To access the data, click or select the words “Appendix 4.” Unsupervised clustering indicated two stable clusters of 41 and 8 cells, as designated by a maximum silhouette value of 0.82 (the silhouette value for each cell is a measure of how similar that cell is to cells in its own cluster when compared to cells in other clusters and ranges from –1 to 1; a high silhouette value suggests that the clustering solution is appropriate). These are visualized in a heatmap with each column representing a single cell and rows genes (>10 fold differentially expressed (p<0.001)). The cow of origin, determined by genotype, is indicated above each cell. (B) Ball and stick visualization of the network of protein–protein interactions between the genes more highly expressed in the small cell cluster (False discovery rate (FDR) <0.01, Fold change >2). The network is significantly enriched for protein-protein interactions (p value: <1.0e-16) and the enrichment in genes in the Reactome Cell cycle pathway (BTA-1640170; nodes colored red) suggests that these are dividing cells. (C) There are fewer interactions, although significantly more than expected by chance (p value: 6.46e-14), among the genes more highly expressed in the larger cluster. Many are extracellular proteins, as indicated by the annotation of the most highly enriched terms from each gene ontology domain (in addition Circulatory System Development, the second most significantly enriched Biologic process is shown). Examples include collagens (COL1A1 and COL1A2), the matrix modifying enzyme Lysyl oxidase homolog 2 (LOXL2) and Connective tissue growth factor (CTGF), which mediates heparin- and divalent cation-dependent cell adhesion.