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Determining the one, two, three, or four long and short loci of human complement C4 in a major histocompatibility complex haplotype encoding C4A or C4B proteins.

ABSTRACT: The complex genetics of human complement C4 with unusually frequent variations in the size and number of C4A and C4B, as well as their neighboring genes, in the major histocompatibility complex has been a hurdle for accurate epidemiological studies of diseases associated with C4. A comprehensive series of novel or improved techniques has been developed to determine the total gene number of C4 and the relative dosages of C4A and C4B in a diploid genome. These techniques include (1) definitive genomic restriction-fragment-length polymorphisms (RFLPs) based on the discrete duplication patterns of the RCCX (RP-C4-CYP21-TNX) modules and on the specific nucleotide changes for C4A and C4B isotypes; (2) module-specific PCR to give information on the total number of C4 genes by comparing the relative quantities of RP1- or TNXB-specific fragments with TNXA-RP2 fragments; (3) labeled-primer single-cycle DNA polymerization procedure of amplified C4d genomic DNA for diagnostic RFLP analysis of C4A and C4B; and (4) a highly reproducible long-range-mapping method that employs PmeI-digested genomic DNA for pulsed-field gel electrophoresis, to yield precise information on the number of long and short C4 genes in a haplotype. Applications of these vigorously tested techniques may clarify the roles that human C4A and C4B gene-dosage variations play in infectious and autoimmune diseases.

SUBMITTER: Chung EK

PROVIDER: S-EPMC378538 | biostudies-literature | 2002 Oct

REPOSITORIES: biostudies-literature

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Determining the one, two, three, or four long and short loci of human complement C4 in a major histocompatibility complex haplotype encoding C4A or C4B proteins.

Chung Erwin K EK Yang Yan Y Rupert Kristi L KL Jones Karla N KN Rennebohm Robert M RM Blanchong Carol A CA Yu C Yung CY

American journal of human genetics 20020910 4

The complex genetics of human complement C4 with unusually frequent variations in the size and number of C4A and C4B, as well as their neighboring genes, in the major histocompatibility complex has been a hurdle for accurate epidemiological studies of diseases associated with C4. A comprehensive series of novel or improved techniques has been developed to determine the total gene number of C4 and the relative dosages of C4A and C4B in a diploid genome. These techniques include (1) definitive gen ...[more]

PMID: 12224044

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Project description:Objectives Low copy numbers and deletion of complement C4 genes are potent risk factors for systemic lupus erythematosus (SLE). However, it is not known whether this genetic association affects the clinical outcome. We investigated C4 copy number variation and its relationship to clinical and serological features in a Northern European lupus cohort. Methods We genotyped the C4 gene locus using polymerase chain reaction (PCR)-based TaqMan assays in 169 patients with SLE classified according to the 1997 revised American College of Rheumatology (ACR) criteria and in 520 matched controls. In the patient group the mean C4 serum protein concentrations nephelometrically measured during a 12-month period prior to genetic analysis were compared to C4 gene copy numbers. Severity of disease was classified according to the intensity of the immunosuppressive regimens applied and compared to C4 gene copy numbers, too. In addition, we performed a TaqMan based analysis of three lupus-associated single-nucleotide polymorphisms (SNPs) located inside the major histocompatibility complex (MHC) to investigate the independence of complement C4 in association with SLE. Results Homozygous deficiency of the C4A isotype was identified as the strongest risk factor for SLE (odds ratio (OR)?=?5.329; p?=?7.7?×?10-3) in the case-control comparison. Moreover, two copies of total C4 were associated with SLE (OR?=?3.699; p?=?6.8?×?10-3). C4 serum levels were strongly related to C4 gene copy numbers in patients, the mean concentration ranging from 0.110?g/l (two copies) to 0.256?g/l (five to six copies; p?=?4.9?×?10-6). Two copies of total C4 and homozygous deletion of C4A were associated with a disease course requiring cyclophosphamide therapy (OR?=?4.044; p?=?0.040 and OR?=?5.798; p?=?0.034, respectively). Homozygous deletion of C4A was associated with earlier onset of SLE (median 24 vs. 34 years; p?=?0.019) but not significant after correction for multiple testing. SNP analysis revealed a significant association of HLA-DRB1*0301 with SLE (OR?=?2.231; p?=?1.33?×?10-5). Conclusions Our findings confirm the important role of complement C4 genes in the development of SLE. Beyond the impact on the susceptibility for lupus, C4 copy numbers may be related to earlier onset and a more severe course of the disease. The association of homozygous deletion of C4A and SLE is accompanied by the presence of HLA-DRB1*0301 without a proven pathophysiological mechanism.

Dataset Information

Determining the one, two, three, or four long and short loci of human complement C4 in a major histocompatibility complex haplotype encoding C4A or C4B proteins.

Publications

Determining the one, two, three, or four long and short loci of human complement C4 in a major histocompatibility complex haplotype encoding C4A or C4B proteins.

Similar Datasets

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