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Biochimica Et Biophysica Acta Dec 2012Oogenesis is a complex process regulated by a vast number of intra- and extra-ovarian factors. Oogonia, which originate from primordial germ cells, proliferate by... (Review)
Review
Oogenesis is a complex process regulated by a vast number of intra- and extra-ovarian factors. Oogonia, which originate from primordial germ cells, proliferate by mitosis and form primary oocytes that arrest at the prophase stage of the first meiotic division until they are fully-grown. Within primary oocytes, synthesis and accumulation of RNAs and proteins throughout oogenesis are essential for oocyte growth and maturation; and moreover, crucial for developing into a viable embryo after fertilization. Oocyte meiotic and developmental competence is gained in a gradual and sequential manner during folliculogenesis and is related to the fact that the oocyte grows in interaction with its companion somatic cells. Communication between oocyte and its surrounding granulosa cells is vital, both for oocyte development and for granulosa cells differentiation. Oocytes depend on differentiated cumulus cells, which provide them with nutrients and regulatory signals needed to promote oocyte nuclear and cytoplasmic maturation and consequently the acquisition of developmental competence.The purpose of this article is to summarize recent knowledge on the molecular aspects of oogenesis and oocyte maturation, and the crucial role of cumulus-cell interactions, highlighting the valuable contribution of experimental evidences obtained in animal models. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.
Topics: Animals; Female; Humans; Oocytes; Oogenesis; Ovarian Follicle
PubMed: 22634430
DOI: 10.1016/j.bbadis.2012.05.013 -
The EMBO Journal Sep 2022In vitro oogenesis is key to elucidating the mechanism of human female germ-cell development and its anomalies. Accordingly, pluripotent stem cells have been induced...
In vitro oogenesis is key to elucidating the mechanism of human female germ-cell development and its anomalies. Accordingly, pluripotent stem cells have been induced into primordial germ cell-like cells and into oogonia with epigenetic reprogramming, yet further reconstitutions remain a challenge. Here, we demonstrate ex vivo reconstitution of fetal oocyte development in both humans and cynomolgus monkeys (Macaca fascicularis). With an optimized culture of fetal ovary reaggregates over three months, human and monkey oogonia enter and complete the first meiotic prophase to differentiate into diplotene oocytes that form primordial follicles, the source for oogenesis in adults. The cytological and transcriptomic progressions of fetal oocyte development in vitro closely recapitulate those in vivo. A comparison of single-cell transcriptomes among humans, monkeys, and mice unravels primate-specific and conserved programs driving fetal oocyte development, the former including a distinct transcriptomic transformation upon oogonia-to-oocyte transition and the latter including two active X chromosomes with little X-chromosome upregulation. Our study provides a critical step forward for realizing human in vitro oogenesis and uncovers salient characteristics of fetal oocyte development in primates.
Topics: Animals; Female; Humans; Macaca fascicularis; Meiosis; Mice; Oocytes; Oogenesis; Ovary
PubMed: 35912849
DOI: 10.15252/embj.2022110815 -
Sexual Development : Genetics,... 2022Whether to produce sperm or eggs is the most basic and important choice from the perspective of germ cell development and differentiation. However, the induction... (Review)
Review
BACKGROUND
Whether to produce sperm or eggs is the most basic and important choice from the perspective of germ cell development and differentiation. However, the induction mechanism has not received much attention until relatively recently. This is because the issue of sexual differentiation has generally been considered a theme of somatic cells to make a testis or ovary. Basically, the sex of individual somatic cells and germ cells matches. Therefore, the sex of germ cells is thought to follow the sex of somatic cells once determined. However, researchers realized that a big, open question remained: What somatic cell signals actually induce the sexual differentiation of germ cells and what is the sex determinant in germ cells?
SUMMARY
In vitro experiments demonstrated that 2 somatic signals (BMP and RA) act directly on germ cells to induce oogonia. Therefore, these 2 signals may be referred to as oogonia inducers. From the viewpoint of germ cells, an independent experiment identified SMAD4 and STRA8, which are directly downstream of BMP and RA, respectively, acting in germ cells as female determinants. However, what about male? If these factors are female determinants, their absence may result in the induction of spermatogonia. This may be true in vivo because germ cells enter a male pathway if they do not receive these signals even in the ovary. However, this has not been confirmed in an in vitro culture system. There should be signals required for germ cells to enter a male pathway.
KEY MESSAGES
The important message is that although testis-specific factors secreted from the testis are considered to include male-inducing factors for germ cells, this may not be the case, and the male-inducing factor, if it exists, also exists in the ovary.
PubMed: 35263749
DOI: 10.1159/000520976 -
Stem Cells International 2021Germ cells are capable of maintaining species continuity through passing genetic and epigenetic information across generations. Female germ cells mainly develop during... (Review)
Review
Germ cells are capable of maintaining species continuity through passing genetic and epigenetic information across generations. Female germ cells mainly develop during the embryonic stage and pass through subsequent developmental stages including primordial germ cells, oogonia, and oocyte. However, due to the limitation of using early human embryos as research model, research models are needed to reveal the early developmental process and related mechanisms of female germ cells. After birth, the number of follicles gradually decreases with age. Various conditions which damage ovarian functions would cause premature ovarian failure. Alternative treatments to solve these problems need to be investigated. Germ cell differentiation from pluripotent stem cells can simulate early embryonic development of female germ cells and clarify unresolved issues during the development process. In addition, pluripotent stem cells could potentially provide promising applications for female fertility preservation after proper differentiation. Mouse female germ cells have been successfully reconstructed and delivered to live offspring. However, the derivation of functional human female germ cells has not been fully achieved due to technical limitations and ethical issues. To provide an updated and comprehensive information, this review centers on the major studies on the differentiation of mouse and human female germ cells from pluripotent stem cells and provides references to further studies of developmental mechanisms and potential therapeutic applications of female germ cells.
PubMed: 33510796
DOI: 10.1155/2021/8849230 -
General and Comparative Endocrinology Oct 2014Although present at relatively low number in the testis, spermatogonial stem cells (SSCs) are crucial for the establishment and maintenance of spermatogenesis in... (Comparative Study)
Comparative Study Review
Although present at relatively low number in the testis, spermatogonial stem cells (SSCs) are crucial for the establishment and maintenance of spermatogenesis in eukaryotes and, until recently, those cells were investigated in fish using morphological criteria. The isolation and characterization of these cells in fish have been so far limited by the lack of specific molecular markers, hampering the high SSCs biotechnological potential for aquaculture. However, some highly conserved vertebrate molecular markers, such as Gfra1 and Pou5f1/Oct4, are now available representing important candidates for studies evaluating the regulation of SSCs in fish and even functional investigations using germ cells transplantation. A technique already used to demonstrate that, different from mammals, fish germ stem cells (spermatogonia and oogonia) present high sexual plasticity that is determined by the somatic microenvironment. As relatively well established in mammals, and demonstrated in zebrafish and dogfish, this somatic environment is very important for the preferential location and regulation of SSCs. Importantly, a long-term in vitro culture system for SSCs has been now established for some fish species. Therefore, besides the aforementioned possibilities, such culture system would allow the development of strategies to in vitro investigate key regulatory and functional aspects of germline stem cells (ex: self-renewal and/or differentiation) or to amplify SSCs of rare, endangered, or commercially valuable fish species, representing an important tool for transgenesis and the development of new biotechnologies in fish production.
Topics: Animals; Biomarkers; Cell Differentiation; Fishes; Male; Mammals; Spermatogenesis; Spermatogonia; Stem Cells; Testis
PubMed: 24967950
DOI: 10.1016/j.ygcen.2014.06.018 -
International Journal of Molecular... Apr 2023It is a well-known fact that the reproductive organs in women, especially oocytes, are exposed to numerous regulatory pathways and environmental stimuli. The maternal... (Review)
Review
It is a well-known fact that the reproductive organs in women, especially oocytes, are exposed to numerous regulatory pathways and environmental stimuli. The maternal age is one cornerstone that influences the process of oocyte fertilization. More precisely, the longer a given oocyte is in the waiting-line to be ovulated from menarche to menopause, the longer the duration from oogenesis to fertilization, and therefore, the lower the chances of success to form a viable embryo. The age of menarche in girls ranges from 10 to 16 years, and the age of menopause in women ranges from approximately 45 to 55 years. Researchers are paying attention to the regulatory pathways that are impacting the oocyte at the very beginning during oogenesis in fetal life to discover genes and proteins that could be crucial for the oocyte's lifespan. Due to the general trend in industrialized countries in the last three decades, women are giving birth to their first child in their thirties. Therefore, maternal age has become an important factor impacting oocytes developmental competence, since the higher a woman's age, the higher the chances of miscarriage due to several causes, such as aneuploidy. Meiotic failures during oogenesis, such as, for instance, chromosome segregation failures or chromosomal non-disjunction, are influencing the latter-mentioned aging-related phenomenon too. These errors early in life of women can lead to sub- or infertility. It cannot be neglected that oogenesis is a precisely orchestrated process, during which the oogonia and primary oocytes are formed, and RNA synthesis takes place. These RNAs are crucial for oocyte growth and maturation. In this review, we intend to describe the relevance of regulatory pathways during the oogenesis in women. Furthermore, we focus on molecular pathways of oocyte developmental competence with regard to maternal effects during embryogenesis. On the background of transcriptional mechanisms that enable the transition from a silenced oocyte to a transcriptionally active embryo, we will briefly discuss the potential of induced pluripotent stem cells.
Topics: Pregnancy; Female; Humans; Maternal Age; Oogenesis; Oocytes; Ovulation; Stem Cells
PubMed: 37047809
DOI: 10.3390/ijms24076837 -
The EMBO Journal May 2023Human in vitro oogenesis provides a framework for clarifying the mechanism of human oogenesis. To create its benchmark, it is vital to promote in vitro oogenesis using a...
Human in vitro oogenesis provides a framework for clarifying the mechanism of human oogenesis. To create its benchmark, it is vital to promote in vitro oogenesis using a model physiologically close to humans. Here, we establish a foundation for in vitro oogenesis in cynomolgus (cy) monkeys (Macaca fascicularis): cy female embryonic stem cells harboring one active and one inactive X chromosome (Xa and Xi, respectively) differentiate robustly into primordial germ cell-like cells, which in xenogeneic reconstituted ovaries develop efficiently into oogonia and, remarkably, further into meiotic oocytes at the zygotene stage. This differentiation entails comprehensive epigenetic reprogramming, including Xi reprogramming, yet Xa and Xi remain epigenetically asymmetric with, as partly observed in vivo, incomplete Xi reactivation. In humans and monkeys, the Xi epigenome in pluripotent stem cells functions as an Xi-reprogramming determinant. We further show that developmental pathway over-activations with suboptimal up-regulation of relevant meiotic genes impede in vitro meiotic progression. Cy in vitro oogenesis exhibits critical homology with the human system, including with respect to bottlenecks, providing a salient model for advancing human in vitro oogenesis.
Topics: Animals; Female; Humans; Macaca fascicularis; Oocytes; Oogenesis; Ovary; Embryonic Stem Cells
PubMed: 36929479
DOI: 10.15252/embj.2022112962 -
Fungal Systematics and Evolution Dec 2022During a survey of gardens in Shiraz County, Iran, aimed at identifying oomycetes associated with roots of ornamental trees, a species of with distinctive morphological...
During a survey of gardens in Shiraz County, Iran, aimed at identifying oomycetes associated with roots of ornamental trees, a species of with distinctive morphological characters separating it from other known species in this genus was recovered from conifers and occasionally from a sp. Five isolates of this species were characterised. Phylogenetic analyses of nuclear (ITS and ) and mitochondrial ( and ) loci using Bayesian inference and maximum likelihood analyses as well as their distinct morphological and cultural characteristics ( abundant production of chlamydospores; globose, ellipsoid to ovoid sporangia; amorphous oogonia with a smooth wall; paragynous to rarely hypogynous antheridia and 1-5 antheridia per oogonium; mostly plerotic oospores) revealed that these isolates belong to a new species grouping in the phylogenetic clade G of . This paper formally describes . as a new species and compares it with other phylogenetically related and already known species, including , , and . Salmaninezhad F, Aloi F, Pane A, Mostowfizadeh-Ghalamfarsa R, Cacciola SO (2022). ., associated with conifers and spp. : 127-137. doi: 10.3114/fuse.2022.10.05.
PubMed: 36741557
DOI: 10.3114/fuse.2022.10.05 -
Reproductive Biology and Endocrinology... Aug 2014Preantral follicles are the majority of the ovarian follicle population and their use as a source of homogeneous oocytes for bovine reproductive biotechnologies could... (Review)
Review
Preantral follicles are the majority of the ovarian follicle population and their use as a source of homogeneous oocytes for bovine reproductive biotechnologies could result in a substantial advance in this field. However, while in other species embryos and offspring have been produced, in bovine species the results have been limited to the follicular activation of small (primordial) preantral follicles and formation of early antral follicles from large (secondary) preantral follicles after in vitro culture. Therefore, this review will highlight the basic aspects of bovine folliculogenesis by focusing on preantral follicles, the methods of harvesting preantral follicles, the main results from in vitro follicular culture during the last 20 years, and the potential candidate substances (basic supplements, growth factors, and hormones) for improving the efficiency of in vitro follicle growth.
Topics: Animals; Cattle; Female; In Vitro Oocyte Maturation Techniques; Oogenesis; Oogonia; Ovarian Follicle; Reproductive Techniques, Assisted; Tissue Culture Techniques
PubMed: 25117631
DOI: 10.1186/1477-7827-12-78