• TROP2 is a tumor-associated calcium ion signal transduction protein and a cell surface glycoprotein, which is highly expressed in tumor tissues. It can promote the growth, proliferation and metastasis of tumor cells by regulating the calcium signaling pathway, the expression of cyclin and reducing the adhesion of fibronectin. 
• The exon 1 of rat Trop2 gene that encode extracellular domain and was replaced by human counterparts in B-hTROP2 rats. The signal peptide, promoter, transmembrane domain, 5’UTR and 3’UTR region of the rat gene were also retained. The chimeric TROP2 expression was driven by endogenous rat Trop2 promoter, while rat Trop2 gene transcription and translation will be disrupted. 
• mRNA expression: SD rats Trop2 mRNA was detectable in wild-type SD rats. Human TROP2 mRNA was detectable only in homozygous B-hTROP2 rats, but not in wild-type SD rats. 
• Protein expression: r/hTROP2 was detectable in uterus, skin, bladder, stomach, colon and ovary of wild-type SD rats and homozygous B-hTROP2 rats.

Gene targeting strategy for B-hTROP2 rats. The exon 1 of rat Trop2 gene that encode extracellular domain and was replaced by human counterparts in B-hTROP2 rats. The signal peptide, promoter, transmembrane domain, 5’UTR and 3’UTR region of the rat gene were also retained. The chimeric TROP2 expression was driven by endogenous rat Trop2 promoter, while rat Trop2 gene transcription and translation will be disrupted. 

Species specific analysis of TROP2 gene expression in wild-type SD rats and homozygous humanized B-hTROP2 rats by RT-PCR. Stomach was collected from wild-type SD rats (+/+) and homozygous B-hTROP2 rats (H/H). SD rats Trop2 mRNA was detectable in wild-type SD rats. Human TROP2 mRNA was detectable only in homozygous B-hTROP2 rats, but not in wild-type SD rats. 

TROP2 expression analysis in homozygous B-hTROP2 rats by western blot. Stomach, colon, ovary, uterus, skin and bladder were collected from wild-type SD rats (+/+) and homozygous B-hTROP2 rats (H/H), and analyzed by western blot with anti-TROP2 antibody (abcam, ab214488). r/hTROP2 was detectable in uterus, skin, bladder, stomach, colon and ovary of wild-type SD rats and homozygous B-hTROP2 rats.