Activation of βh0 transcription is influenced by multiple parameters in mice with reduced Ey transcription. (A) Schematic map of ΔEyhygro allele. (▨) Selectable marker gene PGK-Hygro. (arrow) Its transcriptional direction. Representative gel and quantitation of βh0 expression in e10.5 wild-type D/S and ΔEyhygro/S yolk sacs. Error bars represent SD of at least 3 littermates with the genotype marked throughout. (B) Schematic map of ΔEy(inv)Δβh1 allele. (▪) βh0 gene that was relocated 5 kb further away from the LCR on the mutant allele compared with the wild-type allele. (arrow) Inversion also changed the transcription direction of the βh0 gene on this mutant allele. Representative gel and quantitation of βh0 expression in e10.5 wild-type D/S and ΔEyΔβh1(inv)/S yolk sacs. (C) Comparative summary of βh0 transcription in various mutants in which it has increased transcription.