Alt. symbols: C1QG

Approved name: complement C1q C chain
Alt. names: complement component 1, q subcomponent, gamma polypeptide, complement component 1, q subcomponent, C chain

Location: 1p36.12: 22643014 - 22648110 (+)
Gene type: protein_coding, 8 transcripts.

Scores: LoFtool: 0.231000 | pLI: 0.01738190 | LOEUF: 1.094

HGNC: 1245

NCBI: 714, RefSeq: NG_007565.1

Ensembl: ENSG00000159189.13

LRG_24 | Status: public

OMIM: 120575

Expression | ProteinAtlas

C1QC encodes the C subunit of C1q, the first subcomponent of C1, which has a complicated 18-chain structure comprised of 6 A, 6 B, and 6 C polypeptide chains. Each chain has a stretch of about 80 amino acids with the collagenous triplet Gly-X-Y where X and Y can include hydroxyproline and hydroxylysine. The A, B, and C chains combine to form 6 heteromeric triple helices in the collagenous regions of the chains (PMID: 1706597). C1q then associates with proenzymes C1r and C1s to form C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca2+-dependent C1r2C1s2 proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes.

Biallelic frameshift, nonsense and missense mutations in C1QA, C1QB, or C1QC, all located on chromosome 1p36, are associated with C1q deficiency [OMIM:613652]. This is a rare autosomal recessive disorder characterized by recurrent skin lesions, chronic infections, and increased susceptibility to the development of autoimmune diseases, especially systemic lupus erythematosus (SLE) or SLE-like diseases, as well as isolated chronic glomerulonephritis and renal failure. Disease may be associated wit h either absent C1q protein or the presence of dysfunctional C1q protein. The clinical spectrum is highly variable and can vary from virtually asymptomatic disease to fulminant bacterial infection and localized lupus-like skin, renal or CNS disease. Autoantibodies to ribonucleoproteins such as anti-Sm and Ro may be present. [Load More]