CFI Gene - Complement Factor I
Key regulator of the complement system, associated with atypical hemolytic uremic syndrome and complement deficiencies.
Gene Information Card
| Symbol | CFI |
|---|---|
| Full Name | Complement Factor I |
| Gene Type | protein-coding |
| Chromosomal Location | 4q25 |
| NCBI Gene ID | 3426 ncbi.nlm.nih.gov/gene/3426 |
| Ensembl ID | ENSG00000105403 |
| UniProt ID | P05156 |
| OMIM ID | 217030 |
| HGNC ID | 2154 |
| Aliases | C3b/C4b inactivator, FI, IF |
Description
The CFI gene encodes complement factor I, a serine protease that regulates the complement cascade by cleaving C3b and C4b in the presence of cofactors. This prevents excessive complement activation and tissue damage. Mutations in CFI are associated with atypical hemolytic uremic syndrome (aHUS), complement factor I deficiency, and age-related macular degeneration.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Atypical Hemolytic Uremic Syndrome (aHUS) | Loss-of-function mutations reduce factor I activity, leading to uncontrolled complement activation on endothelial cells, causing thrombotic microangiopathy. | ClinVar, OMIM |
| Complement Factor I Deficiency | Biallelic mutations cause complete or partial deficiency, resulting in recurrent infections due to impaired opsonization and immune complex clearance. | OMIM, NCBI |
| Age-Related Macular Degeneration (AMD) | Certain CFI variants (e.g., rs10033900) are associated with altered complement regulation in the retina, contributing to drusen formation. | NCBI, ClinVar |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 12.5 | High |
| Blood | 8.3 | Medium |
| Kidney | 4.1 | Low |
| Lung | 2.7 | Low |
| Brain | 1.2 | Not detected |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 (liver) | 15.0 | High expression |
| K-562 (leukemia) | 6.5 | Medium expression |
| HeLa (cervical) | 3.0 | Low expression |
| A549 (lung) | 2.1 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1420C>T (p.Arg474Ter) | Nonsense | <0.01% | Loss of function; truncation of serine protease domain |
| c.772G>A (p.Gly258Arg) | Missense | 0.02% | Loss of function; impaired catalytic activity |
| c.1072T>C (p.Tyr358His) | Missense | 0.01% | Loss of function; reduced secretion and activity |
| c.1654G>A (p.Gly552Arg) | Missense | 0.005% | Loss of function; disrupts cofactor binding |
Mutation functional classification
Loss of Function (LOF)
Most CFI mutations are loss-of-function, reducing or abolishing factor I activity, leading to uncontrolled complement activation.
Gain of Function (GOF)
No gain-of-function mutations are reported in CFI.
Dominant Negative (DN)
Dominant-negative effects are not described for CFI mutations; disease typically follows a recessive or haploinsufficient pattern.
View complete mutation data：
Gene Ontology (GO)
Pathways
• Complement cascade (Reactome: R-HSA-166658)
• Regulation of complement cascade (Reactome: R-HSA-977606)
Protein Summary
Complement factor I is a 88 kDa serine protease synthesized primarily in the liver and secreted into plasma. It consists of a heavy chain (containing a factor I membrane attack complex domain and a scavenger receptor cysteine-rich domain) and a light chain (serine protease domain). Factor I cleaves C3b and C4b in the presence of cofactors (e.g., factor H, MCP, C4BP), downregulating the complement cascade. Deficiency or dysfunction predisposes to complement-mediated diseases.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CFI Knockout HEK293 Cell Line | EDJ-KQ50378 | Human | 3426 | Details Get a Quote |
| CFI Knockout HeLa Cell Line | EDJ-KQ53606 | Human | 3426 | Details Get a Quote |
| CFI Knockout A-549 Cell Line | EDJ-KQ62075 | Human | 3426 | Details Get a Quote |
| CFI Knockout HCT 116 Cell Line | EDJ-KQ70557 | Human | 3426 | Details Get a Quote |
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