Identification of the size and antigenic determinants of the human C4 gene by a polymerase chain-reaction-based
Hsien-Hsiung Lee1, Shwu-Fen Chang, Yung-Te Tseng
1Department of Medical Research, Mackay Memorial Hospital, No. 45 Min-Sheng Road, Tanshui, Taipei Co. 251, Taiwan. hhlee@ms1.mmh.org.tw
Insights
A new polymerase chain reaction (PCR) method accurately determines the size of complement component 4 (C4) genes. This technique efficiently identifies C4 gene variants and other genetic variations.
Area of Science:
- Genetics
- Immunology
- Molecular Biology
Background:
- The human complement component 4 (C4) genes, C4A and C4B, are located in the major histocompatibility complex (MHC) on chromosome 6p21.3.
- Gene size variation, distinguishing long (L) and short (S) alleles, is influenced by an endogenous retroviral sequence (HERV-K (C4)) within intron 9 of the long C4 gene.
- Traditional methods for C4 gene typing include Southern blotting and immunoblot analysis for antigenic determinants.
Purpose of the Study:
- To develop and validate a polymerase chain reaction (PCR) amplification method for directly determining C4 gene size and identifying antigenic determinants.
- To compare the efficacy of the PCR method with established techniques like Southern blotting.
Main Methods:
- Utilized PCR amplification to analyze C4 loci adjacent to the RP1 and RP2 genes.
- Employed DNA sequencing to determine C4 gene size and identify antigenic determinants.
- Compared PCR results with Southern blot analysis data.
Main Results:
- All C4 genes adjacent to the RP1 gene were identified as the long gene.
- Approximately 47% of C4 genes adjacent to the RP2 gene were short (S) genes, and 53% were long (L) genes.
- The PCR method's findings were consistent with those obtained from Southern blot analysis.
Conclusions:
- The developed PCR method is a practical and efficient tool for C4 genotyping.
- This PCR approach can reliably distinguish between long and short C4 gene variants.
- The method holds potential for detecting other polymorphisms within C4 gene variants.
Abstract:
The human C4 complement components of the C4 locus are encoded by two genes, C4A and C4B, located on chromosome 6p21.3 of the major histocompatibility complex of the human leukocyte antigen class III region. The size difference between the two genes is due to the presence of HERV-K (C4), an endogenous retroviral sequence (6.7 kb long), in intron 9 of the long C4 gene. Whether the C4 is the long (L) or short (S) gene was determined by the Southern blot method, and the antigenic determinants in residues 1,054-1,106 of Rodgers and Chido were generally identified by immunoblot analysis. Herein, we explore a polymerase chain reaction (PCR) amplification method for directly determining the size of C4 loci adjacent to the respective RP1 and RP2 genes and antigenic determinants by DNA sequencing. From the results of this study, we concluded that all of the C4 genes adjacent to the RP1 gene presented the long gene. In addition, 47% of the C4 genes adjacent to the RP2 gene were the short gene and 53% were the long gene. This result was consistent with that of the Southern blot analysis. The PCR method is practical for identifying the C4 genotype and can be used to detect other polymorphisms among variants of C4 genes.
