Transcriptome changes at the initiation of elongation in the bovine conceptus

Temporal changes in the embryo transcriptome between the blastocyst stage (Day 7) and initiation of elongation (Day 13) differ between in vivo- and in vitro-derived embryos and are reflective of subsequent developmental fate. The aim of this study was to examine the temporal changes in transcriptional profile as the embryo develops from a spherical blastocyst on Day 7 to an ovoid conceptus at the initiation of elongation on Day 13 and to highlight differences in these temporal gene expression dynamics between in vivo- and in vitro-derived blastocysts which may be associated with embryonic survival/mortality using the bovine Affymetrix microarray. All embryos were produced either in vitro by IVF or in vivo by superovulation. A proportion of Day 7 blastocysts were snap frozen and the remainder were transferred (n=10 per recipient) to synchronized heifers, recovered on Day 13 and snap frozen individually. Three pools of Day 7 blastocysts (n=25 per pool for in vitro and in vivo, respectively) and three pools of Day 13 conceptuses (n=5 per pool, for in vivo and in vitro) were used for microarray. analysis.