Fig. 3.
Placental gene expression. (A) Unsupervised hierarchical clustering sorts placental samples based on their anatomical location. The 72 samples from 19 patients with successful pregnancies are designated according to the patient number (Pn), part of the placenta, and fetal gender. Because of anatomic similarity in gene expression, the samples cluster to form shorter branches of amnion, chorion, umbilical cord, and villus parenchyma sections. Gene expression among sections of villus parenchyma forms one branch and varies significantly from the other branch that includes amnion, chorion, and umbilical cord samples. Among villus sections, the clustering relies on similarity in anatomical location and individual differences in gene expression. (B) Placental transcriptome. We selected ≈1,500 genes that were the most variably expressed among the samples by using a criterion of 3-fold change in level of expression in a minimum of two arrays. Each expression measurement represents the normalized ratio of fluorescence from the hybridized experimental material to a common internal reference. The prominent clusters of genes are shown on the right.