Table of Contents

Volume 2, Issue 2

  April/May/June 2012

  Pages 69 - 126

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 Issue Catalogue (MARC XML)

EDITOR'S CORNER

Open Access Article

Letter from the editor

C. Yan Cheng
Page 69
http://dx.doi.org/10.4161/spmg.20831
Full Text | PDF




EDITORIAL

Open Access Article

Drug transporters in spermatogenesis: A re-evaluation of recent data on P-glycoprotein

Dolores D. Mruk and C. Yan Cheng
Pages 70 - 72
http://dx.doi.org/10.4161/spmg.20507
Abstract | Full Text | PDF

Drug transporters are integral membrane proteins expressed by a variety of organs, including the liver, kidney, small intestine and testis, and they are generally known to mediate drug or xenobiotic transport into and out of cells. Previous studies have also reported the presence of several drug transporters at blood-tissue barriers where they are thought to protect organs from harmful agents. In this editorial, we briefly discuss and re-evaluate recent findings that show P-glycoprotein, an efflux pump, to function at the blood-testis barrier. We also put forth a mechanistic model, hoping this information will form a strong basis for future studies.




VIEWS, COMMENTARIES & OPINIONS

Open Access Article

Filamin A: A regulator of blood-testis barrier assembly during post-natal development

Wenhui Su, Dolores D. Mruk and C. Yan Cheng
Pages 73 - 78
http://dx.doi.org/10.4161/spmg.20223
Abstract | Full Text | PDF

Filamins are a family of actin-binding proteins composed of filamin A, B and C. Besides of their ability to induce perpendicular branching of F-actin filaments via their actin binding domains near the N-terminus, filamins can regulate multiple cellular functions because of their unique ability to recruit more than 90 protein binding partners to their primary sequences which are having highly diversified cellular functions. However, this family of proteins has not been examined in the testis until recently. Herein, we highlight recent findings in the field regarding the role of these proteins in cell epithelia, and based on recent data in the testis regarding their role on spermatogenesis, this review provides the basis for future functional studies.




REPORTS

Open Access Article

Peritubular myoid cells have a role in postnatal testicular growth

Mirja Nurmio, Jenny Kallio, Marion Adam, Artur Mayerhofer, Jorma Toppari and Kirsi Jahnukainen
Pages 79 - 87
http://dx.doi.org/10.4161/spmg.20067
Abstract | Full Text | PDF

FSH stimulates testicular growth by increasing Sertoli cell proliferation and elongation of seminiferous cords. Little is known about the peritubular myoid cells in testicular development. In order to investigate the role of peritubular myoid cells in early testicular growth in rodents, two traditional models to induce testicular growth were used: FSH treatment and hemicastration. In order to affect proliferation of peritubular myoid cells, both treatments were combined with imatinib, a tyrosine kinase inhibitor. In addition, effects of imatinib on human testicular peritubular cell proliferation were investigated. Testicular weight, diameter and length of seminiferous cords, numbers of germ, Sertoli and BrdU-positive cells and FSH-levels were measured. FSH treatment and hemicastration increased length of the seminiferous cords and testicular weight by increasing first the early proliferation of peritubular myoid cells and later also the proliferation of the Sertoli cells. Imatinib blocked the FSH and hemicastration -induced testicular hypertrophy and decreased the proliferation of PDGF-stimulated human testicular peritubular cells in vitro. Present results provide new evidence that peritubular myoid cells have an important role in postnatal testicular growth.

Open Access Article

Daily sperm production and evaluation of morphological reproductive parameters of Murrah buffaloes in an extensive breeding system

Patrícia A.C. da Luz, Cristiana Andrighetto, Paulo R.S. Santos, André Jorge, Maria Vitória P. Constantino, Flávia T.V. Pereira, Andrea Mess and Antônio C. Assis Neto
Pages 88 - 93
http://dx.doi.org/10.4161/spmg.20220
Abstract | Full Text | PDF

The development of male sexual maturity varies among buffaloes. The Murrah buffalo is considered the most important and efficient milk and fat producer, but aspects of its reproductive biology are still unknown. The present study aimed to evaluate the daily sperm production (DSP) and spermatogenesis in developing Murrah buffalo bulls by evaluation of the seminiferous tubules, testicular morphometry and using light microscopy and scanning electron microscopy. The testes of Murrah buffalo bulls at 18 mo was immature and at 24 mo could still be considered an average-efficiency breed based on their DSP. At 24 mo, the DSP rate was 0.97 billion sperm per testis and 13 million sperm per gram of testis. However, the animals had superior morphometric parameters compared with those of other livestock animals, except for the seminiferous tubule volume and diameter, which were inferior. In conclusion, our data support former views that the testes of the Murrah breed does not reach sexual maturity before 2 y of age and that important developmental steps occur later than Murrah crossbreeds from Brazil.

Open Access Article

Ontogenic development of spermatids during spermiogenesis in the high altitude bunchgrass lizard (Sceloporus bicanthalis)

Justin Rheubert, Katherine Touzinsky, Oswaldo Hernández-Gallegos, Gisela Granados-González and Kevin Gribbins
Pages 94 - 103
http://dx.doi.org/10.4161/spmg.20410
Abstract | Full Text | PDF

The body of ultrastructural data on spermatid characters during spermiogenesis continues to grow in reptiles, but is still relatively limited within the squamates. This study focuses on the ontogenic events of spermiogenesis within a viviparous and continually spermatogenic lizard, from high altitude in Mexico. Between the months of June and August, testicular tissues were collected from eight spermatogenically active bunchgrass lizards (Sceloporus bicanthalis) from Nevado de Toluca, México. The testicular tissues were processed for transmission electron microscopy and analyzed to access the ultrastructural differences between spermatid generations during spermiogenesis. Interestingly, few differences exist between S. bicanthalis spermiogenesis when compared with what has been described for other saurian squamates. Degrading and coiling membrane structures similar to myelin figures were visible within the developing acrosome that are likely remnants from Golgi body vesicles. During spermiogenesis, an electron lucent area between the subacrosomal space and the acrosomal medulla was observed, which has been observed in other squamates but not accurately described. Thus, we elect to term this region the acrosomal lucent ridge. This study furthers the existing knowledge of spermatid development in squamates, which could be useful in future work on the reproductive systems in high altitude viviparous lizard species.

Open Access Article

Age-dependent alterations in spermatogenesis in itchy mice

Jessica L. Dwyer and John H. Richburg
Pages 104 - 116
http://dx.doi.org/10.4161/spmg.20596
Abstract | Full Text | PDF

Spermatogenesis is an intricate process in which spermatogonial stem cells divide and differentiate to produce mature sperm. This process strongly depends on protein turnover both in the developing germ cells and the supportive Sertoli cells, and recent evidence has demonstrated the role of the ubiquitin-proteasome system in this protein turnover in the testis. Itch, an E3 ligase important in the immune system, has been implicated in regulating the blood testis barrier. Although the specific role of Itch during spermatogenesis is not yet well understood, its ubiquitous expression and wide array of functional targets suggest multiple and tissue-specific roles. Here the testes of mice that lack Itch protein are evaluated at two developmental time points: peri-pubertal postnatal day (PND) 28 and adult PND 56. Itchy mice demonstrate an increased germ cell apoptotic index compared with wild type C57BL/6J mice at both PND 28 and PND 56. A corresponding 27% reduction in the total number of spermatid heads produced in PND 56 itchy mice was also evident. A histological evaluation of itchy mice revealed a delay in spermatogenesis at PND 28 and disorganization of late stage spermatids at PND 56. An analysis of several apoptotic markers revealed an age-dependent change in cleaved caspase 9, an intrinsic apoptosis mediator. The breeding success of the itchy mice was also significantly decreased, possibly due to a developmental defect. Taken together, these findings indicate that Itch is required for functional spermatogenesis, and that it may play differing cellular roles during development.

Open Access Article

Microtubule affinity-regulating kinase 4 (MARK4) is a component of the ectoplasmic specialization in the rat testis

Elizabeth I. Tang, Xiang Xiao, Dolores D. Mruk, Xiaojing Qian, Ka-Wai Mok, Pranitha Jenardhanan, Will M. Lee, Premendu P. Mathur and C. Yan Cheng
Pages 117 - 126
http://dx.doi.org/10.4161/spmg.20724
Abstract | Full Text | PDF

During the seminiferous epithelial cycle of spermatogenesis, the ectoplasmic specialization (ES, a testis-specific adherens junction, AJ, type) maintains the polarity of elongating/elongated spermatids and confers adhesion to Sertoli cells in the seminiferous epithelium, and known as the apical ES. On the other hand, the ES is also found at the Sertoli-Sertoli cell interface at the blood-testis barrier (BTB) known as basal ES, which together with the tight junction (TJ), maintains Sertoli cell polarity and adhesion, creating a functional barrier that limits paracellular transport of substances across the BTB. However, the apical and basal ES are segregated and restricted to the adluminal compartment and the BTB, respectively. During the transit of preleptotene spermatocytes across the BTB and the release of sperm at spermiation at stage VIII of the seminiferous epithelial cycle, both the apical and basal ES undergo extensive restructuring to facilitate cell movement at these sites. The regulation of these events, in particular their coordination, remains unclear. Studies in other epithelia have shown that the tubulin cytoskeleton is intimately related to cell movement, and MARK [microtubule-associated protein (MAP)/microtubule affinity-regulating kinase] family kinases are crucial regulators of tubulin cytoskeleton stability. Herein MARK4, the predominant member of the MARK protein family in the testis, was shown to be expressed by both Sertoli and germ cells. MARK4 was also detected at the apical and basal ES, displaying highly restrictive spatiotemporal expression at these sites, as well as co-localizing with markers of the apical and basal ES. The expression of MARK4 was found to be stage-specific during the epithelial cycle, structurally associating with α-tubulin and the desmosomal adaptor plakophilin-2, but not with actin-based BTB proteins occludin, β-catenin and Eps8 (epidermal growth factor receptor pathway substrate 8, an actin bundling and barbed end capping protein). More importantly, it was shown that the expression of MARK4 tightly associated with the integrity of the apical ES because a diminished expression of MARK4 associated with apical ES disruption that led to the detachment of elongating/elongated spermatids from the epithelium. These findings thus illustrate that the integrity of apical ES, an actin-based and testis-specific AJ, is dependent not only on the actin filament network, but also on the tubulin-based cytoskeleton.