Generation of GATA-1 HRD–GATA-1^V205G transgenic mouse lines and transgenic rescue of GATA-1.05 mutant. (A) Murine GATA-1 genomic locus and GATA-1 HRD–GATA-1^V205G transgene are schematically illustrated. Exons and 3 core regions of GATA-1 HRD (GATA-1 hematopoietic enhancer [G1HE], double GATA, and CACCC²⁷ ) are indicated. NF and CF correspond to N-terminal and C-terminal zinc fingers, respectively. (B) Transactivation activity of wild-type GATA-1 and GATA-1 mutants in the absence or presence of FOG-1. The increase in CAT activity in response to wild-type GATA-1 was arbitrarily set as 100, and all other samples were expressed relative to this value. The average of 3 independent experiments is shown, and the error bars represent the standard error of the mean (SEM). (C) Transgene-derived GATA-1 and mutant mRNA levels. The mRNA levels were determined by semiquantitative RT-PCR. Reverse-transcribed cDNAs were rendered for 27, 30, and 33 cycles of amplification. Filled arrowheads indicate the migration position expected for transgene-derived GATA-1 amplicon, while open arrowheads indicate the position of endogenous GATA-1 amplicon. (D) Transgenic rescue of GATA-1.05 mutant mice from embryonic lethality. The total number of pups in each transgenic rescue line is indicated. The frequency of V205GR mice is expressed as ratios of the number of V205GR mice observed to that predicted from Mendelian expectations. (E) Transgenic rescue of GATA-1.05 mutant embryos from embryonic lethality. Embryos were genotyped at E14.5. Total number of embryos in each transgenic rescue line is indicated. Frequency of V205GR embryos is expressed as ratios of the number V205GR embryos observed to that predicted from Mendelian expectations.