DNA analysis of the immunoglobulin IGHG loci in a Mandenka population from eastern Senegal: correlation with Gm haplotypes and hypotheses for the evolution of the Ig CH region.
This study presents restriction fragment length polymorphism (RFLP) and serological analyses of the immunoglobulin CH loci in a sample of 100 individuals from a Senegalese Mandenka population. The RFLP variability is mostly the result of large DNA insertions or deletions in the non-coding flanking regions of the IGHG genes, and to variable number of tandem repeat-like patterns within their 5'-switch sequences. However, part of the IGHG3 polymorphism also corresponds to a variable number of exons coding for the flexible hinge segment of the IgG3 antibody (the 4-exon and 3-exon forms, and a newly described 2-exon form). This diversity presents relevant associations with Gm haplotypes, suggesting that molecular rearrangements of the G3 hinge are related to the evolution of the Gm polymorphism. Non-significant correlation coefficients are found between Gm haplotypes and A2m alleles in the Mandenka, indicating that these loci may have reached equilibrium through recombination. The effect of recombination on linkage disequilibrium is more generally revealed, across the Ig CH genomic region, by a significant decrease of D' values with increasing physical distances between the loci on the chromosome.
Dard
P
P
Département d'Anthropologie et d'Ecologie, Université de Genève, Switzerland. Dard@sc2a.unige.ch
Sanchez-Mazas
A
A
Dugoujon
J M
JM
De Lange
G
G
Langaney
A
A
Lefranc
M P
MP
Lefranc
G
G
D000483:Alleles; D002883:Chromosomes, Human, Pair 14 / Q000235:genetics*; D019143:Evolution, Molecular; D005787:Gene Frequency / Q000235:genetics; D005803:Genes, Immunoglobulin; D008040:Genetic Linkage / Q000235:genetics; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D007126:Immunoglobulin Allotypes / Q000235:genetics; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007129:Immunoglobulin Gm Allotypes / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D015810:Linkage Disequilibrium / Q000235:genetics; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D012675:Senegal
D007126:Immunoglobulin Allotypes; D007127:Immunoglobulin Constant Regions; D007129:Immunoglobulin Gm Allotypes; D007143:Immunoglobulin Heavy Chains