Fig. 1

Mutations in the gene moonshine (mon) cause early defects in hematopoietic cell development leading to severe anemia. The relative strength of different alleles correlates with expression of GATA-1 mRNA detected by wholemount in situ hybridization. (A-D) Whole-mount in situ hybridization for GATA-1 expression in wildtype and mutant embryos at the 18 somite stage. (A) In wild-type embryos, GATA-1 is expressed in two stripes of hematopoietic cells that converge toward the dorsal midline to form the intermediate cell mass. (B) Embryos with the strongest allele, mon^tb222b, express barely detectable levels of GATA-1. (C) The intermediate allele mon^tc246b, results in a slightly increased GATA-1 expression. (D) The weakest allele, mon^tc239b, has no obvious effect on GATA-1 expression at that stage. All embryos derived from a cross between mon^tc239b heterozygous carriers looked the same as the embryos shown in D. (E-F) Isolated blood cells from wild-type and mutant larvae stained by the Wright-Giemsa method. (E) Blood cells from 5- day old wild-type larvae show the characteristic morphology of differentiated red blood cells. (F) The few blood cells circulating in 5- day old mon^tb222b mutant larvae are large and basophilic. (G-H) Odianisidine staining for hemoglobin (arrow) in 2-day old wild-type and mutant embryos. (G) Hemoglobin in red blood cells is strongly stained in wild-type embryos. (H) In contrast, mon mutant embryos do not express detectable levels of hemoglobin. Scale bar (E,F) 20 µm.