[A quick and efficient method to generate hemophilia B mouse models by the CRISPR/Cas system].

Hemophilia B, or the Christmas disease, is a common human disease caused by coagulation factor Ⅸ (FⅨ) deficiency. It is an X-linked recessive hereditary disease. Here we obtained FⅨ-knockout mouse strains with phenotype of hemophilia B with the CRISPR/Cas system efficiently. We chose the 8th exon as the target locus, and co-injected codon-optimized Cas9 mRNA with sgRNA of FⅨ into C57BL/6 mice zygotes. We obtained 60 mice in total and genotyped them by high resolution melting (HRM) and sequencing. The results showed the mutation rate was 85.0% in total, and 79.5% and 95.2% in males and females, respectively. No off-targets were detected in the similar locus by HRM. We future measured the FⅨ activity of each mice. The FⅨ: C of mutant mice were significantly below the normal level and reduced to 6.82% of wild-type mice. The activity assay demonstrated that all the mutant mice were lack of FⅨ. In summary, we have generated hemophilia B model mice with extreme efficiency, using the RNA-guided Cas9 nuclease gene editing system.