Figure 1.

Dendrogram and heatmap of unsupervised hierarchical agglomerative cluster analysis according to the Z-score–transformed calculated means of the clinical chemistry markers. The Z-score transformation was used to put all analytes on a same scale, thus ensuring that analytes with increased variability did not dominate the clustering. The gray colors between dendrogram and heatmap represent the 4 strains and substrains analyzed and were chosen according to the fur color of the strains. A horizontal line in the dendrogram represents a merge of clusters, whereby the y-coordinate of the horizontal line represents the similarity of the 2 clusters being merged. The dendrogram can be cut where the gap between 2 clusters is largest. In our case, this process results in 2 large clusters—female and male mice—thus indicating that sex-specific differences are more prominent than are strain effects. Additional separation occurs between strains with the C3H and C57BL/6 backgrounds.