Journal Article

Evidence of balancing selection at the <i>HLA-G</i> promoter region

Zheng Tan, Andrew Minsoo Shon and Carole Ober

in Human Molecular Genetics

Volume 14, issue 23, pages 3619-3628
Published in print December 2005 | ISSN: 0964-6906
Published online October 2005 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddi389
Evidence of balancing selection at the HLA-G promoter region

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HLA-G is a class Ib HLA gene with unique tissue expression pattern and immunomodulatory properties. Polymorphisms in the HLA-G promoter region have been associated with miscarriage and asthma, whereas expression levels have been associated with a wide range of pathologic conditions as well as survival of embryos after in vitro fertilization and of organs after transplantation. Here, we characterize the sequence variation and haplotype structure of the HLA-G promoter and flanking sequences in 44 African Americans, 47 European Americans and 43 Han Chinese by haplotype-specific PCR and sequencing. In all three populations, we observed high levels of nucleotide variation, an excess of intermediate-frequency alleles, and a genealogy with two common haplotypes separated by deep branches, features that are suggestive of balancing selection acting in this region. Comparisons to HLA-A and a pseudogene, HLA-J, suggested that the observed pattern of sequence variation in the HLA-G promoter region is not likely due to other selected HLA genes. We suggest that the mechanism for this selection is related to the highly regulated expression pattern of HLA-G and that high- and low-expressing promoters may be favored under temporally and/or spatially varying selective pressures.

Journal Article.  6810 words.  Illustrated.

Subjects: Genetics and Genomics

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