Characterization of ΔneoΔHS Gata1 knockdown megakaryocytes. (A-B) Flow cytometric analysis of megakaryocytes cultured from wild-type or GATA-1 knockdown fetal liver cells stained with the anti-CD41 (A) or CD42 (B) antibody. (C) Following in vitro expansion, wild-type and GATA-1–deficient cells were enriched on a BSA gradient and AChE staining was performed to determine the purity of enriched cells. Images were obtained using a Leica DM4000B light microscope equipped with a 20×/0.04 objective lens (Cambridge, United Kingdom). Original magnification, ×200. Images were captured using a mounted Leica DFC320 camera and Leica Firecam version 1.4 software. (D) Ploidy analysis of BSA gradient-purified megakaryocytes was performed by flow cytometry of cells stained with PI. (E) Light microscopy of differentiated cells in culture. The arrow points to proplatelet forms. Images were obtained using a Zeiss Axiovert S100 inverted microscope equipped with a 20×/0.04 objective lens (Thornwood, NY). Original magnification, ×200. Images were captured with a Nikon Coolpix 990 digital camera (Tokyo, Japan).