• Guanylate cyclase 2C, also known as guanylyl cyclase C (GC-C), intestinal guanylate cyclase, guanylate cyclase-C receptor, or the heat-stable enterotoxin receptor (hSTAR) is an enzyme that in humans is encoded by the GUCY2C gene.
• Guanylyl cyclase is an enzyme found in the luminal aspect of intestinal epithelium and dopamine neurons in the brain. The receptor has an extracellular ligand-binding domain, a single transmembrane region, a region with sequence similar to that of protein kinases, and a C-terminal guanylate cyclase domain. Tyrosine kinase activity mediates the GC-C signaling pathway within the cell.
• The exons 1~11 of mouse Gucy2c gene that encode extracellular domain is replaced by human counterparts in B-hGUCY2C mice. The genomic region of mouse Gucy2c gene that encodes transmembrane domain and cytoplasmic portion is retained. The promoter and 5’UTR region of the mouse gene are replaced by human counterparts. The 3’UTR region of the mouse gene are retained. The chimeric GUCY2C expression is driven by endogenous human promoter.
• Mouse Gucy2c mRNA was detectable only in wild-type mice. Human GUCY2C mRNA was detectable only homozygous B-hGUCY2C mice but not in wild-type mice.
• GUCY2C was detectable in colon and small intestine of B-hGUCY2C mice and wild-type C57BL/6 mice, we have verified that the antibody was cross-reactive between human and mouse.
• Humanized mice can be used to study the in vivo efficacy and safety evaluation of GUCY2C antibody drug.

Gene targeting strategy for B-hGUCY2C mice. The exons 1~11 of mouse Gucy2c gene that encode extracellular domain is replaced by human counterparts in B-hGUCY2C mice. The genomic region of mouse Gucy2c gene that encodes transmembrane domain and cytoplasmic portion is retained. The promoter and 5’UTR region of the mouse gene are replaced by human counterparts. The 3’UTR region of the mouse gene are retained. The chimeric GUCY2C expression is driven by endogenous human promoter.

Strain specific analysis of GUCY2C mRNA expression in wild-type C57BL/6 mice and B-hGUCY2C mice by RT-PCR. Small intestinal RNA were isolated from wildtype C57BL/6 mice (+/+) and homozygous B-hGUCY2C mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human GUCY2C primers. Mouse Gucy2c mRNA was detectable only in wild-type mice. Human GUCY2C mRNA was detectable only homozygous B-hGUCY2C mice but not in wild-type mice.

Strain specific GUCY2C expression analysis in homozygous B-hGUCY2C mice by flow cytometry. Colon and small intestine were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hGUCY2C mice (H/H) and analyzed by flow cytometry with anti-human GUCY2C Antibody (R&D, FAB2157R-100UG). GUCY2C was detectable in colon and small intestine of B-hGUCY2C mice and wild-type C57BL/6 mice, we have verified that the antibody was cross-reactive between human and mouse.