Table of Contents

Volume 1, Issue 4

  October/November/December 2011

  Pages 281 - 365

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EDITORIAL

Open Access Article

Male contraception: Where do we go from here?

C. Yan Cheng and Dolores D. Mruk
Pages 281 - 282
http://dx.doi.org/10.4161/spmg.1.4.19014
Full Text | PDF




VIEWS, COMMENTARIES & OPINIONS

Open Access Article

Environmental contaminants: Is male reproductive health at risk?

Dolores D. Mruk and C. Yan Cheng
Pages 283 - 290
http://dx.doi.org/10.4161/spmg.1.4.18328
Abstract | Full Text | PDF

Contaminants such as cadmium, bisphenol A and lead which pollute our environment affect male reproductive function. There is evidence that toxicant exposure adversely affects fertility. Cadmium and bisphenol A exert their effects in the testis by perturbing blood-testis barrier function, which in turn affects germ cell adhesion in the seminiferous epithelium because of a disruption of the functional axis between these sites. In essence, cadmium mediated its adverse effects at the blood-testis barrier by disrupting cell adhesion protein complexes, illustrating toxicants dismantle cell junctions in the testis. Herein, we will discuss how environmental toxicants affect reproductive function. We will also examine how these adverse effects on fertility may be mediated in part by adipose tissue and bone. Lastly, we will briefly discuss how toxicant-induced damage may be effectively managed so that fertility can be maintaine-d. It is hoped that this information will offer a new paradigm for future studies.

Open Access Article

Adjudin disrupts spermatogenesis via the action of some unlikely partners: Eps8, Arp2/3 complex, drebrin E, PAR6 and 14–3-3

C. Yan Cheng, Pearl P.Y. Lie, Elissa W.P. Wong, Dolores D. Mruk and Bruno Silvestrini
Pages 291 - 297
http://dx.doi.org/10.4161/spmg.1.4.18393
Abstract | Full Text | PDF

Adjudin, 1-(2,4-dichlorobenzyl)-1H-indazole-3-carbohydrazide (formerly called AF-2364), is a potent analog of lonidamine [1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid] known to disrupt germ cell adhesion, most notably elongating and elongated spermatids, in the seminiferous epithelium of adult rat testes and thus, leads to infertility in rats. Since the population of spermatogonia and spermatogonial stem cells (SSCs) in the seminiferous tubules is not significantly reduced by the treatment of rats with adjudin, adjudin-induced infertility is highly reversible with the use of appropriate regimens, which enables re-initiation of spermatogenesis and germ cell re-population of the voided seminiferous epithelium. Furthermore, adjudin appears to exert its effects at the testis-specific atypical adherens junction (AJ) type known as ectoplasmic specialization (ES), most notably the apical ES at the Sertoli cell-spermatid interface. Thus, the hypothalamic-pituitary-gonadal axis is not unaffected and systemic side-effects are minimal. This also makes adjudin a potential candidate for male contraceptive development. Herein, we critically evaluate recent findings in the field and provide an updated model regarding the mechanism underlying adjudin-induced apical ES disruption. In short, adjudin targets actin filament bundles at the apical ES, the hallmark of this testis-specific junction type not found in any other epithelia/endothelia in mammals, by suppressing the expression of Eps8 (epidermal growth factor receptor pathway substrate 8), an actin capping protein that also plays a role in actin bundling, so that actin filament bundles can no longer be maintained at the apical ES. This is concomitant with a mis-localization of Arp3 (actin-related protein 3, a component of the Arp2/3 complex that induces actin nucleation/branching), causing “unwanted” actin branching, further destabilizing actin filament bundles at the apical ES. Additionally, adjudin blocks the expression of PAR6 (partitioning defective protein 6) and 14–3-3 (also known as PAR5) considerably at the apical ES, disrupting the homeostasis of endocytic vesicle-mediated protein trafficking, which in turn leads to an increase in protein endocytosis. The net result of these changes destabilizes cell adhesion and induces degeneration of the apical ES, causing premature release of spermatids, mimicking spermiation.




REVIEWS

Open Access Article

The role of the septin family in spermiogenesis

Ying-Hung Lin, Yung-Che Kuo, Han-Sun Chiang and Pao-Lin Kuo
Pages 298 - 302
http://dx.doi.org/10.4161/spmg.1.4.18326
Abstract | Full Text | PDF

Septins (full name: Septin; symbol name: SEPT) belong to a family of polymerizing GTP binding proteins that are required for many cellular functions, including membrane compartmentalization, vesicle trafficking, mitosis and cytoskeletal remodeling. Two of the 14 family members in the mammalian species, Septin12 and 14 are expressed specifically in the testis. In the mouse, knockout of Septin4 and Septin12 leads to male sterility with distinctive sperm pathology (defective annulus or bent neck). In humans, sperm with abnormal expression pattern of SEPT4, 7 and 12 are more prevalent in infertile men. How septin filament is assembled /dissembled and how the SEPT-related complex regulates spermatogenesis still await further investigation.

Open Access Article

Testicular connexin 43, a precocious molecular target for the effect of environmental toxicants on male fertility

Georges Pointis, Jérome Gilleron, Diane Carette and Dominique Segretain
Pages 303 - 317
http://dx.doi.org/10.4161/spmg.1.4.18392
Abstract | PDF

Many recent epidemiological, clinical and experimental findings support the hypothesis that environmental toxicants are responsible for the increasing male reproductive disorders (congenital malformations, declining sperm counts and testicular cancer) over the past 20 y. It has also been reported that exposure to these toxicants, during critical periods of development (fetal and neonatal), represents a more considerable risk for animals and humans than exposure during adulthood. However, the molecular targets for these chemicals have not been clearly identified. Recent studies showed that a family of transmembranous proteins, named connexins, regulates numerous physiological processes involved in testicular development and function, such as Sertoli and germ cell proliferation, differentiation, germ cell migration and apoptosis. In the testis, knockout strategy revealed that connexin 43, the predominant connexin in this organ, is essential for spermatogenesis. In addition, there is evidence that many environmental toxicants could alter testicular connexin 43 by dysregulation of numerous mechanisms controlling its function. In the present work, we propose first to give an overview of connexin expression and intercellular gap junction coupling in the developing fetal and neonatal testes. Second, we underline the impact of maternally chemical exposure on connexin 43 expression in the perinatal developing testis. Lastly, we attempt to link this precocious effect to male offspring fertility.

Open Access Article

17β-estradiol signaling and regulation of Sertoli cell function

Thaís F.G. Lucas, Maristela T. Pimenta, Raisa Pisolato, Maria Fatima M. Lazari and Catarina S. Porto
Pages 318 - 324
http://dx.doi.org/10.4161/spmg.1.4.18903
Abstract | Full Text | PDF

In this review, we will present an overview of estrogen actions in the testis from immature and adult animals, with special emphasis on signaling mechanisms involved in the 17β-estradiol regulation of Sertoli cell function from in immature rats. 17β-estradiol activates Sertoli cell proliferation in immature rats by a mechanism that involves the translocation of the estrogen receptors ESR1 and ESR2 to the plasma membrane, phosphorylation of epidermal growth factor receptor and activation of mitogen-activated protein kinase 3/1. Activation of the G protein-coupled estrogen receptor (GPER) also induces phosphorylation of mitogen-activated protein kinase 3/1 via epidermal growth factor receptor transactivation, which in turn increases expression of the antiapoptotic protein BCL2 and decreases the expression of proapoptotic protein BAX, indicating an antiapoptotic role of E2-GPER in immature rat Sertoli cells. In conclusion, ESRs and GPER can mediate rapid 17β-estradiol signaling in Sertoli cells, and modulate transcriptional events important for Sertoli cell function and maintenance of normal testis development and homeostasis. Our findings are important to clarify the role of estrogen in a critical period of testicular development and to direct further studies, which may contribute to better understand the causes of male infertility.

Open Access Article

Connexins and pannexins: Coordinating cellular communication in the testis and epididymis

Daniel G. Cyr
Pages 325 - 338
http://dx.doi.org/10.4161/spmg.1.4.18948
Abstract | Full Text | PDF

Gap junctions and connexins are critical for coordinating cellular functions in complex epithelia. In recent years there has been increased interest in understanding the regulation and function of gap junctions in both the testis and epididymis. Studies in transgenic mice in which connexin 43 (Cx43) is mutated or is knocked down only in Sertoli cells have demonstrated the essential role of Cx43 in spermatogenesis and differentiation of Sertoli cells. In the epididymis developmental studies have shown a role for numerous connexins in the differentiation of epithelial cells and communication between the basal cells and both principal and clear cells. In both tissues several factors, such thyroid hormones and androgens, are important in regulating expression and function of connexins. Pannexins, which form cellular channels but are structurally similar to gap junction proteins, have been identified in both testis and epididymis and, in the epididymis, are regulated by androgens. The objective of this review is to summarize the advances that have been made on the role and regulation of connexins and pannexins in the testis and epididymis and their implication in spermatogenesis and sperm maturation.




MEETING REPORT

Open Access Article

They produce the sperm, but whose is it? The 11th Biology of Spermatozoa Meeting, September 5-9, 2011--Derbyshire UK

Stefan Lüpold
Pages 339 - 340
http://dx.doi.org/10.4161/spmg.1.4.18327
Abstract | Full Text | PDF

Sperm biology pervades numerous research areas from clinical research to evolutionary biology and animal conservation. Integrating these fields for a better understanding of each is one of the main goals of the Biology of Spermatozoa meeting, a conference held biennially outside of Sheffield in the United Kingdom. This September, at the 11th meeting, scientists from around the globe presented their ongoing research on numerous aspects of reproductive biology, from assisted reproduction in humans and animal conservation through stem cell research and proteomics to sophisticated evolutionary adaptations of ejaculates and female reproductive traits in order to bias paternity toward one or the other male in situations of female promiscuity. Throughout the conference, ethical controversies with reproductive applications (e.g., sperm banking) found their place just as much as novel clinical technologies (e.g., sperm quality assays) or major advances in understanding the mechanisms underlying fundamental processes of postcopulatory sexual selection (e.g., using transgenic animals that produce fluorescently labeled sperm). Across a wide range of different taxa, this meeting has presented a fascinating synthesis of current research and emerging directions in the study of sperm biology.




REPORTS

Open Access Article

The development of an inducible androgen receptor knockout model in mouse to study the post-meiotic effects of androgens on germ cell development

Ariane Willems, Karel De Gendt, Lodewijk Deboel, Johannes V. Swinnen and Guido Verhoeven
Pages 341 - 353
http://dx.doi.org/10.4161/spmg.1.4.18740
Abstract | Full Text | PDF

A mouse model with a Sertoli cell (SC)-selective ablation of the androgen receptor (AR) -the SCARKO mouse- demonstrated that the effects of androgens on spermatogenesis depend on the presence of an active AR in SC. This model has been extremely valuable in the study of the effects of androgens on the initiation of spermatogenesis. However, due to the early (prenatal) inactivation of the AR SCARKO mice develop a complete block in meiosis, making it impossible to study the effects of androgens on postmeiotic steps of germ cell development. It would therefore be of interest to develop a model in which the AR can be ablated at any chosen time point. Here we used a mouse line ubiquitously expressing a tamoxifen (TM)-inducible Cre recombinase to develop an inducible AR knockout model (iARKO). It is shown that treatment with TM (3 mg/day) for five consecutive days efficiently inactivates the AR in testicular tissue and decreases the expression of known AR-target genes in SC (Rhox5, Spinlw1) without markedly affecting testicular cell composition one day after the final injection. TM treatment did, however, decrease serum gonadotropin levels and the expression of several Leydig cell genes (StAR, Cyp17a1, Insl3), resulting in decreased testosterone levels. Nevertheless, the intratesticular testosterone concentration still far exceeds the estimated concentrations required to saturate the AR. It may be concluded that the study of androgen-responsive postmeiotic genes in SC may be feasible using a TM-inducible AR knockout model provided that appropriate controls are included correcting for off-target effects of TM.

Open Access Article

Identification of testis 14–3-3 binding proteins by tandem affinity purification

Pawan Puri, Amparo Acker-Palmer, Ryan Stahler, Yijing Chen, Douglas Kline and Srinivasan Vijayaraghavan
Pages 354 - 365
http://dx.doi.org/10.4161/spmg.1.4.18902
Abstract | Full Text | PDF

The 14–3-3 family of proteins interacts with various cellular phosphoproteins and regulates multiple cell signaling cascades. Identification of 14–3-3 interactors is important to define 14–3-3 functions in various biological pathways. The binding partners of protein 14–3-3 in testis are not known. The main goal of this study was to identify the 14–3-3 interactome in testis to determine the 14–3-3 regulated cellular processes in testis. We used transgenic mice expressing tandem affinity tagged 14–3-3ζ (TAP-14–3-3ζ) driven by the ubiquitin promoter to isolate 14–3-3 binding proteins. The 14–3-3 complexes in testis were isolated using a two-step tandem affinity purification (TAP) followed by identification with liquid chromatography/tandem mass spectrometry (LC-MS/MS). A total of 135 proteins were found to be associated with 14–3-3 in vivo in testis. Comparison of the testis 14–3-3 proteome with known 14–3-3 binding proteins showed that 71 of the proteins identified in this study are novel 14–3-3 interactors. Eight of these novel 14–3-3 interacting proteins are predominantly expressed in testis. The 14–3-3 interactors predominant in testis are: protein phosphatase1γ2 (PP1γ2), spermatogenesis associated 18 (SPATA18), phosphoglycerate kinase-2 (PGK2), testis specific gene A-2 (TSGA-2), dead box polypeptide 4 (DDX4), piwi homolog 1, protein kinase NYD-SP25, and EAN57. The fact that some of these proteins are indispensable for spermatogenesis suggests that their binding to 14–3-3 may be important for their function in germ cell division and maturation. These findings are discussed in context of the putative functions of 14–3-3 in spermatogenesis.