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https://hdl.handle.net/2440/23191
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Type: | Journal article |
Title: | Molecular basis of oocyte-paracrine signalling that promotes granulosa cell proliferation |
Author: | Gilchrist, R. Ritter, L. Myllymaa, S. Kaivo-Oja, N. Dragovic, R. Hickey, T. Ritvos, O. Mottershead, D. |
Citation: | Journal of Cell Science, 2006; 119(18):3811-3821 |
Publisher: | Company of Biologists Ltd |
Issue Date: | 2006 |
ISSN: | 0021-9533 1477-9137 |
Statement of Responsibility: | Robert B. Gilchrist, Lesley J. Ritter, Samu Myllymaa, Noora Kaivo-Oja, Rebecca A. Dragovic, Theresa E. Hickey, Olli Ritvos and David G. Mottershead |
Abstract: | Oocytes regulate follicle growth by secreting paracrine growth factors that act on neighbouring granulosa cells (GCs). Those factors identified to date are mainly members of the transforming growth factor-ß (TGFß) superfamily, but little is known about which specific receptor/signalling system(s) they employ. This study was conducted to determine the requisite pathways utilised by oocytes to promote GC proliferation. We used an established oocyte-secreted mitogen bioassay, where denuded mouse oocytes are co-cultured with mural GCs. Oocytes, growth differentiation factor-9 (GDF9), TGFß1 and activin-A all promoted GC DNA synthesis, but bone-morphogenetic protein 6 (BMP6) did not. Subsequently, we tested the capacity of various TGFß superfamily receptor ectodomains (ECD) to neutralise oocyte- or specific growth factor-stimulated GC proliferation. The BMP type-II receptor (BMPR-II) ECD antagonised oocyte and GDF9 bioactivity dose-dependently, but had no or minimal effect on TGFß1 and activin-A bioactivity, demonstrating its specificity. The TGFßR-II, activinR-IIA and activinR-IIB ECDs all failed to neutralise oocyte- or GDF9-stimulated GC DNA synthesis, whereas they did antagonise the activity of their respective native ligands. An activin receptor-like kinase (ALK) 4/5/7 inhibitor, SB431542, also antagonised both oocyte and GDF9 bioactivity in a dose-dependent manner. Consistent with these findings, oocytes, GDF9 and TGFß1 all activated SMAD2/3 reporter constructs in transfected GC, and led to phosphorylation of SMAD2 proteins in treated cells. Surprisingly, oocytes did not activate the SMAD1/5/8 pathway in transfected GCs although exogenous BMP6 did. This study indicates that oocyte paracrine factors primarily utilise a similar signalling pathway first identified for GDF9 that employs an unusual combination of TGFß superfamily receptors, the BMPR-II and a SMAD2/3 stimulatory ALK (4, 5 or 7), for transmitting their mitogenic actions in GC. This cell-signalling pathway may also have relevance in the hypothalamic-pituitary axis and in germ-somatic cell interactions in the testis. |
Keywords: | Oocyte-paracrine factors Granulosa cell signalling Growth-differentiation factor 9 Bone morphogenetic protein receptor-II Activin-receptor like kinase SMADs Oocyte mitogen |
Description: | Copyright © 2006 Company of Biologists |
DOI: | 10.1242/jcs.03105 |
Published version: | http://jcs.biologists.org/cgi/content/abstract/119/18/3811 |
Appears in Collections: | Aurora harvest 6 Obstetrics and Gynaecology publications |
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