Gene targeting strategy for B-hDLL4 mice. The exons 2-9 of mouse Dll4 gene that encode the extracellular domain were replaced by human DLL4 exons 2-9 in B-hDLL4 mice.

Strain specific analysis of DLL4 gene expression in wild-type (WT) mice and B-hDLL4 mice by RT-PCR. Mouse Dll4 mRNA was detectable only in heart and lung of WT mice (+/+). Human DLL4 mRNA was detectable only in homozygous B-hDLL4 mice (H/H) but not in WT mice (+/+).