r mechanisms of the embryo-TE transition as well as important insights for the development of diagnostic tests to test blastocyst quality in assisted reproduction programs. Results Dynamic Changes in Overall Gene Expression in Mature MII Oocytes, Single Day 3 Embryos, TE Cells from Day 5 
Blastocysts and hESCs In order to determine the global gene expression variation in the different samples, we established the gene expression profile of mature MII oocytes, day 3 single embryos, TE samples from day 5 blastocysts and hESCs by using high-density oligonucleotide Affymetrix HG-U133P microarray chips. A non-supervised Foretinib site analysis using the principal components analysis showed that samples from the same group clustered together very tightly, corroborating the robustness of the Affymetrix microarrays. Moreover, a non-supervised hierarchical clustering analysis of the array data clustered perfectly the different samples, confirming their very specific expression profiles. Finally, a scatter plot analysis showed that expression variations between mature MII oocytes and single day 3 embryos were high as illustrated by the dispersed scatter plots and the low correlation coefficient. Conversely, the differences in gene expression between day 3 embryos and TE or hESC samples were lower as indicated by the tighter scatter plots and the high correlation coefficients . These results reveal dynamic transcriptome changes during the transition from mature oocyte to day 3 embryo and from day 3 embryo to blastocyst. These ��dynamic patterns��are due to the large-scale degradation of human maternal transcripts and the activation of embryonic genes, as was also observed in the mouse. and Lactate Dehydrogenases. The ��TE molecular signature��comprised genes important for placental development, cytoskeleton-associated genes, and genes encoding S100 calcium binding proteins, retinoid receptor-related testisassociated receptors or the B receptor. Moreover, genes encoding extracellular matrix proteins, such as Laminins and Integrins were also up-regulated. Gene ontology annotations were used to explore the specific functional properties of the two molecular signatures. The day 3 embryo molecular signature was enriched in genes associated with localization in the ��nucleus”, while genes associated with the ��cytoplasm��localization were over-represented in the TE molecular signature. Concerning the ��biological processes”, the day 3 embryo molecular signature was enriched in genes involved in the regulation of cellular processes, transcription and posttranslational protein modifications. Conversely, in the TE molecular signature, genes connected with different metabolic and steroid biosynthetic processes were over-represented. The ��molecular function��analysis showed that genes involved in oxido-reductase activity were significantly enriched in the TE signature, whereas genes related to ��GTPase activity��and DNA binding were over-represented in the day 3 embryo signature. Finally, the expression pattern of 11 genes belonging to PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22201297 the TE or to the day 3 embryo molecular signature was confirmed by qRT-PCR analysis using specific primer pairs. All qRT-PCR data were normalized to GAPDH to control for variations in mRNA recovery and RT efficiency. Expression of Genes Encoding Proteins which Play a Role in Apoptosis in Day 3 Embryos and TE Samples We then investigated the expression of genes coding for proteins linked to the extrinsic and intrinsic apoptosis pathways in day 3 embryos