Fig. 1. Inactivation of Foxp1 in mice. (A) Schematic of Foxp1-targeting construct showing probe and predicted PstI digest pattern. (B) Southern blot analysis of yolk sac DNA using the probe indicated in A. (C) Immunohistochemistry of wild-type (WT) and Foxp1 null (^–/–) hearts at E13.5 using previously characterized Foxp1 antibody (Lu et al., 2002). Note lack of Foxp1 expression in ^–/– heart tissue. (D) Distribution table of embryonic lethality and lack of postnatal survival in Foxp1 homozygous null embryos and mice. (E) Wild-type and Foxp1^–/– embryos at E14.5, showing the perivascular hemorrhage and edema in ^–/– embryos. Scale bars: 50 µm.