Zebrafish hematopoietic mutants. (A) cloche, a mutant in the earliest acting gene in hematopoiesis, upstream of the hemangioblast marker tal1(scl), shows a lack of circulating red hemoglobinized erythrocytes circulating over the yolk compared with wild-type (arrowheads) in brightfield images (left panels), and lacks expression of gata1 (red, erythrocytes) and lcp(l-plastin) (blue, myelomonocytes) in 2-color whole mount in situ hybridization (right panels). (B) The dorsalized alk8 mutant laf ^gl2 lacks anterior expression of the early myeloid marker spi1(pu.1). (C) The ventralized chordin mutant dino has expansion of the intermediate cell mass with increased expression of gata1 (blue). (D) Blood smears comparing wild-type and retsina (a scl4a1 (erythrocyte band 3) mutant) erythrocytes; retsina erythrocytes have distinctive binucleate erythroblasts (closed arrowhead), reminiscent of congenital dyserythropoietic anemia type II. (A-C) Gene expression by whole mount in situ hybridization. Microscopy was performed using a Nikon SMZ-1500 microscope (Nikon) equipped with a 0.75-11.25× objective (A-C). Images were obtained using a Zeiss Axiocam MRc5 digital camera (Carl Zeiss), with Axiovision AC software (Release 4.5). Images were processed using Adobe Photoshop CS2 9.0 and Adobe Illustrator CS2 12.0.1 (Adobe Systems).