BetaA, the major beta globin in definitive red blood cells, is present from the onset of primitive erythropoiesis in chicken.

Reflecting physiological changes in oxygen acquisition and regulatory changes in globin transcription, the makeup of globin chains in erythrocytes varies in development and disease. The relationship between the globin chain composition and erythropoietic lineages/niches is not well-understood. Using a combination of proteomic-, genomic-, and intron-based in situ hybridization analyses, we show that the transcripts and protein product of the major adult beta globin, betaA, are present as early as the major embryonic beta globins during chicken primitive erythropoiesis. A rapid rise in betaA percentage is seen from embryonic day (E) 5, reaching adult profile by E7. Our data suggest that betaA locus is active from the onset of primitive erythropoiesis and that beta globin switching during development may reflect a change in relative transcript abundance rather than a strict on/off switch in gene activation.

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