Browsing by Subject "Spermatogenesis"

Now showing 1 - 8 of 8
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    Connexin 43: its regulatory role in testicular junction dynamics and spermatogenesis
    (F. Hernández y J.F. Madrid. Murcia: Universidad de Murcia, Departamento de Biología Celular e Histología., 2011) Weider, Karola; Bergmann, Martin; Brehm, Ralph
    Spermatogenesis is an intensely regulated process of germ cell development which takes place in the seminiferous tubules of the testis. In addition to known endocrine and autocrine/paracrine signaling pathways, there is now strong evidence that direct intercellular communication via gap junction channels and their specific connexins represents an important mechanism in the regulation of spermatogenesis. Another possibility is that connexins may indirectly regulate the spermatogenic process through modulation of tight and adherens junction proteins, further main structural components of the Sertoli-Sertoli junctional complexes at the blood-testis barrier site. The present review is focused on connexin 43 and updates its possible roles and functions in testicular junction dynamics and in the initiation and maintenance of spermatogenesis. In addition, testicular phenotypes of recently generated (1) conventional connexin 43 knockout mice, (2) connexin 43 knockin mice and (3) transgenic mice exhibiting a cell-specific (conditional) connexin 43 knockout will be discussed.
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    Emergent roles for intercellular adhesion molecule-1 in the restructuring of the blood-testis barrier during spermatogenesis in the mammal
    (Universidad de Murcia. Departamento de Biología Celular e Histología, 2016) Mruk, Dolores D.
    Mammalian spermatogenesis is comprised of a series of molecular, cellular, and morphological events that underscore the movement of developing germ cells across the blood-testis barrier. These events involve the restructuring of tight junctions, basal ectoplasmic specializations, gap junctions, and desmosomes, which constitute blood-testis barrier function. Previous studies show that preleptotene/leptotene spermatocytes traverse the blood-testis barrier while transiently trapped within an intermediate compartment, which sequesters primary spermatocytes away from basal and adluminal compartments of the seminiferous epithelium. Preleptotene/leptotene spermatocytes enter the adluminal compartment when stable junctions ahead of spermatocytes disassemble, while new junctions assemble behind them. While there is enormous restructuring of the seminiferous epithelium, the mechanism of germ cell movement is incompletely understood. In this perspective, the significance of intercellular adhesion molecule-1 in the restructuring of the blood-testis barrier during spermatogenesis in the mammal is discussed.
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    How does retinoic acid (RA) signaling pathway regulate spermatogenesis?
    (Universidad de Murcia, Departamento de Biologia Celular e Histiologia, 2022) Zhang, Hua Zhe; Hao, Shuang Li; Yang, Wan Xi
    Male sterility is a worldwide health problem which has troubled many unfortunate families and attracted widespread attention in the field of reproduction. Retinoic acid (RA) is a metabolite of vitamin A. Previous studies have shown that insufficient intake of vitamin A can lead to male infertility. Similarly, RA-deficiency can lead to abnormal spermatogenesis in men. RA signaling is inseparable from hormone stimulation, such as FSH, testosterone and others. It can regulate spermatogenesis as well, including the proliferation and differentiation of spermatogonia, meiosis, spermiogenesis and spermiation. To promote or inhibit spermatogenesis, RA regulates Stra8, Kit, GDNF, BMP4 and other factors in various pathways. At the self-renewal stage, RA inhibits spermatogonia renewal by directly or indirectly inhibiting DMRT, GDNF and Cyclin. At the stage of differentiation and meiosis, RA controls SSC differentiation through Kit induction and Nanos2 inhibition, and controls spermatogonia meiotic entry through up- regulation of Stra8. At the stage of spermiogenesis, RARα, as a key regulator, regulates spermatogenesis by up regulating Stra8 while binding with RA. Although RA plays an important role in all stages of spermatogenesis, RA signaling is more important in the early stage of spermatogonia (spg) differentiation and spermatocyte (spc) meiosis. According to the principle of RA signaling that regulates spermatogenesis, we also speculate on the future clinical application of RA, such as potential induction of SSC in vitro, contraception and restoring spermatogenesis. This paper reviews the regulatory pathways of RA, and prospects the clinical applications of RA signaling in the future.
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    IGSF4: a new intercellular adhesion molecule that is called by three names, TSLC1, SgIGSF and SynCAM, by virtue of its diverse function
    (Murcia : F. Hernández, 2003) Watanabe, K.; Ito, A.; Koma, Y.; Kitamura, Y.
    Members of the immunoglobulin superfamily often play key roles in intercellular adhesion. IGSF4 is a novel immunoglobulin (Ig)-like intercellular adhesion molecule. Three Ig-like domains are included in the extracellular domain of IGSF4 and mediate homophilic or heterophilic interactions independently of Ca2+. The cytoplasmic domain of IGSF4 contains the binding motifs that connect to actin fibers. Since IGSF4 has been characterized by several independent research groups, this molecule is called by three names, TSLC1, SgIGSF and SynCAM. IGSF4 was first characterized as a tumor suppressor of non-small cell lung cancer and termed TSLC1, although how IGSF4 suppresses tumor growth remains unknown. Silencing of the IGSF4 gene was primarily achieved by allelic loss and promoter methylation in this type of cancers. Soon after this discovery, IGSF4 was found to have roles in adhesion of spermatogenic cells to Sertoli cells and mast cells to fibroblasts and termed SgIGSF. Other researchers revealed that IGSF4 drives synaptic formation of neural cells and termed it SynCAM.
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    Loss of connexin43 (Cx43) in Sertoli cells leads to spatio-temporal alterations in occludin expression
    (F. Hernández y Juan F. Madrid. Universidad de Murcia. Departamento de Biología Celular e Histología, 2014) Gerber, Jonathan; Weider, Karola; Hambruch, Nina; Brehm, Ralph
    Within the testis, Sertoli cell (SC) junctional complexes between somatic SC create a basal and apical polarity within the seminiferous epithelium, restrict movement of molecules between cells, and separate the seminiferous epithelium into a basal and adluminal compartment. This barrier consists of membrane integrated proteins known as tight, adherens, and gap junctions, which promote cell-cell contact along the blood-testis-barrier (BTB). Nevertheless, these junctions, which form the basis of the BTB are structures whose function and dynamic regulation is still poorly understood. Thus, in this study, through the use of immunohistochemistry (IHC), semi quantitative western blot (WB) analysis, and real-time-quantitative-PCR (qRT-PCR) we focused on the expression pattern of the main testicular tight junction protein, occludin, in SC. For this, the established transgenic SC specific connexin 43 (Cx43) knockout (SCCx43KO) mouse line was used; both knockout (KO) and wildtype (WT) males of different ages from juvenile to adult were compared. The object was to elucidate a possible role of Cx43 on the expression pattern and regulation of occludin. This conditional KO mouse line lacks the gap junction gene Gja1 (coding for Cx43) only in SC and reveals impaired spermatogenesis. The qRT-PCR indicates an increase in occludin mRNA in adult KO mice. These results correspond to the occludin protein synthesis of adult mice. Additionally, during puberty, occludin localization at the BTB barrier in KO mice is delayed. Our study demonstrates spatiotemporal alterations in occludin mRNA- and protein-expression, indicating that Cx43 might act as a regulator for BTB formation (and function).
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    Mammalian target of rapamycin complex (mTOR) pathway modulates blood-testis barrier (BTB) function through F-actin organization and gap junction
    (2016) Li, Nan; Yan Cheng, C.
    mTOR (mammalian target of rapamycin) is one of the most important signaling molecules in mammalian cells which regulates an array of cellular events, ranging from cell metabolism to cell proliferation. Based on the association of mTOR with the core component proteins, such as Raptor (regulatoryassociated protein of mTOR) or Rictor (rapamycinintensive companion of mTOR), mTOR can become the mTORC1 (mammalian target of rapamycin complex 1) or mTORC2, respectively. Studies have shown that during the epithelial cycle of spermatogenesis, mTORC1 promotes remodeling and restructuring of the bloodtestis barrier (BTB) in vitro and in vivo, making the Sertoli cell tight junction (TJ)-permeability barrier “leaky”; whereas mTORC2 promotes BTB integrity, making the Sertoli cell TJ-barrier “tighter”. These contrasting effects, coupled with the spatiotemporal expression of the core signaling proteins at the BTB that confer the respective functions of mTORC1 vs. mTORC2 thus provide a unique mechanism to modulate BTB dynamics, allowing or disallowing the transport of biomolecules and also preleptotene spermatocytes across the immunological barrier. More importantly, studies have shown that these changes to BTB dynamics conferred by mTORC1 and mTORC2 are mediated by changes in the organization of the actin microfilament networks at the BTB, and involve gap junction (GJ) intercellular communication. Since GJ has recently been shown to be crucial to reboot spermatogenesis and meiosis following toxicant-induced aspermatogenesis, these findings thus provide new insightful information regarding the integration of mTOR and GJ to regulate spermatogenesis.
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    Testicular cryopreservation: From technical aspects to practical applications
    (Universidad de Murcia, Departamento de Biologia Celular e Histiologia, 2025) Pereira, Ana Glória; Matos, Tayná Moura; Albuquerque, Joana Letícia Cottin de; Silva, Andréia Maria da; Silva, Alexandre Rodrigues; Biología Celular e Histología
    Testicular cryopreservation has been highlighted as a promising alternative for preserving male fertility and can be applied to restore spermatogenesis in prepubertal individuals or cancer patients, preserve biologically valuable genotypes, and in studies on reproductive physiology or toxicity of various substances. This review presents an analysis of the technical aspects and applications of testicular cryopreservation, examining the contributions of important studies in this area and discussing the different factors that can impact the efficiency of the technique. Testicular fragments can be obtained from living or dead individuals, at any age and reproductive stage, through orchiectomy or biopsy. Among the methods used for processing, slow freezing and vitrification in open or closed systems stand out. However, factors such as species, age, medium used, cryoprotectants, and cryopreservation method can influence the viability of the testis after heating. To obtain sperm, the testes can be cultured in vitro or in vivo and the recovered gametes applied in assisted reproduction techniques. However, in some species, mainly wild animals and humans, this is still a limitation to be overcome.
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    What are the germ cell phenotypes from infertile men telling us about spermatogenesis?
    (Murcia : F. Hernández, 1999) Escalier, D.
    Drosophila mutants for known genes and those obtained following germline genetic engineering in mice have led to the identification of genes involved in the initiation and the maintenance of spermatogenesis and in the different steps of meiosis. Mutants allow the definition of meiosis-specific checkpoint controls that ensure the transmission of complete and undamaged genetic information. They reveal what spermatogenesis events are interdependent. In the light of these data, an attempt is made to define which events of spermatogenesis could be defective in some well-defined human spermatogenesis failures. They appear to be good models to study the decouplages of spermatogenesis events, the morphogenetic relationships between germ cell structures and the occurrence of pleiotropic sperm phenotypes. It is discussed whether a germ cell with a normal phenotype can transmit a non-functional gene involved in spermatogenesis and how homologous genes can lead to different germ cell phenotypes depending on the species.