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 |
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Authors: | Patricia Dard Alicia Sanchez-Mazas Jean-Michel Dugoujon Gerda De Lange André Langaney Marie-Paule Lefranc Gérard Lefranc |
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Institution: | (1) Laboratoire de Génétique et Biométrie, Département d’Anthropologie et d’Ecologie, Université de Genève, 12 Rue Gustave-Revilliod, CH-1227 Carouge, Genève, Switzerland Tel.: +41-22-7026978; Fax: +41-22-3000351 e-mail: Dard@sc2a.unige.ch URA 49 CNRS, Musée de l’Homme, Paris, France, CH;(2) Centre d’Immunopathologie et de Génétique Humaine, CIGH-UPR 8291 CNRS, CHU de Purpan, Toulouse, France, FR;(3) Central Laboratory of the Netherlands Red Cross, Blood Transfusion Service, Department of Immunohematology, Amsterdam, The Netherlands, NL;(4) Laboratoire d’Immunogénétique Moléculaire, Institut de Génétique Moléculaire, UMR 9942, CNRS, Universités Montpellier I et II, Montpellier, France, FR |
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Abstract: | 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.
Received: 9 August 1995 / Revised: 6 January 1996 |
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