Globin gene expression in Xenopus laevis: Anemia induces precocious globin transition and appearance of adult erythroblasts during metamorphosis

Abstract

The expression of Xenopus laevis larval and adult globin genes after phenylhydrazine-induced anemia has been investigated at the cellular and molecular levels by means of cloned cDNA probes specific for the four main larval and the four main adult globin mRNA species. In the circulating blood of anemic metamorphic larvae there are at least two distinct populations of erythroblasts containing either larval or adult globin mRNA sequences. The cells expressing adult sequences replace those expressing larval ones at the end of metamorphosis. Under the influence of anemia the qualitative pattern of transcribed RNA species is not changed, but the larval to adult transition takes place earlier during development. This would imply that this transition is not strongly correlated with the morphological changes of metamorphosis. The abundance of the different larval globin mRNA species is similar and, as compared to control animals, not affected by the phenylhydrazine treatment. In anemic adults no reactivation of larval gene expression has been observed. The different adult globin mRNA species are present in comparable abundance, but the phenylhydrazine treatment appears to enhance expression of the α A II and β A II genes, as compared to nonanemic individuals.