Fig. 5. Growth factor sensitivity of XLMO-2. Animal pole explants were dissected from embryos injected with various growth factors. Injections were at the 1-cell stage and animal caps were harvested at stage 8. Basic human fibroblast growth factor (bFGF) (20 ng/ml) was applied to uninjected animal caps immediately after dissection. AVg is a chimeric molecule containing the prodomain of activin fused to the functional domain of Vg1. Explants and untreated control siblings were harvested at stage 33. XLMO-2 and GATA-1 transcripts were assayed by semi-quantitative RT-PCR analysis. ODC is ornithine decarboxylase and is used a loading control; –RT is a standard reaction that lacks reverse transcriptase and is included as a control for genomic DNA contamination. WE is a whole-embryo positive control.