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Population genetic studies of HLA-E: evidence for selection
1Committee on Evolutionary Biology, University of Chicago, IL 60637, USA. cgrimsle@midway.uchicago.edu
Human Immunology
|January 1, 1997
Summary
The human leukocyte antigen E (HLA-E) gene shows variation across ethnic groups, with two alleles identified. This genetic diversity suggests HLA-E polymorphism predates human expansion and is maintained by stabilizing selection.
Area of Science:
- Immunogenetics
- Human evolutionary genetics
Background:
- The human leukocyte antigen E (HLA-E) is a nonclassical class Ib gene with an incompletely understood function.
- Investigating genetic variation in HLA-E is crucial for understanding its role in human populations.
Purpose of the Study:
- To characterize the variation within the HLA-E gene across diverse human ethnic groups.
- To explore the evolutionary history and selective pressures on HLA-E polymorphism.
Main Methods:
- DNA sequencing to identify variations in the HLA-E gene.
- Analysis of allele frequencies in various ethnic populations.
- Linkage disequilibrium analysis with other HLA genes (HLA-A, HLA-B, HLA-C).
Main Results:
- A single nucleotide polymorphism (A-->G at 382, exon 3) was identified, resulting in two alleles: one encoding arginine (R) and the other glycine (G) at codon 107.
- The glycine allele (EG107) was found in ape species, suggesting it is the ancestral human allele.
- Both HLA-E alleles were present in all studied populations, with frequencies deviating from neutrality in Caucasian, African-American, and Hispanic samples, indicating potential balancing selection.
Conclusions:
- The identified HLA-E polymorphism likely predates the expansion of Homo sapiens.
- Stabilizing selection appears to maintain the observed HLA-E allele frequencies in diverse human populations.
- The study provides insights into the evolutionary maintenance of immune gene diversity.