Fig. 6

Fig. 6 spi1 expression in the hematopoietic failure mutants cloche (clo) and spadetail (spt). (A, B) Whole-mount in situ hybridization demonstration of location of spi1 expression in wild-type (A) and clo^m39/clo^m39 (B) zebrafish (20 hpf), showing loss of expression in the clo mutant. At this age, clo homozygotes could not be recognized on the basis of coincident morphological features, but the expected proportion (29/109, 27%) of embryos from the mating of clo heterozygotes showed the appearance in (B). (C–F) Flat preparations of whole-mount in situ hybridization preparations of 14-somite wild-type (C, E) and spt^b104/spt^b104 (D, F) zebrafish embryos. Expression of gata1 in the caudal LPM is present in the wild-type (C) but not spt (D) embryo. (E, F) Rostral spi1 expression is retained in the spt embryo, despite loss of caudal LPM spi1-expressing cells. Panel (F) is representative of spi1 staining in 14 spt embryos in a clutch of 54 (26%) resulting from spt^b104/+ interbreeding. (G, H) Myelopoiesis initiates in spt mutants despite erythropoietic failure. Methylene-blue-stained thick section of a 48-hpf spt embryo (G), indicating (arrow) the location of the granulocyte identified on electron microscopy by its characteristic cytoplasmic electron-dense elliptical granules (H).