Developmental regulation of globin and nonglobin messenger RNAs in avian erythroid cells

During embryonic development in the chicken two morphologically distinct erythroid cell populations sequentially appear. Coincidentally with the change in cell populations that begins on the sixth day of embryonic life, the hemoglobins of the early embryo are gradually replaced by a new set of hemoglobins, which are almost identical to those of the adult chicken. We have used recombinant DNAs to investigate the molecular mechanisms underlying these developmental changes. With respect to the eight nonglobin species of messenger RNA that we have studied, seven are present at approximately equal concentrations in erythroid cells from 5-day embryos and from anemic adults. This suggests that the replacement of erythroid cell populations is not accompanied by a general reorganization of gene expression. With respect to globin gene expression, however, we find that all but one of the globin genes studied (alpha D-globin) undergo dramatic developmental regulation. We have also shown that the expression of the gene for the embryo specific alpha-like globin, pi'-globin, is principally regulated at the level of transcription.