Genetic variation of MHC Class I polymorphic Alu insertions (POALINs) in three sub-populations of the East Midlands, UK

HLA Genetics for the Human Diseases

Highly polymorphic human leukocyte antigen (HLA) molecules (alleles) expressed by different classical HLA class I and class II genes have crucial roles in the regulation of innate and adaptive immune responses, transplant rejection and in the pathogenesis of numerous infectious and autoimmune diseases. To date, over 35,000 HLA alleles have been published from the IPD-IMGT/HLA database, and specific HLA alleles and HLA haplotypes have been reported to be associated with more than 100 different diseases and phenotypes. Next generation sequencing (NGS) technology developed in recent years has provided breakthroughs in various HLA genomic/gene studies and transplant medicine. In this chapter, we review the current information on the HLA genomic structure and polymorphisms, as well as the genetic context in which numerous disease associations have been identified in this region.

Genomic diversity and differentiation of Alu insertion polymorphisms in a native British and four South Asian migrant populations

BACKGROUND

Alu insertions are bi-allelic and primate-specific, this makes them a useful marker for studying genetic variation, migration patterns, forensic analyses, paternity, and evolutionary heritage; however, specific population studies are limited.

AIM

The objective of this study is to document the level and extent of genetic variation at 39 different Alu loci in five populations (British, Indian Punjabi, Indian Gujarati, Pakistani, and Bangladeshi) from the East Midlands region of the UK. Genetic data on migrant populations is currently limited.

SUBJECTS AND METHODS

DNA samples (n = 543) were analysed for 39 Alu insertion polymorphisms using specific primers and standard protocols. Data were analysed for population and forensic genetic parameters.

RESULTS

All studied Alus were polymorphic in the British White population while South Asian migrant populations had a variable number of loci which were monomorphic. Highest heterozygosities and lowest match probabilities were observed in the British sample, while the Bangladeshi sample had the lowest heterozygosity and higher match probability.

CONCLUSION

The analysed Alus insertions (TPA25, Ya5NBC123, Ya5NBC182, Ya5NBC241, and Ya5NBC242) are highly polymorphic and variable among migrant populations. These loci could be useful for population genomic and differentiation studies.

Haplotypic Associations and Differentiation of MHC Class II Polymorphic Alu Insertions at Five Loci With HLA-DRB1 Alleles in 12 Minority Ethnic Populations in China

The analysis of polymorphic variations in the human major histocompatibility complex (MHC) class II genomic region on the short-arm of chromosome 6 is a scientific enquiry to better understand the diversity in population structure and the effects of evolutionary processes such as recombination, mutation, genetic drift, demographic history, and natural selection. In order to investigate associations between the polymorphisms of HLA-DRB1 gene and recent Alu insertions (POALINs) in the HLA class II region, we genotyped HLA-DRB1 and five Alu loci (AluDPB2, AluDQA2, AluDQA1, AluDRB1, AluORF10), and determined their allele frequencies and haplotypic associations in 12 minority ethnic populations in China. There were 42 different HLA-DRB1 alleles for ethnic Chinese ranging from 12 alleles in the Jinuo to 28 in the Yugur with only DRB1^∗08:03, DRB1^∗09:01, DRB1^∗12:02, DRB1^∗14:01, DRB1^∗15:01, and DRB1^∗15:02 present in all ethnic groups. The POALINs varied in frequency between 0.279 and 0.514 for AluDPB2, 0 and 0.127 for AluDQA2, 0.777 and 0.995 for AluDQA1, 0.1 and 0.455 for AluDRB1 and 0.084 and 0.368 for AluORF10. By comparing the data of the five-loci POALIN in 13 Chinese ethnic populations (including Han-Yunnan published data) against Japanese and Caucasian published data, marked differences were observed between the populations at the allelic or haplotypic levels. Five POALIN loci were in significant linkage disequilibrium with HLA-DRB1 in different populations and AluDQA1 had the highest percentage association with most of the HLA-DRB1 alleles, whereas the nearby AluDRB1 indel was strongly haplotypic for only DRB1^∗01, DRB1^∗10, DRB1^∗15 and DRB1^∗16. There were 30 five-locus POALIN haplotypes inferred in all populations with H5 (no Alu insertions except for AluDQA1) and H21 (only AluDPB2 and AluDQA1 insertions) as the two predominant haplotypes. Neighbor joining trees and principal component analyses of the Alu and HLA-DRB1 polymorphisms showed that genetic diversity of these genomic markers is associated strongly with the population characteristics of language family, migration and sociality. This comparative study of HLA-DRB1 alleles and multilocus, lineage POALIN frequencies of Chinese ethnic populations confirmed that POALINs whether investigated alone or together with the HLA class II alleles are informative genetic and evolutionary markers for the identification of allele and haplotype lineages and genetic variations within the same and/or different populations.

Alu elements within the human major histocompatibility class I region in the Comoros Islands: genetic variation and population relationships

Background: Alu elements are attractive markers for population genetics, disease, forensics and paternity analyses, due to their particular characteristics. Five polymorphic Alu insertions within the MHC class I region have been little examined in human populations. Aim: The analysis of the genetic diversity of autochthonous Comorians from the three major islands of the archipelago by these polymorphic MHC Alus and to assess their relationships together and with other populations. Subjects and methods: Two hundred and fifty-seven unrelated participants from the Comoros archipelago, Grande Comore (86), Anjouan (93) and Moheli (78), were examined for five MHC Alu insertions. The data were analysed for intra- and inter-population genetic variation. Results: All MHC Alu were polymorphic in the three samples and only one significant differentiation was observed between Anjouan and Moheli. According to the MDS and AMOVA results, the populations included in the inter-population analyses were grouped in three major clusters according to their genetic ancestry. The haplotype diversity showed by the Comorians is higher than in previously studied African populations and occupies an intermediate position between African and Asian clusters. Conclusion: MHC Alu insertions are useful markers to study micro-geographical genetic variations. Using these polymorphisms, new insights have been obtained about the biological history and evolution of the Comoros.

MHC class I polymorphic Alu insertion (POALIN) allele and haplotype frequencies in the Arabs of the United Arab Emirates and other world populations

Polymorphic Alu insertions (POALINs) are found throughout the human genome and have been used in various studies to infer geographic origin of human populations. The main aim of this study was to determine the allele and haplotype frequencies of five POALINs, AluHF, AluHG, AluHJ, AluTF and AluMICB, within the major histocompatibility complex (MHC) class I region of 95 UAE Arabs, and correlate their frequencies to those of the HLA-A, HLA-C and HLA-B class I allele lineages. Evolutionary relationships between the POALINs of the Arabs and those previously studied in populations of African, Asian and European descent were compared. At each of the five Alu loci (AluHF, AluHG, AluHJ, AluTF and AluMICB), Alu insertion was designated as Alu(locus)*02 and absence was Alu(locus)*01. The AluHG insertion (AluHG*02) had the highest frequency (0.332), followed by AluHF*02 (0.300), AluHJ*02 (0.263), AluMICB*02 (0.111) and AluTF*02 (0.058). Of the 270 Alu-HLA haplotypes pairs in the UAE Arabs, 110 had no Alu insertion, and 54 had an Alu insertion at >50% per haplotype. An Alu insertion >75% per haplotype was found between AluMICB*02 and HLA-B*14, HLA-B*22, HLA-B*44, HLA-B*55, HLA-B*57 and HLA-B*73, and with HLA-C*01 and HLA-C*18; AluHJ*02 with HLA-A*01, HLA-A*19, HLA-A*24 and HLA-A*32; AluHG*02 with HLA-A*02 and HLA-B*18; and AluHF*02 with HLA-A*10. The genotyped allele and haplotype frequencies of the MHC POALINs in UAE Arabs were compared with the results of 30 previously published Asian, European, American and African populations. Phylogenetic and multidimensional scaling (MDS) analysis of the relative MHC POALINs allele and haplotype frequencies revealed that the UAE Arabs have a similar lineage to Caucasians and the most distant genetic relationship to the Waorani native American population of Ecuador. The structure of both the phylogenetic tree and the MDS analysis supports the Out of Africa theory of human evolution. The nature of the clusters suggests the Arabian Middle East represents a crossroads from which human populations migrated towards Asia in the east and Europe to the north-west.

Genetic variation and population structure of five ethnic groups from Punjab, North-West India: Analysis of MHC class I polymorphic Alu insertions (POALINs)

Genetic variation and differentiation of five ethnic groups from Punjab, North-West India was characterized by analyzing data on polymorphic Alu insertions (POALINs) within the class I genomic region of major histocompatibility complex (MHC), which is completely non-existent in Indian population. The haplotype frequency, distribution and heterozygosity among these groups and their potential implications in molecular anthropology and evolutionary studies were also determined. A total of 479 unrelated healthy individuals representing five different ethnic groups: Banias, Brahmins, Khatri, Jat Sikhs and Scheduled Castes were genotyped for five MHC Alu elements (AluHG, AluMICB, AluHJ, AluTF and AluHF) using polymerase chain reaction (PCR). All the loci were found to be polymorphic among the studied populations. No significant deviation from Hardy-Weinberg equilibrium was observed, except for the AluHJ locus in Brahmins. The POALINs varied in allele frequency between 0.0260 and 0.4427. The average heterozygosity among the studied groups ranged from 0.1937 in Banias to 0.2666 in Jat Sikhs. The genetic differentiation among the studied groups was observed to be of the order of 0.01302. Single POALIN haplotypes were found to be more frequent than multiple POALIN haplotypes. The results of inter-population differentiations, haplotype frequencies, genetic distances, multidimensional scaling, phylogenetic and structure analyses indicated close genetic relationships between the five ethnic groups of Punjab, North-West India. Analyses of polymorphic Alu loci of MHC genomic region may represent reliable information about the ancestry, demographic history and geographic origins of the various human populations, facilitating better understanding of the evolutionary, forensic and epidemiological prospective.