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Trends in Genetics : TIG Dec 2017Germ cells develop as a cyst of interconnected sibling cells in a broad range of organisms in both sexes. A well-established function of intercellular connectivity is to... (Review)
Review
Germ cells develop as a cyst of interconnected sibling cells in a broad range of organisms in both sexes. A well-established function of intercellular connectivity is to transport cytoplasmic materials from 'nurse' cells to oocytes, a critical process for developing functional oocytes in ovaries of many species. However, there are situations where connectivity exists without a nursing mechanism, and the biological meaning of such connectivity remains obscure. In this review, we summarize current knowledge on the formation of intercellular connectivity, and discuss its meaning by visiting multiple examples of germ cell connectivity observed in evolutionarily distant species.
Topics: Animals; Cytoplasm; Female; Germ Cells; Oocytes; Oogenesis; Ovary
PubMed: 28947158
DOI: 10.1016/j.tig.2017.09.001 -
Results and Problems in Cell... 2017Germline poses unique challenges to gene expression control at the transcriptional level. While the embryonic germline maintains a global hold on new mRNA transcription,... (Review)
Review
Germline poses unique challenges to gene expression control at the transcriptional level. While the embryonic germline maintains a global hold on new mRNA transcription, the female adult germline produces transcripts that are not translated into proteins until embryogenesis of subsequent generation. As a consequence, translational control plays a central role in governing various germ cell decisions including the formation of primordial germ cells, self-renewal/differentiation decisions in the adult germline, onset of gametogenesis and oocyte maturation. Mechanistically, several common themes such as asymmetric localization of mRNAs, conserved RNA-binding proteins that control translation by 3' UTR binding, translational activation by the cytoplasmic elongation of the polyA tail and the assembly of mRNA-protein complexes called mRNPs have emerged from the studies on Caenorhabditis elegans, Xenopus and Drosophila. How mRNPs assemble, what influences their dynamics, and how a particular 3' UTR-binding protein turns on the translation of certain mRNAs while turning off other mRNAs at the same time and space are key challenges for future work.
Topics: Animals; Female; Gene Expression Regulation; Germ Cells; Humans; Male; Protein Biosynthesis
PubMed: 28247049
DOI: 10.1007/978-3-319-44820-6_6 -
Current Opinion in Cell Biology Dec 2010
Topics: Animals; Cell Cycle; Cell Differentiation; Female; Germ Cells; Male; Sex Factors
PubMed: 21093242
DOI: 10.1016/j.ceb.2010.10.003 -
International Journal of Biological... Apr 2011Stem cells have the potential for self-renewal and differentiation. First stem cell cultures were derived 30 years ago from early developing mouse embryos. These are... (Review)
Review
Stem cells have the potential for self-renewal and differentiation. First stem cell cultures were derived 30 years ago from early developing mouse embryos. These are pluripotent embryonic stem (ES) cells. Efforts towards ES cell derivation have been attempted in other mammalian and non-mammalian species. Work with stem cell culture in fish started 20 years ago. Laboratory fish species, in particular zebrafish and medaka, have been the focus of research towards stem cell cultures. Medaka is the second organism that generated ES cells and the first that gave rise to a spermatogonial stem cell line capable of test-tube sperm production. Most recently, the first haploid stem cells capable of producing whole animals have also been generated from medaka. ES-like cells have been reported also in zebrafish and several marine species. Attempts for germline transmission of ES cell cultures and gene targeting have been reported in zebrafish. Recent years have witnessed the progress in markers and procedures for ES cell characterization. These include the identification of fish homologs/paralogs of mammalian pluripotency genes and parameters for optimal chimera formation. In addition, fish germ cell cultures and transplantation have attracted considerable interest for germline transmission and surrogate production. Haploid ES cell nuclear transfer has proven in medaka the feasibility of semi-cloning as a novel assisted reproductive technology. In this special issue on "Fish Stem Cells and Nuclear Transfer", we will focus our review on medaka to illustrate the current status and perspective of fish stem cells in research and application. We will also mention semi-cloning as a new development to conventional nuclear transfer.
Topics: Animals; Biomarkers; Cell Culture Techniques; Cell Line; Cloning, Organism; Embryonic Stem Cells; Germ Cells; Haploidy; Oryzias
PubMed: 21547056
DOI: 10.7150/ijbs.7.392 -
Cells Jul 2021Assisted reproductive technologies (ARTs) have developed considerably in recent years; however, they cannot rectify germ cell aplasia, such as non-obstructive... (Review)
Review
Assisted reproductive technologies (ARTs) have developed considerably in recent years; however, they cannot rectify germ cell aplasia, such as non-obstructive azoospermia (NOA) and oocyte maturation failure syndrome. In vitro gametogenesis is a promising technology to overcome infertility, particularly germ cell aplasia. Early germ cells, such as primordial germ cells, can be relatively easily derived from pluripotent stem cells (PSCs); however, further progression to post-meiotic germ cells usually requires a gonadal niche and signals from gonadal somatic cells. Here, we review the recent advances in in vitro male and female germ cell derivation from PSCs and discuss how this technique is used to understand the biological mechanism of gamete development and gain insight into its application in infertility.
Topics: Animals; Cells, Cultured; Female; Fertility; Gametogenesis; Germ Cells; Humans; Infertility; Male; Oogenesis; Ovum; Pluripotent Stem Cells; Reproductive Techniques, Assisted; Spermatogenesis; Spermatogonia
PubMed: 34440657
DOI: 10.3390/cells10081889 -
Current Biology : CB Feb 2020Niche cells often wrap membrane extensions around stem cell surfaces. Niche wrapping has been proposed to retain stem cells in defined positions and affect signaling...
Niche cells often wrap membrane extensions around stem cell surfaces. Niche wrapping has been proposed to retain stem cells in defined positions and affect signaling [e.g., 1, 2]. To test these hypotheses and uncover additional functions of wrapping, we investigated niche wrapping of primordial germ cells (PGCs) in the C. elegans embryonic gonad primordium. The gonad primordium contains two PGCs that are wrapped individually by two somatic gonad precursor cells (SGPs). SGPs are known to promote PGC survival during embryogenesis and exit from quiescence after hatching, although how they do so is unknown [3]. Here, we identify two distinct functions of SGP wrapping that are critical for PGC quiescence and survival. First, niche cell wrapping templates a laminin-based basement membrane around the gonad primordium. Laminin and the basement membrane receptor dystroglycan function to maintain niche cell wrapping, which is critical for normal gonad development. We find that laminin also preserves PGC quiescence during embryogenesis. Exit from quiescence following laminin depletion requires glp-1/Notch and is accompanied by inappropriate activation of the GLP-1 target sygl-1 in PGCs. Independent of basement membrane, SGP wrapping performs a second, crucial function to ensure PGC survival. Endodermal cells normally engulf and degrade large lobes extended by the PGCs [4]. When SGPs are absent, we show that endodermal cells can inappropriately engulf and cannibalize the PGC cell body. Our findings demonstrate how niche cell wrapping protects germ cells by manipulating their signaling environment and by shielding germ cells from unwanted cellular interactions that can compromise their survival.
Topics: Animals; Caenorhabditis elegans; Cytophagocytosis; Germ Cells; Stem Cells
PubMed: 32008902
DOI: 10.1016/j.cub.2019.12.021 -
Hormone Research in Paediatrics 2014Germ cells are unique cells that possess the ability to transmit genetic information between generations. Detailed knowledge about the molecular and cellular mechanisms... (Review)
Review
BACKGROUND
Germ cells are unique cells that possess the ability to transmit genetic information between generations. Detailed knowledge about the molecular and cellular mechanisms determining the fate of human male germ cells still remains sparse. This is partially due to ethical issues limiting the access to research material. Therefore, the mechanisms of proliferation, differentiation and apoptosis of human male germ cells still remain challenging study objectives.
METHODS
This review focuses on using English articles accessible in PubMed as well as personal files on the current knowledge of the molecular and cellular mechanisms connected with human testicular germ cell development, maturation failure and the possibility of fertility preservation in patients in whom there is a risk of gonadal failure. However, since rodents, particularly mice, offer the possibility of studying germ cell development by use of genetic modification techniques, some studies using animal models are also discussed.
CONCLUSION
This mini review focuses on the current knowledge about male germ cells. However, the reader is referred to two previous mini reviews focusing on testicular somatic cells, i.e. on Sertoli cells and Leydig cells.
Topics: Adult Stem Cells; Animals; Cell Differentiation; Embryonic Development; Fertility Preservation; Germ Cells; Humans; Male; Mice; Spermatogenesis
PubMed: 24356336
DOI: 10.1159/000355599 -
Journal of Experimental Zoology. Part... May 2024Germ cells (reproductive cells and their progenitors) give rise to the next generation in sexually reproducing organisms. The loss or removal of germ cells often leads... (Review)
Review
Germ cells (reproductive cells and their progenitors) give rise to the next generation in sexually reproducing organisms. The loss or removal of germ cells often leads to sterility in established research organisms such as the fruit fly, nematodes, frog, and mouse. The failure to regenerate germ cells in these organisms reinforced the dogma of germline-soma barrier in which germ cells are set-aside during embryogenesis and cannot be replaced by somatic cells. However, in stark contrast, many animals including segmented worms (annelids), hydrozoans, planaria, sea stars, sea urchins, and tunicates can regenerate germ cells. Here I review germ cell and gonad regeneration in annelids, a rich history of research that dates back to the early 20th century in this highly regenerative group. Examples include annelids from across the annelid phylogeny, across developmental stages, and reproductive strategies. Adult annelids regenerate germ cells as a part of regeneration, grafting, and asexual reproduction. Annelids can also recover germ cells after ablation of germ cell progenitors in the embryos. I present a framework to investigate cellular sources of germ cell regeneration in annelids, and discuss the literature that supports different possibilities within this framework, where germ-soma separation may or may not be preserved. With contemporary genetic-lineage tracing and bioinformatics tools, and several genetically enabled annelid models, we are at the brink of answering the big questions that puzzled many for over more than a century.
Topics: Animals; Annelida; Germ Cells; Gonads; Regeneration; Models, Animal
PubMed: 38078561
DOI: 10.1002/jez.b.23233 -
International Journal of Molecular... Sep 2022The development of germ cells and other physiological events in the differentiated ovary of humans are highly conserved with several mammalian species, except for the... (Review)
Review
The development of germ cells and other physiological events in the differentiated ovary of humans are highly conserved with several mammalian species, except for the differences in timing. However, comparative knowledge on this topic is very scarce with respect to humans and lower vertebrates, such as chickens. In chickens, female germ cells enter into meiosis around embryonic day (E) 15.5 and are arrested in meiotic prophase I as primary oocytes. The oocytes arrested in meiosis I are accumulated in germ-cell cysts; shortly after hatching, they are enclosed by flattened granulosa cells in order to form primordial follicles. In humans, the process of meiotic recombination in female germ cells begins in the 10-11th week of gestation, and primordial follicles are formed at around week 20. In this review, we comprehensively elucidate both the conservation and the species-specific differences between chickens and humans with respect to germ cell, oocyte, and follicle development. Importantly, we provide functional insights into a set of chicken oocyte enriched genes (from E16 to 1 week post-hatch) that show convergent and divergent expression patterns with respect to the human oocyte (from week 11 to 26).
Topics: Animals; Chickens; Female; Germ Cells; Humans; Mammals; Meiosis; Oocytes; Ovarian Follicle
PubMed: 36232712
DOI: 10.3390/ijms231911412 -
International Journal of Molecular... Jan 2019Cellular mRNAs in plants and animals have a 5'-cap structure that is accepted as the recognition point to initiate translation by ribosomes. Consequently, it was long... (Review)
Review
Cellular mRNAs in plants and animals have a 5'-cap structure that is accepted as the recognition point to initiate translation by ribosomes. Consequently, it was long assumed that the translation initiation apparatus was built solely for a cap-dependent (CD) mechanism. Exceptions that emerged invoke structural damage (proteolytic cleavage) to eukaryotic initiation factor 4 (eIF4) factors that disable cap recognition. The residual eIF4 complex is thought to be crippled, but capable of cap-independent (CI) translation to recruit viral or death-associated mRNAs begrudgingly when cells are in great distress. However, situations where CI translation coexists with CD translation are now known. In such cases, CI translation is still a minor mechanism in the major background of CD synthesis. In this review, I propose that germ cells do not fit this mold. Using observations from various animal models of oogenesis and spermatogenesis, I suggest that CI translation is a robust partner to CD translation to carry out the translational control that is so prevalent in germ cell development. Evidence suggests that CI translation provides surveillance of germ cell homeostasis, while CD translation governs the regulated protein synthesis that ushers these meiotic cells through the remarkable steps in sperm/oocyte differentiation.
Topics: Animals; Germ Cells; Humans; Meiosis; Models, Biological; Protein Biosynthesis; RNA Caps; RNA, Messenger
PubMed: 30621249
DOI: 10.3390/ijms20010173