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C4A

Synonyms
C4, C4A2, C4A3, C4A4, C4A6, C4AD, C4S, CO4, CPAMD2, RG
External resources
Summary
This gene encodes the acidic form of complement factor 4, part of the classical activation pathway. The protein is expressed as a single chain precursor which is proteolytically cleaved into a trimer of alpha, beta, and gamma chains prior to secretion. The trimer provides a surface for interaction between the antigen-antibody complex and other complement components. The alpha chain is cleaved to release C4 anaphylatoxin, an antimicrobial peptide and a mediator of local inflammation. Deficiency of this protein is associated with systemic lupus erythematosus and type I diabetes mellitus. This gene localizes to the major histocompatibility complex (MHC) class III region on chromosome 6. Varying haplotypes of this gene cluster exist, such that individuals may have 1, 2, or 3 copies of this gene. Two transcript variants encoding different isoforms have been found for this gene.

Variant counts

The variants found in rare patients tested by 3billion are classified and counted according to ACMG guidelines. The variants with over 5% variant frequency in population genome databases ( gnomAD, dbSNP, etc) are excluded.

Pathogenic
28
Likely pathogenic
0
VUS
5,036
Likely benign
25,286
Benign
0

Patient phenotypes

Proportions of phenotypes among 28 patients carrying pathogenic or likely pathogenic variants on C4A gene are displayed below.

Phenotype class
Patients in 3billion (%)
Abnormality of the cardiovascular system
28.6%
Abnormality of the nervous system
28.6%
Abnormality of the integument
17.9%
Abnormality of head or neck
14.3%
Abnormality of the eye
14.3%
Abnormality of the musculoskeletal system
14.3%
Abnormality of the ear
10.7%
Abnormality of the genitourinary system
10.7%
Abnormality of blood and blood-forming tissues
7.1%
Abnormality of the digestive system
7.1%
Growth abnormality
7.1%
Abnormality of the endocrine system
3.6%
Abnormality of the respiratory system
3.6%
Constitutional symptom
3.6%
Neoplasm
3.6%
Abnormal cellular phenotype
0%
Abnormality of limbs
0%
Abnormality of metabolism homeostasis
0%
Abnormality of prenatal development or birth
0%
Abnormality of the breast
0%
Abnormality of the immune system
0%
Abnormality of the thoracic cavity
0%
Abnormality of the voice
0%

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