Gene-expression patterns suggest that Wnt3a initiates osteoblastic differentiation of OP9 stromal cells. (A) Microarray analyses were conducted comparing Wnt3a-transduced and vector-transduced OP9 stromal cells. The genes were grouped using a hierarchical clustering technique based on patterns of expression, and the heat map shows the hierarchical relationships. Each column represents results from 2 independent experiments that gave nearly identical results. (B) RT-PCR was then used on freshly isolated mRNA to evaluate the expression of hematopoiesis-supporting genes. (C-D) A PCR array was used to assess expression of Wnt ligands and Wnt modulator genes. The results in each panel represent Wnt3a transduced as fold changes from vector control samples. The direction of changes were similar in 3 independent experiments, and pooled results are given ± SD.