MICA新等位基因MICA?008：05的DNA序列鉴定及分析

目的：采用直接测序法及克隆测序法确认新等位基因 MICA?008：05。方法采用 Sequence Base Typing （ SBT）法分型技术对MICA的多态性进行常规基因分型,采用克隆测序法进行确认并与已知的等位基因序列进行比对。结果发现1个样本在外显子3上有1个碱基位置与国际通用MICA数据库不相符。该基因与MICA?008：01：01相比在外显子3的碱基位置591出现突变（ C→T）,密码子位置174由TCC→TCT,相应编码氨基酸是同义突变。结论 DNA测序结果表明该基因序列为新的MICA等位基因,已提交GenBank,并被世界卫生组织HLA因子命名委员会正式命名为MICA?008：05。     

MICA无效等位基因MICA*063N核苷酸序列全长分析

目的 分析主要组织相容复合物I类相关基因A(rnajor histocompatibility complex class Ichain-related gene A,MICA)无效等位基因MICA* 063N的核苷酸序列及探讨其分子基础.方法 采用直接测序法(sequence-based typing,SBT)对MICA* 063N基因进行多态性分析并应用基因克隆测序法检测其碱基序列,应用测序软件比对MICA分型.结果 直接测序法发现该基因序列与MICA* 027类似,在第2外显子编码子62碱基位置184出现信号“Y”,提示该位置出现碱基突变.再以克隆测序法证明,该碱基突变为C→T,在该位置编码子由CAG→TAG,TAG编码终止密码子.由于该等位基因提前出现终止密码子,因此推测可能该基因表达为截短或无效蛋白质.结论 MICA* 063N基因序列已提交GenBank,已于2010年10月获世界卫生组织HLA命名委员会正式命名(编号HWS10011131).     

湖南汉族人群MICA基因多态性分析

为了解湖南地区汉族人群MICA基因第2、3和4外显子多态性分布特点,采用PCR-SSP方法对162名无亲缘关系湖南汉族人群MICA等位基因进行分析。结果显示:在湖南汉族人群中共检测出12个等位基因和28种基因型,各等位基因分布频率有差异,其中以MICA*00801基因频率最高(37.9%),其次为MICA*00201/020(20.1%)和MICA*010(17.3%),频率最低的是MICA*019和MICA*031。将MICA基因在湖南汉族人群中的分布与该基因在其他人群中的分布进行比较,显示MICA基因的分布在不同人群之间存在差异,可作为中国人群的遗传标志。     

湖南北部汉族人群MICA/B基因多态性研究

目的 研究MICA/B等位基因在湖南北部汉族人群中的分布特点.方法 采用PCR-SSP(PCR-sequence-specific primers)方法和PCR-SBT(PCR-sequence-based typing)方法对95名无亲缘关系的个体进行MICA/B基因分型.结果 在湖南北部汉族人群中共检测到11个MICA等位基因,频率最高的依次为MICA *010 (28.95％)、MICA *008∶01(20.53％)和MICA* 002∶01(15.79％);共检测到5种STR(short tandem repeat)型别,其中MICA* A5 (37.89％)和MICA* A5.1(21.05％)频率最高.在湖南北部汉族人群中共检测到10个MICB等位基因,以MICB* 005∶02/010最常见(58.42％),其他较常见的等位基因有MICB* 002∶01(10.00％)、MICB* 008 (7.89％).在湖南北部汉族人群中,单倍型MICA* 004-MICB* 004∶01与MICA* 010-MICB* 005∶02/010具有显著的连锁不平衡.将MICA/B基因在湖南北部汉族人群中的分布与该基因在其他人群中的分布进行比较,显示MICA/B基因的分布在不同人群之间存在差异.结论 湖南北部汉族人群有自己独特的分布特征.     

MICA基因第2～4外显子大规模双向测序及分子克隆检测平台的建立

目的 建立稳定的、大规模的MICA基因第2～4外显子双向测序分型检测技术平台,并分析其单核苷酸多态性(single nucleotide polymorphism,SNP).方法 自行设计MICA基因第2～5外显子扩增引物及测序引物,探索PCR扩增及测序的最佳反应条件.用商品化的MICA基因单向测序分型试剂盒作为平行对照,对4个包含MICA* 010等位基因的样本采用自行设计引物扩增,并进行分子克隆和单倍体测序.结果 采用自行建立的MICA基因双向测序分型方法验证了100人份平行对照组单向测序分型结果.应用本研究建立的方法获得了中国人群MICA基因第2～4外显子22个SNP位点.两个新等位基因MICA* 065、MICA* 066获得了世界卫生组织的正式命名.首次发现了MICA等位基因第3内含子新的SNP位点,序列已提交IMGT/H LA数据库.结论 建立的MICA基因双向测序方法可大规模应用于中国人群的MICA基因多态性、组织器官移植配型和疾病研究.     

人MICA*008等位基因预筛选及其真核表达载体的构建与表达

目的:应用序列特异性PCR技术(PCR-SSP)分析不同细胞系中MICA*008等位基因特异性位点,筛选出人MICA*008基因型,并构建其真核表达载体.方法:PCR-SSP技术分析本实验室保存的多种人源性细胞系中多态性基因MICA的特异性位点,预筛选出包含MICA*008等位基因的细胞系,应用RT-PCR扩增MICA*008基因片段,随后克隆到pcDNA3(+)真核表达载体,用经过测序、鉴定的pcDNA3(+)/MICA*008质粒转染结肠癌细胞系sw480,通过流式细胞术检测MICA膜蛋白表达水平.结果:预筛选出包含MICA*008基因型的细胞系,成功构建了pcDNA3(+)/MICA*008质粒,pcDNA3(+)/MICA*008转染sw480细胞系后,其MICA膜蛋白表达水平明显提高.结论:验证了应用PCR-SSP技术对细胞系中对特定MICA等位基因预筛选的可行性,成功构建了多态性MICA基因中MICA*008等位基因的真核表达载体pcDNA3(+)/MICA*008并转染结肠癌细胞系sw480,为后续体外研究MICA*008在结肠癌及其他肿瘤的作用奠定了基础.     

新等位基因HLA-A*01:130的序列分析及HLA分子三维结构模拟

目的:确认HLA新等位基因HLA-A*01:130并分析其有异常反应格局的核苷酸序列。方法:应用DNA测序分型技术(PCR-SBT)进行HLA分型,对可疑新等位基因采用单链测序基因分型技术直接测定基因序列,分析其与同源性最高的HLA等位基因序列的差异。最后,经Swiss-Model对HLA分子进行三维结构模拟。结果:新基因与所有已知的HLA-A等位基因序列均不相同,与HLA-A*01:66基因序列相比在第3外显子368位碱基由A→G,导致第99位密码子改变,酪氨酸→半胱氨酸。替代氨基酸位于抗原肽结合区β片层上。结论:发现一个新的HLA-A等位基因,现已被世界卫生组织HLA因子命名委员会正式命名为HLA-A*01:130。     

一例HLA-A新等位基因HLA-A*3113的测序分析

目的研究HLA新的等位基因HLA-A * 3113的分子机制。方法样本DNA抽提采用PEL-FREEZ抽提试剂盒,利用PCR方法扩增先证者HLA-A基因的第1～8外显子,PCR产物直接经TOPO TA克降转染到质粒载体中获得等位基因的单链,对所得克隆进行第2、3、4外显子双向测序分析。应用序列特异性引物PCR方法证实测序所发现的突变。结果先证者样本克隆测序得到两个等位基因,其中一个等位基因为A*2402,另一个经BLAST验证其为新的等位基因,新的等位基因序列已递交GenBank(DQ206619,DQ206620,DQ206621)。与最接近的A*310102等位基因序列相比,新的等位基因在第3外显子上有1个核苷酸不同,第456位G→c,导致第128位氨基酸E→D。结论该等化基因为新的HLA-A等位基因,被世界卫生组织HLA因子命名委员会正式命名为HLA-A*3113。     

新等位基因HLA-B*9526的确认和序列分析

目的 鉴定中国人群中人类白细胞抗原(human leukocyte antigen,HLA)新等位基因HLA-B*9526,并进行核苷酸序列分析.方法 使用序列特异性寡核苷酸PCR技术进行HLA基因分型,发现1个反应格局异常的等位基因,应用分子克隆和DNA双向测序技术测定新等位基因的核苷酸序列,并与已知等位基因进行序列比对分析.结果 检出反应格局异常的DNA样本,经过克隆测序得到两个等位基因,分型结果一个为B*5403,另一个的核苷酸序列与已知的HLA等位基因均不同,该基因序列与同源性最高的HLA-B*1507基因序列相比在第3外显子区域中425位碱基发生A→G突变,导致142位编码氨基酸由酪氨酸变成半胱氨酸.结论 一个新的HLA-B等位基因被确认,并被世界卫生组织HLA因子命名委员会正式命名为HLA-B*9526.     

一例新的HLA-B等位基因B*5614的核苷酸序列分析

目的 研究HLA新的等位基因HLA-B*5614的分子基础。方法 样本DNA抽提采用盐析法，利用PCR方法扩增先证者HLA-B基因的第2～4外显子，PCR产物直接经TOPO转染克隆到质粒载体中分离其等位基因，对所得克隆进行第2～4外显子双向测序分析。应用序列特异性引物PCR方法证实测序所发现的突变。结果 先证者样本克隆测序得到两个等位基因，其中1个等位基因为B*1502，另一个经BLAST验证为新的等位基因，新的等位基因序列已递交GenBank(AY601726，AY601727，AY601728)。与最接近的B*5608等位基因序列相比，新的等位基因仅在第2外显子上有1个核苷酸不同，即第277位G→C，导致第93位氨基酸Cly→Arg。结论 该等位基因为新的HLA-B等位基因，被世界卫生组织HLA因子命名委员会正式命名为HLA-B*5614。     

An evaluation of a multicenter study on HLA-DPB1 typing using solid-phase Taq-cycle sequencing chemistry

Abstract: In HLA Class II genes, polymorphism is mainly located in the second exon. Most DNA based typing methods are confined to the identification of specific sequence motifs in the second exon. In contrast, Sequencing Based Typing (SBT) elucidates the entire exon 2 sequence for typing. Comparison of the obtained exon 2 sequence with an allele sequence library results in allele assignment. We tested the applicability of SBT using a protocol for amplification followed by solid phase Taq-cycle sequencing for HLA-DPB1 typing. A panel of 32 samples were typed by SBT at five test sites which are participating in the Sequencing Based Typing component of the 12th International Histocompatibility Workshop. The panel represents the existing polymorphism at all known polymorphic positions of exon 2, both in homozygous and heterozygous combinations. In this multicenter study we focused on the reliability of analyzing heterozygous sequences for HLA typing. A multi-sequence analysis approach, Polall, was developed to evaluate sequences obtained. The assignment of homozygosity and heterozygosity was validated by cluster analysis of chromatographic data of all sequences. Sequence characteristics were examined and considered for appropriate assignment. Differences in sequence characteristics that occurred between the test sites are considered in detail. The evaluation of data of 5 test sites reveals that Taq-cycle sequencing can reliably be performed for HLA-DPB1 SBT.     

A new MICA allele,MICA*007:07, characterized by cloning and sequencing

A new MICA allelic variant, MICA*007:07, was identified in an individual of Mongol ethnicity in the Inner Mongolia Autonomous Region, northern China. Following polymerase chain reaction‐sequence‐based typing (PCR‐SBT), this new allele was further confirmed by cloning and sequencing. MICA*007:07 differs from MICA*007:01 by a synonymous mutation from G to A at the 2nd nucleotide position in exon 2. MICA*007:07 was linked to HLA‐B*27:05.     

Characterization of a novel MICA allele,MICA*012:05, by cloning and sequencing

A new MICA allelic variant, MICA*012:05, has been identified in a Chinese Mongolian population. Following polymerase chain reaction–sequence‐based typing (PCR‐SBT), this new allele was further confirmed by cloning and sequencing. MICA*012:05 was linked to an HLA‐A*24‐C*01‐B*55:02‐DRB1*09 haplotype. MICA*012:05 differs from MICA*012:01 by a single synonymous C to T substitution at nucleotide position 269 in exon 3.     

MICA genetic polymorphism and HLA-A,C,B,MICA and DRB1 haplotypic variation in a southern Chinese Han population: identification of two new MICA alleles, MICA*060 and MICA*062

In this study, 201 healthy, unrelated Han subjects in Hunan province, southern China, were investigated by sequence-based typing (SBT) for the allelic variation of the human major histocompatibility complex (MHC) class I chain-related gene A (MICA). Nineteen MICA alleles were observed, among which MICA*008:01 predominated with gene frequency of 30.35%. There was significant linkage disequilibrium (LD) of MICA*012:01 with HLA-B*54 and HLA-B*55, which was not observed in a northern Chinese Han population. Haplotype HLA-A*11-C*07-B60-MICA*008:01 (9.16%) was highly specific to this southern Chinese Han population. The most common five-locus haplotype in this population was HLA-A*02-C*01-B*46-MICA*010-DRB1*09 (8.73%). A new MICA allele, MICA*060, was identified on an HLA-A*02-C*01-B*55:02-DRB1*14 haplotype through extended family analysis. MICA*060 has probably arisen from MICA*012:01. Another new MICA allele, MICA*062, was identified by screening 1432 subjects using polymerase chain reaction-sequence-specific priming technology. MICA*062 has probably derived from MICA*010. Of particular interest is that MICA*062 was carried on an HLA-C*08-B*48:01-DRB1*14 haplotypic segment, as HLA-B*48 has been consistently shown to be primarily linked to MICA gene deletion in east Asian populations. Our results provide new insight into MICA genetic polymorphism in human populations. The findings reported here are of importance for future studies on the potential role of MICA in allogeneic organ transplantation and disease association in populations of Chinese ancestry.     

The identification of three novel MICA alleles by sequence-based typing

During a study of MICA frequency in a healthy population and a cohort of patients suffering with inflammatory bowel disease, three DNA samples produced unusual reactivity patterns using polymerase chain reaction sequence-specific primers (PCR-SSP). These samples were subsequently characterized by sequence-based typing (SBT). Here, we report the sequence of these three novel MICA alleles.     

MICA polymorphisms and haplotypes with HLA-B and HLA-DRB1 in Koreans

Abstract
Major histocompatibility complex (MHC) class I chain-related gene A ( MICA ) is located within the human MHC, centromeric to HLA-B and telomeric to HLA-DRB1 . The location of MICA in the MHC indicates the presence of linkage disequilibrium with human leukocyte antigen (HLA). Like HLA, MICA is highly polymorphic; however, the information available for MICA polymorphisms is not as comprehensive as that for HLA polymorphisms. We estimated the allelic frequencies of MICA and haplotypes with HLA-B and HLA-DRB1 at high-resolution in a population of 139 unrelated Korean individuals by applying the newly developed method of sequence-based typing (SBT). A total of 17 MICA alleles were identified. The most frequent allele was MICA*010 (19.4%), followed by alleles *00201 (17.6%), *00801 (14.7%), *01201 (9.4%), *004 (8.3%) and *049 (7.9%). The most common two- and three-locus haplotypes were HLA-B*1501-MICA*010 (10.4%), MICA*010-HLA-DRB1*0406 (5.8%) and HLA-B*1501-MICA*010-HLA-DRB1*0406 (5.8%). This is the first study to provide such high-resolution information on the distribution of haplotypes comprising MICA , HLA-B and HLA-DRB1 in Korean individuals, a level of resolution made possible by use of the SBT method. The results of this study should help determine the mechanisms underlying diseases associated with MICA polymorphisms in Korean individuals.     

Sequencing based typing for genetic polymorphisms in exons 2, 3 and 4 of the MICA gene

We have established a sequencing based typing (SBT) method for detection of genetic polymorphism in the exon 2 to 4 domains of the major histocompatibility complex (MHC) class I chain-related gene A (MICA) and applied it to allele typing of 130 healthy Japanese individuals. A 2.2-kb segment including exons 2, 3 and 4 of the MICA gene was amplified by a pair of generic primers followed by cycle sequencing using exon-specific nested primers. In total, 8 alleles were observed in a Japanese population and the most frequent allele was MICA008 with the gene frequency of 30.8%. MICA009 was the second most frequent (16.5%), while the rarest one was MICA007 (1.2%). MICA alleles displayed strong linkage equilibria with HLA-B antigens (i.e. MICA008 with B7, B48, B60 and B61; MICA009 with B51 and B52; MICA002 with B35, B39, B58 and B67; MICA004 with B44, MICA007 with B13 and B27; MICA010 with B46, B62 and B48, MICA012 with B54, B55, B56 and B59; MICA019 and B70, B71 and B62). Recently, the B48 haplotype has been reported to lack the entire MICA gene by a large-scale deletion in a Japanese population. Among 8 serologically B48 homozygous individuals, 4 were found to represent this MICA null allele as assessed by no polymerase chain reaction (PCR) amplification using MICA-specific primers, while the remaining four possessed the intact MICA gene with MICA008 or MICA010.     

Identification of three MICA alleles in the genotype of a patient with chronic lymphocytic leukemia

Major histocompatibility complex (MHC) class I-related chain A gene (MICA) sequence-based genotyping (SBT) was attempted on a peripheral blood sample collected from a patient evaluated for hematopoietic stem cell retransplant. The electropherogram pattern of MICA SBT indicated the possibility of carrying more than two MICA alleles. Subsequent cloning and sequencing of the polymerase chain reaction products revealed the presence of three distinct MICA alleles: MICA*008:01/:04 (A5.1), MICA*007:01(A4), and MICA*002:01 (A9) in the genotype of this patient. The origin of the third extra MICA allele could not be determined and would require MICA genotyping information from other family members, which is unavailable.     

Sequenase sequence profiles used for HLA-DPB1 sequencing-based typing

Abstract: Sequencing-based HLA typing (SBT) is a PCR based high resolution HLA typing method in which polymorphic regions of the gene are sequenced and directly used for typing. Currently, for class II SBT, alleles are identified by comparison of the exon 2 sequence with their corresponding allele sequence library. Routine SBT requires reliable identification of heterozygosity, and automated assignment of the alleles. In sequencing strategies different enzymes can be used for primer extension. The most characteristic difference between sequences obtained by two protocols using Sequenase®, or Taq-cycle sequencing, respectively, is a difference in incorporation of nucleotides in the primer extension leading to different sequence profiles. In Taq-cycling sequencing variable nucleotide incorporation results in irregular, but reproducible peak patterns, whereas Sequenase® incorporates nucleotides in nearly equal amounts, resulting in more even peak patterns. In a previously published multi-center study we evaluated HLA-DPB1 SBT using Taq-cycle sequencing, and showed that typing can reliably be performed, considering the specific sequence profiles. In this study the applicability of Sequenase® for HLA-DPB1 SBT was tested. A panel of samples were typed by SBT at five test sites which participate in the Sequencing Based Typing component of the 12^th International Histocompatibility Workshop. The panel represents the existing polymorphism at all known polymorphic positions of exon 2, both in homozygous and heterozygous combinations. The assignment of homozygosity and heterozygosity was validated by Multi-Sequence Analysis, performing cluster analysis of chromatographic data of all sequences at each position. Sequence characteristics were examined and considered for appropriate assignment. Data reveals that Sequenase® sequencing can also reliably be used for HLA-DPB1 typing.     

Identification of a novel MICA allele: MICA*051

We have identified a novel MICA allele, MICA*051, detected by the polymerase chain reaction using sequence-specific primers and characterized by sequence-based typing. MICA*051 appears to be the result of a recombination between MICA*00801 and MICA*00701 at intron 2.