| 1. |
- Jagarlamudi, Krishna, 1980-, et al.
(författare)
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Oocyte-specific deletion of Pten in mice reveals a stage-specific function of PTEN/PI3K signaling in oocytes in controlling follicular activation
- 2009
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:7, s. e6186-
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Tidskriftsartikel (refereegranskat)abstract
- Immature ovarian primordial follicles are essential for maintenance of the reproductive lifespan of female mammals. Recently, it was found that overactivation of the phosphatidylinositol 3-kinase (PI3K) signaling in oocytes of primordial follicles by an oocyte-specific deletion of Pten (phosphatase and tensin homolog deleted on chromosome ten), the gene encoding PI3K negative regulator PTEN, results in premature activation of the entire pool of primordial follicles, indicating that activation of the PI3K pathway in oocytes is important for control of follicular activation. To investigate whether PI3K signaling in oocytes of primary and further developed follicles also plays a role at later stages in follicular development and ovulation, we conditionally deleted the Pten gene from oocytes of primary and further developed follicles by using transgenic mice expressing zona pellucida 3 (Zp3) promoter-mediated Cre recombinase. Our results show that Pten was efficiently deleted from oocytes of primary and further developed follicles, as indicated by the elevated phosphorylation of the major PI3K downstream component Akt. However, follicular development was not altered and oocyte maturation was also normal, which led to normal fertility with unaltered litter size in the mutant mice. Our data indicate that properly controlled PTEN/PI3K-Akt signaling in oocytes is essential for control of the development of primordial follicles whereas overactivation of PI3K signaling in oocytes does not appear to affect the development of growing follicles. This suggests that there is a stage-specific function of PTEN/PI3K signaling in mouse oocytes that controls follicular activation.
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| 2. |
- Liu, Lian, et al.
(författare)
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Phosphorylation and inactivation of glycogen synthase kinase-3 by soluble kit ligand in mouse oocytes during early follicular development.
- 2007
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Ingår i: Journal of Molecular Endocrinology. - : Bioscientifica. - 0952-5041 .- 1479-6813. ; 38:1-2, s. 137-146
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Tidskriftsartikel (refereegranskat)abstract
- Communication between mammalian oocytes and their surrounding granulosa cells through the Kit-Kit ligand (KL, or stem cell factor, SCF) system has been shown to be crucial for follicular development. Our previous studies (Reddy et al. 2005, Liu et al. 2006) have indicated that the intra-oocyte KL-Kit-PI3 kinase (PI3K)-Akt-Foxo3a cascade may play an important role in follicular activation and early development. In the present study, using in situ hybridization and in vitro culture of growing oocytes from 8-day-old postnatal mice, we have demonstrated that another Akt substrate, glycogen synthase kinase-3 (GSK-3), is expressed in growing oocytes. Also, treatment of cultured mouse oocytes with soluble KL not only leads to increased Akt kinase activity in the oocytes, which can phosphorylate recombinant GSK-3 in vitro, but also leads to phosphorylation of oocyte GSK-3alpha and GSK-3beta, which can result in the inactivation of GSK-3 function in oocytes. In addition, we have shown that the regulation of GSK-3alpha and GSK-3beta in cultured oocytes by soluble KL is accomplished through PI3K, since the PI3K-specific inhibitor LY294002 completely abolished the KL-induced phosphorylation of GSK-3alpha and GSK-3beta. Moreover, blockage of the Kit signaling pathway by a Kit function-blocking antibody, ACK2, resulted in reduced phosphorylation of GSK-3. Taken together, our data suggest that the cascade from granulosa cell-derived KL to Kit-PI3K-Akt-GSK-3 in oocytes may take part in regulation of oocyte growth and early ovarian follicular development.
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| 3. |
- Ottander, Ulrika, et al.
(författare)
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A putative stimulatory role of progesterone acting via progesterone receptors in the steroidogenic cells of the human corpus luteum
- 2000
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Ingår i: Biology of Reproduction. - : Oxford University Press. - 0006-3363 .- 1529-7268. ; 62:3, s. 655-663
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Tidskriftsartikel (refereegranskat)abstract
- To further explore the proposed auto-regulatory role of progesterone action in the human corpus luteum (CL), the expression and functional roles of progesterone receptor (PR) isoforms A and B during the luteal phase (LP) of the menstrual cycle were investigated. A total of 27 otherwise healthy patients previously scheduled for surgery were recruited after informed consent. An LH rise was detected, and CL were grouped according to age (Days 2-5 post-LH-rise, early LP; Days 6-10, mid LP; Days 11-14, late LP). Using a semiquantitative reverse transcription-polymerase chain reaction assay, the PR-B mRNA levels, which were 100- to 1000-fold lower than PR-A/B mRNA, were 46% lower (P < 0.05, n = 24) in mid LP, compared to early and late LP. CL tissue levels of progesterone and PR-A/B protein levels were inversely correlated to increasing CL age; i.e., significantly reduced levels were observed in the late LP (r(2) = 0.34, P < 0.01, n = 23). Expression of PR-A/B mRNA as well as PR-A/B protein were detected by in situ hybridization and immunohistochemistry, respectively. Both methods revealed a clear and distinct localization to cells in the steroidogenic layer of the CL. Freshly obtained mid-luteal CL cells were cultured in vitro, and media were analyzed for progesterone concentrations after treatment by incremental doses of hCG and the stable PR antagonist mifepristone, alone or in combination. Mifepristone did not per se alter progesterone synthesis, but when it was added in conjunction with hCG, a dose-related inhibitory response was seen, with a maximal 47% reduction in progesterone output at a 10 microM addition (P < 0.05, n = 3). Collectively, these data implicate a stimulatory role of progesterone receptor-mediated action in the steroidogenic cells of the human CL, which may serve as an important pathway for maintaining functional homeostasis during early pregnancy.
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| 4. |
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| 5. |
- Reddy, Pradeep, et al.
(författare)
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Formation of E-cadherin-mediated cell-cell adhesion activates AKT and mitogen activated protein kinase via phosphatidylinositol 3 kinase and ligand-independent activation of epidermal growth factor receptor in ovarian cancer cells
- 2005
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Ingår i: Mol Endocrinol. - : The Endocrine Society. - 0888-8809. ; 19:10, s. 2564-2578
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Tidskriftsartikel (refereegranskat)abstract
- E-cadherin is a well characterized adhesion molecule that plays a major role in epithelial cell adhesion. Based on findings that expression of E-cadherin is frequently lost in human epithelial cancers, it has been implicated as a tumor suppressor in carcinogenesis of most human epithelial cancers. However, in ovarian cancer development, our data from the current study showed that E-cadherin expression is uniquely elevated in 86.5% of benign, borderline, and malignant ovarian carcinomas irrespective of the degree of differentiation, whereas normal ovarian samples do not express E-cadherin. Thus, we hypothesize that E-cadherin may play a distinct role in the development of ovarian epithelial cancers. Using an E-cadherin-expressing ovarian cancer cell line OVCAR-3, we have demonstrated for the first time that the establishment of E-cadherin mediated cell-cell adhesions leads to the activation of Akt and MAPK. Akt activation is mediated through the activation of phosphatidylinositol 3 kinase, and both Akt and MAPK activation are mediated by an E-cadherin adhesion-induced ligand-independent activation of epidermal growth factor receptor. We have also demonstrated that suppression of E-cadherin function leads to retarded cell proliferation and reduced viability. We therefore suggest that the concurrent formation of E-cadherin adhesion and activation of downstream proliferation signals may enhance the proliferation and survival of ovarian cancer cells. Our data partly explain why E-cadherin is always expressed during ovarian tumor development and progression.
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