F9 KO Mice

Catalog Number: C001509

Strain Name: C57BL/6JCya-F9^em1/Cya

Genetic Background: C57BL/6JCya

Reproduction: Homozygote x Homozygote

Strain Description

Hemophilia is a group of genetic bleeding disorders that affect the blood’s ability to clot. The common feature of this disease is the generation of abnormal clotting factors, which leads to prolonged clotting time and increased risk of bleeding after minor injuries. In severe cases, spontaneous bleeding can occur even without obvious trauma. As an X-linked recessive disorder, Hemophilia B is more common in males, with approximately 1 in every 30,000 newborn males worldwide being affected ^[1]. Hemophilia B is caused by mutations in the F9 (FIX) gene, which leads to a deficiency of clotting factor IX. The severity of the disease is usually correlated with the activity level of factor IX in the blood plasma. Mild patients (IX factor activity >5%, >0.05 IU/mL) do not experience spontaneous bleeding, but the amount of bleeding after injury or surgery may increase. Moderate patients (IX factor activity 1%-5%, 0.01-0.05 IU/mL) rarely experience spontaneous bleeding, but even minor injuries can cause prolonged bleeding. Severe patients (IX factor activity <1%, <0.01 IU/mL) experience spontaneous bleeding, soft tissue or joint bleeding, and severe subcutaneous hematomas ^[2]. According to the Centers for Disease Control and Prevention (CDC) in the United States, severe Hemophilia B patients account for 30%-40% of all diagnosed patients ^[3].

The F9 gene encodes coagulation factor IX, a vitamin K-dependent serine protease that plays a key role in the intrinsic coagulation pathway. Factor IX circulates in the blood as an inactive zymogen and is converted to its active form, factor IXa, by the cleavage of its activation peptide by factor XIa. Factor IXa then interacts with Ca2+ ions, membrane phospholipids, and factor VIII to activate factor X in the coagulation cascade. The body can normally stop bleeding when the levels of factors VIII and IX are ≥50% of normal values ^[4]. The deficiency of the F9 gene can lead to a clotting disorder with insufficient factor IX, causing X-linked recessive hemophilia B.

F9 KO mice are Hemophilia B disease models constructed by knocking out the mouse F9 gene. F9 KO mice lack F9 mRNA expression and exhibit coagulation dysfunction and other Hemophilia B-related phenotypes. They can be used to study the genetic mechanisms and clinical phenotypes of Hemophilia B in humans and to assist in developing, screening, and evaluating therapeutic drugs. The homozygotes are viable and fertile. Tail docking may lead to significant bleeding. Immediate hemostasis, such as cauterizing the tail incision, is advised to prevent health complications in homozygous mice. Usually, ear tags are applied to mice at 2 to 3 weeks of age (a small notch is made with scissors for identification). After tail clipping for genotyping, the tail wound should be promptly cauterized (using metal forceps heated with an alcohol lamp) to prevent fatal bleeding. Following cauterization, place the mouse in a clean cage to prevent wound infection and add environmental enrichment.

Strain Strategy

The F9 gene is located on the X chromosome. The exon 1-8 of the mouse F9 gene were knocked out, resulting in a lack of F9 gene expression in this strain.

Application

• Research on Hemophilia B.
  
  

Validation Data

1. Detection of mRNA expression

Figure 1. Detection of F9 mRNA expression in 6-week-old male F9 KO mice and wild-type mice (WT) (n=3). The RT-qPCR results showed no expression of F9 mRNA in the liver and cholecyst of F9 KO mice. (ND, Not detected)

2. Coagulation tetrad test

Figure 2. Coagulation four-item indicators of 11-week-old F9 KO mice and wild-type mice (WT) (n=5). The results showed that compared with wild-type mice, the activated partial thromboplastin time (APTT) of F9 KO mice was significantly prolonged, indicating that the mice had coagulation dysfunction and prolonged bleeding time, similar to the phenotype of the classic F9 KO disease model ^[5]. In addition, there were no significant differences in the prothrombin time (PT), thrombin time (TT), and fibrinogen (FIB) between F9 KO mice and wild-type mice, which is consistent with the changes in coagulation indicators of clinical Hemophilia B patients ^[6].

References

[1]Goodeve AC. Hemophilia B: molecular pathogenesis and mutation analysis. J Thromb Haemost. 2015 Jul;13(7):1184-95.
[2]Soroka AB, Feoktistova SG, Mityaeva ON, Volchkov PY. Gene Therapy Approaches for the Treatment of Hemophilia B. International Journal of Molecular Sciences. 2023; 24(13):10766.
[3]Centers for Disease Control and Prevention. Community Counts Registry Report – Males with Hemophilia 2014–2017. [Online] Available at: https://www.cdc.gov/ncbddd/hemophilia/communitycounts/registry-report-males/diagnosis.html
[4]Merck Manuals Professional Edition. Hemophilia - Hematology and Oncology - MSD Manual Professional Edition. [Online] Available at: https://www.msdmanuals.com/en-in/professional/hematology-and-oncology/coagulation-disorders/hemophilia [Accessed 12 Dec. 2023].
[5]Wang L, Zoppè M, Hackeng TM, Griffin JH, Lee KF, Verma IM. A factor IX-deficient mouse model for hemophilia B gene therapy. Proc Natl Acad Sci U S A. 1997 Oct 14;94(21):11563-6.
[6]Thrombosis and Hemostasis Group, Hematology Society of Chinese Medical Association; Hemophilia Treatment Center Collaborative Network of China. [Consensus of Chinese expert on the diagnosis and treatment of hemophilia (version 2017)]. Zhonghua Xue Ye Xue Za Zhi. 2017 May 14;38(5):364-370. Chinese.