Laboratory for Molecular Diagnostics
Center for Nephrology and Metabolic Disorders

Complement component C1q, C chain

The C1QC gene encodes a component of complement C1q which along with C1r and C1s binds to antibody complexes and by that constitutes the first component of the classical complement activation pathway. Autosomal recessive deficiencies of C1q are associated with lupus erythematosus and glomerulonephritis.

Protein Structure

6 C chains complement component C1q add to the total of 18 components of the bouquet-of-flowers-like heteromultimeric macromolecule C1q.

Gene Regulation

The three proteins A, B, and C that compose the heteromultimere C1q are mostly of extrahepatic origin. They are synthesized by immature dendritic cells, monocytes, and macrophages. The mature protein is able to bind several sproteins and to initiate the classical pathway of complement activation. Such proteins include most importantly IgG- and IgM-containing immuncomplexes and several foreign proteins on pathogens and apoptotic cells.

Genetests:

Clinic Method Carrier testing
Turnaround 5 days
Specimen type genomic DNA
Clinic Method Genomic sequencing of the entire coding region
Turnaround 25 days
Specimen type genomic DNA
Clinic Method Massive parallel sequencing
Turnaround 25 days
Specimen type genomic DNA

Related Diseases:

Lupus erythematosus nephritis
C1QA
C1QB
C1QC
CFHR1
CFHR3
Complement component C1q deficiency
C1QA
C1QB
C1QC
Membranoproliferative glomerulonephritis (MPGN)
ADAMTS13
C1QA
C1QB
C1QC
C3
CD46
CFB
CFD
CFH
CFHR1
CFHR2
CFHR3
CFHR4
CFHR5
CFI
CLU
CR1 deficiency
CR1
Complement component C1q deficiency
C1QA
C1QB
C1QC
Complement component C1s deficiency
C1S
DGKE
PIGA
THBD

References:

1.

Lindenbaum RH et. al. (1979) Muscular dystrophy in an X; 1 translocation female suggests that Duchenne locus is on X chromosome short arm.

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2.

Sellar GC et. al. (1992) Localization of the gene cluster encoding the A, B, and C chains of human C1q to 1p34.1-1p36.3.

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3.

Sellar GC et. al. (1991) Characterization and organization of the genes encoding the A-, B- and C-chains of human complement subcomponent C1q. The complete derived amino acid sequence of human C1q.

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4.

Boyd Y et. al. (1988) Mapping of 12 translocation breakpoints in the Xp21 region with respect to the locus for Duchenne muscular dystrophy.

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5.

Diebolder CA et. al. (2014) Complement is activated by IgG hexamers assembled at the cell surface.

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6.

Kirschfink M et. al. (1993) Complete functional C1q deficiency associated with systemic lupus erythematosus (SLE).

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7.

Slingsby JH et. al. (1996) Homozygous hereditary C1q deficiency and systemic lupus erythematosus. A new family and the molecular basis of C1q deficiency in three families.

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Update: Sept. 26, 2018