Definitive Red Blood Cells Research Articles

Hemoglobin switching in chickens. Is the switch initiated post-transcriptionally?

We have investigated the transcriptional specificity of chick embryo erythroid nuclei as a function of developmental age during progression of the hemoglobin switch. Nuclei were allowed to transcribe in vitro in the presence of high specific activity [alpha-32P]CTP and the radioactive transcripts were hybridized to a collection of plasmid clones spanning the beta-like globin gene region of the chicken genome. The results reveal locus-specific waves of transcription appearing during the interval between 5 and 12 days of incubation. The last wave, which comes in at 12 days, is highly specialized in transcription of the adult beta-globin gene locus. The most interesting wave of transcription occurs at 6-7 days. The most actively transcribed gene in the early part of this wave is the embryonic rho gene. As the wave progresses, the rho gene activity gradually gives way to beta gene transcription. Definitive red blood cells, which would be synthesizing little rho globin protein at this stage, appear to be responsible for the rho gene transcription. These results and additional data which we present indicate that during the initial stages of the hemoglobin switch the embryonic globin genes are silenced post-transcriptionally.

Chemical and immunological characterization of developmentally expressed chicken erythroid surface membrane antigens

The expression of two hematopoietic-lymphoid membrane antigens, referred to as chicken fetal antigen (CFA) and chicken adult antigen (CAA) were investigated on primitive and definitive peripheral red blood cells (RBC) from different-aged chickens using chemical and immunological techniques. Differential adsorptions of antisera specific for adult RBC membrane antigens permitted the serological dissection of CAA into eight antigenic determinants. CFA and CAA were assayed by hemagglutination, hemolysis, and immune precipitation of radioiodinated surface antigens of RBC from different-aged chickens. Primitive RBC express CFA, while definitive RBC express three distinct phenotypes: CFA, both CFA and CAA, or CAA, depending on the developmental age of the chicken from which the RBC were obtained. When solubilized membrane extracts of radioiodinated peripheral RBC from chickens at 5 and 18 days embryonic development (E5 and E18, respectively), 13 days posthatch development (H13), and adult chickens were immunoprecipitated and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the major antigen detected by anti-CFA sera was associated with proteins having apparent molecular weights ( M r) of 50,000 daltons (50 kd). The antigens detected by anti-CAA sera were associated with proteins having apparent M r of 102, 81, 48, and 43 kd.

Definitive red blood cell differentiation in a clonal line of mouse teratocarcinoma cultured in vivo in the chick embryo

The results reported in this article show that although erythropoiesis which occurs in organotypic cultures of the established PCC 3/A/1 teratocarcinoma cell line is restricted to the primitive erythrocytic series, stem cells able to differentiate along the definitive erythrocytic lineage are present in the cultures. These precursors can express their potentialities when culture fragments are grafted into the chick embryo. A possible explanation could be found in the lack of liver tissue differentiation in in vitro cultures of this teratocarcinoma line. In contrast, one can see in the grafted teratocarcinoma, a tissue showing the structure of liver parenchyme and associated with numerous anucleated erythrocytes.