Foxo3 is a PI3K-dependent molecular switch controlling the initiation of oocyte growth

John, George B.; Gallardo, Teresa; Shirley, Lane; Castrillón, Diego H.

doi:10.1016/j.ydbio.2008.06.017

Cited by 346 publications

(357 citation statements)

References 40 publications

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“…Furthermore, although the EGFR is among the tyrosine kinase receptors that can activate the phosphatidylinositol 3-kinase (PI3K) pathway (Liu et al, 2006), the intracellular signaling pathways activated during ovine primordial follicle activation remain largely uncharacterized and are fundamental to understand the molecular systems responsible for this fundamental aspect of ovarian development and function that influences fertility (John et al, 2008). Some studies have demonstrated that pharmacological manipulation of the PI3K pathway, using PI3K inhibitors such as LY294002 (Granville et al, 2006), could potentially give a better understanding of the function and regulatory mechanisms of this pathway on Anim.…”

Section: Introductionmentioning

confidence: 99%

Blocking the PI3K pathway or the presence of high concentrations of EGF inhibits the spontaneous activation of ovine primordial follicles in vitro

Santos¹,

Santos²,

Menezes³

et al. 2017

Anim Reprod

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The aims of this study were to verify the effects of Epidermal Growth Factor (EGF) on the morphology, primordial follicle activation, growth and proliferation of granulosa cells of ovine follicles cultured in situ, as well as the effect of a PI3K inhibitor on the follicular activation. Ten ovine ovaries were divided into fragments, being one fixed for histological analysis (fresh control). The remaining fragments were cultured for 7 days in control medium (α-MEM + ) alone or supplemented with EGF (1, 10, 50, 100 or 200 ng/mL). Follicles were classified as normal or atretic, as primordial or growing, and the oocyte and follicle diameters were measured. PCNA immunohistochemistry was performed in the fresh control and in treatment that showed the best results for follicular activation. Pharmacologic inhibition of PI3K activity was performed through pretreatment in media added with 50 µM LY294002 for 1 h. The percentage of normal follicles decreased (P < 0.05) after 7 days of culture in all treatments compared to the fresh control. A significant reduction in the percentage of primordial follicles and an increase (P < 0.05) in the growing ones were observed in all treatments compared to fresh control. Furthermore, both the control medium and 1 ng/mL EGF promoted an increase (P < 0.05) in follicular activation compared to other EGF treatments. The PCNA-positive cells in the EGF treatment were higher (P < 0.05) than in fresh control and α-MEM + . Pretreatment of ovarian tissue with PI3K inhibitor significantly inhibited (P < 0.05) α-MEM + -stimulated primordial follicle activation, but had no effect on EGF-stimulated activation (P > 0.05). In conclusion, PI3K pathway mediates the in vitro spontaneous activation of sheep primordial follicles. Moreover, EGF may act indirectly on follicular activation by promoting granulosa cell proliferation at 1 ng/mL, and EGF inhibited follicle activation in concentrations similar or higher than 10 ng/mL.

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Section: Introductionmentioning

confidence: 99%

Blocking the PI3K pathway or the presence of high concentrations of EGF inhibits the spontaneous activation of ovine primordial follicles in vitro

Santos¹,

Santos²,

Menezes³

et al. 2017

Anim Reprod

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show abstract

“…Studies using mutant mice indicated that oocyte-specific deletion of the Phosphatase with TENsin homology deleted in chromosome 10 (PTEN) gene promotes the growth of all primordial follicles in neonatal and adult animals (3)(4)(5). The PTEN gene encodes a phosphatase enzyme that negatively regulates the PI3K-Akt signaling pathway.…”

mentioning

confidence: 99%

“…The PTEN gene encodes a phosphatase enzyme that negatively regulates the PI3K-Akt signaling pathway. Deletion of PTEN in the oocyte increases protein kinase B (Akt) phosphorylation and nuclear export of downstream Foxo3 proteins (4). Indeed, Foxo3 gene deletion also activated all dormant primordial follicles in mice (6).…”

mentioning

confidence: 99%

Activation of dormant ovarian follicles to generate mature eggs

Kawamura

Cheng

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

374

340

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Although multiple follicles are present in mammalian ovaries, most of them remain dormant for years or decades. During reproductive life, some follicles are activated for development. Genetically modified mouse models with oocyte-specific deletion of genes in the PTEN-PI3K-Akt-Foxo3 pathway exhibited premature activation of all dormant follicles. Using an inhibitor of the Phosphatase with TENsin homology deleted in chromosome 10 (PTEN) phosphatase and a PI3K activating peptide, we found that short-term treatment of neonatal mouse ovaries increased nuclear exclusion of Foxo3 in primordial oocytes. After transplantation under kidney capsules of ovariectomized hosts, treated follicles developed to the preovulatory stage with mature eggs displaying normal epigenetic changes of imprinted genes. After in vitro fertilization and embryo transfer, healthy progeny with proven fertility were delivered. Human ovarian cortical fragments from cancer patients were also treated with the PTEN inhibitor. After xeno-transplantation to immune-deficient mice for 6 months, primordial follicles developed to the preovulatory stage with oocytes capable of undergoing nuclear maturation. Major differences between male and female mammals are unlimited number of sperm and paucity of mature oocytes. Thus, short-term in vitro activation of dormant ovarian follicles after stimulation of the PI3K-Akt pathway allows the generation of a large supply of mature female germ cells for future treatment of infertile women with a diminishing ovarian reserve and for cancer patients with cryo-preserved ovaries. Generation of a large number of human oocytes also facilitates future derivation of embryonic stem cells for regenerative medicine.

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“…FoxO3a -/-mice exhibited global activation of primordial follicles and age-dependent infertility (8,40). Oocyte-specific ablation of phosphatase and tensin homolog (a negative regulator of PI3Ks) led to PI3K-induced Akt activation, and thus, phosphorylated FoxO3a, suppressing its activity, and consequently triggering a phenotype in oocytes equivalent to that in mice lacking FoxO3a (41,42). The reduced phosphorylation of FoxO3a observed in the present study would maintain FoxO3a localization in the nuclei, which prevents the activation of follicle development.…”

Section: Discussionmentioning

confidence: 99%

Effect of high-fat diet-induced obesity on the Akt/FoxO/Smad signaling pathway and the follicular development of the mouse ovary

Zhang

Liao

et al. 2016

Molecular Medicine Reports

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Abstract. Obesity has a negative effect on ovarian functions, which is reported to increase the risk of infertility. The mechanism underlying obesity-induced infertility is not yet clear. The present study established a high-fat diet (HFD)-induced obesity mouse model to elucidate the mechanisms underlying the effect of HFD-induced obesity on follicular development in the mouse ovary. The 4-week-old female mice were fed with HFD or normal control (NC) diet for 15 or 20 weeks. Body mass index was used to demonstrate that the mice were obese following HFD treatment. The follicular development of the ovaries from the HFD group mice was retarded in a time-dependent manner, as demonstrated by morphological and histological examination of the ovaries. Further investigation via western blot analysis demonstrated that the activity of the transcription factor, forkhead box O3a (FoxO3a), was increased by HFD through downregulated FoxO3a phosphorylation, which may contribute to the inhibited development of ovarian follicles. To determine the regulatory mechanism of FoxO3 on the follicular development, the expression levels of FoxO3a target protein, Smad1/5/8, were also determined and there was significant decrease in phosphorylated Smad1/5/8 in the ovaries from the HFD group compared with the NC group, indicating that FoxO3a/Smad1/5/8 may be important in the regulation of follicular development. The expression levels of the upstream regulator of FoxO3a, Akt, were also examined and it was demonstrated that Akt phosphorylation was significantly reduced in the HFD group compared with the NC group, indicating that Akt/FoxO3a may be also involved in follicular development. Together, the experiments demonstrated that HFD-induced obesity affected the activity of the Akt/FoxO3a/Smad1/5/8 signaling pathway in a time-dependent manner during the follicular development of the mouse ovary, leading to abnormal follicular development. These findings may provide part of a theoretical basis for the clinical prevention and treatment of obesity-associated female infertility.

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Foxo3 is a PI3K-dependent molecular switch controlling the initiation of oocyte growth

Cited by 346 publications

References 40 publications

Blocking the PI3K pathway or the presence of high concentrations of EGF inhibits the spontaneous activation of ovine primordial follicles in vitro

Blocking the PI3K pathway or the presence of high concentrations of EGF inhibits the spontaneous activation of ovine primordial follicles in vitro

Activation of dormant ovarian follicles to generate mature eggs

Effect of high-fat diet-induced obesity on the Akt/FoxO/Smad signaling pathway and the follicular development of the mouse ovary

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