Ontogeny of hamster hemoglobins in yolk-sac erythroid cells in vivo and in culture.

Abstract

During mammalian Hb ontogeny, synthesis of the earliest globin chains (embryonic) is ultimately replaced by synthesis of globin chains (adult) characteristic of the fully formed organism. Elements of control of initiation, progression and completion of globin-chain ontogeny are poorly understood. In search of a cell culture system in which ontogeny might be studied under closely controlled experimental conditions, erythroid cells of the hamster embryo were chosen. First, the ontogeny of globin chains was defined in these yolk-sac-derived erythroid cells from day 10 through day 13 in gestation. Amounts of individual embryonic and adult globin chains were quantified, as were their rates of synthesis. Next, analogous studies were performed on yolk-sac erythroid cells from day 10 in gestation (prior to the appearance of fetal liver) growing in culture for 3 days, corresponding to days 10-13 in vivo. The ontogenic program in culture was virtually identical to that in vivo. Approximately 70% of active globin synthesis was embryonic at day 10 in gestation (day 0 of culture), declining to 30% by day 13 in gestation (day 3 of culture). Whereas only trace synthesis of the adult non-.alpha. chains (.beta.major and .beta.minor) were initially observed, their combined active synthesis achieved a level of .apprx. 30% 3 days later both in vivo and in culture. Cell Hb content and cell morphology were similar in both systems. An ontogenic program for globin-chain synthesis exists in these primitive erythroid cells, overriding possible influences of cell environment. These cells in culture may provide a means of examining cell mechanisms associated with globin-gene ontogeny under controlled experimental conditions.