The synthesis of the Gγ and Aγ chains of human fetal hemoglobin in erythroid colonies cultured from peripheral blood BFUe's of normal adults and newborn and of subjects with an Aγ or a Gγ chain abnormal fetal hemoglobin

Peripheral blood mononuclear cells from normal adults, normal newborn infants, and from newborn and adult subjects with one of three γ chain variants (^GγF-Malta I, ^GγF-Port Royal, ^AγF-Hull) were cultured in vitro with erythropoietin. The ³⁵S-methionine-labelled hemoglobin from 13- to 15-day-old BFUe-derived colonies was studied by chromatography on columns of DEAE-cellulose and the quantities of Hbs A₂, F_x, and F₀ determined. The percentages of ^Gγ and ^Aγ chains in isolated Hb F_x and Hb F₀ were determined using high-performance liquid chromatography (HPLC) of the tryptic peptides of these proteins. Calculation of these percentages was based on the total activities of the ^GγT-15 and ^AγT-15 peptides which contain one (³⁵S-labelled) methionyl residue each and can be separated by the HPLC procedure. The data show an increased synthesis of Hb F in the ?adult”? colonies and a decreased synthesis in the ?newborn”? colonies. The ^Gγ to ^Aγ ratio of the Hb F from adult colonies varied greatly. The percentages of ^Gγ and ^Aγ chains in the Hb F from adult colonies correlated with the percentages in the Hb F isolated from the Hb F of circulating red blood cells. The ^Gγ to ^Aγ ratio in the Hb F from newborn colonies was high as in the Hb F from cord blood samples. ^Gγ and ^Aγ chain abnormal Hb F variants were readily detectable in colonies from both adults and newborn. The ^Gγ to ^Aγ ratio in the Hb F of colonies of adult Hb F-Malta I and Hb F-Hull heterozygotes approached 1, but that of adult Hb F-Port Royal heterozygotes remained about as high as in colonies from newborn heterozygotes. The percent Hb F-Port Royal in the Hb F of adult colonies was twice that in the Hb F of newborn colonies. These results are discussed in the light of information from recent detailed studies of genomic DNA assuming controlling functions for the segments of DNA that are interspersed between the various structural genes.