Preimplantation embryo programming: transcription, epigenetics, and culture environment

Abstract

Preimplantation development directs the formation of an implantation-or attachment-competent embryo so that metabolic interactions with the uterus can occur, pregnancy can be initiated, and fetal development can be sustained. The preimplantation embryo exhibits a form of autonomous development fueled by products provided by the oocyte and also from activation of the embryo's genome. Despite this autonomy, the preimplantation embryo is highly influenced by factors in the external environment and in extreme situations, such as those presented by embryo culture or nuclear transfer, the ability of the embryo to adapt to the changing environmental conditions or chromatin to become reprogrammed can exceed its own adaptive capacity, resulting in aberrant embryonic development. Nuclear transfer or embryo culture-induced influences not only affect implantation and establishment of pregnancy but also can extend to fetal and postnatal development and affect susceptibility to disease in later life. It is therefore critical to define the basic program controlling preimplantation development, and also to utilize nuclear transfer and embryo culture models so that we may design healthier environments for preimplantation embryos to thrive in and also minimize the potential for negative consequences during pregnancy and post-gestational life. In addition, it is necessary to couple gene expression analysis with the investigation of gene function so that effects on gene expression can be fully understood. The purpose of this short review is to highlight our knowledge of the mechanisms controlling preimplantation development and report how those mechanisms may be influenced by nuclear transfer and embryo culture.

Genome-wide expression profiling reveals distinct clusters of transcriptional regulation during bovine preimplantation development in vivo

“…Table S2. A novel finding is the rapid degradation of maternal messenger RNAs that occurs after the 4-cell stage concomitantly with the major onset of embryonic transcription at the 8-cell stage (Fig. 3A), instead of the previously assumed gradual degradation of maternal messenger RNAs (26,27). This indicates that maternal RNA is actively degraded in a coordinated manner and that degradation and genome activation are tightly linked.…”

Supplementation of fetal bovine serum alters histone modification H3R26me2 during preimplantation development of in vitro produced bovine embryos

“…Epigenetic mechanisms appear to be the most sensitive factors affected by environmental changes like culture conditions (Niemann & Wrenzycki 2000, Duranthon et al 2008, Kohda et al 2012). Histone modification is one such epigenetic mechanism that is critical to embryo development of several species such as mice (Corry et al 2009), cattle (Santos et al 2003, Enright et al 2005, Wee et al 2006, Maalouf et al 2008, Ross et al 2008, pig (Park et al 2009, Gao et al 2010, sheep (Hou et al 2008) and human (Zhang et al 2012).…”

Porcine Granulocyte-Macrophage Colony-Stimulating Factor Improves the <i>in vitro</i> Development of Cloned Porcine Embryos

“…Despite significant improvements in culture conditions and techniques for porcine embryo research, the development of in vitro-produced embryos is still suboptimal, especially for embryos obtained from somatic cell nuclear transfer (SCNT). Because the preimplantation embryo is extremely sensitive to environmental factors, inadequate culture environments often lead to aberrant embryo development as evidenced by lower rates of blastocyst formation and lower total cell numbers in blastocysts [14]. In addition, cloned embryos have incomplete or incorrect epigenetic reprogramming [reviewed in 17,35].…”