Gene expression landscape of pre-implantation embryonic development. (A) The porcine pre-implantation embryonic developmental process (from left to right: oocytes, 1-cell, 2-cell, 4-cell, 8-cell, morula and blastocyst embryos). (B) Representative Pearson correlation coefficient for replicates of pig oocyte samples calculated using log2-based RPKM. (C) Correlation analysis of the gene expression at corresponding time points of mouse and pig pre-implantation embryos derived in vivo or pig pre-implantation embryos derived in vivo and in vitro. Three methods were used to estimate the similarity between expressed patterns. (D) Unsupervised hierarchical clustering of the gene expression profiles of mouse and pig pre-implantation embryos. Read counts were used as the input for average agglomerative clustering analysis via Euclidean distance measurement.