In this section:
Embryo Production & Foetal Development Projects
Foetal Development in Cloned Livestock
One of the major challenges facing the livestock transgenesis approach using nuclear transfer is the high mortality rate among developing foetuses and the poor health of live animals. From the foetal defects seen, it is probable that during the process of genetic reprogramming that occurs upon nuclear transfer into a recipient oocyte, in many cases there is interference to developmental mechanisms critical for normal growth and differentiation programmes in the embryo. Consequently, we are using Molecular Biology techniques to analyse gene expression in developing ovine peri-implantation embryos produced by in vitro maturation / in vitro fertilisation (IVM/IVF) methodology and by somatic cell nuclear transfer. Outcomes of the reproductive biology experiments at the cellular level are being investigated at the molecular level. The aims are (1) to compare the gene expression profiles of developmentally important genes in ovine peri-implantation embryos produced in vitro by standard IVM/IVF methodology and by somatic cell nuclear transfer, with that in normal in vivo derived embryos, and (2) to identify factors extrinsic or intrinsic to the recipient oocyte and donor nucleus which can improve the normality of development of ovine embryos (and foetuses) produced following somatic cell nuclear transfer. We are currently developing specific for developmentally important gene sequences in order to follow gene expression profiles in embryos produced in the cloning programme real-time PCR assays (qPCR) at Turretfield Research Centre.
Contact:
Dr Simon Bawden
In Vitro Embryo Production
A key requirement for studies into cloning, transgenesis and juvenile in vitro embryo transfer (JIVET) is the ability to handle, manipulate and culture ova/embryos with minimal adverse effect. The aim of this project is to develop and improve techniques for the maturation, fertilisation and culture of ova/embryos from sheep, cattle and goats. The emphasis of the research is on the development of defined media and on the influences on development of various additives (eg amino acids, vitamins and growth factors). The preferred medium is synthetic oviduct fluid medium (SOF) containing amino acids (at oviduct fluid concentrations), growth factors and BSA (depending on the nature of any particular study). In all three species, the rate of production of blastocysts, using slaughterhouse material, is approximately 60 –70% of cleaved ova. Ongoing research is examining the determinants of oocyte quality including maternal nutrition and the number equality of cumulus cells in the oocyte-cumulus complex.
Juvenile In Vitro Embryo Transfer (JIVET)
The ability to collect large numbers of oocytes from juvenile lambs and calves (at 4-12 weeks of age) provides a means whereby generation intervals can be substantially reduced. Substantial research has been conducted in the lamb resulting in substantial improvements in the mean number of oocytes harvested per donor lamb (60-80), the mean number of embryos transferred per donor lamb (40-50) and the mean number of lambs produced per donor lamb (10-15 in the Merino; 5-10 in non-Merino breeds). Research indicates that maternal nutrition, the hormone treatment protocol and the in vitro maturation of the oocyte-cumulus complexes are all important determinants of outcome. Ongoing research is directed towards improving in vitro maturation of oocytes and on the role of nutrition in the recipient on the outcome of embryo transfer.
Contact:
Jen Kelly
Nutrition and Embryo Development
Observations on the in vitro maturation and development of ova and embryos clearly indicate large variation between ova/embryos collected from different groups of animals. It is postulated that this variation is due to differences in the nutritional history of the animals. It is also likely that this variation can be sufficiently large to mask significant differences between treatment groups in terms of rates of embryo development. This project aims to examine the effects of maternal nutrition on ovum maturation and on various parameters of embryo development. This study includes both in vivo and in vitro derived ova/embryos. Data so far collected indicate that variations in nutrition between ovulation and blastocyst formation can significantly influence embryo development, particularly in cell lineage. Future work will examine the impact of current findings on foetal development. Future research will also aim to standardise maternal nutrition to facilitate studied on in vitro embryo development.
Contact:
David Kleemann
