title: Diversity of MICA and linkage disequilibrium with HLA-B in two North American populations.
abstract: The MICA gene has a high degree of polymorphism. Allelic variation of MICA may influence binding of these ligands to the NK cell receptor NKG2D and may affect organ transplantation and/or disease pathogenesis. Knowledge of the population distribution of MICA alleles and their linkage disequilibrium (LD) with class I human leukocyte antigen (HLA) will enhance our understanding of the potential functional significance of the MICA polymorphism. In the present study, we characterized the MICA and HLA-B polymorphisms in two North American populations: European and African. The individual racial groups showed rather limited variation at the MICA locus, where the same set of three most common alleles, MICA*00201, *004, and *00801, account for 64 and 71% of the allele frequency in European-Americans and African-Americans, respectively. Other common alleles (allele frequency >5% in a population) include MICA*00901 and *010. MICA alleles showed strong linkage disequilibrium with HLA-B. Typically, a common MICA allele has strong LD with several HLA-B alleles, whereas most HLA-B alleles and their related serological groups are associated with a single MICA allele. The lack of evidence for an active diversification of the MICA gene after racial separation indicates an evolutionary history distinct from that of the classical HLA genes.
authors.affiliation: Laboratory of Genomic Diversity, NCI-Frederick, Basic Research Program, SAIC Frederick, Frederick, MD 21702, USA.
authors.forename: Xiaojiang
authors.initials: X
authors.lastname: Gao
authors.forename: Richard M
authors.initials: RM
authors.lastname: Single
authors.forename: Peter
authors.initials: P
authors.lastname: Karacki
authors.forename: Darlene
authors.initials: D
authors.lastname: Marti
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: O'Brien
authors.forename: Mary
authors.initials: M
authors.lastname: Carrington
mesh_terms: D001402:B-Lymphocytes / Q000378:metabolism; D044383:Black People; D002460:Cell Line; D005787:Gene Frequency; D015658:HIV Infections / Q000276:immunology; D015235:HLA-B Antigens / Q000235:genetics*; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D015810:Linkage Disequilibrium; D011110:Polymorphism, Genetic; D044465:White People; D001741:Black or African American
chemical_list: D015235:HLA-B Antigens; D015395:Histocompatibility Antigens Class I; C099187:MHC class I-related chain A