormală a actinei.…”