Circulation congestion and erythropoietic dysplasia in the C/ebpαDN transgenic embryos. (A-B) External features of the Tg(lmo2:LDL-EGFP) (A) and Tg(lmo2:LDL-EGFP-C/ebpαDN) (B) embryos at 75 hpf. The circulation congestion is only detected in the C/ebpαDN-expressing embryos (B, arrowheads and supplemental Videos 1 and 2). Black boxes with dashed lines indicate the regions amplified at the bottom. Red boxes and curved arrow indicate the sites where tissue or circulating cells were isolated and genomic DNA were extracted for genotyping shown in panel C. DA indicates dorsal aorta; and CV, caudal vein. (C) Analyses of Cre-mediated genomic recombination by genomic-nested PCR using 2 pairs of primers indicated at the bottom of Figure 1C. The Roman numerals indicate the anatomic sites where tissues and cells are dissected (I-III) or released from the CHT (IV). (D-E) Wright-Giemsa stainings and morphologic characterizations of circulating blood cells released from the CHT of transgenic embryos at 75 hpf from Tg(lmo2:LDL-EGFP). (D) All 3 panels are adopted from the same slide and composited together and Tg(lmo2:LDL-EGFP-C/ebpαDN). (E) Both panels are adopted from the same slide. Arrow indicates the cell undergoing mitosis. Images were acquired with a 100× oil objective. (F-I) Proliferation and apoptosis analyses by pH3 immunochemistry stainings (F-G) and TUNEL assays (H-I) in the embryos expressing EGFP and EGFP-C/ebpαDN at 75 hpf as described in “Immunochemistry and TUNEL assays.”