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Development (Cambridge, England) Mar 2021The peri-implantation window of mammalian development is the crucial window for primordial germ cell (PGC) specification. Whereas pre-implantation dynamics are... (Review)
Review
The peri-implantation window of mammalian development is the crucial window for primordial germ cell (PGC) specification. Whereas pre-implantation dynamics are relatively conserved between species, the implantation window marks a stage of developmental divergence between key model organisms, and thus potential variance in the cell and molecular mechanisms for PGC specification. In humans, PGC specification is very difficult to study To address this, the combined use of human and nonhuman primate embryos, and stem cell-based embryo models are essential for determining the origin of PGCs, as are comparative analyses to the equivalent stages of mouse development. Understanding the origin of PGCs in the peri-implantation embryo is crucial not only for accurate modeling of this essential process using stem cells, but also in determining the role of global epigenetic reprogramming upon which sex-specific differentiation into gametes relies.
Topics: Animals; Cell Differentiation; DNA Methylation; Embryonic Development; Embryonic Stem Cells; Germ Cells; Humans; Models, Biological; X Chromosome
PubMed: 33722957
DOI: 10.1242/dev.189217 -
Animal : An International Journal of... Jun 2018Spermatogenesis is a finely regulated process of germ cell multiplication and differentiation leading to the production of spermatozoa in the seminiferous tubules.... (Review)
Review
Spermatogenesis is a finely regulated process of germ cell multiplication and differentiation leading to the production of spermatozoa in the seminiferous tubules. Spermatogenesis can be divided into three parts: spermatocytogenesis, meiosis and spermiogenesis. During spermatocytogenesis, germ cells engage in a cycle of several mitotic divisions that increases the yield of spermatogenesis and to renew stem cells and produce spermatogonia and primary spermatocytes. Meiosis involves duplication and exchange of genetic material and two cell divisions that reduce the chromosome number and yield four haploid round spermatids. Spermiogenesis involves the differentiation of round spermatids into fully mature spermatozoa released into the lumin of seminiferous tubules. The seminiferous epithelium is composed of several generations of germ cells due to the fact that new generations of sperm cells engage in the spermatogenic process without waiting for the preceding generations to have completed their evolution and to have disappeared as spermatozoa into the lumen of the tubules. In bulls, the duration of the seminiferous epithelium cycle is 13.5 days. The total duration of spermatogenesis is 61 days, that is 4.5 times the duration of the cycle of the seminiferous epithelium. The spermatogenetic wave is used to describe the spatial arrangement of cell associations along the tubules. Several theories have been described to explain the renewal of spermatogonia. Depending on the model, there are five or six spermatogonial mitoses explaining the renewal of stem cells and the proliferation of spermatogonia. Daily sperm production and germ cell degeneration can be quantified from numbers of germ cells in various steps of development throughout spermatogenesis. Bulls have a lower efficiency of spermatogenesis than most species examined, but higher than that of humans.
Topics: Animals; Cattle; Male; Seminiferous Tubules; Spermatocytes; Spermatogenesis; Spermatogonia; Spermatozoa; Testis
PubMed: 29882505
DOI: 10.1017/S1751731118000435 -
Signal Transduction and Targeted Therapy Oct 2022The germline cells are essential for the propagation of human beings, thus essential for the survival of mankind. The germline stem cells, as a unique cell type,... (Review)
Review
The germline cells are essential for the propagation of human beings, thus essential for the survival of mankind. The germline stem cells, as a unique cell type, generate various states of germ stem cells and then differentiate into specialized cells, spermatozoa and ova, for producing offspring, while self-renew to generate more stem cells. Abnormal development of germline stem cells often causes severe diseases in humans, including infertility and cancer. Primordial germ cells (PGCs) first emerge during early embryonic development, migrate into the gentile ridge, and then join in the formation of gonads. In males, they differentiate into spermatogonial stem cells, which give rise to spermatozoa via meiosis from the onset of puberty, while in females, the female germline stem cells (FGSCs) retain stemness in the ovary and initiate meiosis to generate oocytes. Primordial germ cell-like cells (PGCLCs) can be induced in vitro from embryonic stem cells or induced pluripotent stem cells. In this review, we focus on current advances in these embryonic and adult germline stem cells, and the induced PGCLCs in humans, provide an overview of molecular mechanisms underlying the development and differentiation of the germline stem cells and outline their physiological functions, pathological implications, and clinical applications.
Topics: Adult; Cell Differentiation; Embryonic Stem Cells; Female; Germ Cells; Humans; Male; Meiosis; Spermatozoa
PubMed: 36184610
DOI: 10.1038/s41392-022-01197-3 -
Cell Stem Cell Dec 2021Mammalian male germ-cell development consists of three distinct phases: primordial germ cell (PGC) development, male germ-cell specification for spermatogonium...
Mammalian male germ-cell development consists of three distinct phases: primordial germ cell (PGC) development, male germ-cell specification for spermatogonium development, and ensuing spermatogenesis. Here, we show an in vitro reconstitution of whole male germ-cell development by pluripotent stem cells (PSCs). Mouse embryonic stem cells (mESCs) are induced into PGC-like cells (mPGCLCs), which are expanded for epigenetic reprogramming. In reconstituted testes under an optimized condition, such mPGCLCs differentiate into spermatogonium-like cells with proper developmental transitions, gene expression, and cell-cycle dynamics and are expanded robustly as germline stem cell-like cells (GSCLCs) with an appropriate androgenetic epigenome. Importantly, GSCLCs show vigorous spermatogenesis, not only upon transplantation into testes in vivo but also under an in vitro culture of testis transplants, and the resultant spermatids contribute to fertile offspring. By uniting faithful recapitulations of the three phases of male germ-cell development, our study creates a paradigm for the in vitro male gametogenesis by PSCs.
Topics: Animals; Cell Differentiation; Epigenomics; Germ Cells; Male; Mice; Pluripotent Stem Cells; Spermatogenesis; Spermatogonia
PubMed: 34496297
DOI: 10.1016/j.stem.2021.08.005 -
Cell Aug 2011The generation of properly functioning gametes in vitro requires reconstitution of the multistepped pathway of germ cell development. We demonstrate here the generation...
The generation of properly functioning gametes in vitro requires reconstitution of the multistepped pathway of germ cell development. We demonstrate here the generation of primordial germ cell-like cells (PGCLCs) in mice with robust capacity for spermatogenesis. PGCLCs were generated from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) through epiblast-like cells (EpiLCs), a cellular state highly similar to pregastrulating epiblasts but distinct from epiblast stem cells (EpiSCs). Reflecting epiblast development, EpiLC induction from ESCs/iPSCs is a progressive process, and EpiLCs highly competent for the PGC fate are a transient entity. The global transcription profiles, epigenetic reprogramming, and cellular dynamics during PGCLC induction from EpiLCs meticulously capture those associated with PGC specification from the epiblasts. Furthermore, we identify Integrin-β3 and SSEA1 as markers that allow the isolation of PGCLCs with spermatogenic capacity from tumorigenic undifferentiated cells. Our findings provide a paradigm for the first step of in vitro gametogenesis.
Topics: Animals; Cell Culture Techniques; Cell Differentiation; Cell Proliferation; Embryonic Stem Cells; Gene Expression Profiling; Germ Cells; Germ Layers; Induced Pluripotent Stem Cells; Mice; Pluripotent Stem Cells; Spermatogenesis
PubMed: 21820164
DOI: 10.1016/j.cell.2011.06.052 -
Cell Stem Cell Aug 2015Mechanisms underlying human germ cell development are unclear, partly due to difficulties in studying human embryos and lack of suitable experimental systems. Here, we...
Mechanisms underlying human germ cell development are unclear, partly due to difficulties in studying human embryos and lack of suitable experimental systems. Here, we show that human induced pluripotent stem cells (hiPSCs) differentiate into incipient mesoderm-like cells (iMeLCs), which robustly generate human primordial germ cell-like cells (hPGCLCs) that can be purified using the surface markers EpCAM and INTEGRINα6. The transcriptomes of hPGCLCs and primordial germ cells (PGCs) isolated from non-human primates are similar, and although specification of hPGCLCs and mouse PGCs rely on similar signaling pathways, hPGCLC specification transcriptionally activates germline fate without transiently inducing eminent somatic programs. This includes genes important for naive pluripotency and repression of key epigenetic modifiers, concomitant with epigenetic reprogramming. Accordingly, BLIMP1, which represses somatic programs in mice, activates and stabilizes a germline transcriptional circuit and represses a default neuronal differentiation program. Together, these findings provide a foundation for understanding and reconstituting human germ cell development in vitro.
Topics: Animals; Base Sequence; Biomarkers; Cell Differentiation; Cell Lineage; Epigenesis, Genetic; Genes, Reporter; Germ Cells; Gonads; Humans; Induced Pluripotent Stem Cells; Macaca fascicularis; Mesoderm; Mice; Molecular Sequence Data; Neurons; Positive Regulatory Domain I-Binding Factor 1; Repressor Proteins; Signal Transduction; Transcription, Genetic
PubMed: 26189426
DOI: 10.1016/j.stem.2015.06.014 -
Aging Cell Jul 2021The assembly of primordial follicles in mammals represents one of the most critical processes in ovarian biology. It directly affects the number of oocytes available to...
The assembly of primordial follicles in mammals represents one of the most critical processes in ovarian biology. It directly affects the number of oocytes available to a female throughout her reproductive life. Premature depletion of primordial follicles contributes to the ovarian pathology primary ovarian insufficiency (POI). To delineate the developmental trajectory and regulatory mechanisms of oocytes during the process, we performed RNA-seq on single germ cells from newborn (P0.5) ovaries. Three cell clusters were classified which corresponded to three cell states (germ cell cyst, cyst breakdown, and follicle) in the newborn ovary. By Monocle analysis, a uniform trajectory of oocyte development was built with a series of genes showed dynamic changes along the pseudo-timeline. Gene Ontology term enrichment revealed a significant decrease in meiosis-related genes and a dramatic increase in oocyte-specific genes which marked the transition from a germ cell to a functional oocyte. We then established a network of regulons by using single-cell regulatory network inference and clustering (SCENIC) algorithm and identified possible candidate transcription factors that may maintain transcription programs during follicle formation. Following functional studies further revealed the differential regulation of the identified regulon Id2 and its family member Id1, on the establishment of primordial follicle pool by using siRNA knockdown and genetic modified mouse models. In summary, our study systematically reconstructed molecular cascades in oocytes and identified a series of genes and molecular pathways in follicle formation and development.
Topics: Animals; Germ Cell Ribonucleoprotein Granules; Germ Cells; Mice; Oocytes; RNA-Seq; Single-Cell Analysis
PubMed: 34174788
DOI: 10.1111/acel.13424 -
Developmental Cell Feb 2020The mechanisms regulating meiotic initiation in mammals are enigmatic. It is known that retinoic acid (RA) signaling plays a pivotal role during meiotic initiation....
The mechanisms regulating meiotic initiation in mammals are enigmatic. It is known that retinoic acid (RA) signaling plays a pivotal role during meiotic initiation. STRA8, which is expressed in response to RA, is thought to be a key factor promoting meiotic initiation. However, the specific role of STRA8 in meiotic initiation has remained elusive. Here, we identified MEIOSIN as a germ-cell-specific factor that associates with STRA8. MEIOSIN, like STRA8, is expressed in response to RA and plays an essential role in meiotic initiation in both males and females. Functional analyses revealed that MEIOSIN acts as a transcription factor together with STRA8, and that both factors are critical for driving meiotic gene activation. Furthermore, temporally restricted expression of MEIOSIN leads to meiotic entry decision during spermatogenesis. The present study demonstrates that MEIOSIN, in collaboration with STRA8, plays a central role in regulating the mitosis to meiosis germ cell fate decision in mammals.
Topics: Adaptor Proteins, Signal Transducing; Animals; Cell Cycle; Cell Differentiation; Female; Gene Expression Regulation; Germ Cells; Male; Meiosis; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitosis; Signal Transduction; Spermatogenesis; Transcription Factors
PubMed: 32032549
DOI: 10.1016/j.devcel.2020.01.010 -
Advances in Experimental Medicine and... 2013The germline of Caenorhabditis elegans derives from a single founder cell, the germline blastomere P(4). P(4) is the product of four asymmetric cleavages that divide the... (Review)
Review
The germline of Caenorhabditis elegans derives from a single founder cell, the germline blastomere P(4). P(4) is the product of four asymmetric cleavages that divide the zygote into distinct somatic and germline (P) lineages. P(4) inherits a specialized cytoplasm ("germ plasm") containing maternally encoded proteins and RNAs. The germ plasm has been hypothesized to specify germ cell fate, but the mechanisms involved remain unclear. Three processes stand out: (1) inhibition of mRNA transcription to prevent activation of somatic development, (2) translational regulation of the nanos homolog nos-2 and of other germ plasm mRNAs, and (3) establishment of a unique, partially repressive chromatin. Together, these processes ensure that the daughters of P(4), the primordial germ cells Z2 and Z3, gastrulate inside the embryo, associate with the somatic gonad, initiate the germline transcriptional program, and proliferate during larval development to generate ∼2,000 germ cells by adulthood.
Topics: Animals; Caenorhabditis elegans; Cell Lineage; Embryonic Development; Germ Cells
PubMed: 22872473
DOI: 10.1007/978-1-4614-4015-4_2 -
Stem Cell Research & Therapy Feb 2022Reproduction is a key event in life guaranteeing the propagation and evolution of a species. Infertility caused by abnormal germ cell development is a topic of extensive... (Review)
Review
Reproduction is a key event in life guaranteeing the propagation and evolution of a species. Infertility caused by abnormal germ cell development is a topic of extensive concern. Herein, in vitro germline specification studies provide a modeling platform to investigate gametogenesis. The differentiation of pluripotent stem cells (PSCs) into germ cells has been studied for more than 30 years, and there have been many astonishing breakthroughs in the last decade. Fertile sperm and oocytes can be obtained from mouse embryonic stem cells (ESCs) through a primordial germ cell (PGC)-based method. Moreover, human PGC-like cells (PGCLCs) can be derived with a similar strategy as that used for mouse PGCLC derivation. In this review, we describe the reconstitution of PGCs and the subsequent meiosis, as well as the signaling pathways and factors involved in these processes.
Topics: Animals; Cell Differentiation; Germ Cells; Mice; Pluripotent Stem Cells
PubMed: 35189957
DOI: 10.1186/s13287-022-02750-1