Figure 2

Unsupervised analysis of all tissues using U133 2.0 microarrays. (A) Two-way hierarchical clustering of 46 normal tissues (including five fetal cartilage and 41 non-cartilage tissues) and 9483 probesets which vary more than two standard deviations from the mean expression of the probeset. As detailed in the Methods, to generate a cartilage-centric figure, the median cartilage signals were normalized to zero prior to the clustering. This resulted in cartilage gene expression being displayed to the left and expression among the non-cartilage tissues to the right and produced deep branching among the cartilage samples. Mean-centered clustering reflected the high correlation among the cartilage samples (average regression correlation of 0.92) and did not qualitatively alter the correlations among the non-cartilage samples (data not shown). (B) Zoomed image of gene expression from 89 probesets representing 64 genes containing many known cartilage-specific genes which distinguish fetal cartilage expression.