• Background: Complement Factor I (CFI) is a serine protease that regulates the activation of the complement system through the following mechanisms: Degradation of C3b and C4b、Dependence on Cofactors、Modulation of Inflammatory Response.
• Targeting strategy: The exons 1-14 of mouse Cfi gene that encode the whole molecule (ATG to STOP codon), including 3’UTR were replaced by human counterparts in B-hCFI mice. The promoter and 5’UTR region of the mouse gene are retained. The CFI expression is driven by the endogenous mouse Cfi promoter, while mouse Cfi gene transcription and translation will be disrupted.
• Validation: Human CFI mRNA and protein were detected in the B-hCFI mice but not in C57BL/6JNifdc mice.
• Application: Patients with CFI deficiency will suffer from a kidney disease called glomerulonephritis, accompanied by isolated C3 deposits. CFI deficiency may also be associated with autoimmune diseases such as rheumatoid arthritis or systemic lupus erythematosus (SLE).

Gene targeting strategy for B-hCFI mice. The exons 1-14 of mouse Cfi gene that encode the whole molecule (ATG to STOP codon), including 3’UTR were replaced by human counterparts in B-hCFI mice. The promoter and 5’UTR region of the mouse gene are retained. The CFI expression is driven by the endogenous mouse Cfi promoter, while mouse Cfi gene transcription and translation will be disrupted.

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