Xsl and c-kit function are required for primitive erythropoiesis in Xenopus. (A) Xsl-1 RNA containing (+) or lacking (–) the 5′ UTR sequence targeted by the antisense MO was translated in vitro in the presence of increasing doses of MO. Radiolabeled translation products were analyzed by SDS-PAGE and autoradiography. (B) Schematic representation of experiments shown in panels C-H. MOs were targeted to prospective ectoderm by injection into the animal pole and DN-kit mRNAs were targeted to the prospective VBI by injection near the marginal zone. Embryos were allowed to develop to stage 33/34 for analysis of globin. (C) Northern blot analysis of expression of globin and odc (loading control) in embryos injected with MOs or synthetic RNAs as indicated above each lane. (D-H). Whole-mount in situ hybridization analysis of expression of globin in embryos injected with control MO (D), Xsl MO (E), GFP RNA (F) DN-kit RNA targeted to the entire VBI (G), or DN-kit RNA targeted to the posterior VBI only (denoted by arrows; H). Anterior is to the right. The bottom embryo in each panel is a ventral view; all other embryos are shown in a lateral view.