Combined disruption of Ku80 and Dido is lethal in mid-gestation. The figure shows embryos isolated at embryonic day E9.5 (top) and E10.5 (bottom). Ku80 heterozygous Dido mutant embryos are shown at left and Ku80 Dido double mutant embryos at right. At E9.5, double mutant embryos show growth delay in head, heart, and somites. At E10.5, most Ku80 Dido double mutant embryos are being resorbed. Magnification, 40-fold. All animal experiments were performed in compliance with EU and CNB animal committee directives.