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Germ Cell Differentiation (germ + cell_differentiation)
Selected Abstractsp19Ink4d and p18Ink4c cyclin-dependent kinase inhibitors in the male reproductive axisMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 8 2007Gregory M. Buchold Abstract The loss of the cyclin-dependent kinase inhibitors (CKIs) p18Ink4c and p19Ink4d leads to male reproductive defects (Franklin et al., 1998. Genes Dev 12: 2899,2911; Zindy et al., 2000. Mol Cell Biol 20: 372,378; Zindy et al., 2001. Mol Cell Biol 21: 3244,3255). In order to assess whether these inhibitors directly or indirectly affect male germ cell differentiation, we examined the expression of p18Ink4c and p19Ink4d in spermatogenic and supporting cells in the testis and in pituitary gonadotropes. Both p18Ink4c and p19Ink4d are most abundant in the testis after 18 days of age and are expressed in purified populations of spermatogenic and testicular somatic cells. Different p18Ink4c mRNAs are expressed in isolated spermatogenic and Leydig cells. Spermatogenic cells also express a novel p19Ink4d transcript that is distinct from the smaller transcript expressed in Sertoli cells, Leydig cells and in other tissues. Immunohistochemistry detected significant levels of p19Ink4d in preleptotene spermatocytes, pachytene spermatocytes, condensing spermatids, and Sertoli cells. Immunoprecipitation-Western analysis detected both CKI proteins in isolated pachytene spermatocytes and round spermatids. CDK4/6-CKI complexes were detected in germ cells by co-immunoprecipitation, although the composition differed by cell type. p19Ink4d was also identified in FSH+ gonadotrophs, suggesting that this CKI may be independently required in the pituitary. Possible cell autonomous and paracrine mechanisms for the spermatogenic defects in mice lacking p18Ink4c or p19Ink4d are supported by expression of these CKIs in spermatogenic cells and in somatic cells of the testis and pituitary. Mol. Reprod. Dev. 74: 997,1007, 2007. © 2007 Wiley-Liss, Inc. [source] G2/M checkpoint gene expression in developing germ cellsMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 5 2007Suzanne Hasthorpe Abstract Cell cycle progression is prevented by signal transduction pathways known as checkpoints which are activated in response to replication interference and DNA damage. We cloned a G2/M cell cycle phase-related checkpoint gene from a neonatal mouse testis cDNA library which was identified as mouse claspin, a proposed adaptor protein for Chk1. As part of a study on germ cell differentiation we examined the expression of the checkpoint gene, Chk1, and claspin at 12.5 and 14.5 days post coitum (dpc) and in the post-natal phase. Chk1 mRNA expression increased from 12.5 to 14.5 dpc in female gonads and was strong in males at both time points. Claspin however, was not detected until 14.5 dpc. This suggests there may be some dissociation of claspin expression from Chk1 in fetal germ cell development. Chk1 and claspin expression was also studied in testis over the first 3 days following birth, when apoptosis regulates germ stem cell number. We modulated checkpoint-related gene expression in testis using the anti-metabolite, 5-fluorouracil, resulting in increased apoptosis and upregulation of Chk1 (P,<,0.0001) and Cdc2 (P,<,0.02) mRNA. Although we do not fully understand the role checkpoint gene expression has during mammalian germ cell development this report is the first to show the expression of checkpoint-related genes in early mammalian germ cells. Mol. Reprod. Dev. 74: 531,538, 2007. © 2007 Wiley-Liss, Inc. [source] Dynamic expression of Krüppel-like factor 4 (Klf4), a target of transcription factor AP-2, during murine mid-embryogenesisTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2003Julia Ehlermann Abstract Krüppel-like factor 4 (Klf4) belongs to the family of transcription factors that are thought to be involved in the regulation of epithelial and germ cell differentiation, based on their expression in postproliferative cells of the skin, gut, and testes. Gene ablation experiments suggest that Klf4 plays a role in keratinocyte differentiation, since mice lacking Klf4 fail to establish proper barrier function and, as a consequence, die postnatally due to dehydration. Recent studies have shown that Klf4 is also expressed in postnatal male mice, in postmeiotic sperm cells undergoing terminal differentiation into sperm cells. However, prior to the current study, the expression pattern of Klf4 during early and mid-embryogenesis had not been examined. Here we demonstrate that Klf4 transcripts can be detected from embryonic day 4.5 (E4.5) on in the developing conceptus, and that Klf4 expression before E10 is restricted to extraembryonic tissues. The embryo proper displays a highly dynamic and changing Klf4 signal from E10 of murine development on. In addition to being expressed in a stripe of mesenchymal cells extending from the forelimb bud rostrally over the branchial arches to the developing eye, Klf4 is also expressed in the mesenchyme surrounding the nasal pit at day E11.5. In addition, Klf4 has been detected in the apical ectodermal ridge and adjacent mesenchymal cells in the limb buds, and in mesenchymal cells of the developing body wall in trunk areas. These findings suggest that Klf4 plays an important role in regulating cellular proliferation, which underlies the morphogenetic changes that shape the developing embryo. Anat Rec Part A 273A:677,680, 2003. © 2003 Wiley-Liss, Inc. [source] Prenatal development of murine gonads with special reference to germ cell differentiation: a morphological and immunohistochemical studyANDROLOGIA, Issue 3 2007A. E. Zayed Summary The prenatal differentiation of male and female gonads of the mouse was investigated both morphologically and immunohistochemically. Sexual dimorphism could be detected as early as 12 days post-coitum (dpc) by the appearance of the primary elements of the tunica albuginea and positive immunoreactivity for anti-Muellerian hormone in the Sertoli cells of the male gonad. Male germ cells passed two waves of mitotic activity, a first wave between 12 and 14 dpc, which is followed by apoptosis of the old germ cell generation, and a second wave between 17 and 20 dpc. Oct-4 was expressed as a juxtanuclear ring in the cytoplasm of germ cells up to 17 dpc. Subsequently, it was down-regulated and completely disappeared in 20 dpc full-term fetuses. By contrast, M2A antigen revealed only a weak immunoreaction in some germ cells of 14 dpc gonads, but exhibited strong signals in all germ cells of 20 dpc full-term fetuses. Therefore, we postulate that, in the mouse, prenatal germ cells represent two populations: the first is immunopositive for Oct-4 and disappeared in full-term fetuses, whereas the second appeared in 14 dpc and is immunopositive for M2A antigen. [source] Angiotensin I-converting enzyme and potential substrates in human testis and testicular tumoursAPMIS, Issue 1 2003Review article The angiotensin I-converting enzyme (ACE, kininase II, CD143) shows a broad specificity for various oligopeptides. Besides the well-known conversion of angiotensin I to II, ACE degrades efficiently kinins and the tetrapeptide AcSDKP (goralatide) and thus equally participates in the renin-angiotensin system, the kallikrein-kinin system, and the regulation of stem cell proliferation. In the mammalian testis, ACE occurs in two isoforms. The testicular isoform (tACE) is exclusively expressed during spermatogenesis and is generally thought to represent the germ cell-specific isozyme. However, we have previously demonstrated that, in addition to tACE, the somatic isoform (sACE) is also present in human germ cells. Similar to other oncofoetal markers, sACE exhibits a transient expression during foetal germ cell development and appears to be a constant feature of intratubular germ cell neoplasm, the so-called carcinoma-in-situ (CIS) and, in particular, of classic seminoma. This demands the existence of specific paracrine functions during male germ cell differentiation and development of male germ cell tumours, which are mediated by either of the two ACE isoforms. Considering the complexity of current data about ACE, a logical connection is required between () the precise localisation of ACE isoforms, (I) the local access to potential substrates and (II) functional data obtained by knockout mice models. The present article summarises the current knowledge about ACE and its potential substrates with special emphasis on the differentiation-restricted ACE expression during human spermatogenesis and prespermatogenesis, the latter being closely linked to the pathogenesis of human germ cell tumours. [source] Infertility despite surgery for cryptorchidism in childhood can be classified by patients with normal or elevated follicle-stimulating hormone and identified at orchidopexyBJU INTERNATIONAL, Issue 7 2003D. Cortes OBJECTIVE To analyse infertility despite orchidopexy in childhood. PATIENTS AND METHODS The study comprised patients with cryptorchidism (70 bilateral and 65 unilateral) who had a simultaneous biopsy taken at orchidopexy in childhood, and in adulthood had analyses of semen and FSH. In adulthood 42 formerly bilateral cryptorchid boys had repeat testicular biopsies taken. Infertility was suspected in men with < 5 million sperm/mL in the best sample of semen and concomitant poor sperm motility, and who were classified by follicle-stimulating hormone (FSH) values. At orchidopexy the number of spermatogonia/tubule and the germ cell differentiation were measured. In adulthood the percentage of tubules with complete spermatogenesis, spermatogenic arrest and Sertoli-cell only status was assessed. RESULTS Infertility was suspected in 38 of 70 (54%) of formerly bilateral and six of 65 (9%) formerly unilateral cryptorchid patients. High FSH values were expected in these suspected infertile patients, but 15 of 38 (59%) formerly bilateral and five of six formerly unilateral cryptorchid patients had normal FSH values. These patients were identified in childhood at orchidopexy; those with bilateral cryptorchidism generally presented with germ cells, but the mean number of spermatogonia per tubule was < 30% of the lowest normal value, and the germ cells were seldom normally differentiated, whereas those with unilateral cryptorchidism generally lacked germ cells in the biopsies. No patients had a decreased FSH value. CONCLUSION Despite surgery for cryptorchidism, infertility was probable in a third (44 of 135) of the patients. We expected high FSH values in these patients, but in 45% (20/44) the FSH values were normal. These patients may have relative FSH deficiency. At orchidopexy these patients were identified to be bilaterally cryptorchid with few germ cells and those unilaterally cryptorchid had none in the biopsy. After orchidopexy in childhood, additional hormonal treatment, e.g. recombinant FSH or buserelin, may be indicated in these patients. [source] Regulation of the G2/M phase of the cell cycle by sperm associated antigen 8 (SPAG8) proteinCELL BIOCHEMISTRY AND FUNCTION, Issue 5 2009Rong Li Abstract Sperm associated antigen 8 (SPAG8), a testis-specific protein produced during male germ cell differentiation, was isolated from a human testis expression library using antibodies found in the serum obtained from an infertile woman. It was found to have a close functional relationship with microtubules. In this study, we generated a stably expressing SPAG8 CHO-K1 cell line. Immunofluorescence confocal microscopy showed that SPAG8 was concentrated at the microtubule-organizing center (MTOC) during prophase. As the cells progressed into metaphase, it co-localized with , -tubulin on the spindle. In anaphase, it was detected on both astral microtubules and mid-zone. Following cytokinesis, SPAG8 resumed its localization on the MTOC. Meanwhile, flow cytometry analysis found that SPAG8 prolonged the G2/M phase of CHO-K1 cells stably expressing SPAG8. Furthermore, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that SPAG8 inhibited the proliferation of the stable cells. SPAG8 might be involved in the regulation of cell cycle by changing the phosphorylation level of Tyr15 on cdc2. These results suggest that SPAG8 might play a role in cell division during spermatogenesis. Copyright © 2009 John Wiley & Sons, Ltd. [source] Is there a role for thyroid hormone on spermatogenesis?MICROSCOPY RESEARCH AND TECHNIQUE, Issue 11 2009Marcia Santos Wagner Abstract Appropriate level of thyroid hormone is essential for normal development and metabolism in most vertebrate tissues and altered thyroid status impacts adversely on them. For many years the testis was regarded as a thyroid hormone unresponsive organ, but consistent evidence accumulated in the past two decades has definitively changed this classical view. Currently, the concept that thyroid hormone plays a critical role in testis development, in rats and other vertebrate species, is clearly established. Although the effects of thyroid hormone on Sertoli and Leydig cells in the immature testis are well described, its role on the adult organ remains controversial. In this review, we summarize and discuss the recent development on the thyroid hormone effects in immature and adult testes. Particularly, we have attempted to address the role of thyroid hormone in the regulation of spermatogenesis, emphasizing recent data that suggest its involvement in germ cells differentiation and survival. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||