基因组序列分析HLA新等位基因B*3818内含子和外显子同时突变

摘要

目的 分析HLA新等位基因B*3818的基因组序列.方法 克隆测序方法 对PCRSBT中发现的1个未知HLA-B等位基因的基因组序列进行双向全长测序,并采用微量淋巴细胞毒方法 鉴定该等位基因编码分子的抗原特异性,通过群体调查和家系分析了解该等位基因的群体分布频率和单倍型组成情况.结果 新等位基因HLA-B*3818(序列注册号为FJ561482)与B*380201在第4外显子和第5内含子同时存在1个核苷酸的差异.第4外显子的第660位碱基由C变为A,导致第196个密码子由GAC变为GAA,相应氨基酸由天门冬氨酸变为谷氨酸,与IMGT/HLA中的HLA-B等位基因的序列进行对比,该突变为新的单核苷酸多态性位点.第5内含子的第2133位碱基由A变为C,除此之外,B*3818的内含子序列与B*380101、B*380201和B*3814相同.该新HLA等位基因的血清学特异性为B38,其在中国汉族人群中的分布频率小于0.000 5,家系调查结果 表明携带该新等位基因的单倍型为A*030101-CW*010201-B*3818-DRB1-1312-DQB1*060101.结论 新等位基因HLA-B*3818的内含子和外显子同时存在变异,研究新等位基因的基因组序列可为HLA基因相关研究和应用提供更多的序列信息.%Objective To analysis the genomic sequence of a novel human leukocyte antigen (HLA)-B*3818 allele.Methods Full length genomic sequence of an unknown HLA-B allele was cloned,followed by bi-directional sequencing and the specificity of the antigen coded by this novel allele was defined by microcytotoxicity assay.The frequency and haplotype of this novel allele was acquired by population census and parentage analysis.Results The full length genomic sequence of this novel HLA-B*3818 allele with accession number FJ561482 differs from HLA-B*380201 by two nucleotide changes in exon 4 and intron 5,respectively.One change is located at nt 660 in exon 4 where C→A alternation,which results in an amino acid substitution from Asp(GAC)to Glu(GAA)at codon 196.This alternation is a new single nucleotide polymorphism compared with all other HLA-B alleles.Another is located at genomic position 2133 in intron 5(A→C).Except for this substitution,the intron sequences of HLA-B*3818 allele are identical to those of other HLA-B*38 alleles including HLA-B*380101,B*380201 and B*3814.The serological specificity of HLA-B*3818 is B38 and the frequency of this new allele is less than 0.000 5 in Chinese Han population.The parentage analysis showed the haplotype of novel allele is A*030101-Cw*010201-B*3818-DRB1*1312-DOB1*060101.Conclusion The simultaneous mutations in exon and intron were found in the Hovel HLA-B*3818 allele,and so it can present more sequence information for studies and applications associated with HIA genes by analyzing the genomic sequences of novel HLA alleles.