• FXII is a protease that is primarily produced in the liver and circulates as a single-chain zymogen in plasma, playing an important role in the intrinsic pathway of blood coagulation and hemostasis. Upon contact with negatively charged surfaces, FXII converts into its double-stranded active form, FXIIa. The absence of FXII in humans and mice does not affect normal hemostasis ability, and the lack of FXII can inhibit thrombus formation, making it an important target in thrombosis treatment.
• Gene editing strategy: The exons 1~12 of mouse FXII gene were replaced by the exons 1~14 of human FXII gene in B-hFXII mice plus. The promoter, 5’UTR and 3’UTR region of the mouse gene are replaced by human counterparts.
• mRNA expression analysis: Mouse FXII mRNA was detectable in liver of wild-type C57BL/6 (+/+) and heterozygous B-hFXII mice plus (H/+). Human FXII mRNA was detectable in heterozygous B-hFXII mice plus (H/+) but not in wild-type mice.
• Protein expression analysis: Mouse FXII was only detectable in wild-type mice. Human FXII was exclusively detectable in homozygous B-hFXII mice plus but not in wild-type mice.
• In vivo efficacy: FXII-targeted small nucleic acid drugs (synthesized according to patents) were efficacious in B-hFXII mice plus. This strain can be used to screen for the knockdown of the expression level of small nucleic acid drugs.
• Application: This product is used for pharmacodynamics and safety evaluation of cardiovascular diseases such as thrombosis

Gene targeting strategy for B-hFXII mice plus. The exons 1~12 of mouse FXII gene were replaced by the exons 1~14 of human FXII gene in B-hFXII mice plus. The promoter, 5’UTR and 3’UTR region of the mouse gene are replaced by human counterparts.

Strain specific analysis of FXII mRNA expression in wild-type C57BL/6 mice and B-hFXII mice plus by RT-PCR. Liver RNA were isolated from wild-type C57BL/6 mice (+/+) and heterozygous B-hFXII mice plus (H/+), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human FXII primers. Mouse FXII mRNA were detectable in wild-type C57BL/6N and heterozygous B-hFXII mice plus. Human FXII mRNA was only detectable in heterozygous B-hFXII mice plus.

Strain specific FXII expression analysis in homozygous B-hFXII mice plus by ELISA. Serum were collected from wild-type mice C57BL/6 mice (+/+) (n=3, male, 6 weeks old) and homozygous B-hFXII mice plus (H/H) (n=3, male, 6 weeks old), and analyzed by ELISA with species-specific Human Factor XII ELISA Kit  (Abcam, ab192144) and Mouse FXII ELISA kit (Abcam, ab272776). (A) Mouse FXII was only detectable in wild-type mice. (B) Human FXII was exclusively detectable in homozygous B-hFXII mice plus but not in wild-type mice. Values are expressed as mean ± SEM.

The inhibitory efficiency of the FXII-targeted small nucleic acid drug in heterozygous B-hFXII mice plus. B-hFXII mice plus were randomly divided into 2 groups (n=4, 7 weeks old, male). The FXII-targeted small nucleic acid drug (synthesized according to patents) and saline were administered to the mice individually. The nucleic acid drug was administered in the form of saline aqueous solution. (A) The schematic diagram of experimental processing. (B) The changes in FXII expression levels in serum on day 7 after administration, compared to the levels before administration. The human FXII levels in the treatment group were reduced compared to the control group (G1). Values are expressed as mean ± SEM.