Human VHLp30 mRNA rescues vhl^−/− polycythemia. (A,B) Embryos were injected with 7.5 pg of either full-length human VHLp30 or VHL R200W mRNA at the 1-cell stage. Whereas at 3.75 dpf only a few βE1 globin⁺ blood cells are observed in siblings, uninjected vhl mutants show a strong overexpression of βE1 globin mRNA that is most clearly visible in the blood cells accumulated in the heart (). After VHLp30 mRNA injection, this is not observed in 83.3% (15 of 18) of the genotyped vhl mutants, indicating a nearly complete rescue of the polycythemic phenotype by the human protein. Injection of VHL R200W mRNA could not restore the vhl^−/− βE1 globin expression to wild-type levels. (C) Translation of VHLp30 and R200W mRNA is verified by Western analysis at 56 hpf. One lane represents 3 embryo equivalents. β-Actin is used as a loading control. Original magnification, ×5 (A).