# C1QB Gene: Structure, Function, and Clinical Significance ## Key Takeaways - The *C1QB* gene encodes the B-chain of complement component 1q (C1q), a crucial initiator of the classical complement pathway. Its expression is tightly regulated by transcription factors PU.1 and IRF8, particularly in myeloid cells, ensuring stoichiometric assembly of the C1q hexamer. - C1q, through its globular head domains, recognizes immune complexes, apoptotic cell surfaces, and pathogen-associated molecular patterns, initiating downstream complement activation leading to opsonization, inflammation, and cell lysis. - Beyond innate immunity, C1q is a critical regulator of synaptic pruning in the central nervous system, with aberrant expression linked to neurodegenerative diseases like Alzheimer's and psychiatric disorders such as schizophrenia. - Pathogenic mutations in *C1QB* cause C1q deficiency, a severe autosomal recessive disorder with a >90% risk of developing systemic lupus erythematosus (SLE), highlighting C1q's central role in preventing autoimmunity. - C1q is implicated in the tumor microenvironment, with its expression correlating with prognosis in various cancers, including osteosarcoma and melanoma, and it plays a role in host defense against bacterial and viral pathogens. - Therapeutic strategies targeting C1q, such as monoclonal antibodies (e.g., ANX005) and small-molecule inhibitors, are under development for autoimmune diseases and other complement-mediated conditions. --- ## Executive Summary & Key Metadata The **C1QB** gene encodes the B-chain polypeptide of complement component 1q (C1q), the recognition subcomponent of the classical complement pathway. C1q is a 460 kDa hexameric complex assembled from 18 polypeptide chains (6 A-chains, 6 B-chains, and 6 C-chains) encoded by three homologous genes—*C1QA*, *C1QB*, and *C1QC*—clustered on human chromosome 1p36.12. The B-chain is essential for the structural integrity of the C1q heterotrimer and for the initiation of the classical complement cascade upon recognition of immune complexes, apoptotic cell surfaces, and pathogen-associated molecular patterns. Beyond its canonical role in innate immunity, C1q is now recognized as a critical regulator of synaptic pruning in the central nervous system, a driver of tumor microenvironment remodeling, and a biomarker for various inflammatory, autoimmune, and malignant conditions. This manual provides a definitive, publication-grade reference on the genomic architecture, structural biology, signaling networks, pathogenic mutations, and clinical significance of *C1QB*. | **Attribute** | **Value** | |---|---| | **HGNC Symbol** | C1QB | | **UniProt Accession** | P02746 | | **Representative PDB ID** | 1PK6 (C1qB globular domain) | | **Chromosomal Locus** | 1p36.12 (GRCh38: chr1:22,643,636–22,648,804) | | **Primary Molecular Function** | Complement component C1q B-chain; recognition of immune complexes and initiation of classical complement pathway; synaptic pruning; immunomodulation | | **Disease & Pathology Associations** | Systemic lupus erythematosus (SLE), C1q deficiency, schizophrenia, Alzheimer's disease, epilepsy, diabetic nephropathy, tuberculosis, various cancers (melanoma, osteosarcoma, gastric cancer, lung adenocarcinoma) | --- ## 1. Genomic Locus, Chromosomal Organization & Isoforms ### 1.1 Chromosomal Localization and Gene Structure The human *C1QB* gene is located on the short arm of chromosome 1 at band p36.12, a gene-dense region frequently associated with immune-related loci. The gene spans approximately 5.2 kilobases (kb) of genomic DNA on the forward strand. The precise coordinates in the GRCh38 assembly are chr1:22,643,636–22,648,804. The *C1QB* gene is flanked by *C1QA* (centromeric) and *C1QC* (telomeric), forming a tightly linked cluster that spans roughly 25 kb. This genomic organization is evolutionarily conserved; in mice, the orthologous cluster resides on chromosome 4 [86]. The proximity of the three genes is functionally significant, as their synchronized expression is required for the stoichiometric 1:1:1 assembly of the C1q heterotrimer [91]. ### 1.2 Promoter Architecture and Transcriptional Regulation The promoter region of *C1QB* lacks a canonical TATA box but contains a critical initiator (Inr) element and a downstream promoter element (DPE). The core promoter is regulated by a synergistic interaction between the transcription factors PU.1 (encoded by *SPI1*) and interferon regulatory factor 8 (IRF8). Chen et al. demonstrated that PU.1 and IRF8 bind to a composite Ets/IRF element (EICE) within the proximal promoter, and this binding is essential for the synchronized transcription of *C1QA*, *C1QB*, and *C1QC* in macrophages and dendritic cells [91]. This "core promoter" architecture ensures that the three subunit genes are transcribed at equivalent rates, a prerequisite for the correct 1:1:1 stoichiometry of the mature C1q protein. Additional regulatory elements include a cyclic AMP-responsive element (CRE) and binding sites for C/EBP family transcription factors. Epigenetic regulation is also prominent. Pegoraro et al. reviewed the epigenetic landscape of the C1Q gene cluster, noting that DNA methylation at CpG islands within the promoter regions and histone modifications (H3K4me3, H3K27ac) at enhancer elements modulate cell-type-specific expression [15]. In non-myeloid cells, the *C1QB* promoter is typically hypermethylated and transcriptionally silent, whereas in macrophages, dendritic cells, and microglia, the locus adopts an active chromatin state. ### 1.3 Enhancer Elements and Long-Range Interactions Chromatin conformation capture studies have identified putative enhancer elements located in the intergenic regions between *C1QA* and *C1QB*, as well as downstream of *C1QC*. These enhancers are enriched for binding sites for PU.1 and IRF8, reinforcing the role of these factors in coordinating the expression of the entire cluster. A trans-eQTL study by Westra et al. identified *C1QB* as a downstream target of multiple trans-acting genetic variants, suggesting that its expression is modulated by loci elsewhere in the genome [20]. This finding highlights the complex regulatory network governing *C1QB* expression, which extends beyond the immediate promoter region. ### 1.4 Alternative Splicing and Isoforms The *C1QB* gene comprises two exons separated by a single intron of approximately 2.5 kb. The first exon encodes the 5' untranslated region (UTR), the signal peptide, and the N-terminal portion of the collagen-like domain. The second exon encodes the remainder of the collagen-like domain, the kink region, and the entire C-terminal globular domain (gC1qB). Unlike many immune genes, *C1QB* does not undergo extensive alternative splicing. However, a minor splice variant lacking a portion of the 5' UTR has been reported, which may affect translational efficiency. No functionally distinct protein isoforms arising from alternative splicing have been conclusively characterized. The primary transcript produces a 253-amino-acid precursor protein, which is cleaved to remove a 28-amino-acid signal peptide, yielding a mature 225-amino-acid B-chain. --- ## 2. 3D Protein Domain Architecture & Structural Biology ### 2.1 Primary Structure and Domain Organization The mature C1q B-chain (UniProt P02746) is a 225-amino-acid polypeptide that can be divided into three distinct structural regions: 1. **N-terminal Collagen-like Domain (CLD)** (residues 1–89 of the mature protein): This region contains a repeating Gly-X-Y triplet motif, where X is frequently proline and Y is frequently hydroxyproline or hydroxylysine. The CLD forms a left-handed triple helix with the corresponding CLDs of the A- and C-chains. The N-terminal portion of the CLD contains a short, non-collagenous "head" segment (residues 1–3) that participates in inter-chain disulfide bonding. Specifically, Cys4 of the B-chain forms a disulfide bond with Cys4 of the A-chain, stabilizing the heterotrimeric assembly. 2. **Kink Region** (residues 90–112): This short segment interrupts the collagen triple helix and introduces a flexible bend. The kink is critical for the overall "bouquet-like" architecture of the C1q molecule, allowing the six globular heads to project outward from the collagen stalks. The kink region is also a site for proteolytic cleavage by matrix metalloproteinases, which can release the globular heads from the collagen stalks. 3. **C-terminal Globular Domain (gC1qB)** (residues 113–225): This domain adopts a compact, jelly-roll β-sandwich fold composed of two five-stranded β-sheets. The gC1q domain is the primary ligand-binding module of C1q, responsible for recognizing the Fc region of IgG and IgM, as well as a diverse array of self- and non-self-ligands, including phosphatidylserine on apoptotic cells, C-reactive protein (CRP), and pathogen surfaces. The gC1qB domain contains three distinct binding sites: Site 1 (residues 114–129), Site 2 (residues 154–176), and Site 3 (residues 199–215), each with distinct ligand specificities. ### 2.2 Quaternary Structure and the C1q Heterotrimer The functional C1q molecule is a hexamer of heterotrimers, with each heterotrimer composed of one A-chain, one B-chain, and one C-chain. The three chains associate via their collagen-like domains to form a triple helix, and six such triple helices assemble into the characteristic "bunch of tulips" structure. The N-terminal regions of the chains form a central fibril-like stalk, while the C-terminal gC1q domains form six globular heads. The B-chain is positioned in the middle of each heterotrimer, flanked by the A- and C-chains. This precise arrangement is essential for the correct spatial presentation of the globular heads, enabling multivalent binding to target surfaces. The crystal structure of the gC1qB domain (PDB: 1PK6) reveals a canonical C1q domain fold, with a hydrophobic core and a calcium-binding site near the apex of the β-sandwich. Calcium ions are required for the binding of certain ligands, including the Fc region of IgG. Mutations that disrupt the calcium-binding site or the hydrophobic core are predicted to be highly deleterious, as they would destabilize the globular domain and impair ligand recognition. ### 2.3 Post-Translational Modifications The B-chain undergoes several critical post-translational modifications: - **Hydroxylation**: Proline residues within the Gly-X-Y repeats are hydroxylated at the C-3 and C-4 positions by prolyl-4-hydroxylase and prolyl-3-hydroxylase. Lysine residues are hydroxylated by lysyl hydroxylase, and the resulting hydroxylysines are often further glycosylated with galactose or glucosyl-galactose moieties. These modifications are essential for the thermal stability of the collagen triple helix. - **Glycosylation**: The collagen-like domain contains O-linked glycosylation sites at hydroxylysine residues. The glycans contribute to the solubility and stability of the C1q molecule. - **Disulfide Bond Formation**: The N-terminal cysteine residues (Cys4 in the B-chain) form inter-chain disulfide bonds, covalently linking the A- and B-chains within each heterotrimer. ### 2.4 Interactive 3D Visualizer [Interactive 3D Protein Visualizer: Load C1QB (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P02746) The interactive visualizer allows users to explore the three-dimensional structure of the gC1qB domain (PDB: 1PK6) and the full-length C1q heterotrimer. Users can rotate the molecule, highlight specific residues, and visualize the spatial arrangement of the three ligand-binding sites. This tool is invaluable for researchers investigating the structural basis of C1q-ligand interactions and for evaluating the potential impact of pathogenic mutations. --- ## 3. Cellular Signaling Pathways & Molecular Function ### 3.1 The Classical Complement Pathway The primary function of C1q is to initiate the classical complement pathway. Upon binding to immune complexes (antigen-antibody complexes) or to pathogen surfaces, C1q undergoes a conformational change that activates the associated serine proteases C1r and C1s. Activated C1s cleaves C4 and C2, generating the C3 convertase (C4b2a), which in turn cleaves C3 to C3b. The downstream cascade leads to the formation of the membrane attack complex (MAC), opsonization of pathogens, and the release of anaphylatoxins (C3a, C4a, C5a) that recruit inflammatory cells. The B-chain is indispensable for this process. The gC1qB domain contains the primary binding site for the Fc region of IgG. Mutations that impair the IgG-binding capacity of gC1qB abolish the ability of C1q to activate the classical pathway, leading to a functional complement deficiency. The B-chain also contributes to the binding of C1q to pentraxins (e.g., CRP, serum amyloid P), which allows C1q to recognize damaged cells and activate complement in the absence of antibodies. ### 3.2 C1q in Synaptic Pruning and Neuroinflammation Beyond its role in systemic immunity, C1q is a key mediator of synaptic pruning in the central nervous system (CNS). C1q is produced by microglia and, to a lesser extent, by neurons and astrocytes. It tags weak or inappropriate synapses for elimination by microglia, a process that is essential for the refinement of neural circuits during development. In the adult brain, aberrant C1q-mediated synaptic pruning is implicated in neurodegenerative diseases. Wu et al. demonstrated that the transcription factor TCF7L2 directly regulates *C1QB* expression in the epileptic hippocampus, exacerbating synaptic pruning-dependent neuronal injury [5]. This study identified a novel transcriptional regulatory axis in which TCF7L2 binds to the *C1QB* promoter, upregulating C1q expression and driving excessive synapse elimination. The findings suggest that targeting the TCF7L2-C1QB axis could represent a therapeutic strategy for epilepsy. Similarly, C1q expression is elevated in the brains of Alzheimer's disease patients, where it contributes to synapse loss and cognitive decline [59, 83]. In a mouse model of sporadic Alzheimer's disease, deficiency of the C1q-associated adaptor protein TYROBP normalized the complement subnetwork molecular pathology, highlighting the central role of C1q in the disease process [59]. ### 3.3 C1q in the Tumor Microenvironment C1q is abundantly expressed by tumor-associated macrophages (TAMs) and is a component of the tumor microenvironment (TME) in multiple cancer types. The role of C1q in cancer is context-dependent, with both pro- and anti-tumorigenic effects reported. In osteosarcoma, high expression of *C1QA*, *C1QB*, and *C1QC* is associated with poor prognosis and remodeling of the TME [7, 96]. Similarly, in skin cutaneous melanoma (SKCM), C1Q expression correlates with immune infiltration and serves as a prognostic biomarker [8, 9]. Liang et al. identified *C1QA*, *C1QB*, and *GZMB* as novel prognostic biomarkers of SKCM, with high expression associated with improved survival in certain immune contexts [9]. In gastric cancer, *C1QB* and *TYROBP* were identified as key genes with prognostic value, with high expression correlating with worse outcomes [10]. In pancreatic cancer, a macrophage gene signature defined by high expression of *C1qa*, *C1qb*, and *Trem2* is elevated systemically and locally, marking a distinct TAM population [46]. The dual role of C1q in cancer may reflect its ability to promote inflammation and immune surveillance in some contexts while supporting an immunosuppressive TME in others. C1q can opsonize tumor cells, facilitating their phagocytosis by macrophages, but it can also promote the polarization of macrophages toward an M2-like, pro-tumorigenic phenotype. ### 3.4 C1q in Metabolic and Renal Disease C1q expression is upregulated in the adipose tissue of obese individuals, where it contributes to chronic low-grade inflammation [76]. In diabetic nephropathy (DN), *C1QB* has been identified as a potential diagnostic candidate gene, with elevated expression in the kidneys of DN patients [6, 51]. The complement system is activated in the diabetic kidney, leading to glomerular injury and proteinuria. Similarly, C1q is involved in the pathogenesis of chronic antibody-mediated rejection (CAMR) in kidney transplant recipients, where complement activation on the graft endothelium drives tissue injury [12, 22, 26, 37]. ### 3.5 Protein-Protein Interaction Networks C1q interacts with a wide range of proteins, both as part of the complement cascade and independently. Key interaction partners include: - **C1r and C1s**: The C1q collagen stalks bind the C1r-C1s tetramer, forming the C1 complex. - **IgG and IgM**: The gC1q domains bind the Fc regions of immunoglobulins. - **Pentraxins**: CRP, serum amyloid P, and pentraxin-3 bind to gC1q domains. - **Phosphatidylserine**: Exposed on the surface of apoptotic cells, recognized by gC1q domains. - **Receptors**: C1q receptors include cC1qR (calreticulin), gC1qR (C1qBP), and C1qRp (CD93), which mediate the cellular effects of C1q. - **TYROBP (DAP12)**: An adaptor protein that associates with C1q signaling complexes in microglia [59]. STRING and BioGRID databases list over 50 high-confidence interaction partners for C1QB, reflecting its central role in the immune network. ### 3.6 Signaling Pathway Diagram ```mermaid flowchart TD A["Immune Complex / Apoptotic Cell / Pathogen"] -->|"Ligand Recognition"| B["C1q Heterotrimer"] B -->|"Conformational Change"| C["C1r Activation"] C -->|"Proteolytic Cleavage"| D["C1s Activation"] D -->|"Cleaves C4 and C2"| E["C3 Convertase C4b2a"] E -->|"Cleaves C3"| F["C3b + C3a"] F -->|"Opsonization"| G["Phagocytosis"] F -->|"C5 Convertase"| H["C5b-9 MAC"] F -->|"Anaphylatoxin"| I["Inflammation"] B -->|"Synaptic Tagging"| J["Microglial Phagocytosis"] B -->|"TAM Polarization"| K["Tumor Microenvironment Remodeling"] J --> L["Synaptic Pruning / Neurodegeneration"] K --> M["Pro- or Anti-tumor Immunity"] ``` --- ## 4. Pathogenic Hotspot Mutations & Clinical Differentials ### 4.1 C1q Deficiency and Systemic Lupus Erythematosus Homozygous or compound heterozygous mutations in *C1QB* are a well-established cause of C1q deficiency, a rare autosomal recessive disorder characterized by recurrent infections, skin lesions, and a high risk of developing systemic lupus erythematosus (SLE) or SLE-like syndromes. C1q deficiency is the strongest known genetic risk factor for SLE, with over 90% of affected individuals developing the disease. Gorjizadeh et al. identified a novel homozygous *C1QB* mutation in an Iranian girl, expanding the clinical spectrum of C1q deficiency [3]. The patient presented with recurrent skin lesions, chronic infections, and autoimmune features. The mutation was a missense variant located in the gC1qB domain, predicted to disrupt the hydrophobic core and destabilize the globular domain. Higuchi et al. reported a Japanese family with a novel splicing mutation in *C1qB*, leading to a frameshift and premature termination [19]. The proband, a 4-year-old girl, presented with fever, facial erythema, joint pain, and oral ulceration, consistent with pediatric SLE. These cases underscore the clinical heterogeneity of C1q deficiency and the importance of genetic screening in patients with early-onset SLE. ### 4.2 Polymorphisms and Disease Susceptibility Common polymorphisms in the *C1Q* gene cluster have been associated with SLE susceptibility and disease severity. Martens et al. analyzed C1q polymorphisms and found associations with serum C1q levels, CH50 activity, and disease severity in SLE patients [95]. Rafiq et al. assessed common variation in the C1Q gene cluster and found suggestive associations with SLE, although the effect sizes were modest [65]. A targeted next-generation sequencing gene panel for early-onset SLE patients identified pathogenic variants in *C1QB* and other complement genes, confirming the utility of genetic screening in this population [18]. ### 4.3 Neurodegenerative and Psychiatric Disorders *C1QB* polymorphisms have been implicated in schizophrenia. Zakharyan et al. reported an association between a *C1QB* gene polymorphism and schizophrenia in the Armenian population [1]. The study found that a specific single-nucleotide polymorphism (SNP) in the *C1QB* promoter region was associated with altered C1q expression and increased schizophrenia risk. Sager et al. demonstrated divergent changes in complement pathway gene expression in schizophrenia and bipolar disorder, with *C1QB* expression elevated in the subependymal zone of schizophrenia patients [14]. These findings support the hypothesis that aberrant complement-mediated synaptic pruning contributes to the pathophysiology of major psychiatric disorders. ### 4.4 Infectious Disease Susceptibility C1q plays a role in the host defense against various pathogens, including *Mycobacterium tuberculosis*. Cai et al. found that increased complement C1q levels mark active disease in human tuberculosis [62]. Li et al. developed a machine learning model based on *SERPING1*, *C1QB*, and *C1QC* expression for the diagnosis of latent tuberculosis infection (LTBI), demonstrating the utility of C1Q genes as diagnostic biomarkers [4]. In grass carp, the C1qDC gene family, including C1qB, responds to GCRV infection, suggesting an evolutionarily conserved role in antiviral immunity [2]. ### 4.5 Cancer-Associated Mutations and Expression Changes Somatic mutations in *C1QB* are rare in cancer, but alterations in its expression are common. In glioblastoma, *C1QB* is among the upregulated hub genes identified through integrative analysis of gene expression data [16]. In breast carcinoma, spatial transcriptomic analysis identified *C1QB* as part of a gene signature associated with high recurrence risk [49]. In diffuse large B-cell lymphoma (DLBCL), tumor purity-related genes, including *C1QB*, predict prognosis and drug sensitivity [66]. These findings suggest that *C1QB* expression levels, rather than somatic mutations, are the primary driver of its clinical significance in cancer. ### 4.6 ClinVar Classification of Pathogenic Variants ClinVar lists several *C1QB* variants with clinical significance: | **Variant** | **Type** | **Clinical Significance** | **Phenotype** | |---|---|---|---| | c.154C>T (p.Arg52Ter) | Nonsense | Pathogenic | C1q deficiency, SLE | | c.202G>A (p.Gly68Arg) | Missense | Pathogenic | C1q deficiency, SLE | | c.286C>T (p.Arg96Trp) | Missense | Likely pathogenic | C1q deficiency | | c.451G>A (p.Gly151Ser) | Missense | Uncertain significance | C1q deficiency | | c.IVS1+1G>A | Splicing | Pathogenic | C1q deficiency, SLE | --- ## 5. Host-Pathogen & Viral Interactions ### 5.1 Bacterial Interactions C1q binds to a wide range of bacterial pathogens, including Gram-positive and Gram-negative species. The gC1q domains recognize surface molecules such as lipopolysaccharide (LPS), lipoteichoic acid, and porins. In the context of tuberculosis, C1q binds to *M. tuberculosis* and enhances its phagocytosis by macrophages [62]. However, some pathogens have evolved mechanisms to subvert C1q function. For example, the M protein of *Streptococcus pyogenes* binds C1q and inhibits complement activation, contributing to immune evasion. ### 5.2 Viral Interactions C1q can neutralize viruses directly by binding to viral surface proteins and activating the classical complement pathway. It also enhances the antibody-mediated neutralization of viruses. In the context of SARS-CoV-2, transcriptomic analysis of surviving and non-surviving patients infected with the Delta variant identified differential expression of complement genes, including *C1QB*, suggesting a role for complement in COVID-19 severity [36]. The yellow fever vaccine YF-17D induces a strong innate immune response, including the upregulation of complement genes, which predicts the subsequent adaptive immune response [24]. ### 5.3 Parasitic and Fungal Interactions C1q binds to the surface of various parasites, including *Leishmania* and *Trypanosoma*, and can activate complement-mediated lysis. In leprosy, C1q expression is elevated in erythema nodosum leprosum (ENL), a severe inflammatory complication of lepromatous leprosy [87]. The role of C1q in fungal immunity is less well characterized, but it has been shown to bind to *Candida albicans* and *Aspergillus fumigatus*. --- ## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors ### 6.1 Therapeutic Targeting of C1q Given its central role in complement-mediated diseases, C1q is an attractive therapeutic target. Several strategies are being explored: - **Monoclonal Antibodies**: Anti-C1q antibodies have been developed to block C1q function in autoimmune diseases. ANX005, a humanized monoclonal antibody that inhibits C1q, is in clinical trials for Guillain-Barré syndrome and other complement-mediated disorders. By binding to C1q, ANX005 prevents its interaction with target surfaces, thereby inhibiting the classical complement pathway. - **Small-Molecule Inhibitors**: Small molecules that bind to the gC1qB domain and block ligand recognition are in preclinical development. These compounds are designed to disrupt the interaction between C1q and IgG or CRP, without affecting the structural integrity of the C1q molecule. - **Peptide Inhibitors**: Synthetic peptides derived from the gC1qB domain can act as competitive inhibitors of C1q-ligand interactions. These peptides have shown efficacy in animal models of ischemia-reperfusion injury and inflammatory disease. - **Gene Therapy**: For patients with C1q deficiency, gene therapy approaches aimed at delivering a functional *C1QB* gene to macrophages or hematopoietic stem cells are being explored. Adeno-associated virus (AAV) vectors have shown promise in preclinical models. ### 6.2 Pharmacogenomic Considerations The expression of *C1QB* is modulated by genetic variants that may influence drug response. For example, polymorphisms in the *C1QB* promoter that alter PU.1/IRF8 binding could affect the baseline expression of C1q and, consequently, the response to anti-C1q therapies. Additionally, drugs that modulate macrophage polarization, such as CSF-1R inhibitors, indirectly affect C1q expression by altering the abundance of C1q-producing TAMs. ### 6.3 Drug Repurposing Opportunities Given the involvement of C1q in multiple diseases, drug repurposing screens have identified existing compounds that modulate C1q expression or function. For example, methylphenidate, a dopamine reuptake inhibitor, was shown to alleviate apathy-like behavior in 5xFAD mice, partly through effects on central immune signaling, including C1q [33]. Acthar Gel, a formulation of repository corticotropin injection, modulates complement gene expression, including *C1QB*, in a model of focal segmental glomerulosclerosis [31]. --- ## 7. Bioinformatic Resources & Database Accessions | **Database** | **Accession / ID** | **URL** | |---|---|---| | NCBI Gene | 713 | https://www.ncbi.nlm.nih.gov/gene/713 | | Ensembl | ENSG00000173369 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000173369 | | UniProt | P02746 | https://www.uniprot.org/uniprotkb/P02746/entry | | RCSB PDB | 1PK6 | https://www.rcsb.org/structure/1PK6 | | HGNC | 1242 | https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:1242 | | OMIM | 120570 | https://www.omim.org/entry/120570 | | ClinVar | Gene: C1QB | https://www.ncbi.nlm.nih.gov/clinvar/?term=C1QB | | Gene Ontology (GO) | GO:0006956 (complement activation), GO:0006958 (complement activation, classical pathway), GO:0005515 (protein binding), GO:0005886 (plasma membrane) | https://www.ebi.ac.uk/QuickGO/ | | STRING | 9606.ENSP00000307199 | https://string-db.org/ | | BioGRID | 108940 | https://thebiogrid.org/108940 | --- ## 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) * [CFD Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/immunology-checkpoints/cfd-gene-structure-function-pathway) ## References 1. 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