Haemoglobin Synthesis by Fetal Erythroid Cells in an Adult Environment

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Abstract
Although the developmental switch from fetal to adult Hb production has been well characterized in terms of protein synthesis, very little is known about its control at the cellular level. To determine whether the switch is controlled by environmental factors or programmed into the hemopoietic cell population, the effects of transplantation of fetal and adult hemopoietic cells into lethally irradiated lambs on Hb synthesis by the transplanted cells were studied. In 2 lambs which were irradiated but not transplanted, 2 lambs which were grafted with autologous marrow, and 1 lamb which was grafted from an allogeneic twin, Hb synthesis showed an adult pattern following transplantation, with .gamma.-chain synthesis never exceeding 7% of non-.alpha. chain production. Of 11 lambs transplanted with fetal hemopoietic cells, only 2 showed evidence of engraftment. During the 24-26 days that these animals survived, Hb synthesis showed a predominantly fetal pattern, though there was a gradual increase in .beta.-chain production of donor origin. This increase occurred earlier than would be expected from the gestational age of the transplanted cells, but more slowly than might be expected if environmental factors were entirely responsible for expression of adult or fetal Hb synthesis.