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‣ Pesquisa de mutações em genes envolvidos na diferenciação e manutenção das células germinativas em pacientes portadores de distúrbio do desenvolvimento gonadal 46,XX; Mutation analysis of genes involved in differentiation and maintenance of germ cells in patients with 46,XX disorders of gonadal development

Santos, Mariza Augusta Gerdulo dos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/07/2010 Português
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Diversos genes expressos durante a diferenciação das células germinativas atuam no desenvolvimento ovariano. A diferenciação das células somáticas ovarianas depende do número de células germinativas pré-meióticas que migram para a fenda gonadal. A expressão espaço-temporal de genes envolvidos na diferenciação dessas células e a posterior sobrevivência dos oócitos meióticos são de interesse no estudo dos distúrbios do desenvolvimento sexual (DDS) 46,XX. Entre os genes envolvidos nesses processos estão o NANOS3, BMP15 e STRA8. O NANOS3, uma molécula de ligação ao RNA que bloqueia a via apoptótica, assegura a sobrevivência das células germinativas durante sua migração para o interior da gônada. O STRA8 atua no início da meiose das células germinativas na gônada de embriões XX, sendo o primeiro sinal de dimorfismo gonadal. Por outro lado a subseqüente sobrevivência dos oócitos é controlada por fatores de transformação e crescimento como o BMP15, que promove a diferenciação das células da granulosa que por sua vez participam indiretamente da diferenciação dos oócitos e das células da teca. Neste trabalho pesquisamos a presença de mutações inativadoras nos genes NANOS3 e BMP15 em 45 pacientes com disgenesia gonadal (DG) 46...

‣ Estudo biológico das células germinativas caninas; Biological research in primordial canine germ cells

Souza, Aline Fernanda de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/01/2013 Português
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Células germinativas embrionárias são células pluripotentes derivadas das células germinativas primordiais que surgem no período do desenvolvimento embrionário. Sendo precursoras na maturação dos gametas sendo para a proliferação e formação de novas gerações de células germinativas. Estudos em modelos animais com células troncos embrionárias pluripotentes têm sido realizados com sucesso no tratamento de muitas doenças genéticas, principalmente em modelos caninos devido a homologia com humanos. Portanto, objetivamos estabelecer um estudo da biologia das células erminativas caninas para futuras pesquisas, visando sua viabilidade terapêutica. Foram utilizadas fêmeas de cães sem raça definida (SRD), foram submetidas à ovario-salpinge-histerectomia, oriundas de campanhas de castração realizadas por associações e/ou organizações não governamentais na cidade de Pirassununga. Os embriões coletados foram analisados através de um cronograma histológico e também mensurados através da medida Crown-Rump(CR), em seguida em condições ésteres micro-dissecados na região paramesonéfrica próximo a região dos somitos. Os fragmentos foram isolados e colocados em cultivo com meio apropriado para o desenvolvimento e propagação das células germinativas primordiais (PGCs). Obteve-se sucesso nos cultivos com embriões em idades gestacionais próximas a 24 á 32 dias de gestação...

‣ Cytotoxic effects of permethrin in oocytes of Rhipicephalus sanguineus (Acari: Ixodidae) fully engorged females: I. Direct or indirect action of the acaricide in germ cells?

Roma, Gislaine Cristina; Scopinho Furquim, Karim Christina; Bechara, Gervasio Henrique; Camargo Mathias, Maria Izabel
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 287-299
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 07/57809-5; Processo FAPESP: 07/59020-0; Given the wide use of synthetic chemicals to control ticks, this study evaluated the effects of the permethrin pyrethroid on oocytes of Rhipicephalus sanguineus fully engorged females in order to examine whether this compound, in addition to the proven neurotoxic effect, also acts directly on germ cells. The results revealed that permethrin effectively inhibits and/or interrupts the reproductive process of R. sanguineus. Exposed oocytes exhibited prominent structural changes such as altered shape of cells and germ vesicle (oocyte nucleus), cytoplasmic vacuolation, and decrease of yolk granules. The composition of the latter, however, was not altered. These findings confirm those already reported by Roma et al. (Food Chem Toxicol 48:825-830, 2010) demonstrating that permethrin acts on germ cells of R. sanguineus via direct absorption from the hemolymph by pedicel cells, or by the oocyte plasmic membrane. on the other hand, these results contradict studies reporting that acaricides act exclusively on the nervous systems of ticks and that all the changes in other organs are a result from the indirect action of these chemical compounds...

‣ Automatic classification of fish germ cells through optimum-path forest

Papa, Joao P.; Gutierrez, Mario E. M.; Nakamura, Rodrigo Y. M.; Papa, Luciene P.; Vicentini, Irene B. F.; Vicentini, Carlos A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 5084-5087
Português
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The spermatogenesis is crucial to the species reproduction, and its monitoring may shed light over some important information of such process. Thus, the germ cells quantification can provide useful tools to improve the reproduction cycle. In this paper, we present the first work that address this problem in fishes with machine learning techniques. We show here how to obtain high recognition accuracies in order to identify fish germ cells with several state-of-the-art supervised pattern recognition techniques. © 2011 IEEE.

‣ Primordial germ cells (spermatogonial stem cells) of bullfrogs express sex hormone-binding globulin and steroid receptors during seasonal spermatogenesis

Caneguim, Breno Henrique; Beltrame, Flávia Luciana; Da Luz, Juliana Silva; Valentini, Sandro Roberto; Cerri, Paulo Sérgio; Sasso-Cerri, Estela
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 136-144
Português
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In vertebrate species, testosterone seems to inhibit spermatogonial differentiation and proliferation. However, this androgen can also be converted, via aromatase, into estrogen which stimulates spermatogonial differentiation and mitotic activity. During seasonal spermatogenesis of adult bullfrogs Lithobates catesbeianus, primordial germ cells (PGCs) show enhanced testosterone cytoplasm immunoexpression in winter; however, in summer, weak or no testosterone immunolabelling was observed. The aim of this study was to confirm if PGCs express stem cell markers-alkaline phosphatase (AP) activity and GFRα1 (glial-cell-line-derived neurotrophic factor)-and verify whether testosterone is maintained in these cells by androgen receptors (ARs) and/or sex hormone-binding globulin (SHBG) in winter. Furthermore, regarding the possibility that testosterone is converted into estrogen by PGCs in summer, the immunoexpression of estrogen receptor (ER)β was investigated. Bullfrog testes were collected in winter and in summer and were embedded in glycol methacrylate for morphological analyses or in paraffin for the histochemical detection of AP activity. GFRα1, AR, SHBG and ERβ expression were detected by Western blot and immunohistochemical analyses. The expression of AP activity and GFRα1 in the PGCs suggest that these cells are spermatogonial stem cells. In winter...

‣ The ability of mouse nuclear transfer embryonic stem cells to differentiate into primordial germ cells

Mansouri,Vahid; Salehi,Mohammad; Nourozian,Mohsen; Fadaei,Fatemeh; Farahani,Reza Mastery; Piryaei,Abbas; Delbari,Ali
Fonte: Sociedade Brasileira de Genética Publicador: Sociedade Brasileira de Genética
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 Português
Relevância na Pesquisa
674.2972%
Nuclear transfer embryonic stem cells (ntESCs) show stem cell characteristics such as pluripotency but cause no immunological disorders. Although ntESCs are able to differentiate into somatic cells, the ability of ntESCs to differentiate into primordial germ cells (PGCs) has not been examined. In this work, we examined the capacity of mouse ntESCs to differentiate into PGCs in vitro. ntESCs aggregated to form embryoid bodies (EB) in EB culture medium supplemented with bone morphogenetic protein 4(BMP4) as the differentiation factor. The expression level of specific PGC genes was compared at days 4 and 8 using real time PCR. Flow cytometry and immunocytochemical staining were used to detect Mvh as a specific PGC marker. ntESCs expressed particular genes related to different stages of PGC development. Flow cytometry and immunocytochemical staining confirmed the presence of Mvh protein in a small number of cells. There were significant differences between cells that differentiated into PGCs in the group treated with Bmp4 compared to non-treated cells. These findings indicate that ntESCs can differentiate into putative PGCs. Improvement of ntESC differentiation into PGCs may be a reliable means of producing mature germ cells.

‣ Identification of Primordial Germ Cells: Cytological, Histological and Immunohistochemical Aspects

Yön,Nazan Deniz; Akbulut,Cansu
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 Português
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676.2196%
Primordial germ cells (PGCs) constitute an embryonic cell type that migrate to gonadal precursors and form the gametes. In many animals, PGCs are set apart from somatic cells early during embryogenesis. These cells migrate to gonadal precursors and then constitute gonads so they are useful models for cell motility studies. They have a highlighted importance for development and reproduction studies. Primordial germ cells have morphological differences from the somatic cells. Structure of these cells can be detected with light and electron microscopy in early development stages. This review describes the morphological, histological, molecular and ultrastructural features of primordial germ cells in different animals and gives an overview for simplified identification.

‣ Mouse primordial germ cells produce cysts that partially fragment prior to meiosis

Lei, Lei; Spradling, Allan C.
Fonte: Company of Biologists Publicador: Company of Biologists
Tipo: Artigo de Revista Científica
Publicado em 15/05/2013 Português
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Mammalian germ cells divide mitotically and form nests of associated cells just prior to entering meiosis. At least some nests contain germline cysts that arise by synchronous, incomplete mitotic divisions, but others may form by aggregation. To systematically investigate early murine germ cell development, we lineage marked the progeny of individual, newly arrived primordial germ cells in the E10.5 gonad. All the marked germ cells initially develop into clones containing two, four or eight cells, indicating cyst formation. Surprisingly, growing cysts in both sexes partially fragment into smaller cysts prior to completion and associate with cysts from unrelated progenitors. At the time divisions cease, female clones comprise five cysts on average that eventually give rise to about six primordial follicles. Male cyst cells break apart and probably become spermatogonial stem cells. Thus, cysts are invariant units of mouse germ cell development and cyst fragmentation provides insight into the amplification of spermatogonial stem cells and the origin of primordial follicles.

‣ Germ Cells Are Not Required to Establish the Female Pathway in Mouse Fetal Gonads

Maatouk, Danielle M.; Mork, Lindsey; Hinson, Ashley; Kobayashi, Akio; McMahon, Andrew P.; Capel, Blanche
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
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The fetal gonad is composed of a mixture of somatic cell lineages and germ cells. The fate of the gonad, male or female, is determined by a population of somatic cells that differentiate into Sertoli or granulosa cells and direct testis or ovary development. It is well established that germ cells are not required for the establishment or maintenance of Sertoli cells or testis cords in the male gonad. However, in the agametic ovary, follicles do not form suggesting that germ cells may influence granulosa cell development. Prior investigations of ovaries in which pre-meiotic germ cells were ablated during fetal life reported no histological changes during stages prior to birth. However, whether granulosa cells underwent normal molecular differentiation was not investigated. In cases where germ cell loss occurred secondary to other mutations, transdifferentiation of granulosa cells towards a Sertoli cell fate was observed, raising questions about whether germ cells play an active role in establishing or maintaining the fate of granulosa cells. We developed a group of molecular markers associated with ovarian development, and show here that the loss of pre-meiotic germ cells does not disrupt the somatic ovarian differentiation program during fetal life...

‣ Dynamics of 5-methylcytosine and 5-hydroxymethylcytosine during germ cell reprogramming

Yamaguchi, Shinpei; Hong, Kwonho; Liu, Rui; Inoue, Azusa; Shen, Li; Zhang, Kun; Zhang, Yi
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Português
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Previous studies have revealed that mouse primordial germ cells (PGCs) undergo genome-wide DNA methylation reprogramming to reset the epigenome for totipotency. However, the precise 5-methylcytosine (5mC) dynamics and its relationship with the generation of 5-hydroxymethylcytosine (5hmC) are not clear. Here we analyzed the dynamics of 5mC and 5hmC during PGC reprograming and germ cell development. Unexpectedly, we found a specific period (E8.5-9.5) during which both 5mC and 5hmC levels are low. Subsequently, 5hmC levels increase reaching its peak at E11.5 and gradually decrease until E13.5 likely by replication-dependent dilution. Interestingly, 5hmC is enriched in chromocenters during this period. While this germ cell-specific 5hmC subnuclear localization pattern is maintained in female germ cells even in mature oocytes, such pattern is gradually lost in male germ cells as mitotic proliferation resumes during the neonatal stage. Pericentric 5hmC plays an important role in silencing major satellite repeat, especially in female PGCs. Global transcriptome analysis by RNA-seq revealed that the great majority of differentially expressed genes from E9.5 to 13.5 are upregulated in both male and female PGCs. Although only female PGCs enter meiosis during the prenatal stage...

‣ An evolutionary perspective on germ cell specification genes in insects

Ewen-Campen, Benjamin Scott
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
Português
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This dissertation investigates the embryonic specification of a specific group of cells: the germ cells. Germ cells, which give rise to sperm and egg, are the only cells in sexually-reproducing animals that directly contribute hereditary information to the next generation. Germ cells are therefore a universal cell type across animals, and represent a profound novelty that likely arose near the base of the animal phylogeny. Yet despite their conserved, essential function in all animals, there is surprising diversity in the mechanisms that specify these cells during embryonic development. In this dissertation, I address the diversity of germ cell specification mechanisms in insects. I focus on two species, the milkweed bug Oncopeltus fasciatus (Hemiptera) and the cricket Gryllus bimaculatus (Orthoptera), which both branch basally to the Holometabola (those insects which undergo metamorphosis, including the well-studied fruit fly Drosophila melanogaster), and thus provide important phylogenetic breadth to our understanding of germ cell specification across insects. Using functional genetic approaches, I show that germ cell specification in both Oncopeltus and Gryllus differs fundamentally from germ cell specification in Drosophila. Specifically...

‣ In situ demonstration of both TUNEL-labeled germ cell and Sertoli cell in the cimetidine-treated rats

Sasso-Cerri, E.; Miraglia, S.M.
Fonte: Murcia : F. Hernández Publicador: Murcia : F. Hernández
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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Cimetidine has caused dysfunction in the male reproductive system. In the rat testis, intratubu l a r alterations and loss of peritubular tissue due to p e r i t u bular myoid cell death by apoptosis have been recently shown. Thus, the aim of this study is to evaluate which cells of the seminiferous epithelium have been affected and/or died by apoptosis after the treatment with cimetidine. For this purpose, an experimental group containing five male albino Wistar rats received intraperitoneal injections of cimetidine (50 mg/kg body weight) during 52 days. The testes were f i xed with 4% bu ff e r e d f o r m a l d e hyde and were embedded in paraffin. Fo r detection of DNA breaks (apoptosis) in the cells of the seminiferous epithelium, the testicular sections were treated by the TUNEL method (Apop-Tag Plus Peroxidase Kit). In the tubules affected by cimetidine, altered p e r i t u bular tissue, including the presence of TUNEL labeling in the myoid peritubular cells, were usually found. In these tubules, the seminiferous epithelium exhibited low density of germ cells and TUNEL-positive labeling in the germ cells of the basal compartment. The concomitant staining in both germ cells of the basal compartment and late spermatids suggest a sensitivity of these cells in the damaged tubules. Besides germ cells...

‣ The ability of mouse nuclear transfer embryonic stem cells to differentiate into primordial germ cells

Mansouri,Vahid; Salehi,Mohammad; Nourozian,Mohsen; Fadaei,Fatemeh; Farahani,Reza Mastery; Piryaei,Abbas; Delbari,Ali
Fonte: Sociedade Brasileira de Genética Publicador: Sociedade Brasileira de Genética
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2015 Português
Relevância na Pesquisa
674.2972%
Nuclear transfer embryonic stem cells (ntESCs) show stem cell characteristics such as pluripotency but cause no immunological disorders. Although ntESCs are able to differentiate into somatic cells, the ability of ntESCs to differentiate into primordial germ cells (PGCs) has not been examined. In this work, we examined the capacity of mouse ntESCs to differentiate into PGCs in vitro. ntESCs aggregated to form embryoid bodies (EB) in EB culture medium supplemented with bone morphogenetic protein 4(BMP4) as the differentiation factor. The expression level of specific PGC genes was compared at days 4 and 8 using real time PCR. Flow cytometry and immunocytochemical staining were used to detect Mvh as a specific PGC marker. ntESCs expressed particular genes related to different stages of PGC development. Flow cytometry and immunocytochemical staining confirmed the presence of Mvh protein in a small number of cells. There were significant differences between cells that differentiated into PGCs in the group treated with Bmp4 compared to non-treated cells. These findings indicate that ntESCs can differentiate into putative PGCs. Improvement of ntESC differentiation into PGCs may be a reliable means of producing mature germ cells.

‣ Investigating mechanisms of post-transcriptional gene regulation in the germ cells of Zebrafish.

Wiszniak, Sophie
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2011 Português
Relevância na Pesquisa
686.5089%
In most organisms, the primordial germ cells are specified and set aside from the surrounding somatic tissues very early in development. Their ability to carry out a gene regulatory program quite distinct from the surrounding somatic cells, and their capacity to specify entire new organisms has made them a focus of many studies that seek to understand how specific transcriptional and translational programs contribute to cell fate. Zebrafish, a vertebrate with external development of the embryo, is currently one of the best animal models for understanding the molecular basis of germ cell specification. Briefly, germ cell specification is dependent on maternally provided cytoplasmic determinants, termed the germ plasm. The germ plasm, is localised to areas of the embryo that will become the germ cells later in development by inheritance the germ plasm through cleavage divisions. A number of mRNA components of the germ plasm have been identified; interestingly many of them encode RNA-binding proteins, and almost all of them have invertebrate and mammalian orthologues. Evidence suggests that these maternally provided mRNA determinants are specifically maintained in the germ cells throughout embryonic development, and at least some of these gene products are essential for germ cell specification. A number of studies have begun to elucidate the molecular mechanisms that allow germ cell specific maintenance of these mRNAs...

‣ HuB (elavl2) mRNA is restricted to the germ cells by post-transcriptional mechanisms including stabilisation of the message by DAZL

Wiszniak, S.; Dredge, B.; Jensen, K.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
683.01375%
The ability of germ cells to carry out a gene regulatory program distinct from the surrounding somatic tissue, and their capacity to specify an entire new organism has made them a focus of many studies that seek to understand how specific regulatory mechanisms, particularly post-transcriptional mechanisms, contribute to cell fate. In zebrafish, germ cells are specified through the inheritance of cytoplasmic determinants, termed the germ plasm, which contains a number of maternal mRNAs and proteins. Investigation of several of these messages has revealed that the restricted localisation of these mRNAs to the germ plasm and subsequent germ cells is due to cis-acting sequence elements present in their 39UTRs. Here we show that a member of the Hu family of RNA-binding proteins, HuB, is maternally provided in the zebrafish embryo and exhibits germ cell specific expression during embryogenesis. Restriction of HuB mRNA to the germ cells is dependent on a number of sequence elements in its 39UTR, which act to degrade the mRNA in the soma and stabilise it in the germ cells. In addition, we show that the germ cell specific RNA-binding protein DAZL is able to promote HuB mRNA stability and translation in germ cells, and further demonstrate that these activities require a 30 nucleotide element in the 39UTR. Our study suggests that DAZL specifically binds the HuB 39UTR and protects the message from degradation and/or enhances HuB translation...

‣ NOTCH1 Gain of Function in Germ Cells Causes Failure of Spermatogenesis in Male Mice

Huang, Zaohua; Rivas, Bryan; Agoulnik, Alexander I.
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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NOTCH1 is a member of the NOTCH receptor family, a group of single-pass trans-membrane receptors. NOTCH signaling is highly conserved in evolution and mediates communication between adjacent cells. NOTCH receptors have been implicated in cell fate determination, as well as maintenance and differentiation of stem cells. In the mammalian testis expression of NOTCH1 in somatic and germ cells has been demonstrated, however its role in spermatogenesis was not clear. To study the significance of NOTCH1 in germ cells, we applied a cre/loxP approach in mice to induce NOTCH1 gain- or loss-of function specifically in male germ cells. Using a Stra8-icretransgene we produced mice with conditional activation of the NOTCH1 intracellular domain (NICD) in germ cells. Spermatogenesis in these mutants was progressively affected with age, resulting in decreased testis weight and sperm count. Analysis of downstream target genes of NOTCH1 signaling showed an increased expression of Hes5, with a reduction of the spermatogonial differentiation marker, Neurog3 expression in the mutant testis. Apoptosis was significantly increased in mouse germ cells with the corresponding elevation of pro-apoptotic Trp53 and Trp63genes' expression. We also showed that the conditional germ cell-specific ablation of Notch1 had no effect on spermatogenesis or male fertility. Our data suggest the importance of NOTCH signaling regulation in male germ cells for their survival and differentiation.

‣ Ectopic expression of Cvh (Chicken Vasa homologue) mediates the reprogramming of chicken embryonic stem cells to a germ cell fate

Lavial, Fabrice; Acloque, Hervé; Bachelard, Élodie; Nieto, M. Ángela; Samarut, Jacques; Pain, Bertrand
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 918459 bytes; application/pdf
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10 pages, 6 figures.-- PMID: 19324033 [PubMed].-- Printed version published Jun 1, 2009.-- Supporting information available at: http://dx.doi.org/10.1016/j.ydbio.2009.03.012; When they are derived from blastodermal cells of the pre-primitive streak in vitro, the pluripotency of Chicken Embryonic Stem Cells (cESC) can be controlled by the cPouV and Nanog genes. These cESC can differentiate into derivatives of the three germ layers both in vitro and in vivo, but they only weakly colonize the gonads of host embryos. By contrast, non-cultured blastodermal cells and long-term cultured chicken primordial germ cells maintain full germline competence. This restriction in the germline potential of the cESC may result from either early germline determination in the donor embryos or it may occur as a result of in vitro culture. We are interested in understanding the genetic determinants of germline programming. The RNA binding protein Cvh (Chicken Vasa Homologue) is considered as one such determinant, although its role in germ cell physiology is still unclear. Here we show that the exogenous expression of Cvh, combined with appropriate culture conditions, induces cESC reprogramming towards a germ cell fate. Indeed, these cells express the Dazl...

‣ Cytogenetic effects of irradiation on somatic and germ cells

Egozcue, Josep,; Álvarez Arpal, Ricardo; Barquinero, J. F.; Barrios, L.; Caballín, M. R.; Genescà i Garrigosa, Anna; Miró, Rosa; Ponsa Arjona, Immaculada; Tusell Padrós, Laura
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //1999 Português
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668.1718%
This paper summarizes the results obtained in two of the research projects carried out in our laboratory within the radiation protection programs of the Consejo de Seguridad Nuclear and the European Union. These two research lines are fundamentally interconnected, since the analysis of the cytogenetic effects of radiation on somatic cells studies the consequences of occupational or accidental exposure to radiation for the individual, especially from the point of view of developing some type of malignancy, while the studies carried out in germ cells evaluate the risk of exposure for future generations, through the transmission of chromosome abnormalities via affected spermatozoa. In both cases these studies, which were mainly carried out during the last six years, in addition to providing basic data for the assessment of the consequences of radiation exposure and defining the steps to be taken to prevent the transmission of chromosome anomalies to the offspring in cases of therapeutic exposure, have also been fundamental in developing more effective techniques for the evaluation of the cytogenetic consequences of exposure to radiation.;

‣ Expression of arf tumor suppressor in spermatogonia facilitates meiotic progression in male germ cells

Churchman, Michelle L.; Roig Navarro, Ignasi; Jasin, Maria; Keeney, Scott; Sherr, Charles J.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2011 Português
Relevância na Pesquisa
671.7516%
The mammalian Cdkn2a (Ink4a-Arf) locus encodes two tumor suppressor proteins (p16Ink4a and p19Arf) that respectively enforce the anti-proliferative functions of the retinoblastoma protein (Rb) and the p53 transcription factor in response to oncogenic stress. Although p19Arf is not normally detected in tissues of young adult mice, a notable exception occurs in the male germ line, where Arf is expressed in spermatogonia, but not in meiotic spermatocytes arising from them. Unlike other contexts in which the induction of Arf potently inhibits cell proliferation, expression of p19Arf in spermatogonia does not interfere with mitotic cell division. Instead, inactivation of Arf triggers germ cell–autonomous, p53-dependent apoptosis of primary spermatocytes in late meiotic prophase, resulting in reduced sperm production. Arf deficiency also causes premature, elevated, and persistent accumulation of the phosphorylated histone variant H2AX, reduces numbers of chromosome-associated complexes of Rad51 and Dmc1 recombinases during meiotic prophase, and yields incompletely synapsed autosomes during pachynema. Inactivation of Ink4a increases the fraction of spermatogonia in S-phase and restores sperm numbers in Ink4a-Arf doubly deficient mice but does not abrogate γ-H2AX accumulation in spermatocytes or p53-dependent apoptosis resulting from Arf inactivation. Thus...

‣ Hijacking Germ Cells for Cancer: Examining a 'Dead End' in Male Germ Cell Development

Cook, Matthew Simon
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 15350079 bytes; application/pdf
Publicado em //2010 Português
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584.549%

Germ cells represent the immortal line: they are guardians of a totipotent genome and are essential for the genetic survival of an individual organism and ultimately a species. An error at any stage in development (specification, migration, colonization, differentiation, adult maintenance) can lead to one of two disastrous outcomes: (1) germ cell death or (2) unchecked growth and proliferation leading to tumorigenesis. The work in this dissertation utilizes a classic mouse model (Ter) resulting in both of these phenotypes to further explore the molecular mechanisms important for development of germ cells.

A homozygous nonsense mutation (Ter) in murine Dnd1 (Dnd1Ter/Ter) results in a significant (but not complete) early loss of primordial germ cells (PGCs) prior to colonization of the gonad in both sexes and all genetic backgrounds tested. The same mutation also leads to testicular teratomas only on the 129/SvJ background. Male mutants on other genetic backgrounds ultimately lose all PGCs with no incidence of teratoma formation. It is not clear how these PGCs are lost, develop into teratomas, or what factors directly control the strain-specific phenotype variation.

Work here demonstrates that Dnd1 expression is restricted to germ cells and that the Ter mutant defect is cell autonomous. The early loss of germ cells is due in part to BAX–mediated apoptosis which also affects the incidence of tumorigenesis on a mixed genetic background. Moreover...