Intracellular signals for developmental hemoglobin switching

Abstract We have detected trans -acting factors that regulate developmental hemoglobin switching by fusing erythroid cells of different developmental programs. Adult erythroid cells of one anuran species, Xenopus laevis , were fused with tadpole erythroid cells of another frog, Rana catesbeiana . In a second set of experiments, dimethyl sulfoxide-induced murine erythroleukemia cells, which express only adult mouse globins, were fused with Rana tadpole erythroid cells, which express only embryonic and fetal-like globins. Adult Rana globin gene expression was detected in both sets of transient heterokaryons at 6 hr after fusion. Dot blots and Northern blots of total RNA from the heterokaryons contained material that reacted with an adult Rana α-globin probe; newly synthesized adult Rana hemoglobin tetramers were detected with native polyacrylamide gel electrophoresis. These results show that developmental stage-specific trans -acting factors for globin genes can function across vertebrate classes (mammalia to amphibia) and suggest that the mechanisms that regulate developmental hemoglobin switching are highly conserved.