Coexpression of ε, Gγ and Aγ Globin mRNA in Embryonic Red Blood Cells from a Single Copy β-YAC Transgenic Mouse

We utilized reverse transcription polymerase chain reaction (RT-PCR) to amplify ε, Gγ and Aγ globin cDNAs from single red blood cells isolated from a day-10 transgenic fetus harboring a single copy of the human β-YAC. A detailed structural analysis of the β-YAC showed a single copy of each β-like globin gene is present and linked to the locus control region (LCR). RNAse protection analysis of RNA isolated from all erythroid tissues from day-8 to day-16 of development and the adult stage showed proper developmental switching of the β-like globin gene expression. Using ε/γ and Gγ/Aγ primer sets in separate RT-PCR reactions on RNA from single day-10 red blood cells we observed an intercellular variation in the ε and γ RT-PCR products that may be indicative of a change in the LCR preference from the ε gene promoter to the γ gene promoter during switching. We also found that the majority of the red blood cells examined contain all three globin mRNA species. These observations suggest that either the LCR is capable of interacting simultaneously with more than one globin gene promoter or alternatively, the LCR may interact with only one promoter at any given time, but its interaction oscillates between promoters (flip-flop mechanism) resulting in similar expression of more than one gene from a single β-globin locus.