The presence of minute amounts of embryonic zeta-globin chains in adult hemolysates is a marker for carriers of alpha-thalassemia-1 resulting from (--SEA/) deletion. Recently, we developed a murine monoclonal antihuman embryonic zeta-globin chain antibody, 8E8. By using this antibody, we have now established a slot-blot immunobinding assay for the rapid detection of zeta-globin chains in adult hemolysates. zeta- globin chains were found to be present in 30 blood samples obtained from individuals who were carriers of alpha-thalassemia-1. In another 30 blood samples from individuals who were not carriers of the (--SEA/) deletion, zeta-globin chains were not detected. This simple diagnostic test can be used in appropriate populations to identify those couples at risk of conceiving fetuses afflicted with the Hb Bart's hydrops fetalis syndrome due to homozygous alpha-thalassemia.

The human alpha-globin-like embryonic zeta-globin chains are present in abundance during the first 5 to 6 weeks of gestation. Subsequently, zeta-globin chains are present in fetal blood at a very low level, which is supplanted by the expression of alpha-globin chains. Adult individuals who are carriers of the (--SEA/) alpha-thalassemia deletion, in contrast to normal adults, have low levels of embryonic zeta-globin chains in their circulating erythrocytes. In this investigation, we constructed stable mouse-human hybrid cells with murine erythroleukemia cells bearing human chromosome 16, with either the normal alpha-globin gene cluster (alpha alpha/) or the (--SEA/) type of alpha-thalassemia deletion. The results on the human zeta- globin gene expression in these hybrid cells indicate that murine adult erythroid transcription factors can induce the expression of human embryonic zeta-globin gene is cis to the (--SEA/) deletion, in parallel with the endogenous mouse alpha-globin gene expression. These data also show the importance of the DNA sequences within the (--SEA) deletion in regulating the expression of zeta-globin gene in cis during normal human hemoglobin ontogeny.

Human embryonic epsilon globin chains were isolated from lysates of cultured human leukemic K562 cells induced with hemin. Mice were immunized with epsilon globin chains, and a murine hybridoma cell line was established that secreted monoclonal anti-epsilon globin antibody. A sensitive and specific slot blot immunoassay for epsilon globin chains has been developed. epsilon Globin chains were shown to be present in hemolysates from fetuses of 20 weeks' gestation but were not detected in normal cord blood hemolysates. This immunoassay is useful for the study of epsilon globin ontogeny during embryonic and fetal development as well as for searching for inappropriate epsilon globin chain expression in hematologic disorders resulting from genetic abnormalities or neoplastic processes.