Opposite effects of interleukin-1alpha and transforming growth factor-beta2 induce stage-specific regulation of junctional adhesion molecule-B gene in Sertoli cells

MAPKs signaling is obligatory for male reproductive function in a development-specific manner

Mitogen-activated protein kinases (MAPKs) represent widely expressed and evolutionarily conserved proteins crucial for governing signaling pathways and playing essential roles in mammalian male reproductive processes. These proteins facilitate the transmission of signals through phosphorylation cascades, regulating diverse intracellular functions encompassing germ cell development in testis, physiological maturation of spermatozoa within the epididymis, and motility regulation at ejaculation in the female reproductive tract. The conservation of these mechanisms appears prevalent across species, including humans, mice, and, to a limited extent, livestock species such as bovines. In Sertoli cells (SCs), MAPK signaling not only regulates the proliferation of immature SCs but also determines the appropriate number of SCs in the testes at puberty, thereby maintaining male fertility by ensuring the capacity for sperm cell production. In germ cells, MAPKs play a crucial role in dynamically regulating testicular cell-cell junctions, supporting germ cell proliferation and differentiation. Throughout spermatogenesis, MAPK signaling ensures the appropriate Sertoli-to-germ cell ratio by regulating apoptosis, controlling the metabolism of developing germ cells, and facilitating the maturation of spermatozoa within the cauda epididymis. During ejaculation in the female reproductive tract, MAPKs regulate two pivotal events-capacitation and the acrosome reaction essential for maintaining the fertility potential of sperm cells. Any disruptions in MAPK pathway signaling possibly may disturb the testicular microenvironment homeostasis, sperm physiology in the male body before ejaculation and in the female reproductive tract during fertilization, ultimately compromising male fertility. Despite decades of research, the physiological function of MAPK pathways in male reproductive health remains inadequately understood. The current review attempts to combine recent findings to elucidate the impact of MAPK signaling on male fertility and proposes future directions to enhance our understanding of male reproductive functions.

Inhibition of miR-143-3p Restores Blood-Testis Barrier Function and Ameliorates Sertoli Cell Senescence

Due to the increasing trend of delayed childbirth, the age-related decline in male reproductive function has become a widely recognized issue. Sertoli cells (SCs) play a vital role in creating the necessary microenvironment for spermatogenesis in the testis. However, the mechanism underlying Sertoli cell aging is still unclear. In this study, senescent Sertoli cells showed a substantial upregulation of miR-143-3p expression. miR-143-3p was found to limit Sertoli cell proliferation, promote cellular senescence, and cause blood-testis barrier (BTB) dysfunction by targeting ubiquitin-conjugating enzyme E2 E3 (UBE2E3). Additionally, the TGF-β receptor inhibitor SB431542 showed potential in alleviating age-related BTB dysfunction, rescuing testicular atrophy, and reversing the reduction in germ cell numbers by negatively regulating miR-143-3p. These findings clarified the regulatory pathways underlying Sertoli cell senescence and suggested a promising therapeutic approach to restore BTB function, alleviate Sertoli cell senescence, and improve reproductive outcomes for individuals facing fertility challenges.

Bisphenols as promoters of the dysregulation of cellular junction proteins of the blood-testis barrier in experimental animals: A systematic review of the literature

Daily, people are exposed to chemicals and environmental compounds such as bisphenols (BPs). These substances are present in more than 80% of human fluids. Human exposure to BPs is associated with male reproductive health disorders. Some of the main targets of BPs are intercellular junction proteins of the blood-testis barrier (BTB) in Sertoli cells because BPs alter the expression or induce aberrant localization of these proteins. In this systematic review, we explore the effects of BP exposure on the expression of BTB junction proteins and the characteristics of in vivo studies to identify potential gaps and priorities for future research. To this end, we conducted a systematic review of articles. Thirteen studies met our inclusion criteria. In most studies, animals treated with bisphenol-A (BPA) showed decreased occludin expression at all tested doses. However, bisphenol-AF treatment did not alter occludin expression. Cx43, ZO-1, β-catenin, nectin-3, cortactin, paladin, and claudin-11 expression also decreased in some tested doses of BP, while N-cadherin and FAK expression increased. BP treatment did not alter the expression of α and γ catenin, E-cadherin, JAM-A, and Arp 3. However, the expression of all these proteins was altered when BPA was administered to neonatal rodents in microgram doses. The results show significant heterogeneity between studies. Thus, it is necessary to perform more research to characterize the changes in BTB protein expression induced by BPs in animals to highlight future research directions that can inform the evaluation of risk of toxicity in humans.

Role of p38 MAPK Signalling in Testis Development and Male Fertility

The testis is an important male reproductive organ, which ensures reproductive function via the secretion of testosterone and the generation of spermatozoa. Testis development begins in the embryonic period, continues after birth, and generally reaches functional maturation at puberty. The stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), regulates multiple cell processes including proliferation, differentiation, apoptosis, and cellular stress responses. p38 MAPK signalling plays a crucial role in testis development by regulating spermatogenesis, the fate determination of pre-Sertoli, and primordial germ cells during embryogenesis, the proliferation of testicular cells in the postnatal period, and the functions of mature Sertoli and Leydig cells. In addition, p38 MAPK signalling is involved in decreased male fertility when exposed to various harmful stimuli. This review will describe in detail the biological functions of p38 MAPK signalling in testis development and male reproduction, together with its pathological role in male infertility.

Junctional adhesion molecule-A deletion increases phagocytosis and improves survival in a murine model of sepsis

Expression of the tight junction–associated protein junctional adhesion molecule-A (JAM-A) is increased in sepsis, although the significance of this is unknown. Here, we show that septic JAM-A ^–/– mice have increased gut permeability, yet paradoxically have decreased bacteremia and systemic TNF and IL-1β expression. Survival is improved in JAM-A^–/– mice. However, intestine-specific JAM-A^–/– deletion does not alter mortality, suggesting that the mortality benefit conferred in mice lacking JAM-A is independent of the intestine. Septic JAM-A^–/– mice have increased numbers of splenic CD44^hiCD4⁺ T cells, decreased frequency of TNF⁺CD4⁺ cells, and elevated frequency of IL-2⁺CD4⁺ cells. Septic JAM-A^–/– mice have increased numbers of B cells in mesenteric lymph nodes with elevated serum IgA and intraepithelial lymphocyte IgA production. JAM-A^–/– × RAG^–/– mice have improved survival compared with RAG^–/– mice and identical mortality as WT mice. Gut neutrophil infiltration and neutrophil phagocytosis are increased in JAM-A^–/– mice, while septic JAM-A^–/– mice depleted of neutrophils lose their survival advantage. Therefore, increased bacterial clearance via neutrophils and an altered systemic inflammatory response with increased opsonizing IgA produced through the adaptive immune system results in improved survival in septic JAM-A^–/– mice. JAM-A may be a therapeutic target in sepsis via immune mechanisms not related to its role in permeability.

Common Variation in the PIN1 Locus Increases the Genetic Risk to Suffer from Sertoli Cell-Only Syndrome

We aimed to analyze the role of the common genetic variants located in the PIN1 locus, a relevant prolyl isomerase required to control the proliferation of spermatogonial stem cells and the integrity of the blood–testis barrier, in the genetic risk of developing male infertility due to a severe spermatogenic failure (SPGF). Genotyping was performed using TaqMan genotyping assays for three PIN1 taggers (rs2287839, rs2233678 and rs62105751). The study cohort included 715 males diagnosed with SPGF and classified as suffering from non-obstructive azoospermia (NOA, n = 505) or severe oligospermia (SO, n = 210), and 1058 controls from the Iberian Peninsula. The allelic frequency differences between cases and controls were analyzed by the means of logistic regression models. A subtype specific genetic association with the subset of NOA patients classified as suffering from the Sertoli cell-only (SCO) syndrome was observed with the minor alleles showing strong risk effects for this subset (OR_addrs2287839 = 1.85 (1.17–2.93), OR_addrs2233678 = 1.62 (1.11–2.36), OR_addrs62105751 = 1.43 (1.06–1.93)). The causal variants were predicted to affect the binding of key transcription factors and to produce an altered PIN1 gene expression and isoform balance. In conclusion, common non-coding single-nucleotide polymorphisms located in PIN1 increase the genetic risk to develop SCO.

Regulation of STUB1 expression and its biological significance in mouse Sertoli cells

STIP1 Homology and U-Box Containing Protein 1 (STUB1), a ubiquitin E3 ligase initially involved in immune responses, has recently emerged as a pleiotropic regulator of different biological systems, including skeletal and male reproduction systems. On the latter, a homozygous mutation in the STUB1 gene has been identified in patients with hypogonadism. However, the pattern of expression and biological actions of STUB1 in testis remains so far unexplored. Herein, we report analyses on the testicular expression of STUB1 in human testes with impaired spermatogenesis and paracrine regulation of STUB1 expression in mouse testis development and the direct effects of ablation STUB1 on Sertoli cell (SC) functions. STUB1 was expressed abundantly in pachytene spermatocytes and SCs, and weakly in spermatogonia and differentiating spermatids in normal human testis. In contrast, Sertoli-specific expression of STUB1 was significantly decreased in the human testes with impaired spermatogenesis. Throughout postnatal development of mouse testis, however, STUB1 was expressed exclusively in the nuclei of the functionally mature SCs. The adjacent germ cell (GC)-derived IL-1α overtly regulated STUB1 expression through promoting the ETS domain transcription factor Elk-1 (ELK1)-mediated transactivation. Importantly, ablation of endogenous STUB1 caused lipid accumulation and senescence in GC co-incubated SCs. Together with previous reports on the stimulatory effects of IL-1α on cell senescence, our findings suggest that STUB1 may serve as an important negative feedback signaling to modulate the magnitude of GCs-derived IL-1α, which is normally maintained at low levels within testis.

The Roles of Junctional Adhesion Molecules (JAMs) in Cell Migration

The review briefly summarizes the role of the family of adhesion molecules, JAMs (junctional adhesion molecules), in various cell migration, covering germ cells, epithelial cells, endothelial cells, several leukocytes, and different cancer cells. These functions affect multiple diseases, including reproductive diseases, inflammation-related diseases, cardiovascular diseases, and cancers. JAMs bind to both similar and dissimilar proteins and take both similar and dissimilar effects on different cells. Concluding relevant results provides a reference to further research.

Bacterial Infections Affect Male Fertility: A Focus on the Oxidative Stress-Autophagy Axis

Numerous factors trigger male infertility, including lifestyle, the environment, health, medical resources and pathogenic microorganism infections. Bacterial infections of the male reproductive system can cause various reproductive diseases. Several male reproductive organs, such as the testicles, have unique immune functions that protect the germ cells from damage. In the reproductive system, immune cells can recognize the pathogen-associated molecular patterns carried by pathogenic microorganisms and activate the host's innate immune response. Furthermore, bacterial infections can lead to oxidative stress through multiple signaling pathways. Many studies have revealed that oxidative stress serves dual functions: moderate oxidative stress can help clear the invaders and maintain sperm motility, but excessive oxidative stress will induce host damage. Additionally, oxidative stress is always accompanied by autophagy which can also help maintain host homeostasis. Male reproductive system homeostasis disequilibrium can cause inflammation of the genitourinary system, influence spermatogenesis, and even lead to infertility. Here, we focus on the effect of oxidative stress and autophagy on bacterial infection in the male reproductive system, and we also explore the crosslink between oxidative stress and autophagy during this process.

Multiple signaling pathways in Sertoli cells: recent findings in spermatogenesis

The functions of Sertoli cells in spermatogenesis have attracted much more attention recently. Normal spermatogenesis depends on Sertoli cells, mainly due to their influence on nutrient supply, maintenance of cell junctions, and support for germ cells' mitosis and meiosis. Accumulating evidence in the past decade has highlighted the dominant functions of the MAPK, AMPK, and TGF-β/Smad signaling pathways during spermatogenesis. Among these pathways, the MAPK signaling pathway regulates dynamics of tight junctions and adherens junctions, proliferation and meiosis of germ cells, proliferation and lactate production of Sertoli cells; the AMPK and the TGF-β/Smad signaling pathways both affect dynamics of tight junctions and adherens junctions, as well as the proliferation of Sertoli cells. The AMPK signaling pathway also regulates lactate supply. These signaling pathways combine to form a complex regulatory network for spermatogenesis. In testicular tumors or infertile patients, the activities of these signaling pathways in Sertoli cells are abnormal. Clarifying the mechanisms of signaling pathways in Sertoli cells on spermatogenesis provides new insights into the physiological functions of Sertoli cells in male reproduction, and also serves as a pre-requisite to identify potential therapeutic targets in abnormal spermatogenesis including testicular tumor and male infertility.

Selenium deficiency impaired immune function of the immune organs in young grass carp (Ctenopharyngodon idella)

This study aimed to investigate the effects of dietary selenium on resistance to skin haemorrhages and lesions and on immune function as well as the underlying mechanisms of those effects in the head kidney, spleen and skin of young grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp with initial body weight (226.48 ± 0.68 g) were randomly divided into six groups and fed six separate diets with graded dietary levels of selenium (0.025, 0.216, 0.387, 0.579, 0.795 and 1.049 mg/kg diet) for 80 days. After the feeding period, an immunization trial was performed by infection with Aeromonas hydrophila for 14 days. The results showed that, compared with the optimal selenium level, (1) selenium deficiency impaired the production of antibacterial compounds and immunoglobulins and down-regulated the transcript abundances of antimicrobial peptides and selenoproteins; (2) selenium deficiency aggravated inflammatory responses in part by up-regulating pro-inflammatory cytokines and down-regulating anti-inflammatory cytokines mRNA levels, which were partially related to [IKKα, β, γ/IκBα/NF-κB] signalling and [TOR/(S6K1, 4E-BP1)] signalling, respectively. Interestingly, selenium deficiency had no effect on the expression of TGF-β2, IL-4/13B, IL-10, IL-12p35, IL-15 (skin only) or 4E-BP2 in the head kidney, spleen and skin of young grass carp. Finally, based on the percent weight gain (PWG), the morbidity of skin haemorrhages and lesions, the ACP activity in the head kidney and the lysozyme activity in spleen, the optimal dietary selenium requirements for young grass carp were estimated to be 0.546-0.604 mg/kg diet. In summary, selenium deficiency decreased the growth performance and impaired the immune function in the head kidney, spleen and skin of young grass carp.

Testosterone Reduces Spinal Cord Injury-Induced Effects on Male Reproduction by Preventing CADM1 Defect

Objective

This study evaluated the effects of exogenous testosterone molecule-1 (CADM1) pathological defect during early and chronic periods of spinal cord injury (SCI).

Materials and Methods

In this experimental study, testosterone was administered immediately or after one week of SCI induction. Along with quantification of CADM1 gene expression and its immunoreactivity, we evaluated sperm parameters and serum testosterone level post-SCI.

Results

Different grades of abnormalities in sperm parameters and testis architecture were observed along with significant reductions in the level of CADM1 expression and its immunoreactivity in the seminiferous tubules of both acute and chronic SCI groups. Exogenous testosterone, by compensating the serum testosterone level. reduced the percentage of apoptotic and both short head and abnormal sperm froms in the caudal epididymis. Importantly, the beneficial effects of immediate administration of testosterone were prominent. Increases in the level of CADM1 transcription and its immunoreactivity in the testis of SCI mice treated with testosterone were accompanied by improvement of sperm motility as well as testicular Johnsen’s and Miller’s criteria.

Conclusion

Since immediate testosterone treatment improved the immunoreactivity and transcription level of CADM1, the observed beneficial effect of exogenouse testosterone can be attributed to its effect on CADM1 dynamics.

Genetic, structural, and chemical insights into the dual function of GRASP55 in germ cell Golgi remodeling and JAM-C polarized localization during spermatogenesis

Spermatogenesis is a dynamic process that is regulated by adhesive interactions between germ and Sertoli cells. Germ cells express the Junctional Adhesion Molecule-C (JAM-C, encoded by Jam3), which localizes to germ/Sertoli cell contacts. JAM-C is involved in germ cell polarity and acrosome formation. Using a proteomic approach, we demonstrated that JAM-C interacted with the Golgi reassembly stacking protein of 55 kDa (GRASP55, encoded by Gorasp2) in developing germ cells. Generation and study of Gorasp2-/- mice revealed that knock-out mice suffered from spermatogenesis defects. Acrosome formation and polarized localization of JAM-C in spermatids were altered in Gorasp2-/- mice. In addition, Golgi morphology of spermatocytes was disturbed in Gorasp2-/- mice. Crystal structures of GRASP55 in complex with JAM-C or JAM-B revealed that GRASP55 interacted via PDZ-mediated interactions with JAMs and induced a conformational change in GRASP55 with respect of its free conformation. An in silico pharmacophore approach identified a chemical compound called Graspin that inhibited PDZ-mediated interactions of GRASP55 with JAMs. Treatment of mice with Graspin hampered the polarized localization of JAM-C in spermatids, induced the premature release of spermatids and affected the Golgi morphology of meiotic spermatocytes.

Functional activity of the porcine Gnrhr2 gene promoter in testis-derived cells is partially conferred by nuclear factor-κB, specificity protein 1 and 3 (SP1/3) and overlapping early growth response 1/SP1/3 binding sites

Unlike the classical gonadotropin-releasing hormone (GnRH1), the second mammalian isoform (GnRH2) is ubiquitously expressed, suggesting a divergent function. Indeed, we demonstrated that GnRH2 governs LH-independent testosterone secretion in porcine testes via interaction with its receptor (GnRHR2) on Leydig cells. Transient transfections with luciferase reporter vectors containing 3009bp of 5' flanking sequence for the porcine Gnrhr2 gene (-3009pGL3) revealed promoter activity in all 15 cell lines examined, including swine testis-derived (ST) cells. Therefore, ST cells were utilized to explore the molecular mechanisms underlying transcriptional regulation of the porcine Gnrhr2 gene in the testis. Reporter plasmids containing progressive 5' deletions of the Gnrhr2 promoter indicated that the -708/-490 region contained elements critical to promoter activity. Electrophoretic mobility shift assays (EMSAs) with radiolabeled oligonucleotides spanning the -708/-490bp region and ST nuclear extracts, identified specific binding complexes for the -513/-490, -591/-571 and -606/-581bp segments of promoter. Antibody addition to EMSAs indicated that the p65 and p52 subunits of nuclear factor-κB (NF-κB) comprised the specific complex bound to the oligonucleotide probe for the -513/-490bp promoter region, specificity protein (SP) 1 and 3 bound the -591/-571bp probe and early growth response 1 (EGR1), SP1 and SP3 bound the -606/-581 radiolabeled oligonucleotide. Transient transfections with vectors containing mutations of the NF-κB (-499/-493), SP1/3 (-582/-575) or overlapping EGR1/SP1/3 (-597/-587) binding sites reduced luciferase activity by 26%, 61% and 56%, respectively (P<0.05). Thus, NF-κB, SP1/3 and overlapping EGR1/SP1/3 binding sites are critical to expression of the porcine Gnrhr2 gene in ST cells.

Differential mouse-strain specific expression of Junctional Adhesion Molecule (JAM)-B in placental structures

The junctional adhesion molecule (JAM)-B, a member of the immunoglobulin superfamily, is involved in stabilization of interendothelial cell-cell contacts, formation of vascular tubes, homeostasis of stem cell niches and promotion of leukocyte adhesion and transmigration. In the human placenta, JAM-B protein is abundant and mRNA transcripts are enriched in first-trimester extravillous trophoblast in comparison to the villous trophoblast. We here aimed to elucidate the yet unexplored spatio-temporal expression of JAM-B in the mouse placenta. We investigated and semi-quantified JAM-B protein expression by immunohistochemistry in early post-implantation si tes and in mid- to late gestation placentae of various murine mating combinations. Surprisingly, the endothelium of the placental labyrinth was devoid of JAM-B expression. JAM-B was mainly present in spongiotrophoblast cells of the junctional zone, as well as in the fetal vessels of the chorionic plate, the umbilical cord and in maternal myometrial smooth muscle. We observed a strain-specific placental increase of JAM-B protein expression from mid- to late gestation in Balb/c-mated C57BL/6 females, which was absent in DBA/2J-mated Balb/c females. Due to the essential role of progesterone during gestation, we further assessed a possible modulation of JAM-B in mid-gestational placentae deficient in the progesterone receptor (Pgr(-/-)) and observed an increased expression of JAM-B in Pgr(-/-) placentae, compared to Pgr(+/+) tissue samples. We propose that JAM-B is an as yet underappreciated trophoblast lineage-specific protein, which is modulated via the progesterone receptor and shows unique strain-specific kinetics. Future work is needed to elucidate its possible contribution to placental processes necessary to ensuring its integrity, ultimately facilitating placental development and fetal growth.

Expression of tight junction molecule in the human serum-induced aggregation of human abdominal adipose-derived stem cells in vitro

Previously we have shown that human abdominal adipose derived-stem cells (ADSCs) could aggregate during the high-density culture in the presence of human serum (HS). In the present study, we observed that human cord blood serum (CBS) and follicular fluid (HFF) also induced aggregation. Similarly, porcine serum could induce aggregation whereas bovine and sheep sera induced little aggregation. qRT-PCR analyses demonstrated that, compared to FBS-cultured ADSCs, HScultured cells exhibited higher level of mRNA expression of CLDN3, -6, -7, -15, and -16 genes among the tight junction proteins. ADSCs examined at the time of aggregation by culture with HS, BSA, HFF, CBS, or porcine serum showed significantly higher level of mRNA expression of JAM2 among JAM family members. In contrast, cells cultured in FBS, bovine serum or sheep serum, showed lower level of JAM2 expression. Immunocytochemical analyses demonstrated that the aggregates of HS-cultured cells (HS-Agg) showed intense staining against the anti-JAM2 antibody whereas neither non-aggregated cells (HS-Ex) nor FBS-cultured cells exhibited weak staining. Western blot results showed that HS-Agg expressed JAM2 protein more prominently than HS-Ex and FBS-cultured cells, both of latter reveled weaker intensity. These results suggest that the aggregation property of ADSCs during high-density culture would be dependent on the specific components of serum, and that JAM2 molecule could play a role in the animal sera-induced aggregation in vitro.

A mRNA landscape of bovine embryos after standard and MAPK-inhibited culture conditions: a comparative analysis

Background

Genes and signalling pathways involved in pluripotency have been studied extensively in mouse and human pre-implantation embryos and embryonic stem (ES) cells. The unsuccessful attempts to generate ES cell lines from other species including cattle suggests that other genes and pathways are involved in maintaining pluripotency in these species. To investigate which genes are involved in bovine pluripotency, expression profiles were generated from morula, blastocyst, trophectoderm and inner cell mass (ICM) samples using microarray analysis. As MAPK inhibition can increase the NANOG/GATA6 ratio in the inner cell mass, additionally blastocysts were cultured in the presence of a MAPK inhibitor and changes in gene expression in the inner cell mass were analysed.

Results

Between morula and blastocyst 3,774 genes were differentially expressed and the largest differences were found in blastocyst up-regulated genes. Gene ontology (GO) analysis shows lipid metabolic process as the term most enriched with genes expressed at higher levels in blastocysts. Genes with higher expression levels in morulae were enriched in the RNA processing GO term. Of the 497 differentially expressed genes comparing ICM and TE, the expression of NANOG, SOX2 and POU5F1 was increased in the ICM confirming their evolutionary preserved role in pluripotency. Several genes implicated to be involved in differentiation or fate determination were also expressed at higher levels in the ICM. Genes expressed at higher levels in the ICM were enriched in the RNA splicing and regulation of gene expression GO term. Although NANOG expression was elevated upon MAPK inhibition, SOX2 and POU5F1 expression showed little increase. Expression of other genes in the MAPK pathway including DUSP4 and SPRY4, or influenced by MAPK inhibition such as IFNT, was down-regulated.

Conclusion

The data obtained from the microarray studies provide further insight in gene expression during bovine embryonic development. They show an expression profile in pluripotent cells that indicates a pluripotent, epiblast-like state. The inability to culture ICM cells as stem cells in the presence of an inhibitor of MAPK activity together with the reported data indicates that MAPK inhibition alone is not sufficient to maintain a pluripotent character in bovine cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1448-x) contains supplementary material, which is available to authorized users.

Transforming growth factor-β3 regulates cell junction restructuring via MAPK-mediated mRNA destabilization and Smad-dependent protein degradation of junctional adhesion molecule B (JAM-B)

Junctional adhesion molecule-B (JAM-B) is found between Sertoli cells at the blood-testis barrier (BTB) as well as between Sertoli and germ cells at the apical ectoplasmic specializations (ES) in the testis. The expression of JAM-B is tightly regulated to modulate the passage of spermatocytes across the BTB as well as the release of mature spermatozoa from the seminiferous epithelium. Transforming growth factor beta (TGF-β) family is implicated in the regulation of testicular cell junction dynamics during spermatogenesis. This study aims to investigate the effects of TGF-β3 on the expression of JAM-B as well as the underlying mechanisms on how TGF-β3 regulates JAM-B expression to facilitate the disassembly of the BTB and apical ES. Our results revealed that TGF-β3 suppresses JAM-B at post-transcriptional and post-translational levels. Inhibitor, siRNA knockdown and co-immunoprecipitation have shown that TGF-β3 induces JAM-B protein degradation via ubiquitin-proteasome pathway. Immunofluorescence staining further confirmed that blockage of ubiquitin-proteasome pathway could abrogate TGF-β3-induced loss of JAM-B at the cell-cell interface. siRNA knockdown and immunofluorescence staining also demonstrated that activation of Smad signaling is required for TGF-β3-induced JAM-B protein degradation. In addition, TGF-β3 reduces JAM-B mRNA levels, at least in part, via post-transcriptional regulation. mRNA stability assay has confirmed that TGF-β3 promotes the degradation of JAM-B transcript and TGF-β3-mediated mRNA destabilization requires the activation of ERK1/2 and p54 JNK signal cascades. Taken together, TGF-β3 significantly downregulates JAM-B expression via post-transcriptional and post-translational modulation and results in the disruption of BTB and apical ES.

Expression of Tight Junction Molecule In The Human Serum-Induced Aggregation of Human Abdominal Adipose-Derived Stem Cells In Vitro

Previously we have shown that human abdominal adipose derived-stem cells (ADSCs) could aggregate during the high-density culture in the presence of human serum (HS). In the present study, we observed that human cord blood serum (CBS) and follicular fluid (HFF) also induced aggregation. Similarly, porcine serum could induce aggregation whereas bovine and sheep sera induced little aggregation. qRT-PCR analyses demonstrated that, compared to FBS-cultured ADSCs, HScultured cells exhibited higher level of mRNA expression of CLDN3, -6, -7, -15, and -16 genes among the tight junction proteins. ADSCs examined at the time of aggregation by culture with HS, BSA, HFF, CBS, or porcine serum showed significantly higher level of mRNA expression of JAM2 among JAM family members. In contrast, cells cultured in FBS, bovine serum or sheep serum, showed lower level of JAM2 expression. Immunocytochemical analyses demonstrated that the aggregates of HS-cultured cells (HS-Agg) showed intense staining against the anti-JAM2 antibody whereas neither non-aggregated cells (HS-Ex) nor FBS-cultured cells exhibited weak staining. Western blot results showed that HS-Agg expressed JAM2 protein more prominently than HS-Ex and FBS-cultured cells, both of latter reveled weaker intensity. These results suggest that the aggregation property of ADSCs during high-density culture would be dependent on the specific components of serum, and that JAM2 molecule could play a role in the animal sera-induced aggregation in vitro.

Dysregulation of nectin-2 in the testicular cells: an explanation of cadmium-induced male infertility

Nectin-2, a junction molecule, is found at the basal and apical ectoplasmic specializations (ES) for the formation of the blood-testis barrier (BTB) (constituted by tight junctions and basal ES) and Sertoli-spermatid adhesion. Loss of nectin-2 causes male infertility, suggesting nectin-2-based ES is crucial for spermatogenesis. Cadmium (Cd) has been known to induce severe testicular injury. Recent evidence has shown that the basal ES at the BTB and apical ES are the targets of Cd, suggesting that unique junction protein at the ES may explain why testis is more susceptible than other tissues. Since nectin-2 is expressed exclusively at the ES, it is highly possible that nectin-2 is the direct target of Cd. In this study, we investigate if nectin-2 is the target protein of Cd toxicity and the mechanism on how Cd down-regulates nectin-2 to achieve ES disruption. Our results revealed that Cd suppresses nectin-2 at transcriptional and post-translational levels. Inhibitor and shRNA knockdown have shown that Cd induces nectin-2 protein degradation via clathrin-dependent endocytosis. Immunofluorescence staining and endocytosis assays further confirmed that nectin-2 internalization is promoted upon Cd treatment. Besides, Cd directly represses nectin-2 transcription. EMSA and ChIP assays showed that Cd inhibits the binding of positive regulators to nectin-2 promoter. siRNA and overexpression analyses have demonstrated that Cd reduces the expression and binding affinity of positive regulators for transcription. Taken together, nectin-2 is the direct molecular target of Cd and its disruptive effects are mediated via direct repressing nectin-2 transcription and endocytosis of nectin-2 for degradation.

Synergistic effect of interferon-gamma and tumor necrosis factor-alpha on coxsackievirus and adenovirus receptor expression: an explanation of cell sloughing during testicular inflammation in mice

Coxsackievirus and adenovirus receptor (CAR) is a junction molecule that expresses on Sertoli and germ cells. It mediates Sertoli-germ cell adhesion and facilitates migration of preleptotene/leptotene spermatocytes across the blood-testis barrier, suggesting that CAR-based cell adhesion and migration are crucial for spermatogenesis. Interferon-gamma (IFNG) and tumor necrosis factor alpha (TNF) are two major cytokines that are elevated during testicular inflammation and cause reduced fertility. We investigated the mechanism by which IFNG and TNF exert their disruptive effects on testicular cell adhesion. We have demonstrated that combined treatment with IFNG and TNF (IFNG+TNF) exerts a synergistic effect by downregulating CAR mRNA and protein levels. Immunofluorescence staining revealed that IFNG+TNF treatment effectively removes CAR from the site of cell-cell contact. Using inhibitor and co-immunoprecipitation, we confirmed that IFNG+TNF mediates CAR protein degradation via ubiquitin-proteasome and NFKB pathways. Blockage of ubiquitin-proteasome pathway significantly inhibits CAR degradation, as indicated by the reappearance of CAR at the site of cell-cell contact. Additionally, IFNG+TNF reduces CAR mRNA via transcriptional regulation. Mutational studies have shown that IFNG+TNF-induced CAR repression is achieved by suppression of the basal transcription. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays further confirmed that IFNG+TNF treament not only inhibits binding of the basal transcription factors but also promotes binding of NFKB subunits and Sp1 (negative regulators) to the CAR promoter region. Taken together, IFNG+TNF treatment significantly downregulates CAR expression, which provides an explanation of how cell sloughing in the epithelium mediates, by loss of CAR-based cell adhesion, during testicular inflammation.

Transforming growth factor-β1 (TGF-β1) regulates cell junction restructuring via Smad-mediated repression and clathrin-mediated endocytosis of nectin-like molecule 2 (Necl-2)

Nectin-like molecule-2 (Necl-2), a junction molecule, is exclusively expressed by spermatogenic cells. It mediates homophilic interaction between germ cells and heterophilic interaction between Sertoli and germ cells. Knockout studies have shown that loss of Necl-2 causes male infertility, suggesting Necl-2-based cell adhesion is crucial for spermatogenesis. Transforming growth factor-βs (TGF-βs) are crucial for regulating cell junction restructuring that are required for spermatogenesis. In the present study, we aim to investigate the mechanism on how TGF-β1 regulates Necl-2 expression to achieve timely junction restructuring in the seminiferous epithelium during spermatogenesis. We have demonstrated that TGF-β1 reduces Necl-2 mRNA and protein levels at both transcriptional and post-translational levels. Using inhibitor and clathrin shRNA, we have revealed that TGF-β1 induces Necl-2 protein degradation via clathrin-dependent endocytosis. Endocytosis assays further confirmed that TGF-β1 accelerates the internalization of Necl-2 protein to cytosol. Immunofluorescence staining also revealed that TGF-β1 effectively removes Necl-2 from cell-cell interface. In addition, TGF-β1 reduces Necl-2 mRNA via down-regulating Necl-2 promoter activity. Mutational studies coupled with knockdown experiments have shown that TGF-β1-induced Necl-2 repression requires activation of Smad proteins. EMSA and ChIP assays further confirmed that TGF-β1 promotes the binding of Smad proteins onto MyoD and CCAATa motifs in vitro and in vivo. Taken together, TGF-β1 is a potent cytokine that provides an effective mechanism in controlling Necl-2 expression in the testis via Smad-dependent gene repression and clathrin-mediated endocytosis.

Intercellular adhesion molecules (ICAMs) and spermatogenesis

BACKGROUND

During the seminiferous epithelial cycle, restructuring takes places at the Sertoli-Sertoli and Sertoli-germ cell interface to accommodate spermatogonia/spermatogonial stem cell renewal via mitosis, cell cycle progression and meiosis, spermiogenesis and spermiation since developing germ cells, in particular spermatids, move 'up and down' the seminiferous epithelium. Furthermore, preleptotene spermatocytes differentiated from type B spermatogonia residing at the basal compartment must traverse the blood-testis barrier (BTB) to enter the adluminal compartment to prepare for meiosis at Stage VIII of the epithelial cycle, a process also accompanied by the release of sperm at spermiation. These cellular events that take place at the opposite ends of the epithelium are co-ordinated by a functional axis designated the apical ectoplasmic specialization (ES)-BTB-basement membrane. However, the regulatory molecules that co-ordinate cellular events in this axis are not known.

METHODS

Literature was searched at http://www.pubmed.org and http://scholar.google.com to identify published findings regarding intercellular adhesion molecules (ICAMs) and the regulation of this axis.

RESULTS

Members of the ICAM family, namely ICAM-1 and ICAM-2, and the biologically active soluble ICAM-1 (sICAM-1) are the likely regulatory molecules that co-ordinate these events. sICAM-1 and ICAM-1 have antagonistic effects on the Sertoli cell tight junction-permeability barrier, involved in Sertoli cell BTB restructuring, whereas ICAM-2 is restricted to the apical ES, regulating spermatid adhesion during the epithelial cycle. Studies in other epithelia/endothelia on the role of the ICAM family in regulating cell movement are discussed and this information has been evaluated and integrated into studies of these proteins in the testis to create a hypothetical model, depicting how ICAMs regulate junction restructuring events during spermatogenesis.

CONCLUSIONS

ICAMs are crucial regulatory molecules of spermatogenesis. The proposed hypothetical model serves as a framework in designing functional experiments for future studies.

Genomic organisation, embryonic expression and biochemical interactions of the zebrafish junctional adhesion molecule family of receptors

The mammalian JAM family is composed of three cell surface receptors. Interactions between the proteins have well-characterised roles in inflammation and tight junction formation, but little is known about their function in early development. Recently, we identified a role for jamb and jamc in zebrafish myocyte fusion. Genome duplication in the teleost lineage raised the possibility that additional JAM family paralogues may also function in muscle development. To address this, we searched the zebrafish genome to identify potential paralogues and confirmed their homology, bringing the total number of zebrafish jam family members to six. We then compared the physical binding properties of each paralogue by surface plasmon resonance and determined the gene expression patterns of all zebrafish jam genes at different stages of development. Our results suggest a significant sub-functionalisation of JAM-B and JAM-C orthologues with respect to binding strength (but not specificity) and gene expression. The paralogous genes, jamb2 and jamc2, were not detected in the somites or myotome of wild-type embryos. We conclude that it is unlikely that the paralogues have a function in primary myogenesis.

Transforming growth factor-β1 attenuates junctional adhesion molecule-A and contributes to breast cancer cell invasion

Transforming growth factor-β1 (TGF-β1) is a potent regulator in promoting the invasion and proliferation of breast cancer cells. Junctional adhesion molecule-A (JAM-A) is a tight junction protein that displays an inverse relationship to cell invasiveness in breast cancer cells. Whether TGF-β1 signaling induces alteration of JAM-A expression leading to cell invasion has not been investigated. In this study, we report that TGF-β1 down-regulated JAM-A expression via its effect on both transcriptional and post-translational regulations of JAM-A, thus inducing cell invasion. On exploring whether TGF-β1 might be the upstream regulator of JAM-A expression, we found that knockdown of TGF-β receptors and canonical Smad signaling could upregulate JAM-A level and inhibit cell invasion in MDA-MB-231 cells. TGF-β1 treatment of MCF-7 cells caused a significant reduction of JAM-A mRNA and protein and induced cell invasion. Delineating the signal mechanisms involved in TGF-β1-mediated JAM-A repression, we found that TGF-β1 significantly inhibited JAM-A gene transcription via the activation of Smads. In addition to Smad activation, we found that involvement of p54 JNK is crucial for post-translational modification of TGF-β1-mediated JAM-A protein degradation. Blockage of JNK pathway by inhibitor could attenuate TGF-β1-induced cell invasion. We provide evidences for the first time that TGF-β1 induces breast cancer cell invasion via TGF-β1-mediated control on JAM-A expression. Identification of JAM-A as a downstream target of TGF-β1 represents a crucial mechanism in cancer progression.

The biology of interleukin-1: emerging concepts in the regulation of the actin cytoskeleton and cell junction dynamics

Interleukin (IL)-1 is a proinflammatory cytokine with important roles in innate immunity, as well as in normal tissue homeostasis. Interestingly, recent studies have also shown IL-1 to function in the dynamics of the actin cytoskeleton and cell junctions. For example, treatment of different epithelia with IL-1α often results in the restructuring of the actin network and cell junctions, thereby leading to junction disassembly. In this review, we highlight new and interesting findings that show IL-1 to be a critical player of restructuring events in the seminiferous epithelium of the testis during spermatogenesis.

Transcriptional regulation of cell adhesion at the blood-testis barrier and spermatogenesis in the testis

Spermatogenesis involves precise co-ordination of multiple cellular events that take place in the seminiferous epithelium composed of Sertoli cells and developing germ cells during the seminiferous epithelial cycle. Given the cyclic and co-ordinated nature of spermatogenesis, temporal and spatial expression of certain genes pertinent to a specific cellular event are essential. As such, transcriptional regulation is one of the major regulatory machineries in controlling the cell type- and stage-specific gene expression, some of which are under the influence of gonadotropins (e.g., FSH and LH) and sex steroids (e.g., testosterone and estradiol-17beta). Recent findings regarding transcriptional control of spermatogenesis, most notably target genes at the Sertoli-Sertoli and Sertoli-spermatid interface at the site of the blood-testis barrier (BTB) and apical ectoplasmic specialization (apical ES), respectively, involving in cell adhesion are reviewed and discussed herein. This is a much neglected area of research and a concerted effort by investigators is needed to understand transcriptional regulation of cell adhesion function in the testis particularly at the BTB during spermatogenesis.

Asynchronous expression of the homeodomain protein CUX1 in Sertoli cells and spermatids during spermatogenesis in mice

The homeodomain CUX1 protein exists as multiple isoforms that arise from proteolytic processing of a 200-kDa protein or an alternate splicing or from the use of an alternate promoter. The 200-kDa CUX1 protein is highly expressed in the developing kidney, where it functions to regulate cell proliferation. Transgenic mice ectopically expressing the 200-kDa CUX1 protein develop renal hyperplasia associated with reduced expression of the cyclin kinase inhibitor p27. A 55-kDa CUX1 isoform is expressed exclusively in the testes. We determined the pattern and timing of CUX1 protein expression in developing testes. CUX1 expression was continuous in Sertoli cells from prepubertal testes but became cyclic when spermatids appeared. In testes from mature mice, CUX1 was highly expressed only in round spermatids at stages IV-V of spermatogenesis, in both spermatids and Sertoli cells at stages VI-X of spermatogenesis, and only in Sertoli cells at stage XI of spermatogenesis. While most of the seminiferous tubules in wild-type mice were between stages VI and X of spermatogenesis, there was a significant reduction in the percentage of seminiferous tubules between stages VI and X in Cux1 transgenic mice and a significant increase in the percentage of seminiferous tubules in stages IV-V and XI. Moreover, CUX1 was not expressed in proliferating cells in testes from either wild-type or transgenic mice. Thus, unlike the somatic form of CUX1, which has a role in cell proliferation, the testis-specific form of CUX1 is not involved in cell division and appears to play a role in signaling between Sertoli cells and spermatids.

Cytokines and junction restructuring events during spermatogenesis in the testis: an emerging concept of regulation

During spermatogenesis in mammalian testes, junction restructuring takes place at the Sertoli-Sertoli and Sertoli-germ cell interface, which is coupled with germ cell development, such as cell cycle progression, and translocation of the germ cell within the seminiferous epithelium. In the rat testis, restructuring of the blood-testis barrier (BTB) formed between Sertoli cells near the basement membrane and disruption of the apical ectoplasmic specialization (apical ES) between Sertoli cells and fully developed spermatids (spermatozoa) at the luminal edge of the seminiferous epithelium occur concurrently at stage VIII of the seminiferous epithelial cycle of spermatogenesis. These two processes are essential for the translocation of primary spermatocytes from the basal to the apical compartment to prepare for meiosis, and the release of spermatozoa into the lumen of the seminiferous epithelium at spermiation, respectively. Cytokines, such as TNFalpha and TGFbeta3, are present at high levels in the microenvironment of the epithelium at this stage of the epithelial cycle. Since these cytokines were shown to disrupt the BTB integrity and germ cell adhesion, it was proposed that some cytokines released from germ cells, particularly primary spermatocytes, and Sertoli cells, would induce restructuring of the BTB and apical ES at stage VIII of the seminiferous epithelial cycle. In this review, the intricate role of cytokines and testosterone to regulate the transit of primary spermatocytes at the BTB and spermiation will be discussed. Possible regulators that mediate cytokine-induced junction restructuring, including gap junction and extracellular matrix, and the role of testosterone on junction dynamics in the testis will also be discussed.