Combinatorial genetic loss of Tr2/Tr4 leads to elevated expression of the murine embryonic β-type globin genes. (A) Breeding strategy to generate conditional tandem loss of Tr2 and Tr4 function and schematic showing the location of the primers used in qPCR for detection of the floxed (unrecombined) and total DNA. (B-C) Time-course analyses of Cre-mediated Tr4^f/f deletion and TR4 mRNA change in Tr2^−/−:Tr4^f/f Lin⁻ BM cells, either mock-infected (Cre⁻) or infected with Ad-Cre (Cre⁺), on days 0 and 2 of culture. Tr4^f/f genomic DNA and TR4 mRNA quantification were performed using SBYR Green-based qPCR. (D-I) Combined loss of TR2/TR4 leads to elevated embryonic β-type globin gene expression. Values of tested genes are first expressed relative to the expression of housekeeping gene Oaz1, and then relative to the transcript of interest in Cre⁻ cells (arbitrarily set at 100% or onefold).