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PloS One 2011Genetic variants resulting in non-expression of complement C4A and C4B genes are common in healthy European populations and have shown association with a number of...
Genetic variants resulting in non-expression of complement C4A and C4B genes are common in healthy European populations and have shown association with a number of diseases, most notably the autoimmune disease, systemic lupus erythematosus. The most frequent cause of a C4 "null" allele, following that of C4 gene copy number variation (CNV), is a non-sense mutation arising from a 2 bp CT insertion into codon 1232 of exon 29. Previous attempts to accurately genotype this polymorphism have not been amenable to high-throughput typing, and have been confounded by failure to account for CNV at this locus, as well as by inability to distinguish between paralogs. We have developed a novel, high-throughput, paralog-specific assay to detect the presence and copy number of this polymorphism. We have genotyped healthy cohorts from the United Kingdom (UK) and Spain. Overall, 30/719 (4.17%) individuals from the UK cohort and 8/449 (1.78%) individuals from the Spanish cohort harboured the CT insertion in a C4A gene. A single Spanish individual possessed a C4B CT insertion. There is weak correlation between the C4 CT insertion and flanking MHC polymorphism. Therefore it is important to note that, as with C4 gene CNV, disease-association due to this variant will be missed by current SNP-based genome-wide association strategies.
Topics: Base Sequence; Cohort Studies; Complement C4; Complement C4a; Complement C4b; DNA Copy Number Variations; Exons; Female; Gene Frequency; Genotype; Genotyping Techniques; HLA-DRB1 Chains; Haplotypes; Humans; Lupus Erythematosus, Systemic; Male; Molecular Sequence Data; Mutagenesis, Insertional; Pedigree; Polymorphism, Single Nucleotide; Spain; United Kingdom
PubMed: 21857912
DOI: 10.1371/journal.pone.0022128 -
Biology of Blood and Marrow... May 2019HLA matching is a prerequisite for successful allogeneic hematopoietic stem cell transplantation (HSCT) because it lowers the occurrence and severity of...
HLA matching is a prerequisite for successful allogeneic hematopoietic stem cell transplantation (HSCT) because it lowers the occurrence and severity of graft-versus-host disease (GVHD). However, matching a few alleles of the classic HLA genes only may not ensure matching of the entire MHC region. HLA haplotype matching has been reported to be beneficial in HSCT because of the variation relevant to GVHD risk in the non-HLA region. Because polymorphism in the MHC is highly population specific, we hypothesized that donors from the Finnish registry are more likely to be matched at a higher level for the Finnish patients than donors from other registries. In the present study we determined 25 single nucleotide polymorphisms (SNPs) of the complement component 4 (C4) gene in the γ-block segment of MHC from 115 Finnish HSCT patients and their Finnish (n = 201) and non-Finnish (n = 280) donor candidates. Full matching of HLA alleles and C4 SNPs, independently or additively, occurred more likely in the Finnish-Finnish group as compared with the Finnish-non-Finnish group (P < .003). This was most striking in cases with HLA haplotypes typical of the Finnish population. Patients with ancestral HLA haplotypes (AH) were more likely to find a full HLA and C4 matched donor, regardless of donor origin, as compared with patients without AH (P < .0001). Despite the clear differences at the population level, we could not find a statistical association between C4 matching and clinical outcome. The results suggest that screening C4 SNPs can be advantageous when an extended MHC matching or HLA haplotype matching in HSCT is required. This study also supports the need for small population-specific stem cell registries.
Topics: Adult; Complement C4; Finland; Haplotypes; Hematopoietic Stem Cell Transplantation; Histocompatibility; Humans; Polymorphism, Single Nucleotide; Registries; Unrelated Donors
PubMed: 30592985
DOI: 10.1016/j.bbmt.2018.12.759 -
Annals of the Rheumatic Diseases Apr 1991Deficiencies of early components of the classical complement pathway are known to be associated with systemic lupus erythematosus (SLE). C4 null alleles, C4A Q0 and C4B...
Deficiencies of early components of the classical complement pathway are known to be associated with systemic lupus erythematosus (SLE). C4 null alleles, C4A Q0 and C4B Q0, are prime candidates for the major histocompatibility complex associated factor which determines susceptibility to SLE. There is poor correlation, however, between the presence of low concentrations of C4 and possession of C4 null alleles, and thus the basis of the association between C4A Q0, C4B Q0 and SLE remains obscure. The possibility that activation of C4 may be related to the possession of C4 null alleles was examined. C4 phenotypes were investigated, and C4 concentration and activation were estimated in patients with SLE. C4 activation was determined by measuring the concentration of C4d--a split product of C4. Twenty five of 35 patients had C4 phenotypes which include null alleles. No association between low C4 concentrations and C4 null alleles was found, but a significant association between low C4d concentrations and C4 phenotypes including null alleles, particularly those with C4A Q0, was noted. No correlation between concentrations of C4 and C4d was found. These results show an influence of C4 null alleles on the activation of the C4 molecule, which is independent of the concentration of C4. The possession of silent genes coding for C4 null alleles might predispose to SLE by conditioning poor C4 activation, a critical event for the clearance of immune complexes mediated by the classical complement pathway.
Topics: Alleles; Complement Activation; Complement C4; Complement C4a; Complement C4b; Gene Expression; Humans; Lupus Erythematosus, Systemic; Nephelometry and Turbidimetry; Peptide Fragments; Phenotype
PubMed: 2029208
DOI: 10.1136/ard.50.4.251 -
Journal of Virology May 2011The fourth component of human complement (C4) plays an important role in innate immune function. C4 activity has been observed to be significantly lower in patients with...
The fourth component of human complement (C4) plays an important role in innate immune function. C4 activity has been observed to be significantly lower in patients with chronic hepatitis C virus (HCV) infections, although the mechanism remains unknown. In this study, we have examined the mechanisms of C4 regulation by HCV. Liver biopsy specimens from patients with chronic HCV infections displayed significantly lower C4 mRNA levels than liver tissue samples from patients with unrelated liver disease. Further, C4 mRNA levels of the two isoforms (C4A and C4B) were significantly reduced in hepatocytes transfected with RNA from HCV genotype 1a or 2a. Subsequently, a significant C4 regulatory role of HCV core or NS5A upon C4 promoter activity was observed. HCV core or NS5A transgenic mice displayed a reduction in C4 mRNA. Gamma interferon (IFN-γ)-induced C4 promoter activation was also impaired in the presence of HCV proteins. We further demonstrated that HCV core reduced the expression of upstream stimulating factor 1 (USF-1), a transcription factor important for basal C4 expression. On the other hand, the expression of interferon regulatory factor 1 (IRF-1), which is important for IFN-γ-induced C4 expression, was inhibited by hepatocytes expressing HCV NS5A. These results underscore the roles of HCV proteins in innate immune regulation in establishing a chronic infection.
Topics: Animals; Biopsy; Complement C4; Female; Gene Expression Profiling; Gene Expression Regulation; Hepacivirus; Hepatitis C, Chronic; Humans; Liver; Male; Mice; Mice, Transgenic; Transcription, Genetic
PubMed: 21345967
DOI: 10.1128/JVI.02449-10 -
Annals of the Rheumatic Diseases Jul 1989In a study of 66 patients with systemic lupus erythematosus (SLE) and 80 controls it was found that the presence of two deficiency (null) alleles of C4 had a significant...
In a study of 66 patients with systemic lupus erythematosus (SLE) and 80 controls it was found that the presence of two deficiency (null) alleles of C4 had a significant effect on mean C4 concentrations in serum. In six controls who each had two C4 null alleles the mean C4 concentration in serum was 56% lower than in 43 controls without C4 null alleles; the nadir of the C4 concentration in four patients with SLE with two null alleles was also lower by a mean of 55% than in 32 patients who did not have null alleles. Reduced production of C4 allotypes in subjects with two null alleles may be an important determinant of total C4 concentration in patients with SLE. For optimal interpretation of C4 concentrations in SLE, C4 allotyping appears to be indicated, particularly to identify patients who have two null alleles of C4.
Topics: Adult; Aged; Aged, 80 and over; Alleles; Complement C4; Female; Humans; Lupus Erythematosus, Systemic; Male; Middle Aged
PubMed: 2774701
DOI: 10.1136/ard.48.7.600 -
Nucleic Acids Research Mar 1986cDNA clones specific for the fourth component of complement (C4) and its androgen-regulated isotype, sex-limited protein (Slp), have been isolated from two mouse... (Comparative Study)
Comparative Study
cDNA clones specific for the fourth component of complement (C4) and its androgen-regulated isotype, sex-limited protein (Slp), have been isolated from two mouse haplotypes (H-2d and H-2w7) that show differential C4 activity and differential regulation of Slp. Clones were first isolated using a cDNA probe enriched by subtractive hybridization. Subsequent screening has resulted in cDNAs spanning the entire C4d mRNA, as well as much of C4w7, Slpw7 and a short region of Slpd. The cDNAs for C4 and Slp show extensive sequence homology, but can be distinguished using oligonucleotide probes synthesized to regions of greatest sequence divergence. Sequence differences between C4 and Slp indicate structurally important features of C4 that have been altered in Slp such that Slp is unable to participate in the complement pathway. Of the few nucleotide differences between C4d and C4w7, a single base change resulting in one less glycosylation site in the C4w7 alpha chain could account for its 4-fold reduced hemolytic efficiency. Sequence comparison of multiple alleles of C4 and Slp indicates that possible gene conversion events occurred in the H-2w7 strain that has multiple Slp genes.
Topics: Alleles; Animals; Blood Proteins; Complement C4; DNA; DNA Restriction Enzymes; Mice; Mice, Inbred Strains; Nucleic Acid Hybridization; Sequence Homology, Nucleic Acid
PubMed: 3008092
DOI: 10.1093/nar/14.6.2539 -
Proceedings of the National Academy of... Sep 2012An essential aspect of innate immunity is recognition of molecular patterns on the surface of pathogens or altered self through the lectin and classical pathways, two of...
An essential aspect of innate immunity is recognition of molecular patterns on the surface of pathogens or altered self through the lectin and classical pathways, two of the three well-established activation pathways of the complement system. This recognition causes activation of the MASP-2 or the C1s serine proteases followed by cleavage of the protein C4. Here we present the crystal structures of the 203-kDa human C4 and the 245-kDa C4·MASP-2 substrate·enzyme complex. When C4 binds to MASP-2, substantial conformational changes in C4 are induced, and its scissile bond region becomes ordered and inserted into the protease catalytic site in a manner canonical to serine proteases. In MASP-2, an exosite located within the CCP domains recognizes the C4 C345C domain 60 Å from the scissile bond. Mutations in C4 and MASP-2 residues at the C345C-CCP interface inhibit the intermolecular interaction and C4 cleavage. The possible assembly of the huge in vivo enzyme-substrate complex consisting of glycan-bound mannan-binding lectin, MASP-2, and C4 is discussed. Our own and prior functional data suggest that C1s in the classical pathway of complement activated by, e.g., antigen-antibody complexes, also recognizes the C4 C345C domain through a CCP exosite. Our results provide a unified structural framework for understanding the early and essential step of C4 cleavage in the elimination of pathogens and altered self through two major pathways of complement activation.
Topics: Binding Sites; Complement C4; Crystallography; HEK293 Cells; Humans; Immunity, Innate; Mannans; Mannose-Binding Protein-Associated Serine Proteases; Molecular Conformation; Mutation; Protein Binding; Protein Conformation; Protein Structure, Tertiary; Proteins; Proteolysis; Recombinant Proteins; Static Electricity; Substrate Specificity
PubMed: 22949645
DOI: 10.1073/pnas.1208031109 -
The Biochemical Journal Feb 1986Disulphide bonds contribute significantly to the maintenance of structural/functional integrity of many proteins. Therefore it was of interest to study the distribution...
Disulphide bonds contribute significantly to the maintenance of structural/functional integrity of many proteins. Therefore it was of interest to study the distribution and the effect of disulphides on conformation of complement components C3 and C4. These proteins are precursors of several fragments with various binding sites and distinct physiological functions. The constituents of C3c (beta, alpha 27, alpha 43) and those of C4c (beta, alpha 27, alpha 16, gamma) were investigated, since other fragments of C3 or C4 do not participate in interchain linkages. Inter-and intra-chain disulphide bonds in C3c and C4c were localized by using a modification of conventional SDS (sodium dodecyl sulphate)/polyacrylamide-gel electrophoresis such that the change in mobility of disulphide-bond-containing proteins can be detected throughout the transition from a non-reduced to a fully reduced state. Several forms of the alpha 43 fragment from C3, and of the gamma-chain of C4, with different mobilities can exist, depending on the number of intra-chain disulphide bonds reduced. The intermediates (heterodimers) generated by a partial reduction of C3c or C4c were characterized by two-dimensional SDS/polyacrylamide-gel electrophoresis performed in the absence, then in the presence, of beta-mercaptoethanol. The inter-chain linkages in C3c were determined to be beta-alpha 27 and alpha 27- alpha 43, thus indicating the presence of only one interchain bond in C3. The two interchain bonds in C4c are beta-alpha 27 and alpha 16-gamma. The third interchain bond in C4 (alpha 27-gamma, tentative) remains to be determined.
Topics: Complement C3; Complement C3c; Complement C4; Complement C4b; Disulfides; Dithiothreitol; Electrophoresis, Polyacrylamide Gel; Humans; Oxidation-Reduction; Peptide Fragments; Sulfhydryl Reagents; Thiocyanates
PubMed: 3707529
DOI: 10.1042/bj2330819 -
PloS One 2014Genetic factors have been estimated to account for about 25% of the variation in an adult's life span. The complement component C4 with the isotypes C4A and C4B is an...
Genetic factors have been estimated to account for about 25% of the variation in an adult's life span. The complement component C4 with the isotypes C4A and C4B is an effector protein of the immune system, and differences in the overall C4 copy number or gene size (long C4L; short C4S) may influence the strength of the immune response and disease susceptibilities. Previously, an association between C4B copy number and life span was reported for Hungarians and Icelanders, where the C4B*Q0 genotype, which is defined by C4B gene deficiency, showed a decrease in frequency with age. Additionally, one of the studies indicated that a low C4B copy number might be a genetic trait that is manifested only in the presence of the environmental risk factor "smoking". These observations prompted us to investigate the role of the C4 alleles in our large German longevity sample (∼ 700 cases; 94-110 years and ∼ 900 younger controls). No significant differences in the number of C4A, C4B and C4S were detected. Besides, the C4B*Q0 carrier state did not decrease with age, irrespective of smoking as an interacting variable. However, for C4L*Q0 a significantly different carrier frequency was observed in the cases compared with controls (cases: 5.08%; controls: 9.12%; p = 0.003). In a replication sample of 714 German cases (91-108 years) and 890 controls this result was not replicated (p = 0.14) although a similar trend of decreased C4L*Q0 carrier frequency in cases was visible (cases: 7.84%; controls: 10.00%).
Topics: Adult; Aged; Aged, 80 and over; Alleles; Complement C4; DNA Copy Number Variations; Female; Gene Frequency; Genotype; Germany; Humans; Longevity; Male; Middle Aged; Risk Factors; Young Adult
PubMed: 24465950
DOI: 10.1371/journal.pone.0086188 -
The Journal of Biological Chemistry Sep 1985The nucleotide sequence coding for the fourth component of mouse complement (C4) has been determined from a cloned genomic DNA fragment and a cloned cDNA fragment. The... (Comparative Study)
Comparative Study
The nucleotide sequence coding for the fourth component of mouse complement (C4) has been determined from a cloned genomic DNA fragment and a cloned cDNA fragment. The amino acid sequence of the protein was deduced. The single chain precursor protein (pro-C4) consists of 1719 amino acid residues. The mature beta, alpha, and gamma subunits contain 654, 766, and 291 amino acids, respectively. One potential carbohydrate attachment site is predicted for the beta chain, three for the alpha chain, and none for the gamma chain. From a comparison with human C4 cDNA sequence an extensive overall sequence homology, 79% in nucleotides and 76% in amino acids, is observed. There is conservation in both the position and number of cysteine residues in human and mouse C4. We compared the mouse C4 amino acid sequences with those of mouse C3 and human alpha 2-macroglobulin and the evolutionary relationship among these three proteins is discussed.
Topics: Amino Acid Sequence; Animals; Base Sequence; Biological Evolution; Cloning, Molecular; Complement C4; DNA; DNA Restriction Enzymes; Macromolecular Substances; Mice; Mice, Inbred Strains; Species Specificity
PubMed: 2993295
DOI: No ID Found