Identifying sperm-egg receptor pairs essential for mammalian fertilization to select new targets for fertility treatment and contraception.

Lead Research Organisation: Wellcome Sanger Institute
Department Name: Wellcome Trust Genome Campus


In humans and many other organisms, new life starts when a sperm and an egg recognise each other and permit the fusion of the membranes that surround them to form an embryo in a process we call fertilization. The way in which sperm and egg are able to recognise each other is very likely to involve a pair of recognition molecules: one displayed on the surface of the sperm and the other on the egg's surface that specifically bind to each other and finally enable the sperm and egg to fuse and create a genetically distinct embryo. Despite the fact that fertilization is a fundamental biological process our current molecular understanding is remarkably poor, particularly in mammals. This can be partly explained in humans due to the ethical issues involved, but there are also significant technical challenges that make working with sperm and eggs and the molecules on their surface in the laboratory very difficult. For example, eggs are a very rare cell type in mammals (humans usually release just a single egg each fertility cycle and mice less than ten) limiting the amount of biological material available. In addition, the interactions between cell surface recognition molecules are known to be extremely weak (often having half-lives of just fractions of a second), requiring the use of specialised approaches to detect them. The Cell Surface Signalling Laboratory at the Sanger Institute specialises in identifying these transient receptor interactions and we have developed a set of tools and techniques to circumvent these difficulties. We have recently shown, by identifying the first essential sperm-egg receptor pair (see Bianchi et al. Nature 2014 v508 p483), that applying these techniques can make important discoveries in this field. In this grant application, we propose to apply the same techniques in a systematic manner to identify additional sperm-egg recognition molecules but also begin to apply these findings to reveal new targets for fertility treatment and contraceptives.
Identifying the cell surface receptors that are important for fertilization could have significant implications for the development of novel contraceptives and fertility treatments. For example, identifying which receptors are required for fertilization and how they interact could provide the starting point to develop new drugs that specifically block the interaction and therefore be used as a contraceptive. Perhaps surprisingly, no new contraceptives have been developed for over 40 years. The rapidly expanding human population (currently over 7 billion and predicted to reach 10 billion by 2050) has raised concerns globally that the limited resources on the planet will not sustain such a continued expansion. A drug that blocks the interaction between sperm and egg could conceivably be taken by both men and women and be effective for just a short period of time (a few hours to several days). It is also likely that the receptor interaction will be used by other animal species and so could be used to design methods to effectively control animal populations in a humane way.
Finally, our previous work has shown that interactions between sperm and egg receptors can be essential for fertilization and so our planned research may reveal the identity of new infertility genes. Infertility is a growing problem, particularly in Western countries where the average age of couples having their first child has increased in recent years. By discovering new infertility genes, this research could open up the possibility of offering simple and inexpensive genetic screening tests to infertile couples that may guide their fertility treatment and save the expense and inconvenience of failed rounds of fertility treatment. In addition, by providing a molecular explanation for infertility, this may suggest methods of clinical intervention to help couples conceive.

Technical Summary

Fertilization involves the cellular recognition and subsequent fusion of haploid gametes to create a diploid zygote. We know little about the molecular events involved in mammalian fertilization, including the identity of the sperm-egg receptor pairs involved. Largely, this is due to technical challenges due to the rarity of eggs and because the interactions between extracellular receptors are weak requiring specialised techniques to identify them. We have developed methods based on creating highly avid binding probes to detect weak extracellular interactions and have applied them to the problem of sperm-egg recognition and identified the first sperm-egg receptor pair that is essential for mammalian fertilization (Bianchi et al. Nature 2014 v508 p483). There is good evidence to suggest that there are additional important sperm-egg recognition molecules and this grant application outlines how we intend to apply the same approach to identify additional sperm-egg receptor pairs that could be useful for developing novel contraceptives and fertility treatments.
We will use a library of ~40 highly avid recombinant proteins that represents the secretome and cell surface receptor repertoire of the mouse spermatozoon and systematically test them for interactions with the oolemma and zona pellucida. For those sperm probes that exhibit positive staining with the egg, we will identify the molecular nature of the egg receptor using expression cloning (an approach we have successfully used in the past) and other receptor matching techniques that we have developed in the laboratory. The function of any identified interactions will be determined using transgenic mice.

Planned Impact

The successful conclusion of this research would have a range of beneficiaries.
1) Academics: There would be a wide range of immediate academic beneficiaries of this work ranging from scientists who are specifically interested in the molecular mechanism of fertilization to those interested in other biological systems that involve membrane fusion such as the development and function of skeletal muscle, placenta and osteoclasts.
2) Commercial sector: The main impact that this research could have on society would be to identify a starting point for the development of novel contraceptives. No new contraceptives have been developed since the development of "the pill", which works by hormonal control, over 40 years ago. While this method is effective, many women are unable or recommended not to use it for medical or religious reasons. The identification of a new target/s required for fertilization could therefore benefit the pharmaceutical industry in the development of novel contraceptives and improve the lives of the recipients of these novel drugs. Naturally, because of the long development time and necessary safety testing for new drugs, these benefits would not be realised for 10 to 15 years.
3) Health workers, particularly those working in fertility clinics: The identification of receptor-ligand pairs involved in mammalian fertilization would potentially provide an explanation for couples who are unable to conceive naturally, and may lead to the development of novel fertility treatments.
4) Governments and wider society: If this research led to the development of new contraceptives then the ultimate beneficiaries of this research could include large sections of society. Related to this, a major issue facing the world is overpopulation. Improvements in healthcare systems have meant that people are now living much longer, so that today, there are over 7 billion humans on the planet and some forecasts predict that this will rise to 10 billion by the year 2050. Such a vast and rapidly increasing human population has already led governments to consider how they can maintain and improve future living standards within the confines of the planet's finite resources. Scientists will have to provide solutions to these problems and having new targets that could result in novel contraceptives would be an important starting point.
5) Veterinary science: Veterinary science may also benefit from this research since it is likely that contraceptives for other animal species could also be developed. This would be useful in controlling animal populations in an ethically agreeable manner. For example, based on our findings, one might be able to develop a contraceptive vaccine that could easily and irreversibly sterilise animals to control their populations within certain geographical areas where they are considered pests (such as badgers, elephants, deer, horses etc..) or for animal welfare (e.g. pets, zoo animals) without the need for surgical neutering. Again this may take up to 10 years to develop.
6) Scientific training: This grant would involve the employment of both a postdoctoral scientist and a research assistant. By joining the Cell Surface Signalling Laboratory at the Sanger Institute, they will be trained in a range of specialist biochemical techniques that are specifically designed to identify low affinity extracellular interactions. The product of this training would be an individual who would be ideally placed to apply these novel techniques to wider problems of gamete recognition to gain a more complete understanding of the molecular basis of fertilization.


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Description Functional dissection of Tmem95: a sperm cell surface protein essential for mammalian fertilization
Amount £437,926 (GBP)
Funding ID BB/T006390/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 03/2020 
End 03/2023
Description Sanger Institute Translation fund
Amount £16,000 (GBP)
Organisation The Wellcome Trust Sanger Institute 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2017 
Title S. mansoni infection challenge improvement 
Description We have developed apparatus to improve the welfare of animals (mice) for percutaneous S. mansoni infections. 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Year Produced 2016 
Provided To Others? Yes  
Impact This method has improved the welfare of animals for percutaneous infection by S. mansonsi. The apparatus has already been used by other teams at the Institute and our named veterinary surgeon has passed the details onto other groups nationally. The details of the apparatus will be published. 
Description Alex McCarthy 
Organisation University College London
Country United Kingdom 
Sector Academic/University 
PI Contribution We have provided proteins to investigate a sperm-leukocyte interaction
Collaborator Contribution They have provided cell lines and experimental data to support the research.
Impact Data to support the role of the sperm-leukocyte interaction
Start Year 2022
Description Bill and Melinda Gates with Jeffrey Lee 
Organisation University of Toronto
Country Canada 
Sector Academic/University 
PI Contribution We will be using our resource of human receptors to identify host receptors for sperm ligands
Collaborator Contribution They have obtained funding from BMGF to develop non hormonal contraceptives and need to collaborate to accesss our resources to identify hoat oocyte receptors.
Impact Funding
Start Year 2023
Description Biophysics of fusion 
Organisation University of California, Los Angeles (UCLA)
Department Semel Institute for Neuroscience and Human Behavior
Country United States 
Sector Academic/University 
PI Contribution We have provided recombinant proteins for biophysical studies.
Collaborator Contribution The have used our recombinant proteins to explore the biophysics of membrane fusion using biophysical techniques such as SAXS.
Impact A draft manuscript has been prepared.
Start Year 2015
Description Identification of a receptor for TMEM95 
Organisation Genentech, Inc
Country United States 
Sector Private 
PI Contribution We provided a recombinant protein for systematic receptor screening
Collaborator Contribution The screened the protein we provided against their collection of receptor ectodomains
Impact Candidate receptors are being evaluated
Start Year 2018
Description Juno sheedding in mice 
Organisation Osaka University
Country Japan 
Sector Academic/University 
PI Contribution We identified an egg receptor that we beleive is shed from the egg surface and controbute to the polyspermy block and we would like to demonstrate this using a mouse transgenic model. The access to mouse transgenesis is poor in the UK and so we have collaborated with Masahito Ikawa in Japan for these experiments.
Collaborator Contribution Our collaborators will create a transgenic line of mouse that is unable to shed the egg receptor we are interested in and we will explore its role in the membrane block to polyspermy.
Impact Meetings which we hope will lead to a publication.
Start Year 2021
Description Roger Sturmey 
Organisation Hull York Medical School
Country United Kingdom 
Sector Academic/University 
PI Contribution We have identified a new interaction that invovles sperm - leukocyte biology
Collaborator Contribution Our collaborators have access to human eggs
Impact Preparations for publication
Start Year 2023
Description Structural work 
Organisation Karolinska Institute
Country Sweden 
Sector Academic/University 
PI Contribution We provided recombinant proteins and mapped protein interaction sites to complement structural data.
Collaborator Contribution They solved the structure of the egg receptor, Juno and also sperm ligand Izumo1.
Impact Divergent evolution of vitamin B9 binding underlies Juno-mediated adhesion of mammalian gametes. Han L, Nishimura K, Sadat Al Hosseini H, Bianchi E, Wright GJ, Jovine L. Curr Biol. 2016 Feb 8;26(3):R100-1. doi: 10.1016/j.cub.2015.12.034. PMID: 26859261 The structure of sperm Izumo1 reveals unexpected similarities with Plasmodium invasion proteins. Nishimura K, Han L, Bianchi E, Wright GJ, de Sanctis D, Jovine L. Curr Biol. 2016 Jul 25;26(14):R661-2. doi: 10.1016/j.cub.2016.06.028. PMID: 27374339
Start Year 2014
Description Targeting sperm-egg interaction to reduce polyspermy in pig IVF 
Organisation University of Murcia, Spain
Country Spain 
Sector Academic/University 
PI Contribution We have provided proteins and intellectual contributions to this project and led a successful application for additional funding.
Collaborator Contribution Our partners have provided porcine tissues for the project and will be involved in testing antibodies for reducing polyspermy in pig IVF.
Impact The collaboration is multi-disciplinary. We contribute expertise in recombinant protein production, monoclonal antibody selection and protein interaction analysis. Our collaborators contribute expertise in pig IVF.
Start Year 2017
Description Zebrafish fertility 
Organisation Research Institute of Molecular Pathology (IMP)
Country Austria 
Sector Academic/University 
PI Contribution We have provided protein expression and extracellular receptor-ligand expertise to this collaboration. Our contribution will be to try and determine a molecular mechanism for male infertility.
Collaborator Contribution They have identified and validated new sperm fertility factors.
Impact Regular meetings and discussions hopfully leading to publications.
Start Year 2021
Description identification of receptors for cell surface receptors important for fertility 
Organisation Genetech, Inc
Country United States 
Sector Private 
PI Contribution We have provided recombinant proteins for systematic receptor screens on the Genentech platforms.
Collaborator Contribution Genentech provided access to their large scale receptor interaction screening platforms and screened two recombinant proteins supplied by us. The have a protein library of over 2000 receptor ectodomains and 3,500 expression plasmids.
Impact The result of the interaction screens were several candidate interactions which we are now following up.
Start Year 2015
Description French fertility TV documentary 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact We have been asked to contribute to a French TV documentary about fertility. This will include a short interview aimed at the public.
Year(s) Of Engagement Activity 2017
Description Teaching on M.Sc course in Spain 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Invited to attend a MSc course in Murcia Spain. I will give a talk and contribute to the course over 2 days.
Year(s) Of Engagement Activity 2017
Description Wellcome Trust Advanced Course 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact A co-organiser on a Wellcome Trust Advanced course entitled "Protein interactions and Networks". This course last for 10 days and involves intensive training of a small group of 18 postgraduate scientists in protein interaction techniques and analysis.
Year(s) Of Engagement Activity 2017
Description Wellcome Trust Advanced course 2017 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Co-Organiser of a Wellcome Trust Advanced Course on protein-protein interactions.
Year(s) Of Engagement Activity 2017