qRT-PCR of PAF receptor isoforms during megakaryopoiesis. mRNA for PAFR-1 (PAFR Tr1) and PAFR-2 (PAFR Tr2) was quantified by qRT-PCR and relative values of megakaryocyte precursors and differentiated megakaryocytes were compared with culture day 0 (CD34⁺ cells) by the 2^−ΔΔCt method.³⁴  mRNA for PAFR-1 was normalized to β-actin transcript levels. PAFR-2 was not detected (ND) in CD34⁺ cells, megakaryocyte precursors, or megakaryocytes (also see Figure S4).