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Nucleotide sequence analyses of human complement 6 (C6) gene suggest balancing selection

M Soejima1, H Tachida, M Tsuneoka

  • 1Department of Forensic Medicine and Human Genetics, Kurume University School of Medicine, Kurume 830-0011, Japan.

Annals of Human Genetics
|April 23, 2005
PubMed

Insights

The sixth complement component (C6) exhibits common C6A and C6B charge polymorphisms. Evidence suggests these C6 alleles are maintained by balancing selection in human populations.

Area of Science:

  • Immunogenetics
  • Human Population Genetics

Background:

  • The sixth complement component (C6) possesses common charge polymorphisms, C6A and C6B, with consistent frequencies across major human populations.
  • A distinct C6B2 variant is observed in Japanese populations at approximately 6% frequency.

Purpose of the Study:

  • To investigate the evolutionary origins and population genetics of C6 charge polymorphisms.
  • To determine if common C6 alleles in humans are influenced by balancing selection.

Main Methods:

  • Sequence analysis of the C6 coding region in human and ape alleles.
  • Examination of sequence variation in a 3.86 kb region including exon 3.
  • Application of neutrality test statistics using sliding window methods.

Main Results:

  • Sequence analysis revealed genetic differences between C6*B2 and C6*A, suggesting a recombination event.
  • Extensive linkage disequilibrium (LD) was observed among single nucleotide polymorphisms (SNPs) in the C6 exon 3 region.
  • Neutrality tests indicated significant values in the polymorphism-residing subregion across human populations.

Conclusions:

  • The findings suggest that the common C6A and C6B alleles in human populations may be maintained through balancing selection.
  • Recombination events may have contributed to the evolution of C6B2.

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