CXCR4 gene expression in normal bone marrow CD34⁺ cells, megakaryocytes, platelets, and megakaryocytic cell lines. RT-PCR was performed as described in Materials and Methods. The PCR products were electrophoresed on a 3% agarose gel and visualized by ethidium bromide staining. RNA isolated from CXCR4-transfected L1.2 cells was used as a positive control and RT-PCR without RNA was used as a negative control. Lanes 1 through 11 represent negative control, CD34⁺ cells, CD61⁺ cells, platelets, HEL, CMK, Dami, Mo7E, UT-7, positive control, and DNA marker, respectively.