Dmrt1 regulates the immune response by repressing the TLR4 signaling pathway in goat male germline stem cells

Double sex and mab-3-related transcription factor 1(Dmrt1),which is expressed in goat male germline stem cells(mGSCs)and Sertoli cells,is one of the most conserved transcription factors involved in sex determination.In this study,we highlighted the role of Dmrt1 in balancing the innate immune response in goat mGSCs.Dmrt1 recruited promyelocytic leukemia zinc finger(Plzf),also known as zinc finger and BTB domain-containing protein 16(Zbtb16),to repress the Toll-like receptor 4(TLR4)-dependent inflammatory signaling pathway and nuclear factor(NF)-κB.Knockdown of Dmrt1 in seminiferous tubules resulted in widespread degeneration of germ and somatic cells,while the expression of proinflammatory factors were significantly enhanced.We also demonstrated that Dmrt1 stimulated proliferation of mGSCs,but repressed apoptosis caused by the immune response.Thus,Dmrt1 is sufficient to reduce inflammation in the testes,thereby establishing the stability of spermatogenesis and the testicular microenvironment.

An efficient strategy for generation of transgenic mice by lentiviral transduction of male germline stem cells in vivo

Background： Male germline stem cells（MGSCs） are a subpopulation of germ cells in the testis tissue. MGSCs are capable of differentiation into spermatozoa and thus are perfect targets for genomic manipulation to generate transgenic animals.Method： The present study was to optimize a protocol of production of transgenic mice through transduction of MGSCs in vivo using lentiviral-based vectors. The recombinant lentiviral vectors with either EF-1 or CMV promoter to drive the expression of enhanced green fluorescent protein（e GFP） transgene were injected into seminiferous tubules or inter-tubular space of 7-day-old and 28-day-old mouse testes. At 5 or 6 wk post-surgery, these pre-founders were mated with wild-type C57BL/6J female mice（1.5 to 2.0-month-old）.Results： Sixty-seven percent of F1 generation and 55.56 % of F2 offspring were positive for eG FP transgene under the control of EF-1 promoter via PCR analysis. The transgenic pups were generated in an injection site-and age-independent manner. The expression of transgene was displayed in the progeny derived from lentiviral vector containing CMV promoter to drive transgene, but it was silenced or undetectable in the offspring derived from lentiviral vector with transgene under EF-1 promoter. The methylation level of g DNA in the promoter region of transgene was much higher in the samples derived lentiviral vectors with EF-1 promoter than that with CMV promoter,suggesting e GFP transgene was suppressed by DNA methylation in vivo.Conclusion： This research reported here an effective strategy for generation of transgenic mice through transduction of MGSCs in vivo using lentivirus vectors with specific promoters, and the transgenic offspring were obtained in an injection site-and age-independent manner. This protocol could be applied to other animal species, leading to advancement of animal transgenesis in agricultural and biomedical fields.

GDNF Up-Regulates c-Myc Transcription via the PI3K/Akt Pathway to Promote Dairy Goat Male Germline Stem Cells (mGSC) Proliferation

Studies have demonstrated that regulation of GDNF on male germline stem cells （mGSCs） mainly through Ras/Erk1/2, Src family kinase and PI3K/Akt signaling pathways, but the signaling pathways GDNF-mediated are different when the species and cell lines varied. Whether GDNF regulates self-renewal of mGSCs isolated from livestock has not been reported. Here, we purified mGSCs from dairy goat testis using mixed enzymes and fibronectin. Immunofluoresce staining revealed the cultured dairy mGSCs expressed Vasa, Nanos2, Ngn3, Tert, Dazl, Lin28, Oct4, CD49f, Stra8 and GFRa1, reflecting that these cells were mGSCs phenotype. Then we cultured these dairy goat mGSCs in different concentrations of GDNF （0, 5, 10, or 20 ng mL-1） to optimize the best concentration of GDNF to sustain the dairy goat mGSCs self-renewal, after that the inhibitor of PI3K （LY294002, 10 μmol L-1） was added to the medium which contains the optimal concentration of GDNF we obtained by experiments. The mGSCs cultured in different media were compared through the population doubling time （PDT）, capacity of cell proliferation evaluated by PCNA and BrdU immunofluorescence staining, RT-PCR, QRT-PCR, Western blotting and flow cytometry. Results showed that 10 ng mL-1 was the optimal concentration of GDNF to maintain goat mGSCs self-renewal and GDNF up-regulates c-Myc transcription via the PI3K/Akt pathway to promote goat mGSCs proliferation. This study provides us an efficient model to study the mechanism in mGSCs proliferation and differentiation in goat, and has important implications in unveiling signaling pathways in livestock GSCs.

ALK Family Inhibitor A83-01 Promotes the Proliferation of Mouse Male Germline Stem Cells (mGSCs) Under Serum- and Feeder-Free Conditions

A83-01 is a selective inhibitor of the TGF-β type I receptor ALK,which inhibits the TGF-β-induced epithelial-to-mesenchymal transition（EMT） via the inhibition of Smad2 phosphorylation.Previous studies have showed that A83-01 promoted somatic cellular reprogramming significantly.Male germline stem cells（mGSCs）,as an alternative resource of pluripotent stem cells derived adult testis,have promising valuable in clinic medicine and regeneration,however,the derivation of mGSCs was complex and difficult.What the role A83-01 plays in promoting the proliferation of mGSCs is still unknown.In this study,combined with A83-01 and knockout serum replacement（KSR） medium,we obtained a relatively feeder-and serum-free system for mGSCs culturing in vitro and the optimal concentration of A83-01 was 0.25 μmol L-1.After continuous culturing,the proliferation efficiency of undifferentiated mGSCs and differentiation capacity of mGSC were examined as well.Results showed that,A83-01 dramatically increased the number of mGSCs and AP positive colonies,and the mitosis index according to the BrdU assay.A83-01 could also increase the expression of pluripotent markers including Oct4,Klf4,Nanog and c-Myc,analyzed byreal-time quantative PCR.mGSCs cultured in the optimal feeder-and serum-free system combined with A83-01 could form embryoid bodies（EBs）,which consisted of three embryonic layers detected by immunofluorescence and RT-PCR.Remarkably,the results demonstrated 0.25 μmol L-1A83-01 could promote the proliferation of mouse mGSC colonies and maintain their undifferentiated status under feeder-and serum-free systems.

Conversion of female germline stem cells from neonatal and prepubertal mice into pluripotent stern cells

Pluripotent stem cells derived from neonatal or adult testes are a useful tool to examine the mechanisms of pluripotency and a resource for cell-based therapies. However, therapies usingthese cells will only benefit males but not females. Recently, female germline stem cells （FGSCs） were discovered in ovaries. Whether FGSCs can be converted into pluripotent stem cells, similar to spermatogonial stem cells, is unknown. Here, we demonstrate that female embryonic stem-like cells （fESLCs） can be generated within 1 month from the stably proliferating FGSCs cultured in embryonic stem cell （ESC） medium, fESLCs exhibit properties similar to those of ESCs in terms of marker expression and differentiation potential. Thus, our findings suggest that generation of patient-specific fESLCs is feasible and provides a foundation for personalized regenerative applications.

Production of transgenic mice by random recombination of targeted genes in female germline stem cells

Oocyte production in most mammalian species is believed to cease before birth.However,this idea has been challenged with the finding that postnatal mouse ovaries possess mitotically active germ cells.A recent study showed that female germline stem cells(FGSCs)from adult mice were isolated,cultured long term and produced oocytes and progeny after transplantation into infertile mice.Here,we demonstrate the successful generation of transgenic or gene knock-down mice using FGSCs.The FGSCs from ovaries of 5-day-old and adult mice were isolated and either infected with recombinant viruses carrying green fluorescent protein,Oocyte-G1 or the mouse dynein axonemal intermediate chain 2 gene,or transfected with the Oocyte-G1 specific shRNA expression vector(pRS shOocyte-G1 vector),and then transplanted into infertile mice.Transplanted cells in the ovaries underwent oogenesis and produced heterozygous offspring after mating with wild-type male mice.The offspring were genetically characterized and the biological functions of the transferred or knock-down genes were investigated.Efficiency of genetransfer or gene knock-down was 29%–37%and it took 2 months to produce transgenic offspring.Gene manipulation of FGSCs is a rapid and efficient method of animal transgenesis and may serve as a powerful tool for biomedical science and biotechnology.

Hsp83 regulates the fate of germline stem cells in Drosophila ovary

In adult tissues,stem cells are defined by their unique capacity to self-renew and produce differentiated cells to maintain tissue homeostasis.Drosophila ovarian germline stem cells（GSCs）provide a powerful model for investigating the regulatory mechanisms underlying stem cell fate determination in vivo（Chen and Mckearin.

Establishment and characterization of immortalized bovine male germline stem cell line

Male germline stem cells （mGSCs） are unique adult germ cells with self-renewal potential and spermatogenesis function in the testis. However, further studies are needed to establish a long-term cultural system of mGSCs in vitro, especially for large animals such as bovine mGSCs. In this study, we first established a stable immortalized bovine male germline stem cell line by transducing Simian virus 40 （SV40） large T antigen. The proliferation of these cells was improved significantly. These cells could express spermatogonial stem cell （SSC）-specific markers, such as PLZF, PGP9.5, VASA, LIN28A, and CD49F, both in the mRNA and protein levels. Additionally, these cells could be differentiated into three germ layer cells to enter meiosis, form colonies, and proliferate in the seminiferous tubules of busulfan-induced infertile mice. The immortalized bovine mGSCs maintain the criteria of mGSCs.

The Drosophila ovary: an active stem cell community

Only a small number of cells in adult tissues （the stem cells） possess the ability to self-renew at every cell division, while producing differentiating daughter cells to maintain tissue homeostasis for an organism＇s lifetime. The Drosophila ovary harbors three different types of stem cell populations （germline stem cell （GSC）, somatic stem cell （SSC） and escort stem cell （ESC）） located in a simple anatomical structure known as germarium, rendering it one of the best model systems for studying stem cell biology due to reliable stem cell identification and available sophisticated genetic tools for manipulating gene functions. Particularly, the niche for the GSC is among the first and best studied ones, and studies on the GSC and its niche have made many unique contributions to a better understanding of relationships between stem cells and their niche. So far, both the GSC and the SSC have been shown to be regulated by extrinsic factors originating from their niche and intrinsic factors functioning within. Multiple signaling pathways are required for controlling GSC and SSC self-renewal and differentiation, which provide unique opportunities to investigate how multiple signals from the niche are interpreted in the stem cell. Since the Drosophila ovary contains three types of stem cells, it also provides outstanding opportunities to study how multiple stem cells in a given tissue work collaboratively to contribute to tissue function and maintenance. This review highlights recent major advances in studying Drosophila ovarian stem cells and also discusses future directions and challenges.

Recent advances in isolation,identification,and culture of mammalian spermatogonial stem cells

Continuous spermatogenesis depends on the self-renewal and differentiation of spermatogonial stem cells(SSCs).SSCs,the only male reproductive stem cells that transmit genetic material to subsequent generations,possess an inherent self-renewal ability,which allows the maintenance of a steady stem cell pool.SSCs eventually differentiate to produce sperm.However,in an in vitro culture system,SSCs can be induced to differentiate into various types of germ cells.Rodent SSCs are well defined,and a culture system has been successfully established for them.In contrast,available information on the biomolecular markers and a culture system for livestock SSCs is limited.This review summarizes the existing knowledge and research progress regarding mammalian SSCs to determine the mammalian spermatogenic process,the biology and niche of SSCs,the isolation and culture systems of SSCs,and the biomolecular markers and identification of SSCs.This information can be used for the effective utilization of SSCs in reproductive technologies for large livestock animals,enhancement of human male fertility,reproductive medicine,and protection of endangered species.

Dual roles of juvenile hormone signaling during early oogenesis in Drosophila

Juvenile hormone(JH)signaling plays crucial roles in insect metamorphosis and reproduction.Function of JH signaling in germline stem cells(GSCs)remains largely unknown.Here,we found that the number of GSCs significantly declined in the ovaries of Met,Gee and JHAMT mutants.Then we inhibited JH signaling in selected cell types of ovaries by expressing Met and Gee or Kr-hl double-stranded RNAs(dsRNAs)using different Gal4 drivers.Blocking of JH signaling in muscle cells has no effect on GSC numbers.Blocking of JH signaling in cap cells reduced GSCs cells.Inductive expression of Met and Gee dsRNA but not Kr-hl by Nos-Gal4 increased GSC cells.These results indicate that JH signaling plays an important role in GSC maintenance.

Insights into female germ cell biology： from in vivo development to in vitro derivations

Understanding the mechanisms of human germ cell biology is important for developing infertility treatments. However, little is known about the mechanisms that regulate human gametogenesis due to the difficulties in collecting samples, especially germ cells during fetal development. In contrast to the mitotic arrest of spermatogonia stem cells in the fetal testis, female germ cells proceed into meiosis and began folliculogenesis in fetal ovaries. Regulations of these developmental events, including the initiation of meiosis and the endowment of primordial follicles, remain an enigma. Studying the molecular mechanisms of female germ cell biology in the human ovary has been mostly limited to spatiotemporal characterizations of genes or proteins. Recent efforts in utilizing in vitro differentiation system of stem cells to derive germ cells have allowed researchers to begin studying molecular mechanisms during human germ cell development. Meanwhile, the possibility of isolating female germline stem cells in adult ovaries also excites researchers and generates many debates. This review will mainly focus on presenting and discussing recent in vivo and in vitro studies on female germ cell biology in human. The topics will highlight the progress made in understanding the three main stages of germ cell developments： namely, primordial germ cell formation, meiotic initiation, and folliculogenesis.