High-level fetal liver chimerism in embryos generated from W⁴¹/W⁴¹ blastocyst complementations. (A) GFP-expressing ES cells were injected into wild-type or W⁴¹/W⁴¹ blastocysts, and fetal livers were isolated from E14.5 embryos. The percentage of GFP⁺ cells in each liver was measured by FACS analysis within the Lin⁻ subpopulation. Distribution of GFP chimerism in the fetal liver of embryos from W⁴¹/W⁴¹ or wild-type blastocysts. (B) GFP⁺ ES cells were injected into W⁴¹/W⁴¹ or wild-type blastocysts. E14.5 embryos were harvested, and 2 million chimeric fetal liver cells (CD45.2) were transplanted into CD45.1 recipient mice. FACS profiles for 5 mice transplanted with pooled cells from 4 randomly picked W⁴¹/W⁴¹ chimeric embryos. A control mouse transplanted with cells from a high-level wild-type chimera is shown as reference. Percentage of GFP⁺ donor cells in peripheral blood (PB) and bone marrow (BM) after 8 and 18 weeks, respectively.