title: Cumulin, an Oocyte-secreted Heterodimer of the Transforming Growth Factor-β Family, Is a Potent Activator of Granulosa Cells and Improves Oocyte Quality.
abstract: Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are oocyte-specific growth factors with central roles in mammalian reproduction, regulating species-specific fecundity, ovarian follicular somatic cell differentiation, and oocyte quality. In the human, GDF9 is produced in a latent form, the mechanism of activation being an open question. Here, we produced a range of recombinant GDF9 and BMP15 variants, examined their in silico and physical interactions and their effects on ovarian granulosa cells (GC) and oocytes. We found that the potent synergistic actions of GDF9 and BMP15 on GC can be attributed to the formation of a heterodimer, which we have termed cumulin. Structural modeling of cumulin revealed a dimerization interface identical to homodimeric GDF9 and BMP15, indicating likely formation of a stable complex. This was confirmed by generation of recombinant heterodimeric complexes of pro/mature domains (pro-cumulin) and covalent mature domains (cumulin). Both pro-cumulin and cumulin exhibited highly potent bioactivity on GC, activating both SMAD2/3 and SMAD1/5/8 signaling pathways and promoting proliferation and expression of a set of genes associated with oocyte-regulated GC differentiation. Cumulin was more potent than pro-cumulin, pro-GDF9, pro-BMP15, or the two combined on GC. However, on cumulus-oocyte complexes, pro-cumulin was more effective than all other growth factors at notably improving oocyte quality as assessed by subsequent day 7 embryo development. Our results support a model of activation for human GDF9 dependent on cumulin formation through heterodimerization with BMP15. Oocyte-secreted cumulin is likely to be a central regulator of fertility in mono-ovular mammals.
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and Mottasis Oy Ltd., 00430 Helsinki, Finland.
authors.forename: David G
authors.initials: DG
authors.lastname: Mottershead
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and the Institute of Agriculture, Department of Biological Production, Tokyo University of Agriculture and Technology, Tokyo 183-0057, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sugimura
authors.affiliation: the Hudson Institute of Medical Research, Clayton, Victoria 3168, Australia.
authors.forename: Sara L
authors.initials: SL
authors.lastname: Al-Musawi
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and the Center of Reproductive Medicine, the Sixth Affiliated Hospital, Sun Yat-sen University, 510655 Guangzhou, China.
authors.forename: Jing-Jie
authors.initials: JJ
authors.lastname: Li
authors.affiliation: the Discipline of Obstetrics & Gynaecology, School of Women's & Children's Health, University of New South Wales, Sydney, New South Wales 2052, Australia, and.
authors.forename: Dulama
authors.initials: D
authors.lastname: Richani
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: White
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and.
authors.forename: Georgia A
authors.initials: GA
authors.lastname: Martin
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Trotta
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and the Australian Research Council Centre of Excellence in Nanoscale BioPhotonics, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Lesley J
authors.initials: LJ
authors.lastname: Ritter
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and.
authors.forename: Junyan
authors.initials: J
authors.lastname: Shi
authors.affiliation: the Department of Plant Physiology and Biophysics, Julius-von-Sachs Institute of the University Wuerzburg, D-97082 Wuerzburg, Germany.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Mueller
authors.affiliation: the Hudson Institute of Medical Research, Clayton, Victoria 3168, Australia.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Harrison
authors.affiliation: From the Robinson Research Institute and Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health and the Discipline of Obstetrics & Gynaecology, School of Women's & Children's Health, University of New South Wales, Sydney, New South Wales 2052, Australia, and r.gilchrist@unsw.edu.au.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gilchrist
mesh_terms: D000818:Animals; D055430:Bone Morphogenetic Protein 15 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006107:Granulosa Cells / Q000166:cytology / Q000378:metabolism*; D055429:Growth Differentiation Factor 9 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C525901:BMP15 protein, human; C525902:Bmp15 protein, mouse; D055430:Bone Morphogenetic Protein 15; C525897:GDF9 protein, human; C525898:Gdf9 protein, mouse; D055429:Growth Differentiation Factor 9; D051785:Smad Proteins
keywords: IVM; SMAD transcription factor; bone morphogenetic protein (BMP); cumulin; cumulus granulosa cell; growth differentiation factor; oocyte quality; protein assembly; protein secretion; transforming growth factor beta (TGF-β)