Genetics of human complement component C4 and evolution the central MHC
O P Martinez1, N Longman-Jacobsen, R Davies
1Centre for Molecular Immunology and Instrumentation, University of Western Australia, PO Box 5100, Canning Vale WA 6155, Australia. Patricia.Martinez@health.wa.gov.au
Frontiers in Bioscience : a Journal and Virtual Library
|August 7, 2001
Summary
Human complement proteins C4A and C4B exhibit distinct reactivities and binding properties. Gene variations in C4A and C4B likely evolved for parasite defense, mirroring fish complement C3 evolution.
Area of Science:
- Immunology
- Evolutionary Biology
- Genetics
Background:
- Human complement component C4 proteins, C4A and C4B, possess differing reactivities and binding affinities.
- Multiple polymorphic allotypes of C4A and C4B exist, with complex gene multiplication patterns in the population.
- This genetic variation is likely driven by evolutionary pressure to combat diverse parasites.
Purpose of the Study:
- To explore the evolutionary history and genetic basis of human complement C4 genes.
- To understand the functional divergence of C4A and C4B allotypes.
- To investigate the role of gene duplication and divergence in the evolution of the complement system.
Main Methods:
- Comparative genomics analysis of human complement genes.
- Examination of gene duplication and rearrangement events within the MHC region.
- Analysis of protein family evolution, including C3, C4, and C5.
Main Results:
- C4A and C4B display differential reactivity and binding, influenced by polymorphic allotypes and gene dosage variations.
- Complex gene multiplication patterns of C4A and C4B suggest adaptation to parasitic challenges.
- Human C4 genes are located in the MHC on chromosome 6p21.3, with paralogous genes found on other chromosomes.
Conclusions:
- The evolution of complement C4, C3, and C5 involves domain acquisition, gene duplication, and sequence divergence.
- This evolutionary model aids in understanding innate and adaptive immunity.
- Investigating these genetic mechanisms may explain diseases linked to MHC ancestral haplotypes.
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