(A) RT-PCR expression of Mk (TGF-β1, PDGF, FGF-A, and VEGF) and osteoblast-derived growth factors (osteocalcin) in the whole femurs (left panel) and in Mk cells (right panel) isolated from the spleens of wild type and Gata-1^low mice.

β₂-microglobulin was amplified as positive control, and mock-extracted RNA was amplified as negative control (not shown). Each product was amplified for increasing numbers of cycles within the linear portion of the respective amplification kinetics (21, 24, and 27 cycles for β₂-microglobulin and 25, 30, and 35 cycles for all the other genes), as indicated by the triangle on the top of the panel. Similar results were obtained in 2 additional experiments. (B) Flow cytometry reanalysis for purity of the Mk cells isolated by immunomagnetic selection from the spleens of wild-type (left) and GATA-1^low (right) mice as described in “Materials and methods” and used for the RT-PCR shown in panel A.