V205GR are prone to die from massive anemia during the perinatal period. (A) The frequency of live V205GR pups at embryonic (E18.5; open bars) or postnatal (within 3 days after birth; filled bars). Rescue efficiency was calculated as previously described.¹⁶  Total number of pups in each transgenic rescue line is indicated in parentheses. (B) Transgene derived (open arrowhead) or endogenous (filled arrowhead) Gata1 mRNA expression in GATA1^V205G transgenic mouse lines. The mRNA levels were determined by semi-quantitative RT-PCR. Hprt mRNA is used as an internal control. Gata1 expression level normalized to Hprt is shown under each lane. The most left WT sample is set to 1.