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Complement component C1q, A chain

The C1QA 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 A 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 Massive parallel sequencing
Turnaround 25 days
Specimen type genomic DNA
Clinic Method Genomic sequencing of the entire coding region
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.

Petry F et al. (1997) Multiple identification of a particular type of hereditary C1q deficiency in the Turkish population: review of the cases and additional genetic and functional analysis.

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2.

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

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3.

Stevens B et al. (2007) The classical complement cascade mediates CNS synapse elimination.

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4.

Petry F et al. (1995) Non-sense and missense mutations in the structural genes of complement component C1q A and C chains are linked with two different types of complete selective C1q deficiencies.

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5.

Gilmour S et al. (1980) The conformation of subcomponent C1q of the first component of human complement.

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6.

Bing DH et al. (1982) Fibronectin binds to the C1q component of complement.

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7.

None (1974) A collagen-like amino acid sequence in a polypeptide chain of human C1q (a subcomponent of the first component of complement).

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8.

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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9.

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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10.

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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11.

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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12.

Degn SE et al. (2011) Disease-causing mutations in genes of the complement system.

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13.

Lewis MJ et al. (2009) Immunoglobulin M is required for protection against atherosclerosis in low-density lipoprotein receptor-deficient mice.

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14.

Botto M et al. (1998) Homozygous C1q deficiency causes glomerulonephritis associated with multiple apoptotic bodies.

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15.

Topaloglu R et al. (1996) Molecular basis of hereditary C1q deficiency associated with SLE and IgA nephropathy in a Turkish family.

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16.

Orphanet article

Orphanet ID 221162 external link
17.

NCBI article

NCBI 712 external link
18.

OMIM.ORG article

Omim 120550 external link
19.

Wikipedia article

Wikipedia EN (C1QA) external link
Update: Aug. 14, 2020
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