Gene targeting strategy for B-hHER3 mice. The exons 1-17 of mouse Her3 gene that encode the extracellular domain and transmembrane domain were replaced by human HER3 exons 1-17 in B-hHER3 mice.

Strain specific analysis of HER3 gene expression in wild type (WT) mice and B-hHER3 mice by RT-PCR. Mouse Her3 mRNA was detectable only in liver of WT mice (+/+). Human HER3 mRNA was detectable only in homozygous B-hHER3 mice (H/H) but not in WT mice (+/+).

Immunohistochemical (IHC) analysis of HER3 expression in homozygous B-hHER3 mice. The liver and colon were collected from WT and homozygous B-hHER3 mice (H/H) and analyzed by IHC with anti-HER3 antibody. HER3 was detectable in WT mice and homozygous B-hHER3 mice due to the cross-reactivity of the antibody. The arrow indicates tissue cells with positive HER3 staining (brown).