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Loss of gremlin delays primordial follicle assembly but does not affect female fertility in mice.

ABSTRACT: The transforming growth factor beta (TGFB) protein family is renowned for its diverse roles in developmental biology including reproduction. Gremlin is a member of the differential screening-selected gene aberrative in neuroblastoma (DAN)/cerberus family of bone morphogenetic protein (BMP) antagonists. Recent studies on gremlin focus on its involvement in embryonic skeletal, lung, and kidney development. To define the role of gremlin (Grem1) in female reproduction, we analyzed postnatal folliculogenesis using global and conditional knockout (cKO) mice for gremlin. Grem1(-/-) mice die within 48 h after birth, and ovaries collected from neonatal Grem1(-/-) mice demonstrated reduced oocyte numbers and delayed primordial follicle development. Transplanting Grem1(-/-) neonatal ovaries showed that folliculogenesis proceeded to large antral follicle stage, but Grem1(-/-) ovaries contained corpora lutea-like structures not found in control-transplanted ovaries. However, Grem1 cKO mice had comparable fertility to control mice. These data suggest that gremlin plays a previously uncharacterized role in the regulation of oocyte numbers and the timing of primordial follicle development, but either it is not required for later folliculogenesis or its loss is possibly compensated by other BMP antagonists.

SUBMITTER: Myers M

PROVIDER: S-EPMC3223251 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Loss of gremlin delays primordial follicle assembly but does not affect female fertility in mice.

Myers Michelle M Tripurani Swamy K SK Middlebrook Brooke B Economides Aris N AN Canalis Ernesto E Pangas Stephanie A SA

Biology of reproduction 20110810 6

The transforming growth factor beta (TGFB) protein family is renowned for its diverse roles in developmental biology including reproduction. Gremlin is a member of the differential screening-selected gene aberrative in neuroblastoma (DAN)/cerberus family of bone morphogenetic protein (BMP) antagonists. Recent studies on gremlin focus on its involvement in embryonic skeletal, lung, and kidney development. To define the role of gremlin (Grem1) in female reproduction, we analyzed postnatal follicul ...[more]

PMID: 21832168

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Project description:BackgroundChemotherapy improves the survival rates of patients with various cancers but often causes some adverse effects, including ovarian damage, characterised by a decrease in primordial follicle stockpiles. Recent studies have revealed that chemotherapy may stimulate the PI3K signalling pathway, thereby resulting in accelerated primordial follicle activation and a decreased ovarian reserve. Quercetin is an inhibitor of the PI3K pathway; however, its protective effects against chemotherapy-induced follicle loss in mice have not been established. In this study, the effects of quercetin in a mouse model of cyclophosphamide-induced ovarian dysfunction were investigated.MethodsC57BL/6 female mice were used for the study. Paraffin sections of mouse ovaries (n = 30 mice) were stained with haematoxylin and eosin for differential follicle counts. Apoptosis (n = 5 mice per group) was evaluated by TUNEL assay. Immunohistochemical staining for ki67 and Foxo3a (n = 5 mice per group) was performed to evaluate the activation of primordial follicles. The role of the PI3K signalling pathway in the ovaries (n = 45 mice) was assessed by western blotting.ResultsQuercetin attenuated the cyclophosphamide-induced reduction in dormant primordial follicles. Analysis of the PI3K/Akt/Foxo3a pathway showed that quercetin decreased the phosphorylation of proteins that stimulate follicle activation in cyclophosphamide-induced ovaries. Furthermore, quercetin prevented cyclophosphamide-induced apoptosis in early growing follicles and early antral follicles, maintained anti-Müllerian hormone levels secreted by these follicles, and preserved the quiescence of the primordial follicle pool, as determined by intranuclear Foxo3a staining.ConclusionsQuercetin attenuates cyclophosphamide-induced follicle loss by preventing the phosphorylation of PI3K/Akt/Foxo3a pathway members and maintaining the anti-Müllerian hormone level through reduced apoptosis in growing follicles. Accordingly, quercetin is expected to improve fertility preservation and the prevention of endocrine-related side effects of chemotherapy.

Project description:Primordial follicle assembly is the process by which ovarian primordial follicles are formed. During follicle assembly oocyte nests break down and a layer of pre-granulosa cells surrounds individual oocytes to form primordial follicles. The pool of primordial follicles formed is the source of oocytes for ovulation during a femaleM-bM-^@M-^Ys reproductive life. Complex networks of cellular signaling and gene expression are essential for any biological process. A systems biology experimental approach provides a global view of these gene relationships in a particular developmental process. The current study utilized a systems approach to detect all genes that are differentially expressed in response to seven different growth factor and hormone treatments known to influence primordial follicle assembly in a neonatal rat ovary culture system. One novel growth factor, basic fibroblast growth factor (FGF2), was experimentally determined to inhibit follicle assembly. The different growth factor and hormone treatments were all found to affect the same physiological pathways, but each treatment affected a unique set of differentially expressed genes (signature gene set). A gene bionetwork analysis identified gene modules of coordinately expressed interconnected genes and it was found that different gene modules appear to accomplish distinct tasks during primordial follicle assembly. Unique gene networks were identified for a number of the modules and signature gene sets. Predictions of physiological pathways important to follicle assembly were validated using ovary culture experiments in which ERK1/2 (MAPK1) activity was increased. A number of the highly interconnected genes in these gene networks have previously been linked to primary ovarian insufficiency (POI) and polycystic ovarian disease syndrome (PCOS). Observations have identified novel factors and gene networks that regulate primordial follicle assembly. This systems approach has helped elucidate the molecular control of primordial follicle assembly and provided potential therapeutic targets for the treatment of ovarian disease. We used microarrays to determine genes expressed differentially between control and P0 ovaries treated with 7 growth factors: AMH, CTGF, estradiol (E2), Activin-a, FGF2, progesterone (P4), and TNFa. RNA samples from 7 control samples are compared to 3 growth factor treated ovary samples for each AMH (human Anti-MM-CM-<lerian hormone), CTGF (connective tissue growth factor ), estradiol (E2), TNF (tumor necrosis factor ), FGF2 (fibroblast growth factor 2), Inhba (inhibin, beta A), and 2 samples for progesterone (P4).

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Loss of gremlin delays primordial follicle assembly but does not affect female fertility in mice.

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Loss of gremlin delays primordial follicle assembly but does not affect female fertility in mice.

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