Co-ordinating the transition from egg to embryo in mammals

Lead Research Organisation: University College London
Department Name: Neuroscience Physiology and Pharmacology

Abstract

The egg drives the process of early embryo development. As such understanding how we produce a healthy egg is of fundamental importance to reproductive success. The trigger that switches the egg along the path of embryo development is an explosive release of Ca2+ that is started when the sperm fuses with the egg. This Ca2+ signal needs to co-ordinate a series of events, including exit from an arrested state, an increase in metabolism and the release of granules from the egg that serve to prevent extra sperm fertilizing the egg. In this research proposal we will use fluorescent light to follow these processes in single living mouse eggs and embryos. This research will provide an understanding of how the egg turns into an embryo and what happens when this process goes wrong. We will communicate this research through scientific literature but also through the respective PR departments at UCL and the MRC.

Technical Summary

The transition from egg to embryo in mammals is stimulated by fertilization. The trigger supplied by the fertilizing sperm is a series of Ca2+ oscillations that initially lasts for 4 hours and then continues during the first mitotic division. The dynamics of the Ca2+ oscillations is known to have a wide-ranging impact on the development of the embryo, ranging from, successful resumption of meiosis, to exocytosis of cortical granules for the prevention of polyspermy, to longer term consequences on post-implantation development. Recent advances have explained the mechanism of generation of sperm triggered Ca2+ oscillations but how the oocyte prepares for the generation of Ca2+ oscillations and how the Ca2+ transients are decoded by molecular Ca2+ sensors in the egg is not known. To tackle these questions we will investigate:
1. the mechanisms and functional consequences of the reorganization of the endoplasmic reticulum that takes place during oocyte maturation;
2. the role of PKC in downstream signalling of Ca2+ in the regulation of Ca2+ influx, cortical granule exocytosis and cell cycle resumption;
3. the role Ca2+ signalling in stimulating the activity of mitochondria at the start of development;
4. the roles of Ca2+ signalling and PKC during the first differentiation events in the mammalian embryo.
To investigate these questions we will perform live cell fluorescence imaging on mouse oocytes and embryos as they undergo maturation, fertilization, cell division and differentiation. We will monitor cytosolic and mitochondrial Ca2+ and GFP fusion proteins using conventional, confocal and 2-photon microscopy. Imaging will be combined with morpholino and RNAi approaches to investigate the roles of specific signalling molecules in these events. The increased understanding of the physiology of the oocyte and embryo will be used to identify new sensitive assays of developmental potential of the mammalian oocyte and embryo.

Publications

10 25 50
 
Description EMBO Fellowship
Amount £70,000 (GBP)
Organisation European Molecular Biology Organisation 
Sector Charity/Non Profit
Country Germany
Start 01/2008 
End 12/2010
 
Description cell cycle control in oocytes 
Organisation University College London
Department Institute for Women's Health
Country United Kingdom 
Sector Academic/University 
PI Contribution We provided ongoing input into experimental design and analysis of data and contributed to writing the paper.
Collaborator Contribution Provided access to IVF lab and human oocytes
Impact It has resulted in one paper published in Science (see pubs list). It is increasingly translational as it brings the work to human material.
Start Year 2008
 
Description conference on motherhood 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact We ran a conference on motherhood in the 21st century.

Interviews on press, national radio and television.
Year(s) Of Engagement Activity 2009