Expression of PTP-RO mRNA in megakaryocytic cell lines. 6 μg of Poly(A⁺) mRNA extracted from the indicated human megakaryocytic cell lines (A) and 100 nmol/L PMA-treated (6 and 18 hours) CMK cells (B) were electrophoresed in a denatured 1% agarose-formaldehyde gel and transferred to nylon membranes. Hybridization was performed with a ³²P-labeled PTP-RO probe (upper panel), followed by hybridization with a ³²P-labeled GAPDH probe or actin probe (lower panel). The positions of PTP-RO, GAPDH, and actin mRNAs are indicated.