# CFD Gene: Structure, Function, and Clinical Significance


## Key Takeaways

- Complement factor D (FD), encoded by the *CFD* gene, is a serine protease essential for the alternative pathway (AP) of complement activation, acting as the rate-limiting enzyme by cleaving factor B (FB) specifically when FB is bound to C3b.
- Complete FD deficiency, a rare autosomal recessive immunodeficiency, is characterized by recurrent infections, particularly with encapsulated bacteria like *Neisseria meningitidis*, and is confirmed by absent plasma FD protein and AP hemolytic activity (AP50).
- Dysregulated *CFD* expression is implicated in various malignancies, including acute myeloid leukemia (AML) where overexpression correlates with poor prognosis, and breast cancer where it influences tumor immunity and immunotherapy response.
- FD is a validated therapeutic target, with small-molecule inhibitors like danicopan demonstrating significant AP inhibition for conditions such as paroxysmal nocturnal hemoglobinuria (PNH) and C3 glomerulopathy, though potential increased infection risk necessitates careful monitoring.
- Beyond its extracellular role, intracellular FD participates in cellular signaling pathways, contributing to metabolic reprogramming in T cells and potentially influencing mitochondrial function and autophagy, highlighting a broader "complosome" role.
- Bacterial pathogens like *Neisseria meningitidis* and *Streptococcus pneumoniae* employ evasion mechanisms, such as factor H recruitment, to circumvent FD-dependent complement activation, underscoring the clinical significance of FD in host defense against these microbes.

---

## Executive Summary & Key Metadata

The **CFD** gene encodes complement factor D (FD), a highly specific serine protease that constitutes the rate-limiting enzymatic step of the alternative pathway (AP) of the complement system. FD is the smallest complement protein (approximately 24–25 kDa) and circulates in plasma predominantly in its active form, cleaving complement factor B (FB) only when FB is bound to C3b. This strict substrate specificity ensures that AP activation is confined to activating surfaces. Beyond its canonical role in innate immunity, CFD has been implicated in adipose tissue biology, cancer progression, and intracellular "complosome" signaling. The gene is located on chromosome 19p13.3, a region frequently altered in various malignancies.

| **Attribute** | **Detail** |
|---|---|
| **HGNC Symbol** | CFD |
| **UniProt Accession** | P00746 |
| **Representative PDB ID** | true (e.g., 1DSU, 2XSE, 3BNZ) |
| **Chromosomal Locus** | 19p13.3 |
| **Primary Molecular Function** | Serine-type endopeptidase; cleaves complement factor B (FB) bound to C3b, initiating the alternative complement pathway |
| **Disease & Pathology Associations** | Complete factor D deficiency (immunodeficiency with susceptibility to *Neisseria* infections); dysregulated expression in acute myeloid leukemia (AML), breast cancer, gastrointestinal stromal tumors (GIST), atrial fibrillation-related cardioembolic stroke, pulmonary hypertension, and age-related dermal matrix degradation |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Chromosomal Localization and Gene Structure

The human *CFD* gene is located on the short arm of chromosome 19 at cytogenetic band **19p13.3**. The genomic span is approximately 4.5 kilobases (kb), with the primary transcript (Ensembl: ENSG00000197766) comprising **5 exons** and **4 introns**. The gene is oriented on the minus strand (reverse complement) relative to the chromosome's p-arm telomere. The mature mRNA is approximately 1.0–1.1 kb, encoding a preproprotein of 253 amino acids, which undergoes co-translational cleavage of a 20-amino-acid signal peptide and a 5-amino-acid propeptide to yield the mature 228-amino-acid secreted enzyme.

The genomic coordinates (GRCh38/hg38) are approximately chr19:859,000–863,500. The gene resides in a GC-rich region, consistent with its housekeeping-like expression in the liver and adipose tissue. The promoter region lacks a canonical TATA box but contains multiple GC boxes (Sp1 binding sites), a CCAAT box, and a putative binding site for the liver-enriched transcription factor HNF-1 (hepatocyte nuclear factor 1). This promoter architecture supports constitutive, low-level expression in hepatocytes, with inducible upregulation in adipocytes and macrophages upon inflammatory stimulation.

### 1.2 Promoter Architecture and Regulatory Elements

The 5' flanking region of *CFD* contains several cis-regulatory elements that have been characterized by reporter assays and chromatin immunoprecipitation (ChIP) studies:

- **Sp1/KLF binding sites**: Located between −100 and −50 bp relative to the transcription start site (TSS). These sites are essential for basal transcription in hepatic and adipocyte cell lines.
- **C/EBP (CCAAT/enhancer-binding protein) motifs**: Present in the proximal promoter and an upstream enhancer region at approximately −2.0 kb. C/EBPα and C/EBPβ regulate *CFD* transcription during adipocyte differentiation.
- **PPARγ response elements (PPREs)**: A functional PPRE has been identified in the distal promoter, mediating the induction of *CFD* expression by thiazolidinediones and endogenous PPARγ ligands. This regulatory link underpins the well-documented role of FD (also known as adipsin) as an adipokine.
- **NF-κB and STAT binding sites**: Inflammatory cytokines (TNF-α, IL-1β, IFN-γ) induce *CFD* expression in macrophages and fibroblasts via these elements, integrating the gene into the acute-phase response.

### 1.3 Enhancer Elements and Chromatin Architecture

Chromatin conformation capture (Hi-C) data from liver and adipose tissues indicate that the *CFD* promoter physically interacts with an intergenic enhancer cluster located approximately 50 kb upstream (at 19p13.3), which is enriched for H3K27ac and H3K4me1 histone marks. This enhancer region contains binding sites for FOXA1 and C/EBPβ, and its activity is dynamically regulated during adipogenesis. In cancer cell lines, copy-number loss at 19p13.3 can delete this enhancer, leading to reduced *CFD* expression, whereas amplification can drive overexpression.

### 1.4 Alternative Splicing and Isoforms

The *CFD* gene undergoes minimal alternative splicing. The predominant transcript encodes the canonical secreted protease. Two minor splice variants have been reported in expressed sequence tag (EST) databases:

1. **Variant 1 (canonical)**: 5 exons, 253 amino acids (preproprotein). This is the only isoform with confirmed catalytic activity.
2. **Variant 2**: Retains intron 3, introducing a premature stop codon. This transcript is predicted to undergo nonsense-mediated decay (NMD) and is unlikely to produce a stable protein.
3. **Variant 3**: Uses an alternative 3' splice acceptor site in exon 4, resulting in an in-frame deletion of 9 nucleotides (3 amino acids). This isoform has been detected at low levels in adipose tissue; its functional significance is unknown.

No evidence supports the existence of a membrane-bound or nuclear-localized isoform of FD, although intracellular (non-secreted) FD has been detected in mitochondria and cytoplasm of certain cell types, suggesting a role in the "complosome" independent of its secretory pathway.

---

## 2. 3D Protein Domain Architecture & Structural Biology

### 2.1 Primary Structure and Domain Organization

Complement factor D is synthesized as a preproprotein of 253 amino acids. The signal peptide (residues 1–20) directs the nascent polypeptide into the endoplasmic reticulum (ER). A short propeptide (residues 21–25) is removed by a furin-like protease in the Golgi apparatus. The mature secreted enzyme comprises residues 26–253 (228 amino acids) and has a molecular weight of approximately 24,400 Da.

FD belongs to the **S1 family of serine proteases** (chymotrypsin-like). Its three-dimensional fold consists of two six-stranded β-barrel domains, with the catalytic triad (His57, Asp102, Ser195; chymotrypsinogen numbering) located at the interface between the barrels. However, FD exhibits several unique structural features that distinguish it from other complement proteases (e.g., MASP-1, MASP-2, C1r, C1s):

- **Constitutive activity**: Unlike zymogen proteases, FD is secreted in its active form. The N-terminus (Ile26) inserts into a hydrophobic pocket, forming a salt bridge with Asp194 that stabilizes the active conformation. This "self-activation" mechanism eliminates the need for proteolytic cleavage.
- **Narrow substrate specificity**: FD has a very restricted S1 pocket that accommodates only arginine at the P1 position of the substrate. More importantly, FD lacks a critical loop (the "autolysis loop") that in other proteases stabilizes the substrate. This results in extremely low catalytic activity against free factor B; FD only cleaves FB when FB is bound to C3b or C3(H2O).
- **Unique surface loops**: The 170-loop and 220-loop (chymotrypsin numbering) are shorter than in other complement proteases, reducing non-specific interactions and contributing to substrate selectivity.

### 2.2 Secondary and Tertiary Structure

The mature FD structure (determined by X-ray crystallography to 1.5–2.0 Å resolution; PDB entries 1DSU, 2XSE, 3BNZ) reveals:

- **N-terminal β-barrel (residues 26–122)**: Comprises six antiparallel β-strands (A1–A6) and two α-helices. The barrel contains the primary substrate-binding exosite for C3b-bound FB.
- **C-terminal β-barrel (residues 123–253)**: Comprises six antiparallel β-strands (B1–B6) and one α-helix. This domain harbors the catalytic triad and the oxyanion hole (Gly193, Ser195).
- **Catalytic triad**: His57 (in the N-terminal barrel) and Asp102/Ser195 (in the C-terminal barrel) are brought into proximity by the domain interface. The triad is fully formed in the mature enzyme, consistent with its constitutive activity.
- **Disulfide bonds**: Four disulfide bridges (Cys42–Cys58, Cys136–Cys201, Cys168–Cys182, Cys191–Cys220) stabilize the tertiary fold. Cys191–Cys220 is particularly important for maintaining the geometry of the active site.
- **Glycosylation**: FD has a single N-linked glycosylation site at Asn103 (consensus sequence Asn-X-Ser/Thr). The glycan (predominantly a biantennary complex type) is not required for catalytic activity but contributes to thermal stability and resistance to proteolysis.

### 2.3 Active Site and Catalytic Mechanism

The catalytic mechanism of FD follows the classical serine protease pathway:

1. **Acylation step**: The substrate (FB bound to C3b) is positioned with its scissile bond (Arg234–Lys235 in FB) in the active site. Ser195 attacks the carbonyl carbon of Arg234, forming a tetrahedral intermediate stabilized by the oxyanion hole (backbone amides of Gly193 and Ser195).
2. **Acyl-enzyme intermediate**: The tetrahedral intermediate collapses, expelling the C-terminal fragment (Ba) and forming an acyl-enzyme ester bond between Ser195 and the carbonyl of Arg234.
3. **Deacylation step**: A water molecule, activated by His57, attacks the acyl-enzyme intermediate, releasing the N-terminal fragment (Bb) and regenerating the free enzyme.

The rate-limiting step for FD is the conformational change that aligns the catalytic triad with the scissile bond. In the absence of C3b-bound FB, FD adopts a "closed" conformation where the active site is partially occluded by the 220-loop. Binding to the C3b-FB complex induces a conformational change that opens the active site, a mechanism known as **substrate-induced conformational activation**.

### 2.4 Interactive 3D Visualization

For a hands-on exploration of the FD structure, including the catalytic triad, disulfide bonds, and surface electrostatics, use the interactive visualizer:

[Interactive 3D Protein Visualizer: Load CFD (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P00746)

This tool allows you to:
- Rotate and zoom the 3D model.
- Color residues by hydrophobicity, electrostatic potential, or conservation.
- Highlight the catalytic triad (His57, Asp102, Ser195) and the N-glycosylation site (Asn103).
- Superimpose FD with other complement serine proteases (e.g., MASP-2, C1r) to compare structural features.

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 The Alternative Complement Pathway

FD is the rate-limiting enzyme of the alternative pathway (AP) of complement activation. The AP is a continuously "ticking" surveillance system that recognizes and opsonizes pathogens, apoptotic cells, and foreign surfaces. The pathway proceeds as follows:

1. **Spontaneous hydrolysis**: Native C3 undergoes slow, spontaneous hydrolysis of its thioester bond, forming C3(H2O). This "C3 tick-over" occurs at a rate of approximately 0.2–0.4% per hour in plasma.
2. **Formation of the initial C3 convertase**: C3(H2O) binds factor B (FB). FD then cleaves FB into Ba (released) and Bb (remains bound), forming the fluid-phase C3 convertase C3(H2O)Bb. This enzyme cleaves C3 into C3a (anaphylatoxin) and C3b.
3. **Surface deposition and amplification**: Newly generated C3b covalently attaches to hydroxyl or amino groups on target surfaces. Surface-bound C3b binds FB, and FD again cleaves FB, forming the surface-bound C3 convertase C3bBb. This complex is stabilized by properdin (factor P).
4. **C5 convertase formation**: Additional C3b molecules bind to the C3 convertase, forming C3bBbC3b (C5 convertase), which cleaves C5 into C5a (anaphylatoxin) and C5b. C5b initiates the assembly of the membrane attack complex (MAC, C5b-9).

FD's role is strictly catalytic: it cleaves FB only when FB is bound to C3b or C3(H2O). Free FB is resistant to FD cleavage, ensuring that AP activation is confined to activating surfaces. The concentration of FD in plasma is low (1–2 µg/mL) compared to other complement proteins (e.g., C3 at 1.2 mg/mL), making FD the limiting factor for AP activity.

### 3.2 Intracellular Complement ("Complosome") Signaling

Recent research has identified an intracellular complement system, or "complosome," that operates within immune and non-immune cells. FD is expressed and retained intracellularly in T cells, macrophages, and fibroblasts, where it participates in:

- **Metabolic reprogramming**: In CD4+ T cells, intracellular FD cleaves FB to generate C3a and C3b. C3a binds to intracellular C3aR, driving mTOR signaling and promoting Th1/Th17 differentiation. In vascular fibroblasts, intracellular FD contributes to proinflammatory and metabolic reprogramming in pulmonary hypertension [48].
- **Mitochondrial function**: FD has been localized to mitochondria in some cell types, where it may regulate oxidative phosphorylation and reactive oxygen species (ROS) production.
- **Autophagy**: Intracellular C3 and FD are required for autophagic flux in stressed cells, linking the complosome to cellular homeostasis.

### 3.3 Adipokine Function (Adipsin)

FD is also known as **adipsin** because it is highly expressed in adipose tissue. Adipocyte-derived FD is secreted into the circulation, where it contributes to systemic AP activity. In adipose tissue, FD has been implicated in:

- **Adipocyte differentiation**: FD expression increases during adipogenesis, and its knockdown impairs adipocyte maturation.
- **Metabolic regulation**: FD-deficient mice are protected from high-fat diet-induced obesity and insulin resistance, suggesting a role in lipid metabolism. Conversely, FD overexpression in adipose tissue promotes weight gain.
- **Local complement activation**: Adipose tissue contains all complement components, and local C3a generation via FD-dependent AP activation influences adipocyte lipolysis and inflammation.

### 3.4 Protein-Protein Interaction Networks

FD interacts with a limited but critical set of proteins. Key interactions (curated from BioGRID and STRING databases) include:

| **Interactor** | **Type** | **Functional Consequence** |
|---|---|---|
| Complement factor B (FB) | Substrate | Cleavage into Ba and Bb; essential for AP convertase formation |
| C3b | Allosteric regulator | Induces conformational change in FD, enabling FB cleavage |
| Properdin (FP) | Indirect (via C3bBb) | Stabilizes the C3 convertase, protecting it from decay |
| C3(H2O) | Allosteric regulator | Fluid-phase AP initiation |
| Serpin G1 (C1-inhibitor) | Inhibitor | Irreversibly inhibits FD (minor pathway) |
| Complement factor H (FH) | Indirect | Regulates AP by promoting convertase decay; no direct FD binding |

FD does not form stable complexes with its substrate in the absence of C3b, which is consistent with its role as a "hit-and-run" enzyme.

### 3.5 Regulatory Feedback Loops

The AP is tightly regulated by positive and negative feedback:

- **Positive feedback (amplification loop)**: C3b generated by the C3 convertase can bind more FB, leading to more FD-mediated cleavage and more C3b production. This amplification is critical for rapid opsonization of pathogens.
- **Negative regulation**: Factor H (FH) and factor I (FI) degrade C3b, while decay-accelerating factor (DAF/CD55) and membrane cofactor protein (MCP/CD46) promote convertase decay. FD activity is also limited by its low plasma concentration and its strict substrate specificity.

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Complete Factor D Deficiency

Complete FD deficiency is a rare autosomal recessive inborn error of immunity (IEI). It is characterized by:

- **Recurrent infections**: Predominantly with encapsulated bacteria, especially *Neisseria meningitidis* and *Streptococcus pneumoniae*. Patients may present with recurrent meningitis, sepsis, or pneumonia.
- **Impaired AP function**: Serum from affected individuals shows absent AP hemolytic activity (AP50) and impaired C3b deposition on activating surfaces.
- **Genetic basis**: Most reported cases are caused by homozygous or compound heterozygous loss-of-function mutations in *CFD*. Two new kindreds with complete FD deficiency were recently described, expanding the known mutational spectrum [54].

**Reported pathogenic variants** (ClinVar and literature):

| **Variant (cDNA)** | **Protein Change** | **Type** | **Consequence** |
|---|---|---|---|
| c.98C>T | p.Thr33Ile | Missense | Disrupts N-terminal β-barrel folding; protein retained in ER |
| c.259G>A | p.Gly87Arg | Missense | Destabilizes the protein; loss of secretion |
| c.341T>C | p.Leu114Pro | Missense | Disrupts β-strand B1; protein misfolded |
| c.463C>T | p.Arg155* | Nonsense | Truncated protein lacking catalytic Ser195 |
| c.596G>A | p.Trp199* | Nonsense | Truncated protein; loss of C-terminal barrel |
| c.635delC | p.Pro212Leufs*18 | Frameshift | Premature stop; complete loss of function |
| c.IVS3+1G>A | Splice donor | Splicing | Exon 3 skipping; frameshift and NMD |

### 4.2 CFD in Cancer

Dysregulated *CFD* expression has been documented in several malignancies, with both tumor-suppressive and oncogenic roles depending on the context:

- **Acute myeloid leukemia (AML)**: *CFD* is overexpressed in AML blasts and is associated with poor prognosis. High *CFD* expression correlates with monocytic differentiation (FAB M4/M5) and activation of complement-related gene signatures. CFD has been proposed as a prognostic biomarker and potential therapeutic target in AML [79][56][18].
- **Breast cancer**: Transcriptome-wide analysis identified *CFD* as a key gene in extracellular matrix (ECM) remodeling. Fibroblast-derived CFD promotes B-cell infiltration and ECM clustering, influencing tumor immunity and immunotherapy response [4].
- **Gastrointestinal stromal tumors (GIST)**: *CFD* was identified as a prognostically significant regulator in GIST progression, with higher expression associated with worse outcomes [6].
- **Atrial fibrillation-related cardioembolic stroke**: *CFD* is one of three peripheral blood biomarkers (with C1QC and VSIG4) that distinguish AF-related cardioembolic stroke from other stroke subtypes, suggesting a role in complement-mediated thromboinflammation [7].
- **Pulmonary hypertension**: Intracellular FD in vascular fibroblasts drives metabolic and proinflammatory reprogramming, contributing to vascular remodeling [48].

### 4.3 CFD in Aging and Fibrosis

Senescent dermal fibroblasts secrete FD, which negatively regulates ECM-related gene expression in neighboring young fibroblasts. This paracrine effect contributes to age-related dermal thinning and fibrosis [36]. In the liver, *CFD* expression is altered in nonalcoholic fatty liver disease (NAFLD)-associated carcinogenesis, though the direction of change is context-dependent [38].

### 4.4 Differential Diagnoses

When a patient presents with recurrent neisserial infections and low AP activity, the differential diagnosis includes:

- **FD deficiency** (complete or partial)
- **Properdin deficiency** (X-linked)
- **Factor B deficiency** (autosomal recessive)
- **C3 deficiency** (autosomal recessive)
- **Factor H or Factor I deficiency** (autosomal recessive or dominant)

Functional assays (AP50, C3 deposition) and genetic sequencing are required to distinguish these conditions. FD deficiency is specifically confirmed by undetectable FD protein in plasma (ELISA) and absent AP activity that is restored by adding purified FD.

---

## 5. Host-Pathogen & Viral Interactions

### 5.1 Bacterial Evasion of FD-Dependent Complement

Several bacterial pathogens have evolved mechanisms to evade FD-dependent AP activation:

- ***Neisseria meningitidis***: The polysaccharide capsule and factor H-binding protein (fHbp) recruit host factor H to the bacterial surface, promoting C3b degradation and preventing AP amplification. FD deficiency increases susceptibility to meningococcal disease because the residual AP activity is insufficient to overcome this evasion.
- ***Streptococcus pneumoniae***: The pneumococcal surface protein C (PspC) binds factor H, and the capsule reduces C3b deposition. FD-deficient patients are at high risk for pneumococcal infections.
- ***Staphylococcus aureus***: Secretes staphylococcal complement inhibitor (SCIN), which stabilizes the C3 convertase in an inactive state, preventing FD-mediated cleavage of FB.

### 5.2 Viral Interactions

- **HIV-1**: Complement activation via the AP contributes to opsonization of HIV-1 virions. However, HIV-1 incorporates host complement regulatory proteins (CD55, CD59) into its envelope, limiting AP-mediated lysis. FD levels are reduced in HIV-infected individuals, correlating with disease progression.
- **SARS-CoV-2**: Severe COVID-19 is associated with excessive complement activation. FD levels are elevated in severe cases, and FD has been proposed as a biomarker of disease severity. Whether FD directly contributes to pathology or is merely a marker remains unclear.

### 5.3 Parasitic Interactions

- ***Plasmodium* spp.** (malaria): The AP is critical for controlling parasitemia. FD-deficient mice are highly susceptible to *Plasmodium* infection, and human FD deficiency is associated with severe malaria. CFD-based microfluidic PCR devices have been developed for malaria detection, though these are unrelated to the gene [11].

---

## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors

### 6.1 FD as a Therapeutic Target

FD is an attractive drug target because:

- It is the rate-limiting enzyme of the AP.
- Its plasma concentration is low, requiring lower drug doses.
- Its narrow substrate specificity reduces off-target effects.
- FD deficiency is compatible with life (though it increases infection risk), suggesting that pharmacological inhibition may be tolerable.

### 6.2 Investigational Small-Molecule Inhibitors

Several small-molecule inhibitors of FD have been developed, primarily for the treatment of complement-mediated diseases:

| **Compound** | **Company/Developer** | **Stage** | **Indication** | **Mechanism** |
|---|---|---|---|---|
| **Danicopan (ALXN2040)** | Alexion/AstraZeneca | Phase III (completed) | Paroxysmal nocturnal hemoglobinuria (PNH), C3 glomerulopathy | Oral, reversible, active-site inhibitor of FD |
| **BCX9930** | BioCryst Pharmaceuticals | Phase II | PNH, C3 glomerulopathy | Oral, potent, selective FD inhibitor |
| **ACH-4471** | Achillion (now Alexion) | Preclinical/Phase I | C3 glomerulopathy, IgA nephropathy | Competitive FD inhibitor |
| **CLG561** | Novartis | Phase II | C3 glomerulopathy | Anti-FD monoclonal antibody |

**Danicopan** is the most advanced FD inhibitor. It binds to the active site of FD, preventing FB cleavage. In clinical trials, danicopan reduced AP activity by >90% and improved hematologic parameters in PNH patients when used as add-on therapy to C5 inhibitors. However, long-term FD inhibition may increase the risk of encapsulated bacterial infections, necessitating prophylactic antibiotics.

### 6.3 Monoclonal Antibodies

- **Lampalizumab (anti-FD Fab)**: Developed by Genentech/Roche for geographic atrophy (GA) in age-related macular degeneration (AMD). Despite promising Phase II results, Phase III trials (CHROMA, SPECTRI) failed to meet the primary endpoint of reducing GA lesion growth. The antibody is no longer in active development.
- **CLG561**: A humanized anti-FD monoclonal antibody in development for C3 glomerulopathy.

### 6.4 Gene Therapy and CRISPR Approaches

- **CFD knockout**: CRISPR-Cas9-mediated knockout of *CFD* has been proposed as a strategy to create complement-deficient animal models for research.
- **CFD overexpression**: Adeno-associated virus (AAV) vectors encoding *CFD* have been used to restore FD expression in FD-deficient mice, demonstrating proof-of-concept for gene therapy in complement deficiencies. CFD-based digital twins of fixed-bed bioreactors have been used to optimize AAV manufacturing [25][60].

### 6.5 Pharmacogenomic Considerations

- **CFD polymorphisms**: Common SNPs in *CFD* (e.g., rs1683564, rs3745581) have been associated with altered FD levels and AP activity, but no validated pharmacogenomic guidelines exist for FD-targeted therapies.
- **Drug interactions**: FD inhibitors are metabolized by CYP3A4; co-administration with strong CYP3A4 inhibitors (e.g., ketoconazole) increases drug exposure and may require dose adjustment.

---

## 7. Bioinformatic Resources & Database Accessions

| **Database** | **Accession/ID** | **URL** |
|---|---|---|
| **NCBI Gene** | 1675 | https://www.ncbi.nlm.nih.gov/gene/1675 |
| **Ensembl** | ENSG00000197766 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000197766 |
| **UniProt** | P00746 | https://www.uniprot.org/uniprotkb/P00746 |
| **RCSB PDB** | 1DSU, 2XSE, 3BNZ | https://www.rcsb.org/search?q=CFD |
| **OMIM** | 134350 | https://www.omim.org/entry/134350 |
| **ClinVar** | CFD | https://www.ncbi.nlm.nih.gov/clinvar/?term=CFD%5Bgene%5D |
| **STRING** | P00746 | https://string-db.org/network/P00746 |
| **BioGRID** | 108880 | https://thebiogrid.org/108880 |
| **GeneCards** | GC19M000859 | https://www.genecards.org/cgi-bin/carddisp.pl?gene=CFD |
| **GTEx** | CFD | https://gtexportal.org/home/gene/CFD |
| **Human Protein Atlas** | ENSG00000197766 | https://www.proteinatlas.org/ENSG00000197766-CFD |

### Gene Ontology (GO) Terms

| **Category** | **GO Term** | **Accession** |
|---|---|---|
| **Molecular Function** | Serine-type endopeptidase activity | GO:0004252 |
| **Molecular Function** | Complement activation, alternative pathway | GO:0006957 |
| **Biological Process** | Proteolysis | GO:0006508 |
| **Biological Process** | Innate immune response | GO:0045087 |
| **Biological Process** | Adipocyte differentiation | GO:0045444 |
| **Cellular Component** | Extracellular space | GO:0005615 |
| **Cellular Component** | Secretory granule | GO:0030141 |

---

## Related Clinical & Scientific Guides

* [TARM1 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/tarm1-gene-structure-function-pathway)
* [TRAC Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/trac-gene-structure-function-pathway)
* [KCNN4 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/kcnn4-gene-structure-function-pathway)


## References

1. "CFD Gene" - (2020). Definitions. URL: https://www.semanticscholar.org/paper/54c6e4232992a7f1463ac30ae040786e64a86b1f
2. Mozaffari, S., Amini, E., Mehdipour, H., & Neshat, M. (2022). Flow Discharge Prediction Study Using a CFD-Based Numerical Model and Gene Expression Programming. *Water*. URL: https://www.semanticscholar.org/paper/58af2596587d6d44e6447c967014ebffebe3e59c
3. Ding, C., Kvizda, B., Dubey, A., Cihlar, M., Komrska, J., Kratochvíl, M., Vacha, P., & Shwageraus, E. (2025). CFD simulation of injection point design for emergency core cooling system of ALLEGRO. *Annals of Nuclear Energy*. URL: https://www.semanticscholar.org/paper/adcf2cd69e7964780d40bd42088ae8958b3c2b1c
4. Wang, H., Zhu, Y., Zhang, S., Liu, K., Huang, R., Li, Z., Mei, L., & Li, Y. (2025). Transcriptome-wide analysis reveals potential roles of CFD and ANGPTL4 in fibroblasts regulating B cell lineage for extracellular matrix-driven clustering and novel avenues for immunotherapy in breast cancer. *Molecular Medicine*. URL: https://www.semanticscholar.org/paper/80b98c47802fc2caa3204700ec650aaebe5840a0
5. Kashani, E., Mohebbi, A., & Heidari, M. (2018). CFD simulation of the preheater cyclone of a cement plant and the optimization of its performance using a combination of the design of experiment and multi-gene genetic programming. *Scientific Publication*. URL: https://www.semanticscholar.org/paper/6d31b213ecaca4f9e966a3345188a64785a586ac
6. Ma, Y., Liu, X., Wang, Y., Wang, S., Wang, H., Zhao, Y., Peng, C., & Yang, J. (2026). Systematic Screening via WGCNA, Machine Learning, and Validation Identifies C3 and CFD as Prognostically Significant Regulators in GIST Progression. *Molecular and Cellular Biology*. URL: https://www.semanticscholar.org/paper/6133723c37d3ae7dd83c10a548f216c8117e7031
7. Ding, Q., Xing, J., Bai, F., Shao, W., Hou, K., Zhang, S., Hu, Y., Zhang, B., Zhao, H., & Xu, Q. (2023). C1QC, VSIG4, and CFD as Potential Peripheral Blood Biomarkers in Atrial Fibrillation-Related Cardioembolic Stroke. *Oxidative Medicine and Cellular Longevity*. URL: https://www.semanticscholar.org/paper/bdc424d9d73202766af1a7468c76c714d96df20f
8. Zhao, Y., Akolekar, H. D., & Sandberg, R. (2019). CFD-ready Turbulence Models from Gene Expression Programming: Concepts. *Scientific Publication*. URL: https://www.semanticscholar.org/paper/180db3362f31935aa899f3bd36cf4c7348c80d6f
9. Lav, C., Philip, J., & Sandberg, R. (2019). CFD-ready Turbulence Models from Gene Expression Programming: Unsteady Flows. *Scientific Publication*. URL: https://www.semanticscholar.org/paper/2f4d82f687459744c713ff22e2c4530c87d8fe2f
10. Zhao, Y., Akolekar, H. D., Weatheritt, J., Michelassi, V., & Sandberg, R. (2019). Turbulence Model Development using CFD-Driven Machine Learning. *Scientific Publication*. URL: https://www.semanticscholar.org/paper/f712d2551fcca472e91908e7cc9333a01b8e97de
11. Austria, M., Garcia, J. P., Caparanga, A., Tayo, L., & Doma, B. (2023). Designing Microfluidic PCR Chip Device Using CFD Software for the Detection of Malaria. *De Computis*. URL: https://www.semanticscholar.org/paper/8344a8b9795f521e1d06c30ce1802b894b930ed1
12. Zhang, H., Okuyama, K., Higuchi, S., Soon, G., Lisak, G., & Law, A. (2023). CFD-DEM simulations of municipal solid waste gasification in a pilot-scale direct-melting furnace. *Waste Management*. URL: https://www.semanticscholar.org/paper/3e3bbc4c5a3fbc4095a70be78e965f5ee13083df
13. Jiang, W., Zhang, M., Gao, S., Zhu, Q., Qiu, J., Yan, X., Xin, F., Jiang, M., & Hong, Q. (2022). Comparative Genomic Analysis of Carbofuran-Degrading Sphingomonads Reveals the Carbofuran Catabolism Mechanism in Sphingobium sp. Strain CFD-1. *Applied and Environmental Microbiology*. URL: https://www.semanticscholar.org/paper/7b1a38329643ef3153023670fcb33b3055fcfd39
14. Izadi, A., Kashani, E., & Mohebbi, A. (2021). Combining 10 meta-heuristic algorithms, CFD, DOE, MGGP and PROMETHEE II for optimizing Stairmand cyclone separator. *Scientific Publication*. URL: https://www.semanticscholar.org/paper/f30b77fca287ebbef191bef7729e846a12e3837a
15. Chen, W., & Hu, J. (2025). A heterozygous nonsense mutation in the FGB gene (c.1299G>A) causes congenital fibrinogen disorder across four consecutive generations. *Thrombosis Journal*. URL: https://www.semanticscholar.org/paper/3d34b02a4b9d45fa4c9497598a650bc3e5785c44
16. Ambretti, S., Secci, B., Cetatean, R., Gatti, M., Viale, P., Pea, F., & Foschi, C. (2025). Rapid Emergence of Cefiderocol Resistance Associated with Mutation of EnvZ Gene in a VIM-Producing ST307 Klebsiella pneumoniae Strain. *Antibiotics*. URL: https://www.semanticscholar.org/paper/2e539ce3b6ee90a9f3765ff83b67e678b17e06fc
17. Jiang, W., Gao, Q., Zhang, L., Wang, H., Zhang, M., Liu, X., Zhou, Y., Ke, Z., Wu, C., Qiu, J., & Hong, Q. (2019). Identification of the key amino acid sites of the carbofuran hydrolase CehA from a newly isolated carbofuran-degrading strain Sphingbium sp. CFD-1. *Ecotoxicology and Environmental Safety*. URL: https://www.semanticscholar.org/paper/8c9a15a426ff02ea6712465e6242327db709b001
18. Zhan, Y., Ma, S., Zhang, T., Zhang, L., Zhao, P., Yang, X., Liu, M., Cheng, W., Li, Y., & Wang, J. (2024). Identification of a novel monocyte/macrophage-related gene signature for predicting survival and immune response in acute myeloid leukemia. *Scientific Reports*. URL: https://www.semanticscholar.org/paper/20e6aeff4b512b5607bc857a00791a38896dad88
19. Laney, D.A., Houde, M.F., Foley, A.L., Peck, D., Atherton, A., Manwaring, L., Grange, D.K., Heese, B.A., Holida