HLA-DRB1 and HLA-DQB1 polymorphisms in Pacific Islands populations

Allele frequency distributions of the HLA-DRB1 and HLA-DQB1 genes were investigated in four Pacific Islands populations from the Cook Islands, Samoa, Tokelau and Tonga. Limited diversity was observed for both the HLA-DRB1 and HLA-DQB1 loci. Five HLA-DRB1 alleles were observed to be the most frequent amongst all the studied Pacific Islands populations. They were: HLA-DRB1*0403, HLA-DRB1*08032, HLA-DRB1*09012, HLA-DRB1*11011 and HLA-DRB1*1201. Cook Islanders had the largest number of low frequency DRB1 alleles followed by Samoans, Tokelauans and Tongans, most of which may be attributed to reported non-Polynesian admixture. The most frequently observed DQB1 alleles in the four studied Pacific Islands populations were those of the DQ3 subgroup of alleles HLA-DQB1*03011, HLA-DQB1*0302 and HLA-DQB1*03032 as well as HLA-DQB1*05031 and HLA-DQB1*06011. Cook Islanders had the highest number of rare HLA-DQB1 alleles, the distibution being similar to that of the HLA-DRB1 allele. While, in general, the values of homozygosity for DRB1 and DQB1 were observed to be lower then expected under neutrality, a statistical significance was observed in Tongans, Samoans and Tokelauans for the DQB1 locus and in Tongans for the DRB1 locus. Differences were observed between allele frequency distributions for Tokelauans compared to the other three populations. This was also demonstrated by principal component analysis of DRB1 and DQB1 allele frequencies, which separated the Tokelauan population from Cook Islanders, Tongans and Samoans. Tongans and Samoans were separate from the other Polynesian populations in the phylogenetic trees. Observed allele and haplotype frequencies were found to be in agreement with previously published HLA-DRB and HLA-DQB Polynesian data.     

HLA DPA1/DPB1 genotype and haplotype frequencies, and linkage disequilibria in Nigeria, Liberia, and Gabon

Abstract: The frequencies of DPA1 and DPB1 alleles and their occurrence in haplotypic linkage were assessed and compared in Nigerian, Liberian, and Gabonese individuals. Differences were seen in the distribution patterns; these differences were more pronounced between the Gabonese and the other two populations than between Liberians and Nigerians. Several haplotypic DPA1-DPB1 combinations could be verified by homozygosity. Linkage disequilibria of DPA1-DPB1 combinations, indicating further probable haplo-types, were estimated. Although different allele and haplotype frequencies were recognized in the three subgroups, the linkage disequilibria were mostly either positive or negative in all populations.     

浙江汉族人群HLA-DPA1和-DPB1基因多态性分析

目的 检测浙江地区汉族人群HLA-DPA1和HLA-DPB1等位基因及单倍型频率.方法 应用PCR-直接测序分型法对100名健康、无血缘关系的浙江汉族人外周血标本进行HLA-DPA1和HLADPB1等位基因分析.结果 在100份标本中检出8个HLA-DPA1等位基因和19个HLA-DPB1等位基因.HLA-DPA1等位基因频率较高的依次为DPA1*020202(47.0%)、DPA1*010301(38.5%)和DPA1*020101(10.5%).HLA-DPB1等位基因中,频率较高的依次为DPB1*0501(39.5%)、DPB1*020102(13.5%)和DPB1*040101(13.0%).连锁分析发现共有44个HLA-DPA1-DPB1单倍型,单倍型频率最高为DPA1*020202-DPB1*0501(29.5%).结论 浙江地区汉族人群HLA-DPA1和DPB1基因座等位基因具有丰富的多态性,2个基因座呈现连锁不平衡.     

HLA-DPA1 typing by PCR amplification with sequence-specific primers (PCR-SSP) and distribution of DPA1 alleles in Caucasian, African and Oriental populations

In the present study PCR primers were designed for detecting all known DPA1 variability, i.e. the presently recognized six DPA1 alleles 0103 to 0401, and also for separation of the four DPA1*02 alleles, by PCR amplification with sequence-specific primers (PCR-SSP). For each sample seven different PCR reactions were performed which allowed the identification of all DPAl alleles and the resolution of all DPA1 genotypes. Forty-eight cell lines and 100 donor spleen cells were investigated by the DPA1 PCR-SSP technique. In the forty-eight known workshop cell-lines no false positive or false negative results were obtained. The 100 donor spleen cells were only typed by the PCR-SSP technique and in their DNAs only one or two DPA1 alleles were found. Twenty cell lines and twenty donor spleen cells were typed on two separate occasions and interpreted blindly. The reproducibility between the repeated typings was 100%. The length of the specific products ranged from 103 to 258 base pairs and the amplification patterns obtained were easy to interpret. In conclusion, DPA1 typing by the PCR-SSP method is an accurate typing technique with high sensitivity, specificity and reproducibility. Analysis of the distribution of DPA1 alleles was performed in 100 Caucasian samples, 100 African samples and 80 Oriental samples, including separation of the four DPA1*02 alleles. The population study showed a characteristic distribution of HLA-DPA1 alleles. Each ethnic group appeared to have one (Caucasians), or two (Africans and Orientals), frequent DPA1 allele(s) and a high frequency of DPA1 homozygotes, suggesting that, like for the DPB1 locus, balancing selection does not appear to be affecting the evolution of the DPA1 locus.