Investigating a novel molecular diagnostic tool for identification and stratification of pregnancy complications

Lead Research Organisation: King's College London
Department Name: Genetics and Molecular Medicine

Abstract

Babies who grow poorly in the womb, called small for gestational age (SGA), are at increased risk of health problems for both mother and baby. For example, full-term infants who are SGA have up to 30 times higher risk of neonatal death compared to term infants born at average weight. Screening pregnant women in an attempt to detect SGA babies has the potential to reduce the number of these adverse outcomes -the combined deaths from stillbirth and neonatal problems exceed 5000 babies every year in the UK. Currently it is difficult to monitor growth of the baby in the womb, and even harder to predict if there will be health problems associated with this. While there are a number of scan and blood markers for SGA babies, none of these is good enough on its own to predict them.

We have recently found that by measuring a protein called DLK1 in the mother's blood we can improve the prediction of whether the baby will be small. In this first study we examined only a small selection of pregnant women, but the data suggested that abnormal DLK1 levels were associated with failure to make an efficient placenta. The placenta is a temporary organ that is necessary for providing nutrition and oxygen to the baby from the mother's blood, and for removing waste. Many of the complications of pregnancy are thought to occur because the placenta does not develop properly. However, we still have much to discover about which genes are needed to make a healthy placenta, and how this goes wrong if the genes are mutated. Interestingly, DLK1 is made in the placenta. When we studied mice with a mutated DLK1 gene we found that they had smaller placentas and a reduced area for nutrient and oxygen exchange between the maternal and fetal blood. However, we currently don't understand why DLK1 is required to make a healthy placenta.

The aim of this project is firstly to see how measuring DLK1 in the blood of a large number of pregnant women can help us improve prediction of small babies. We have access to scan information, blood samples and placental samples from a large scale study of unselected women in their first pregnancy (~3000 women). The overarching aim of the present application is to see if we can find better markers in the mother's blood of poorly grown babies, and further link the levels of DLK1 to problems with the placenta. Secondly, because we have mice without a working DLK1 gene, we can study them to understand the processes necessary to make a healthy placenta. We will use the new ideas generated by studying the mice to design experiments using the human placental samples to test if our findings can help to understand why placentation goes wrong in humans.

Technical Summary

Small for gestational age infants (SGA) are at considerably increased risk of fetal and maternal mortality. Moreover, low birth weight at term is correlated not only with health problems in early life, but also predisposes to metabolic and cognitive dysfunction later. Despite the enormous cost to public health, little is known about the causes of SGA and few diagnostic tools are available to predict compromised fetal growth. This is important because there is evidence that perinatal outcome can be improved by increasing maternal surveillance and optimising the timing of delivery. The 2008 NICE Guideline on Antenatal Care identified improving detection of SGA infants as one of 5 major research priorities. Therefore early prediction of the onset and etiology of SGA would considerably improve perinatal wellbeing and survival.

Failures of placentation are thought to be a common cause of pregnancy complications leading to early termination and/or growth restriction. The placenta forms the critical interface between the maternal and fetal circulations, facilitating the exchange of gases and metabolites. We have recently produced exciting data that links the expression dosage of an imprinted gene, Delta-like homologue 1 (DLK1), to fetal growth and placental function. Importantly, conceptus-derived DLK1 enters the maternal circulation and can be measured during pregnancy. Our first small study in a human cohort indicated that low DLK1 levels are predictive of SGA secondary to a specific type of placental failure. These data are supported by our preliminary studies in mice lacking Dlk1 which have small placentas with reduced nutrient exchange surface area. We believe that further study of DLK1 signalling in pregnancy will help to define critical molecular pathways for healthy placentation, and provide a candidate for prenatal, non-invasive diagnostic testing for the complications of pregnancy.

Planned Impact

We will seek to impact the wider community in 3 ways:
1) Small for gestational age infants (SGA) are at increased risk of a number of adverse outcomes. Screening for SGA has the potential to reduce the number of adverse outcomes, in particular population rates of stillbirth, which account for the death of about 4000 babies per annum in the UK. The 2008 NICE Guideline on Antenatal Care identified improving detection of SGA infants as one of 5 major research priorities. Our project could ultimately lead to new diagnostic tests to predict adverse outcomes of pregnancy. The ultimate aim is to generate an algorithm for the identification of pathologically SGA infants that might ultimately be tested in a randomised controlled trial of screening the general population. Production of such a test will also have value to the economy.
2) Disseminating basic research findings and technical skills to the medical/clinical training community. As members of a COST Action: European Network of Human Imprinting Disorders and the Genomics England Clinical Interpretation Partnership: Imprinting Disorders we are particularly well placed to rapidly communicate our work to the clinical imprinting syndrome community. GS is a research clinician at the Rosie Hospital in Cambridge, and is actively involved in teaching and clinical training.
3) Public dissemination of science. GS has strong links to patient and parent groups who have been affected by adverse pregnancy outcome, in particular Sands (the Stillbirth and Neonatal Death Society). He is chair of the Sands research grant panel and was the founding chair of the RCOG Stillbirth Clinical Study Group, which is sponsored by SANDS and has bereaved parents among its members. Moreover, GS has experience of engagement with national and devolved government.

Publications

10 25 50
 
Description Merck Grant for Growth Innovation
Amount € 90,000 (EUR)
Organisation Merck 
Sector Private
Country Germany
Start 11/2020 
End 10/2022
 
Description NIHR-Guy's and St Thomas' Biomedical Research Centre Doctoral Training Partnership PhD
Amount £100,000 (GBP)
Funding ID BRC Doctoral Training Partnership 
Organisation National Institute for Health Research 
Sector Public
Country United Kingdom
Start 10/2018 
End 09/2021
 
Description NIHR-Guy's and St Thomas' Biomedical Research Centre Doctoral Training Partnership PhD
Amount £100,000 (GBP)
Funding ID BRC Doctoral Training Partnership 
Organisation National Institute for Health Research 
Sector Public
Country United Kingdom
Start 10/2019 
End 09/2023
 
Description Society for Endocrinology Summer Studentship
Amount £2,420 (GBP)
Organisation Society for Endocrinology 
Sector Charity/Non Profit
Country United Kingdom
Start 07/2018 
End 08/2018
 
Title Purification of cell populations in the murine placenta 
Description The mature haemochorial placenta in both mice and humans contains an exchange compartment comprised of several cell types. Fetal blood is enclosed by fetal endothelial (FE) cells that derive from the epiblast, whereas the maternal blood is circulated within 'vessels' comprised of three layers of trophoblast (TB) cells. One of the greatest technical challenges for performing gene expression studies in the placenta is separating and purifying highly interdigitated heterogeneous cell populations. We have developed a lineage tracing method to genetically label placental FE and TB cells and purify them using fluorescence-activated cell sorting (FACS). Meox2Cre is expressed in all cells of the epiblast, which gives rise to the placental FE. when combined with the mTmG reporter, Cre+ cells delete a red (mTom) reporter allowing expression of GFP. Green and red cell populations can be separated from subdissected labyrinth zones by FACS. 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Year Produced 2019 
Provided To Others? No  
Impact We have recently used this method to generate a high quality transcriptomics dataset. 
 
Description Pregnancy Outcome Prediction Study 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution We initiated this collaboration when data from our reseach indicated that there may be important clinical translation. We have performed experiments and guided the intellectual progress of this collaboration, which uses our experimental models to address clinically-relevant issues.
Collaborator Contribution Our collaborators have established a unique clinical resource, an extremely well phenotyped large prospective cohort of pregnant women. Measurements were taken during pregnancy and after birth, and biological materials are available from these women. We have used these data and materials to generate experimental data that translates our primary findings into the clinical sphere.Our collaborators are experts in diagnosis and treatment of obstetric disorders - we benefit from their considerable expertise.
Impact Our intial collaboration resulted in a paper published in Nature Genetics in 2017, Cleaton, et. al. With Profs Gordon Smith and Steven Charnock-Jones who led the POP study, I applied for further funding to follow up the initial finding of the 2017 paper. We were awarded a project grant by the MRC, MR/R022836/1, which commenced in August 2018.
Start Year 2017
 
Description A year in Genetics: Centenary celebrations of the UK Genetics Society 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact In its centenary year, the Genetics Society viewed the world-renowned Royal Horticultural Society event as on opportunity to create a garden showcasing plants which have been studied by geneticists throughout history. Led by Professor Bickmore, the exhibit showcased plants such as peas, snapdragons, petunias, lilies and strawberries, telling the story of genetics and why its study is fundamental to our understanding of health and disease. Visitors to the garden could watch the genome of a plant being sequenced live in front of them.The focal point of the exhibit was a hybrid zone of snapdragons, in colours ranging from yellow through to red, plus a DNA double helix sculpture made by the John Innes Centre which represented Mendel's work with peas and pyloric snapdragons. The centenary garden, named 'The Flowering of Genetics' was awarded a silver medal by the RHS Chelsea Flower Show. It is now a permanent exhibit at the Royal Horticultural Society in Edinburgh.
Year(s) Of Engagement Activity 2019
URL https://genetics.org.uk/centenary/