Assisted reproductive technologies in livestock: from the field to fundamental studies
From the nineties, our lab developed assisted reproductive techniques (ART) in the bovine including in vitro production (IVP) of bovine embryos from immature oocytes, embryo and semen cryopreservation or definition of oocyte and embryo quality markers. The studies performed highlighted the high plasticity of the mammalian embryo that is able to adapt its metabolism to different environmental conditions. Those adaptations can however lead to delayed embryo/foetal death or have long term effects on the offspring through epigenetic modifications.
Our research first focused on the development of optimal culture conditions to obtain high quality IVP embryos. By the time, the IVP bovine embryo proved to be an excellent model to study oocyte maturation and early embryo development in mammals. We thus started to use it as main model for fundamental studies aiming to understand the roles of some proteins in early embryo development. For example, we established for the first time the expression profile of several HOX genes before gastrulation and showed that the kinetics of expression and protein localization of HOXB9 sustain its implication in the regulation of crucial events, like the onset of the embryonic genome or the first differentiation steps.
Those last years, we evaluated the different behaviour of male and female embryos cultured in various artificial environments and submitted to various stresses. Indeed it has been shown in several species that the random inactivation of one X chromosome in female embryos is only starting at the blastocyst stage. This probably explains most gender differences observed at those early developmental stages. Differences in metabolism lead to different adaptive mechanisms; in turn, those different mechanisms can induce preferential loss of embryos of one sex, resulting in shifts in sex ratio.
We are also involved in projects aiming to improve the fertility of Belgian blue bulls and high producing dairy cows, namely through nutritional optimization, and we house a regional cryobank developed to preserve the genetic diversity of endangered local livestock breeds.