Figure 5.

Clustering of gene expression profiles identified novel genes potentially involved in skeletal development. A) 148 genes among the genes regulated during wk 4–9 were found to be in GO categories associated with skeletal development and were clustered based on their expression patterns. Four clusters indicated with colored bars were used for further analysis. B) The 148 genes were clustered with the 1218 genes whose GO categories were unknown, and the genes in the four color-coded clusters shown in A were identified in the combined clusters. The clusters that were highly enriched for the genes in the four color-coded clusters in A were identified and shown in the four panels here. The genes indicated with a blue bar are genes of unknown GO categories, whereas those labeled with colored bars correspond to the genes in A. The red stars indicate 2 unknown genes, C2orf40 (chromosome 2 open reading frame 40) (top left panel) and C1orf61 (chromosome 1 open reading frame 61) (bottom left panel), that were used as examples in this study (Fig. 6 and C, respectively). C) In situ hybridization confirmed that C1orf61 was indeed involved in skeletal development. Cells with brown/yellow stains were considered positive. Note that C1orf61 was expressed at very low levels in wk 4 but was highly up-regulated in the skeletal system, including the vertebrae and limbs, by wk 7–9.