• Background: Mannose receptor C-type 2 (MRC2) is a type I transmembrane protein and a member of the mannose receptor family. It binds to collagen and internalizes it through clathrin-dependent endocytosis, leading to collagen degradation in lysosomes. Additionally, it can form a complex with uPA (urokinase plasminogen activator) and uPAR (uPA receptor) to convert plasminogen into plasmin, resulting in the degradation of extracellular matrix (ECM) components. This protein participates in ECM remodeling, cell chemotaxis, and migration under both physiological and pathological conditions, such as fibrosis and cancer. It also facilitates lymphangiogenesis and is involved in the clearance of collectins and the regulation of the immune system. This target can be investigated as a biomarker and therapeutic target for various cancers.
• Targeting strategy: The exons 1-30 of mouse Mrc2 gene that encode signal peptide, extracellular domain and part of transmembrane domain are replaced by human counterparts in B-hMRC2 mice. The genomic region of mouse Mrc2 gene that encodes cytoplasmic portion is retained. The promoter, 5’UTR and 3’UTR region of the mouse gene are also retained. The chimeric MRC2 expression is driven by endogenous mouse Mrc2 promoter, while mouse Mrc2 gene transcription and translation will be disrupted.
• Validation: Human MRC2 mRNA and protein were detectable in the B-hMRC2 mice but not in C57BL/6JNifdc mice.
• Application: Tumor cell lines inoculated in B-hMRC2 mice can be used to study the in vivo efficacy and safety evaluation of antibody drugs

Gene targeting strategy for B-hMRC2 mice. The exons 1-30 of mouse Mrc2 gene that encode signal peptide, extracellular domain and part of transmembrane domain are replaced by human counterparts in B-hMRC2 mice. The genomic region of mouse Mrc2 gene that encodes cytoplasmic portion is retained. The promoter, 5’UTR and 3’UTR region of the mouse gene are also retained. The chimeric MRC2 expression is driven by endogenous mouse Mrc2 promoter, while mouse Mrc2 gene transcription and translation will be disrupted.

Western blot analysis of MRC2 protein expression in homozygous B-hMRC2 mice. Various tissue lysates were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hMRC2 mice (H/H), and then analyzed by western blot with species-specific anti-mouse Mrc2 antibody (R&D, AF4789) and anti-human MRC2 antibody (abcam, ab317323). 40 μg total proteins were loaded for western blotting analysis. Mouse Mrc2 was only detectable in wild-type C57BL/6JNifdc mice. Human MRC2 was exclusively detectable in B-hMRC2 mice.

Strain specific analysis of MRC2 mRNA expression in wild-type C57BL/6JNifdc mice and homozygous B-hMRC2 mice by RT-PCR. Lung RNA were isolated from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hMRC2 mice (H/H). mouse Mrc2 mRNA was only detectable in wild-type mice. Human MRC2 mRNA was exclusively detectable in homozygous B-hMRC2 mice but not in wild-type mice.