Experimental approaches to embryonic erythropoiesis.

Erythroid systems in several developing organisms (including the human foetus and neonate, the chick embryo, the mouse embryo and the metamorphosing tadpole) have changing erythroid cell populations, changing haemoglobins and changing sites of erythropoiesis. The first two characteristics can be studied in vitro through organ cultures and cell cultures derived from early chick embryos. The prevention of early globin synthesis by specific inhibitors helps to define the mechanisms. There are interesting changes in the histone patterns during embryonic erythroid development and maturation. Changes in the composition and modification or erythroid chromatin proteins in the developing chick embryo and in the stimulated Friend erythroleukaemic system are discussed.