Transcriptional regulation of hemoglobin switching in chicken embryos.

Abstract

We used recombinant chicken deoxyribonucleic acid clones containing embryonic and adult ,8-globin genes and "runoff" endogenous nuclear transcription to investigate the expression of embryonic and adult f-globin genes during hematopoiesis in the developing chicken embryo. Purified, cloned deoxyribonucleic acids were digested with various restriction enzymes, separated on agarose gels, blotted to nitrocellulose, and annealed with purified nuclear [3P]ribonucleic acid synthesized in vitro from embryonic or adult red cell nuclei. Transcription of the respective globin genes was assayed by hybridization of nuclear [3P]ribonucleic acid to specific restriction fragments containing adult or embryonic coding sequences. Our results indicate that little, if any, transcription from the adult or embryonic ,8-globin genes is detectable in the heterologous red cell nuclei, even under conditions in which ribonucleic acid processing probably does not occur.Differential expression of hemoglobin genes during avian development offers a model system for studying gene regulation at both the cellular and molecular levels. In the developing chicken embryo, hemoglobin first appears in first-generation erythroblasts at approximately 30 to 35 h of development. These cells then serve as the progenitors of six subsequent maturational generations of erythroblasts, each of which contains characteristic amounts of hemoglobin and displays unique morphological characteristics. These cells mature rather synchronously and, by day 6 of embryonic development, most have become erythrocytes. Between days 6 and 7, another lineage ofhematopoietic cells, the definitive embryonic lineage, enters the circulating erythrocyte population, arising from the endothelial lining of the blood vessels. The relationship between these two lineages and the possible generation of the definitive series from the immediate precursors of the primitive lineage are the focus of current investigation (2,16,17).The definitive series enters the circulating erythroid compartment between days 6 and 7 as fairly mature erythroblasts and by days 11 to 13 matures into inactive erythrocytes. These cells are the major erythroid cells in circulation until hatching, at which time a second definitive line appears. Although minor differences occur, by and large both definitive lines produce similar types of hemoglobin chains (1), and both differ from the primitive series in the synthesis of specific fi chains.In this and former studies, we have focused on the switch in f-chain synthesis between the primitive and first definitive series. Given the similarities in fl-chain synthesis between the two definitive lines, we have not distinguished between the two types of definitive cells, and, for convenience, refer to both as adult red cells since they both produce adult, chains. In contrast, given the distinctive embryonic, chains synthesized in the primitive series, we refer to these cells as embryonic red cells. In examining the control of embryonic and adult globin gene expressions, we previ...

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Suppression of metastasis-associated S100A4 gene expression by gamma-interferon in human colon adenocarcinoma cells

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Translocation of an erythroid-specific hypersensitive site in deletion-type hereditary persistence of fetal hemoglobin.

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