Loss of MT1-MMP and MT2-MMP leads to embryonic demise. (A) Whole mount darkfield images of mouse embryos. Double-deficient embryos (1−/−; 2−/−) at E9.5 are indistinguishable from their control littermates; at E10.5, however, they are easily distinguished by their retarded growth. (B) Double-mutant embryos moreover display dilated vasculature (v) and enlarged pericardia (P). All double-deficient embryos are dead at E11.5. Scale bars: (A) 1 mm; (B) 0.3 mm.