Virtual Presentation SRB Virtual Awards 2020

Engineering ovarian TGF-β ligands to improve female fertility outcomes (#17)

William A Stocker 1 2 , Kelly L Walton 1 , Dulama Richani 3 , Robert B Gilchrist 3 , Craig A Harrison 1
  1. Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
  2. Department of Chemistry and Biotechnology, Swinburne University of Technology, Hawthorn, Victoria, Australia
  3. Discipline of Obstetrics & Gynaecology, School of Women’s & Children’s Health, University of New South Wales, Sydney, NSW, Australia

Ovarian growth factors including anti-Müllerian hormone (AMH), growth differentiation factor-9 (GDF9) and bone morphogenetic protein-15 (BMP15) play central roles during folliculogenesis. AMH is secreted by the granulosa cells of small growing follicles, and acts via the SMAD1/5/8 signalling pathway to prevent primordial follicle activation. Oocyte-secreted factors GDF9 and BMP15 act via distinct SMAD signalling pathways to drive acquisition of the cumulus cell phenotype in the granulosa cells located immediately around the oocyte. The ability of these growth factors to influence ovulation rates and oocyte developmental competence makes them attractive therapeutic targets for improving female fertility. Here, I describe how we are using our detailed structural knowledge of these growth factors to guide the generation of potent GDF9/BMP15 and AMH therapies. First, we generated more potent GDF9 forms by targeted substitution of receptor-binding sites on GDF9. Site-directed mutagenesis was used to introduce different combinations of BMP15 residues into GDF9, with the aim of enhancing the ability of GDF9 to improve oocyte developmental competence via activation of the SMAD2/3 pathway. Using this approach, we engineered “Super-GDF9” which proved to be >1000-fold more potent than wild-type GDF9 in SMAD2/3-responsive luciferase bioassays in COV434 human granulosa cells. In vitro maturation (IVM) of immature mouse cumulus-oocyte complexes in the presence of Super-GDF9 increased blastocyst formation by 5 days post-fertilisation (p < 0.05), supporting that Super-GDF9 is an effective agent for improving oocyte developmental competence. I have since adopted this mutagenic approach to develop potent AMH therapies, which are >5-fold more bioactive in AMH-responsive in vitro assays. It is anticipated that our Super-AMH therapy will protect the ovary from age- and chemotherapy-related insults. Our patented “super growth factors” have strong potential to improve female fertility outcomes.