| 1. |
- Adhikari, Deepak, et al.
(författare)
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Inhibitory phosphorylation of Cdk1 mediates prolonged prophase I arrest in female germ cells and is essential for female reproductive lifespan
- 2016
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Ingår i: Cell Research. - : Springer Science and Business Media LLC. - 1001-0602 .- 1748-7838. ; 26, s. 1212-1225
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 IBCB, SIBS, CAS. A unique feature of female germ cell development in mammals is their remarkably long arrest at the prophase of meiosis I, which lasts up to 50 years in humans. Both dormant and growing oocytes are arrested at prophase I and completely lack the ability to resume meiosis. Here, we show that the prolonged meiotic arrest of female germ cells is largely achieved via the inhibitory phosphorylation of Cdk1 (cyclin-dependent kinase 1). In two mouse models where we have introduced mutant Cdk1 T14AY15F which cannot be inhibited by phosphorylation (Cdk1AF) in small meiotically incompetent oocytes, the prophase I arrest is interrupted, leading to a premature loss of female germ cells. We show that in growing oocytes, Cdk1AF leads to premature resumption of meiosis with condensed chromosomes and germinal vesicle breakdown followed by oocyte death, whereas in dormant oocytes, Cdk1AF leads to oocyte death directly, and both situations damage the ovarian reserve that maintains the female reproductive lifespan, which should be around 1 year in mice. Furthermore, interruption of the inhibitory phosphorylation of Cdk1 results in DNA damage, which is accompanied by induction of the Chk2 (checkpoint kinase 2)-p53/p63-dependent cell death pathway, which eventually causes global oocyte death. Together, our data demonstrate that the phosphorylation-mediated suppression of Cdk1 activity is one of the crucial factors that maintain the lengthy prophase arrest in mammalian female germ cells, which is essential for preserving the germ cell pool and reproductive lifespan in female mammals.
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| 2. |
- Adhikari, Deepak, et al.
(författare)
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Mastl is required for timely activation of APC/C in meiosis I and Cdk1 reactivation in meiosis II.
- 2014
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Ingår i: The Journal of cell biology. - : Rockefeller University Press. - 1540-8140 .- 0021-9525. ; 206:7, s. 843-853
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Tidskriftsartikel (refereegranskat)abstract
- In mitosis, the Greatwall kinase (called microtubule-associated serine/threonine kinase like [Mastl] in mammals) is essential for prometaphase entry or progression by suppressing protein phosphatase 2A (PP2A) activity. PP2A suppression in turn leads to high levels of Cdk1 substrate phosphorylation. We have used a mouse model with an oocyte-specific deletion of Mastl to show that Mastl-null oocytes resume meiosis I and reach metaphase I normally but that the onset and completion of anaphase I are delayed. Moreover, after the completion of meiosis I, Mastl-null oocytes failed to enter meiosis II (MII) because they reassembled a nuclear structure containing decondensed chromatin. Our results show that Mastl is required for the timely activation of anaphase-promoting complex/cyclosome to allow meiosis I exit and for the rapid rise of Cdk1 activity that is needed for the entry into MII in mouse oocytes.
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| 3. |
- Adhikari, Deepak, et al.
(författare)
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Pharmacological Inhibition of mTORC1 Prevents Over-Activation of the Primordial Follicle Pool in Response to Elevated PI3K Signaling
- 2013
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The majority of ovarian primordial follicles must be preserved in a quiescent state to allow for the regular production of gametes over the female reproductive lifespan. However, the molecular mechanism that maintains the long quiescence of primordial follicles is poorly understood. Under certain pathological conditions, the entire pool of primordial follicles matures simultaneously leading to an accelerated loss of primordial follicles and to premature ovarian failure (POF). We have previously shown that loss of Pten (phosphatase and tensin homolog deleted on chromosome ten) in mouse oocytes leads to premature activation of the entire pool of primordial follicles, subsequent follicular depletion in early adulthood, and the onset of POF. Lack of PTEN leads to increased phosphatidylinositol 3-kinase (PI3K)-Akt and mammalian target of rapamycin complex 1 (mTORC1) signaling in the oocytes. To study the functional and pathological roles of elevated mTORC1 signaling in the oocytes, we treated the Pten-mutant mice with the specific mTORC1 inhibitor rapamycin. When administered to Pten-deficient mice prior to the activation of the primordial follicles, rapamycin effectively prevented global follicular activation and preserved the ovarian reserve. These results provide a rationale for exploring the possible use of rapamycin as a drug for the preservation of the primordial follicle pool, and the possible prevention of POF.
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| 4. |
- Adhikari, Deepak, et al.
(författare)
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The Safe Use of a PTEN Inhibitor for the Activation of Dormant Mouse Primordial Follicles and Generation of Fertilizable Eggs
- 2012
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Primordial ovarian follicles, which are often present in the ovaries of premature ovarian failure (POF) patients or are cryopreserved from the ovaries of young cancer patients who are undergoing gonadotoxic anticancer therapies, cannot be used to generate mature oocytes for in vitro fertilization (IVF). There has been very little success in triggering growth of primordial follicles to obtain fertilizable oocytes due to the poor understanding of the biology of primordial follicle activation. Methodology/Principal Findings: We have recently reported that PTEN (phosphatase and tensin homolog deleted on chromosome ten) prevents primordial follicle activation in mice, and deletion of Pten from the oocytes of primordial follicles leads to follicular activation. Consequently, the PTEN inhibitor has been successfully used in vitro to activate primordial follicles in both mouse and human ovaries. These results suggest that PTEN inhibitors could be used in ovarian culture medium to trigger the activation of primordial follicle. To study the safety and efficacy of the use of such inhibitors, we activated primordial follicles from neonatal mouse ovaries by transient treatment with a PTEN inhibitor bpV(HOpic). These ovaries were then transplanted under the kidney capsules of recipient mice to generate mature oocytes. The mature oocytes were fertilized in vitro and progeny mice were obtained after embryo transfer. Results and Conclusions: Long-term monitoring up to the second generation of progeny mice showed that the mice were reproductively active and were free from any overt signs or symptoms of chronic illnesses. Our results indicate that the use of PTEN inhibitors could be a safe and effective way of generating mature human oocytes for use in novel IVF techniques.
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| 5. |
- Ascani, Angelo, et al.
(författare)
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The role of B cells in immune cell activation in polycystic ovary syndrome.
- 2023
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Ingår i: eLife. - 2050-084X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Variations in B cell numbers are associated with polycystic ovary syndrome (PCOS) through unknown mechanisms. Here, we demonstrate that B cells are not central mediators of PCOS pathology and that their frequencies are altered as a direct effect of androgen receptor activation. Hyperandrogenic women with PCOS have increased frequencies of age-associated double-negative B memory cells and increased levels of circulating immunoglobulin M (IgM). However, the transfer of serum IgG from women into wild-type female mice induces only an increase in body weight. Furthermore, RAG1 knockout mice, which lack mature T- and B cells, fail to develop any PCOS-like phenotype. In wild-type mice, co-treatment with flutamide, an androgen receptor antagonist, prevents not only the development of a PCOS-like phenotype but also alterations of B cell frequencies induced by dihydrotestosterone (DHT). Finally, B cell-deficient mice, when exposed to DHT, are not protected from developing a PCOS-like phenotype. These results urge further studies on B cell functions and their effects on autoimmune comorbidities highly prevalent among women with PCOS.
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| 6. |
- Risal, Sanjiv, et al.
(författare)
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MASTL is essential for anaphase entry of proliferating primordial germ cells and establishment of female germ cells in mice
- 2017
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Ingår i: Cell Discovery. - : Springer Science and Business Media LLC. - 2056-5968. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- In mammals, primordial germ cells (PGCs) are the embryonic cell population that serve as germ cell precursors in both females and males. During mouse embryonic development, the majority of PGCs are arrested at the G2 phase when they migrate into the hindgut at 7.75-8.75 dpc (days post coitum). It is after 9.5 dpc that the PGCs undergo proliferation with a doubling time of 12.6 h. The molecular mechanisms underlying PGC proliferation are however not well studied. In this work. Here we studied how MASTL (microtubule-associated serine/threonine kinase-like)/Greatwall kinase regulates the rapid proliferation of PGCs. We generated a mouse model where we specifically deleted Mastl in PGCs and found a significant loss of PGCs before the onset of meiosis in female PGCs. We further revealed that the deletion of Mastl in PGCs did not prevent mitotic entry, but led to a failure of the cells to proceed beyond metaphase-like stage, indicating that MASTL-mediated molecular events are indispensable for anaphase entry in PGCs. These mitotic defects further led to the death of Mastl-null PGCs by 12.5 dpc. Moreover, the defect in mitotic progression observed in the Mastl-null PGCs was rescued by simultaneous deletion of Ppp2r1a (a subunit of PP2A). Thus, our results demonstrate that MASTL, PP2A, and therefore regulated phosphatase activity have a fundamental role in establishing female germ cell population in gonads by controlling PGC proliferation during embryogenesis.
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| 7. |
- Risal, Sanjiv
(författare)
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Molecular pathways mediating the development of female germ cells
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In mice, primordial germ cells (PGCs) dramatically increase in their number from 200 cells at 9.5 dpc to 10 000 cells at 12.5 dpc with doubling time of 12.6 hours. Thus, cell proliferation of PGCs seems a unique compared to proliferation of other cell types. How Mastl (microtubule-associated serine/threonine kinase-like) is involved in the rapidly dividing PGCs is not known. PGC-specific deletion of Mastl resulted in a significant loss of PGCs by interfering with cell cycle progression beyond metaphase. This mitotic defect further led to the activation of DNA damage and the apoptotic cell death of Mastl-null PGCs by 12.5 dpc. Therefore, indicating that Mastl-mediated molecular events are indispensable for cell cycle progression in PGCs. However, the metaphase-anaphase transition defects observed in the Mastl-null PGCs is rescued by simultaneous deletion of Ppp2r1a ( subunit of PP2A). Collectively, our results indicated that the Mastl-PP2A axis plays a fundamental role in controlling PGCs proliferation. At 13.5 dpc, PGCs started to differentiate into female germ cells by entering prophase I of meiosis. Around the time of birth, the primordial follicles assembly occurs in mammalian ovary. In mice, there exist two classes of primordial follicles: the first wave of primordial follicles develops immediately after birth, whereas the second wave of primordial follicles activated later in adult life. To label and trace the in vivo development and activation of two waves (or classes) of primordial follicles, we used two different mouse models: Foxl2-CreERT2 and Sohlh1-CreERT2. Our study showed that the first wave of primordial follicles get exhausted around three months of age in mice. Additionally, this class of primordial follicles contributes to the onset of puberty and to early fertility in mice. On the other hand, the primordial follicles in the cortical region of the ovary are activated after three months of age of mice contributing to fertility until the end of reproductive life. One of the hallmarks of the activation of primordial follicles is a squamous-cuboidal transition of primordial follicle granulosa cells (pfGCs). However, how pfGCs–oocytes dialog regulate the activation of primordial follicles and determines their developmental fates are still unclear. To study this, we used Foxl2-CreERT2 mouse model to show that for maintenance of quiescence of primordial follicles, inhibition of mammalian target of rapamycin complex 1 (mTORC1) signaling in pfGCs is imperative. For this purpose, we deleted Tsc1 and Rptor from pfGCs, which caused over-activation and suppression of activation of primordial follicles respectively. Furthermore, our study also demonstrated that mTORC1-KITL cascade trigger the awakening of dormant oocytes in primordial follicles as initiated by cellular and molecular changes in pfGCs. Mammalian females are endowed with fixed number of primordial follicles in the ovaries, which are depleted gradually and menopause ensued with the exhaustion of pool of primordial follicles. However, many ovarian pathological conditions lead to premature ovarian failure due to early depletion of follicles pool. Therefore, the existence of OSCs (oogonial stem cells) in ovaries generated excitement in many females suffering from infertility resulting from various reproductions related ailments. This also changed the notion that OSCs might contribute to renewable of follicles as shown by OSCs purified from human and mouse ovaries by DDX4 antibody-based FACS. However, technically the isolation of OSCs by DDX4 antibody-based FACS is in controversy. To verify this claim, we followed the published reported method to isolate OSCs from human and mouse ovaries. Our results showed that isolated DDX4 positive cells from human ovary did not express any DDX4 mRNA as shown by single-cell mRNA sequencing analysis. Additionally, when these DDX4-positve cells were injected into SCID mice, no follicle formation was noted, thus refuting the reported evidence. Similarly, Ddx4-antibody based FACS sorted mouse ovarian cells also displayed an absence of Ddx4 mRNA and unable to generate follicles. Our results claimed that previously reported DDX4 positive ovarian cells purified from human and mouse are neither DDX4 expressing cells nor are they functional OSCs.
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| 8. |
- Risal, Sanjiv, et al.
(författare)
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Prenatal androgen exposure and transgenerational susceptibility to polycystic ovary syndrome
- 2019
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Ingår i: Nature Medicine. - : Nature Publishing Group. - 1078-8956 .- 1546-170X. ; 25:12, s. 1894-1904
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Tidskriftsartikel (refereegranskat)abstract
- How obesity and elevated androgen levels in women with polycystic ovary syndrome (PCOS) affect their offspring is unclear. In a Swedish nationwide register-based cohort and a clinical case-control study from Chile, we found that daughters of mothers with PCOS were more likely to be diagnosed with PCOS. Furthermore, female mice (F0) with PCOS-like traits induced by late-gestation injection of dihydrotestosterone, with and without obesity, produced female F1-F3 offspring with PCOS-like reproductive and metabolic phenotypes. Sequencing of single metaphase II oocytes from F1-F3 offspring revealed common and unique altered gene expression across all generations. Notably, four genes were also differentially expressed in serum samples from daughters in the case-control study and unrelated women with PCOS. Our findings provide evidence of transgenerational effects in female offspring of mothers with PCOS and identify possible candidate genes for the prediction of a PCOS phenotype in future generations.
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| 9. |
- Risal, Sanjiv, et al.
(författare)
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Transgenerational transmission of reproductive and metabolic dysfunction in the male progeny of polycystic ovary syndrome
- 2023
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Ingår i: Cell Reports Medicine. - : Cell Press. - 2666-3791. ; 4:5
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Tidskriftsartikel (refereegranskat)abstract
- The transgenerational maternal effects of polycystic ovary syndrome (PCOS) in female progeny are being revealed. As there is evidence that a male equivalent of PCOS may exists, we ask whether sons born to mothers with PCOS (PCOS-sons) transmit reproductive and metabolic phenotypes to their male progeny. Here, in a register-based cohort and a clinical case-control study, we find that PCOS-sons are more often obese and dyslipidemic. Our prenatal androgenized PCOS-like mouse model with or without diet-induced obesity confirmed that reproductive and metabolic dysfunctions in first-generation (F1) male offspring are passed down to F3. Sequencing of F1–F3 sperm reveals distinct differentially expressed (DE) small non-coding RNAs (sncRNAs) across generations in each lineage. Notably, common targets between transgenerational DEsncRNAs in mouse sperm and in PCOS-sons serum indicate similar effects of maternal hyperandrogenism, strengthening the translational relevance and highlighting a previously underappreciated risk of transmission of reproductive and metabolic dysfunction via the male germline.
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| 10. |
- Stener-Victorin, Elisabet, et al.
(författare)
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Origins and Impact of Psychological Traits in Polycystic Ovary Syndrome
- 2019
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Ingår i: Medical sciences. - : MDPI. - 2076-3271. ; 7:8
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Forskningsöversikt (refereegranskat)abstract
- Women with polycystic ovary syndrome (PCOS) exhibit compromised psychiatric health. Independent of obesity, women with PCOS are more susceptible to have anxiety and depression diagnoses and other neuropsychiatric disorders. During pregnancy women with PCOS display high circulating androgen levels that may cause prenatal androgen exposure affecting the growing fetus and increasing the risk of mood disorders in offspring. Increasing evidence supports a non-genetic, maternal contribution to the development of PCOS and anxiety disorders in the next generation. Prenatal androgenized rodent models reflecting the anxiety-like phenotype of PCOS in the offspring, found evidence for the altered placenta and androgen receptor function in the amygdala, together with changes in the expression of genes associated with emotional regulation and steroid receptors in the amygdala and hippocampus. These findings defined a previously unknown mechanism that may be critical in understanding how maternal androgen excess can increase the risk of developing anxiety disorders in daughters and partly in sons of PCOS mothers. Maternal obesity is another common feature of PCOS causing an unfavorable intrauterine environment which may contribute to psychiatric problems in the offspring. Whether environmental factors such as prenatal androgen exposure and obesity increase the offspring’s susceptibility to develop psychiatric ill-health will be discussed.
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| 11. |
- Tu, Zhaowei, et al.
(författare)
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Speedy A-Cdk2 binding mediates initial telomere-nuclear envelope attachment during meiotic prophase I independent of Cdk2 activation
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 114:3, s. 592-597
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Tidskriftsartikel (refereegranskat)abstract
- Telomere attachment to the nuclear envelope (NE) is a prerequisite for chromosomemovement duringmeiotic prophase I that is required for pairing of homologous chromosomes, synapsis, and homologous recombination. Here we show that Speedy A, a noncanonical activator of cyclin-dependent kinases (Cdks), is specifically localized to telomeres in prophase I male and female germ cells in mice, and plays an essential role in the telomere-NE attachment. Deletion of Spdya in mice disrupts telomere-NE attachment, and this impairs homologous pairing and synapsis and leads to zygotene arrest in male and female germ cells. In addition, we have identified a telomere localization domain on Speedy A covering the distal N terminus and the Cdk2-binding Ringo domain, and this domain is essential for the localization of Speedy A to telomeres. Furthermore, we found that the binding of Cdk2 to Speedy A is indispensable for Cdk2' s localization on telomeres, suggesting that Speedy A and Cdk2 might be the initial components that are recruited to the NE for forming the meiotic telomere complex. However, Speedy A-Cdk2-mediated telomere-NE attachment is independent of Cdk2 activation. Our results thus indicate that Speedy A and Cdk2 might mediate the initial telomere-NE attachment for the efficient assembly of the telomere complex that is essential for meiotic prophase I progression.
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| 12. |
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| 13. |
- Zhang, Hua, et al.
(författare)
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Somatic Cells Initiate Primordial Follicle Activation and Govern the Development of Dormant Oocytes in Mice
- 2014
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 24:21, s. 2501-2508
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Tidskriftsartikel (refereegranskat)abstract
- Background: The majority of oocytes in the mammalian ovary are dormant oocytes that are enclosed in primordial follicles by several somatic cells, which we refer to as primordial follicle granulosa cells (pfGCs). Very little is known, however, about how the pfGCs control the activation of primordial follicles and the developmental fates of dormant oocytes. Results: By targeting molecules in pfGCs with several mutant mouse models, we demonstrate that the somatic pfGCs initiate the activation of primordial follicles and govern the quiescence or awakening of dormant oocytes. Inhibition of mTORC1 signaling in pfGCs prevents the differentiation of pfGCs into granulosa cells, and this arrests the dormant oocytes in their quiescent states, leading to oocyte death. Overactivation of mTORC1 signaling in pfGCs accelerates the differentiation of pfGCs into granulosa cells and causes premature activation of all dormant oocytes and primordial follicles. We further show that pfGCs trigger the awakening of dormant oocytes through KIT ligand (KITL), and we present an essential communication network between the somatic cells and germ cells that is based on signaling between the mTORC1-KITL cascade in pfGCs and KIT-PI3K signaling in oocytes. Conclusions: Our findings provide a relatively complete picture of how mammalian primordial follicles are activated. The microenvironment surrounding primordial follicles can activate mTORC1-KITL signaling in pfGCs, and these cells trigger the awakening of dormant oocytes and complete the process of follicular activation. Such communication between the microenvironment, somatic cells, and germ cells is essential to maintaining the proper reproductive lifespan in mammals.
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| 14. |
- Zheng, Wenjing, et al.
(författare)
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Two classes of ovarian primordial follicles exhibit distinct developmental dynamics and physiological functions.
- 2014
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 23:4, s. 920-928
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Tidskriftsartikel (refereegranskat)abstract
- In the mammalian ovary, progressive activation of primordial follicles serves as the source of fertilizable ova, and disorders in the development of primordial follicles lead to various ovarian diseases. However, very little is known about the developmental dynamics of primordial follicles under physiological conditions, and the fates of distinct populations of primordial follicles also remain unclear. In this study, by generating the Foxl2-CreERT2 and Sohlh1-CreERT2 inducible mouse models, we have specifically labeled and traced the in vivo development of two classes of primordial follicles, the first wave of simultaneously activated follicles after birth and the primordial follicles that are gradually activated in adulthood. Our results show that the first wave of follicles exists in the ovaries for ∼3 months and contributes to the onset of puberty and to early fertility. The primordial follicles at the ovarian cortex gradually replace the first wave of follicles and dominate the ovary after 3 months of age, providing fertility until the end of reproductive life. Moreover, by tracing the time periods needed for primordial follicles to reach various advanced stages in vivo, we were able to determine the exact developmental dynamics of the two classes of primordial follicles. We have now revealed the lifelong developmental dynamics of ovarian primordial follicles under physiological conditions and have clearly shown that two classes of primordial follicles follow distinct, age-dependent developmental paths and play different roles in the mammalian reproductive lifespan.
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