We have previously shown that, while the intrinsic quality of the oocyte is the main factor affecting blastocyst yield during bovine embryo developme

Using reverse transcriptase-amplified fragment length polymorphism (RT-AFLP) analysis of differential mRNA expression and semiquantitative reverse tr

Although genetically identical for autosomal Chrs (Chr), male and female preimplantation embryos could display sex-specific transcriptional regulation. To illustrate sex-specific differences at the mRNA level, we compared gene-expression patterns between male and female blastocysts by DNA microarray comparison of nine groups of 60 bovine in vitro-produced blastocysts of each sex. Almost one-third of the transcripts detected showed sexual dimorphism (2,921 transcripts; false-discovery rate, P < 0.05), suggesting that in the absence of hormonal influences, the sex Chrs impose an extensive transcriptional regulation upon autosomal genes. Six genes were analyzed by qPCR in in vivo-derived embryos, which displayed similar sexual dimorphism. Ontology analysis suggested a higher global transcriptional level in females and a more active protein metabolism in males. A gene homolog to an X-linked gene involved in network interactions during spliceosome assembly was found in the Y-Chr. Most of the X-linked-expressed transcripts (88.5%) were up-regulated in females, but most of them (70%) exhibited fold-changes lower than 1.6, suggesting that X-Chr inactivation is partially achieved at the blastocyst stage. Almost half of the transcripts up-regulated in female embryos exhibiting more than 1.6-fold change were present in the X-Chr and eight of them were selected to determine a putative paternal imprinting by gene expression comparison with parthenogenetic embryos. Five ( BEX , CAPN6 , BEX2 , SRPX2 , and UBE2A ) exhibited a higher expression in females than in parthenotes, suggesting that they are predominantly expressed by the paternal inherited X-Chr and that imprinting may increase the transcriptional skew caused by double X-Chr dosage.

The steroid hormone progesterone (P4) plays a key role in the reproductive events associated with pregnancy establishment and maintenance. High concentrations of circulating P4 in the immediate post-conception period have been associated with an advancement of conceptus elongation, an associated increase in interferon-τ production and higher pregnancy rates in cattle. Using in vitro and in vivo models and ∼8500 bovine oocytes across six experiments, the aim of this study was to establish the route through which P4 affects bovine embryo development in vitro and in vivo. mRNA for P4 receptors was present at all stages of embryo development raising the possibility of a direct effect of P4 on the embryo. Exposure to P4 in vitro in the absence or presence of oviduct epithelial cells did not affect the proportion of embryos developing to the blastocyst stage, blastocyst cell number or the relative abundance of selected transcripts in the blastocyst. Furthermore, exposure to P4 in vitro did not affect post-hatching elongation of the embryo following transfer to synchronized recipients and recovery on Day 14. By contrast, transfer of in vitro derived blastocysts to a uterine environment previously primed by elevated P4 resulted in a fourfold increase in conceptus length on Day 14. These data provide clear evidence to support the hypothesis that P4-induced changes in the uterine environment are responsible for the advancement in conceptus elongation reported previously in cattle and that, interestingly, the embryo does not need to be present during the period of high P4 in order to exhibit advanced elongation.