The genetic study on a rare inter-allelic recombination of HLA-C locus in a Chinese Han family / 中华检验医学杂志

ABSTRACT

Objective To study the inter-allelic recombination event occurring in the HLA-C locus in a family of Chinese Han nationality, and to evaluate the molecular genetic background of the new HLA allele.Methods Peripheral blood samples were collected from a Chinese leukemia woman patient, as well as her healthy parents and two brothers.HLA-A, C, B, DRB1 and DQB1 alleles were typed by high-resolution PCR-sequence-based typing (SBT) method using Atria Genetic AlleleSEQR HLA SBT kits.The Protrans S4 HLA-C single allele-specific sequencing strategy was used to separate the two HLA-C alleles and to determine novelty of the allele.The full length sequences of HLA-C alleles of the patient and her parents were further analyzed using cloning and haplotype sequencing method. The HLA five loci linked haplotypes and the recombination site were analyzed by family study, meanwhile the full length sequences of the five HLA-C alleles were compared with the IMGT/HLA database by the program BLAST.Results The two haplotypes of the father and mother were aA*0207-C*010201-B*550201-DRB1*090102-DRQ1*030302 and bA*240201-C*120202-B*5201-DRB1*1502-DRQ1*0601, cA*300101-C*060201-B*130201-DRB1*0405-DRQ1*0401 and dA*110101-C*070201-B*4001-DRB1*080302-DRQ1*0601,respectively.The two brothers inherited their parent′s haplotypes a, d and b, c respectively.The two haplotypes of the patient were the maternal c and paternal recombinant a/b haplotype.The recombinant a/b haplotype A*240201-C*new-B*550201-DRB1*090102-DRQ1*030302, A*240201 came from the paternal haplotype b,while B*550201-DRB1*090102-DRQ1*030302 came from the other paternal haplotype a.When comparing the full length sequences of the HLA-C new allele with the father′s allele C*010201 and C*120202, it could deduce that the recombinant a/b haplotype derived from a recombination event occurring between the paternal chromosome 6 during meiosis.The crossover site was between genomic nt273 and nt330 of HLA-C alleles, which created a HLA-C new allele and the fifth haplotype of the family, and inherited it to the patient.The full length sequences of the new allele had been submitted to Genbank, and officially named C*0121 by WHO nomenclature committee.Conclusion This study demonstrates a rare inter-allelic recombination event occurring in the HLA-C locus within a Chinese Han family and illustrates the process of novel allele and haplotype, and provides direct theory for further studying the mechanisms of gene recombination and HLA polymorphism.