The proposed research is relevant to NIH's mission because it will shed light on the processes of human growth and development with the potential to improve health. More specifically, the work proposed is expected to provide a detailed reference epigenome of preimplantation embryos and adult tissue of mice conceived in vitro and in vivo. Such findings are expected to have an important positive impact, because they will help optimize and improve culture conditions with important benefits for both human and animal preimplantation embryo culture, in addition to fundamentally advance our understanding of how the epigenome is modified during early stages of development because of manipulation and culture.
It is becoming increasingly clear that the preimplantation period is a time of genomic reprogramming. Preimplantation embryos may respond to an environmental factor by altering their developmental trajectory with the net results that their adult phenotype is altered. This observation has wide clinical implications, since in vitro fertilization (IVF) and preimplantation embryo culture are routinely used to treat patients with infertility and as of today, more than 5 million children have been conceived with assisted reproductive technologies (ART). The laboratory of the PI (Rinaudo) has devoted extensive resources to define the phenotype of mice following ART. We have found that 1) preimplantation embryos are sensitive to the culture conditions they are exposed to; 2) culture conditions more dissimilar to the physiologic in vivo conditions are associated with a more significant alteration of long term phenotypes; 3) glucose intolerance is a common phenotypic change present in adults generated by IVF; 4) using a candidate gene approach, selected chromatin alterations are present in preimplantation embryos and maintained in adult animals in a tissue specific and sexual dimorphic fashion. Although these data are valuable, multiple questions still remain unresolved. We still do not know what global epigenomic changes are present in embryos following ART and if these epigenetic changes persist in the adult. The laboratory of the co-PI (Ramalho-Santos) has an established track record on epigenetic regulation of early mouse development and the germline, with expertise in analyses of histone variants, histone marks and DNA methylation. They have recently developed methods for genome-wide analyses of histone marks using low numbers of cells. This proposal, in response to PAR 13-385, aims to leverage the expertise of both laboratories to determine how ART may program adult physiology. Our long term goal is to define how preimplantation culture conditions affect embryo development and postnatal growth, as a direct test to the Barker hypothesis. The specific goal of this application is to assess epigenetic changes in preimplantation embryos and adult tissues of control and IVF mice. The central hypothesis is that culturing preimplantation embryos in vitro will result in epigenetic changes in the blastocyst; these changes will persist in selected adult tissues in a sexual dimorphic fashion; the identified epigenetic changes might explain the observed adult phenotype. We plan to test our central hypothesis and thereby accomplish the objective of this application by analyzing DNA methylation and describing selected histone marks in the inner cell mass (ICM) of preimplantation embryos of different mouse strains generated in vivo or in vitro. Further, we will confirm if selected epigenetic marks persist in adult tissues. With respect to the expected outcomes, the work proposed is expected to provide a detailed reference epigenome of 1) preimplantation embryos and 2) adult tissue of mice conceived in vitro and in vivo.