Home About us Contact
|
Home About us Contact | ||
|
|
||
Germ Cell Development (germ + cell_development)
Selected AbstractsGenes involved in the RNA interference pathway are differentially expressed during sea urchin developmentDEVELOPMENTAL DYNAMICS, Issue 11 2007Jia L. Song Abstract RNA-mediated interference (RNAi) is a conserved gene silencing mechanism that involves double-stranded RNA as a signal to trigger the sequence-specific degradation of target mRNA, resulting in posttranscriptional silencing and/or translational repression. Bioinformatic searches in the sea urchin genome database identified homologs of Drosha, DGCR5, Dicer, TRBP, Exportin-5, and Argonautes. Quantitative, real-time polymerase chain reaction indicated that all mRNA accumulate in eggs and in variable levels throughout early development. Whole-mount in situ RNA hybridization showed that all of the important players of the RNAi silencing pathway have abundant mRNA accumulation in oocytes and eggs, but have distinct spatial and temporal expression patterns throughout development. Sequence analysis revealed that each of the four Argonautes examined contain conserved residues important for RNAseH activity within the Piwi domain. This study elucidated that genes involved in the RNAi silencing pathway have dynamic expression and, thus, may have regulatory roles during germ cell development and embryogenesis. Developmental Dynamics 236:3180,3190, 2007. © 2007 Wiley-Liss, Inc. [source] Age-dependent differential expression of genes involved in steroid signalling pathway in the brain of protandrous black porgy, Acanthopagrus schlegeliDEVELOPMENTAL NEUROBIOLOGY, Issue 5 2009Sherly Tomy Abstract The mechanisms underlying brain sex differentiation in animals are poorly understood. In the present study, using black porgy, Acanthopagrus schlegeli, as primary experimental model, we investigated the temporal expression patterns of receptors for androgen (ar) and estrogen (esr1 and esr2a) in the brain during posthatching ages and analyzed them against the timing of gonadal germ cell development. We hypothesized that endogenous estrogens naturally masculinize the brain of black porgy. The expression of sex steroid receptors was studied in relation to a wider suite of other related genes (nr5a2, nr0b1, star, and cyp19a1b) to provide some insight into the monomale sex differentiation pattern observed in this species. Our results revealed a highly significant increase in esr1 together with the increase in esr2a at 120 dph (days posthatching), suggesting a significant role for esr in sex differentiation in this species. Temporal expression patterns of nr5a2, nr0b1, star, sex steroid receptors, and cyp19a1b in the brain provided evidence for their physiological roles in the monomale sex differentiation in this species. The expression of nr5a2, star, ar, esr1, esr2a, and cyp19a1b increased at 120 dph, a period when brain sex differentiation probably occurs in this species. The study also suggests that neurosteroidogenesis in black porgy may be regulated by both nr5a2 -dependent and nr5a2 -independent mechanisms. The results demonstrated striking differences in the abundance of the gene transcripts in discrete brain region throughout ontogeny. In addition, the sex steroid hormone levels and aromatase activity in brain at different developmental states and the changes in the gene expression patterns in response to aromatase inhibitor treatment are also discussed. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] A gene trap knockout of the abundant sperm tail protein, outer dense fiber 2, results in preimplantation lethality,GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 11 2006Nicholas A. Salmon Abstract Outer dense fiber 2 (Odf2) is highly expressed in the testis where it encodes a major component of the outer dense fibers of the sperm flagellum. Furthermore, ODF2 protein has recently been identified as a widespread centrosomal protein. While the expression of Odf2 highlighted a potential role for this gene in male germ cell development and centrosome function, the in vivo function of Odf2 was not known. We have generated Odf2 knockout mice using an Odf2 gene trapped embryonic stem cell (ESC) line. Insertion of a gene trap vector into exon 9 resulted in a gene that encodes a severely truncated protein lacking a large portion of its predicted coil forming domains as well as both leucine zipper motifs that are required for protein,protein interactions with ODF1, another major component of the outer dense fibers. Although wild-type and heterozygous mice were recovered, no mice homozygous for the Odf2 gene trap insertion were recovered in an extended breeding program. Furthermore, no homozygous embryos were found at the blastocyst stage of embryonic development, implying a critical pre-implantation role for Odf2. We show that Odf2 is expressed widely in adults and is also expressed in the blastocyst stage of preimplantation development. These findings are in contrast with early studies reporting Odf2 expression as testis specific and suggest that embryonic Odf2 expression plays a critical role during preimplantation development in mice. genesis 44:515,522, 2006. Published 2006 Wiley-Liss, Inc. [source] JKT-1 is not a human seminoma cell lineINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 4 2007Jeroen de Jong Summary The JKT-1 cell line has been used in multiple independent studies as a representative model of human testicular seminoma. However, no cell line for this specific tumour type has been independently confirmed previously; and therefore, the seminomatous origin of JKT-1 must be proven. The genetic constitution of the JKT-1 cells was determined using flow cytometry and spectral karyotyping, as well as array comparative genomic hybridization and fluorescent in situ hybridization. Marker profiling, predominantly based on differentially expressed proteins during normal germ cell development, was performed by immunohistochemistry and Western blot analyses. Moreover, genome wide affymetrix mRNA expression and profiling of 157 microRNAs was performed, and the status of genomic imprinting was determined. A germ cell origin of the JKT-1 cells was in line with genomic imprinting status and marker profile (including positive staining for several cancer-testis antigens). However, the supposed primary tumour, from which the cell line was derived, being indeed a classical seminoma, was molecularly proven not to be the origin of the cell line. The characteristic chromosomal anomalies of seminoma, e.g. gain of the short arm of chromosome 12, as well as the informative marker profile (positive staining for OCT3/4, NANOG, among others) were absent in the various JKT-1 cell lines investigated, irrespective of where the cells were cultured. All results indicate that the JKT-1 cell line is not representative of human seminoma. Although it can originate from an early germ cell, a non-germ cell derivation cannot be excluded. [source] Aromatase and oestrogens in human male germ cellsINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 5 2005SOPHIE LAMBARD Summary The mammalian testis serves two main functions: production of spermatozoa and synthesis of steroids, among them oestrogens are the end products obtained from the irreversible transformation of androgens by aromatase (P450arom). Up today P450arom has been demonstrated in male germ cells of all mammals so far studied (mice, rat, bank vole, bear, monkey). In man Leydig cells and immature germ cells as well as ejaculated spermatozoa express a biologically active aromatase. Moreover germ cells and spermatozoa contain oestrogen receptors (ER- , and ER- ,) and it is of note that a truncated form of ER- , is present in spermatozoa. These observations clearly suggest that oestrogens are likely concerned in various stages of male germ cell development. [source] Identification and gene expression profiling of the Pum1 and Pum2 members of the Pumilio family in the chickenMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 1 2008Jee Young Lee Abstract Members of the Pumilio (Pum) family of RNA-binding proteins act as translational repressors and are required for germ cell development and asymmetric division. We identified the chicken Pum1 and Pum2 genes and analyzed their expression patterns in various tissues. Comparative sequence analysis of the Pum1 and Pum2 proteins from the drosophila, chicken, mouse, and human revealed a high degree of evolutionary conservation in terms of the levels of homology of the peptide sequences and the structure of Pumilio homology domain (PUM-HD), C-terminal RNA-binding domain, with similar spacing between the adjacent Pum eight tandem repeats. In addition, phylogenetic patterns of pumilio family showed that Pum 1 and 2 of chicken are more closely related to those of mouse and human than other species and Pum1 is more conserved than Pum2. Using real-time RT-PCR, the expression levels of the Pum1 and Pum2 genes were found to be highest in hatched female gonads, and high-level expression of Pum2 was detected in 12-day and hatched gonads among the various chicken embryonic tissues tested. In adult tissues, the expression levels of Pum1 and Pum2 were expressed at higher levels in the testis and muscle than in any other tissue. The characteristics of the tissue-specific expression of Pum genes suggest that Pum1 and Pum2 have effects crucially in particular stage during development of chicken gonads depending on sexual maturation. Mol. Reprod. Dev. 75: 184,190, 2008. © 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] Mechanisms of imprint dysregulation,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 3 2010Bernhard Horsthemke Abstract Genomic imprinting is an epigenetic process by which the male and the female germ line confer specific marks (imprints) onto certain gene regions, so that one allele of an imprinted gene is active and the other allele is silent. Genomic imprints are erased in primordial germ cells, newly established during later stages of germ cell development, and stably inherited through somatic cell divisions during postzygotic development. Defects in imprint erasure, establishment, or maintenance result in a paternal chromosome carrying a maternal imprint or in a maternal chromosome carrying a paternal imprint. A wrong imprint leads to activation of an allele that should be silent or silencing of an allele that should be active. Since the dosage of imprinted genes is very important for development and growth, imprinting defects lead to specific diseases. Imprinting defects can occur spontaneously without any DNA sequence change (primary imprinting defect) or as the result of a mutation in a cis -regulatory element or a trans -acting factor (secondary imprinting defect). The distinction between primary and secondary imprinting defects is important for assessing the recurrence risk in affected families. © 2010 Wiley-Liss, Inc. [source] OCT4: biological functions and clinical applications as a marker of germ cell neoplasiaTHE JOURNAL OF PATHOLOGY, Issue 1 2007L Cheng Abstract Germ cell tumours (GCTs) are a heterogeneous group of neoplasms, which develop in the gonads as well as in extragonadal sites, that share morphological patterns and an overall good prognosis, owing to their responsiveness to current surgical, chemotherapeutic, and radiotherapeutic measures. GCTs demonstrate extremely interesting biological features because of their close relationships with normal embryonal development as demonstrated by the pluripotentiality of some undifferentiated GCT variants. The similarities between GCTs and normal germ cell development have made it possible to identify possible pathogenetic pathways in neoplastic transformation and progression of GCTs. Genotypic and immunophenotypic profiles of these tumours are also useful in establishing and narrowing the differential diagnosis in cases of suspected GCTs. Recently, OCT4 (also known as OCT3 or POU5F1), a transcription factor that has been recognized as fundamental in the maintenance of pluripotency in embryonic stem cells and primordial germ cells, has been proposed as a useful marker for GCTs that exhibit features of pluripotentiality, specifically seminoma/dysgerminoma/germinoma and embryonal carcinoma. The development of commercially available OCT4-specific antibodies suitable for immunohistochemistry on paraffin-embedded specimens has generated increasing numbers of reports of OCT4 expression in a wide variety of gonadal and extragonadal GCTs. OCT4 immunostaining has been shown to be a sensitive and specific marker for seminomatous/(dys)germinomatous tumours and in embryonal carcinoma variants of non-seminomatous GCTs, whether in primary gonadal or extragonadal sites or in metastatic lesions. Therefore, OCT4 immunohistochemistry is an additional helpful marker both in the differential diagnosis of specific histological subtypes of GCTs and in establishing a germ cell origin for some metastatic tumours of uncertain primary. OCT4 expression has also been reported in pre-invasive conditions such as intratubular germ cell neoplasia, unclassified (IGCNU) and the germ cell component of gonadoblastoma. Additionally, OCT4 immunostaining shows promise as a useful tool in managing patients known to be at high risk for the development of invasive GCTs. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Y chromosome haplogroups: A correlation with testicular dysgenesis syndrome?APMIS, Issue 1 2003KEN McELREAVEY Testicular dysgenesis syndrome encompasses low sperm quality, hypospadias, cryptorchidism and testicular cancer. Epidemiological studies and genetic data from familial cases suggest that testicular dysgenesis syndrome has a common etiology. The Y chromosome is known to encode genes that are involved in germ cell development or maintenance. We have therefore investigated if different classes of Y chromosomes in the general population (Y chromosome haplogroups) are associated with aspects of the testicular dysgenesis syndrome. We defined the Y chromosome haplogroups in individuals from different European counties who presented with either (i) oligo- or azoospermia associated with a Y chromosome microdeletion, (ii) unexplained reduced sperm counts (<20×106/ml) or (iii) testicular cancer. We failed to find Y chromosome haplotype associations with either microdeletion formation or testicular cancer. However, in a study of the Danish population, we found that a specific Y chromosome haplogroup (hg26) is significantly overrepresented in men with unexplained reduced sperm counts compared with a Danish control population. The factors encoded by genes on this class of Y chromosome may be particularly susceptible to environmental influences that cause testicular dysgenesis syndrome. Our current data highlight the need for further analyses of clinically well-defined patient groups from a wide range of ethnic and geographic origins. [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] Development of germ cells and reproductive biology in the sipunculid Phascolosoma esculentaAQUACULTURE RESEARCH, Issue 3 2009Xue-Ping Ying Abstract Sipuncula are of increasing interest for fisheries and aquaculture in China. Sustainable harvests will rely on a better knowledge of reproductive characteristics and stock enhancement. Here, we investigated the structural characteristics of and seasonal changes in germ cell development of the sipunculid Phascolosoma esculenta from the south-eastern coast of Zhejiang, China. An annual survey of egg numbers in the coelom (body cavity) fluid by light and electron microscopy of the females indicates that P. esculenta is dioecious. No defined gonad but dissociated germ cells were found in the coelomic cavity during the 1-year observation. The germ cells showed multiplication and development in the coelomic cavity. Reproduction took place from May to September, with a peak in July and August. The oogenesis can be divided into four phases: cell proliferation, pre-vitellogenesis, vitellogenesis and egg envelope formation and maturation. The process of spermatogenesis can also be divided into four phases: cell multiplication, cell growth, cell maturation and metamorphosis. Monthly changes in the relative number of eggs in each stage indicate that P. esculenta lays eggs in batches. The sperm thrives in the coelomic fluid in the form of cell groups with patterns of genesis and release similar to those of the eggs. Eggs of P. esculenta were fertilized only when reaching the nephridium. The sex ratio was about 1:1 throughout the year. [source] | |||||||||||||