Principal component analysis (PCA) plot of gene expression profiles from endometrial samples and Venn diagrams from differentially expressed transcripts. A, The profiles from infertile women (group A (n = 5); red dots) cluster separately to clusters representative of women with embryo implantation (groups B (n = 6) and C (n = 6); green and blue dots, respectively). B, hierarchical clustering analysis represented in a tree-like dendogram revealing the similarities on gene expression profiles of endometrial samples. A clear segregation of samples into two major clustering branches, one with samples from group A and the other with samples form groups B and C that self-cluster together. C, Venn diagrams showing the differentially expressed genes in each group, which are either 2-fold down- (panel C) or up-regulated (panel D) in endometrial samples from women with implantation failure (group A) compared to those from women that conceived either by IVF (Group B) or naturally (group C).