MHC Class I Chain-related Gene A Gene Research Articles

Association of MHC Class I Chain-Related Gene a (MICA) Polymorphisms with Allogeneic Hematopoietic Cell Transplantation Outcomes in Acute Myeloid Leukemia

Association of MHC Class I Chain-Related Gene a (MICA) Polymorphisms with Allogeneic Hematopoietic Cell Transplantation Outcomes in Acute Myeloid Leukemia

Allelic and haplotypic diversity of 5′promoter region of the MICA gene

In this study, the 5′promoter region of MHC class I chain-related gene A (MICA) was investigated in 104 healthy, unrelated Han individuals recruited from northern China, using PCR-sequencing method. Twelve variable sites were detected, which were in very strong linkage disequilibrium with each other. Twelve different MICA 5′promoter haplotypes were identified, among which Promoter-7 predominated (0.5529). Twenty-six extended haplotypes incorporating MICA 5′promoter and MICA exons 2–5 were observed in this population, 9 of which were in significant linkage disequilibrium (LD). Phylogenetic analysis of 5′promoter refined MICA sub-lineage structure previously constructed according to MICA coding and 3′untranslated regions. Ewens–Watterson homozygosity statistics at MICA 5′promoter region were consistent with neutral expectations. None of the five variable sites detected within the minimal promoter of MICA gene was located in the putative binding sites for transcription factor. Our study provided for the first time the sequence information about 5′promoter of MICA gene at a human population level. The data will facilitate the understanding of regulation of MICA gene expression, which represents a promising pathway for immune intervention against cancer, autoimmune disorders and infections.

The genetic architecture of 3′untranslated region of the MICA gene: Polymorphisms and haplotypes

In this study, the 3'untranslated region (3'UTR) of MHC class I chain-related gene A (MICA) were investigated in 104 healthy, unrelated Han individuals recruited from northern China, using PCR-sequencing method. Nine polymorphic sites were detected, which were in very strong linkage disequilibrium with each other .Seven different MICA 3'UTR alleles were identified, among which UTR1 predominated (0.6971),followed by UTR2 (0.2356). Twenty-one extended haplotypes incorporating the 3'UTR and MICA exons 2-5 were observed in this population. Phylogenetic analysis revealed the existence of two MICA lineages, each with multiple subsets. The 2 lineages were primarily linked to UTR1 and UTR2 in the 3'UTR, respectively. Ewens-Watterson homozygosity statistics at MICA coding and 3'UTR regions were consistent with neutral expectations. Our data provided for the first time the data of genetic variation in the 3'UTR of MICA gene in human populations. The findings are valuable for future studies of the mechanisms underlying MICA post-transcriptional regulation, and will inform studies of evolution of the MHC gene complex.

MHC Class I Chain‐Related Gene‐A Is Associated with IA2 and IAA but Not GAD in Swedish Type 1 Diabetes Mellitus

In type 1 diabetes mellitus (T1DM), the frequency of antibodies against insulin (IAA), glutamic acid decarboxylase-65 (GAD65), ICA512/IA2 (IA2), and islet cell antigens (ICA) vary with human leukocyte antigen (HLA) composition of the patient. IAA, IA2 autoantibodies, and ICA are increased in DQ8 positives; GAD65 antibodies are increased in DQ2 positives. MHC class I chain-related gene-A (MICA) is another genetic marker that has been proposed to be associated with T1DM. In this article, we looked at microsatellite polymorphism of MICA and its association with autoantibodies (IAA, IA2, and GAD65) in Swedish T1DM patients and if the association explains its importance in early events in autoimmune response. We studied 635 T1DM patients between 0-35 years. Frequency of MICA5/5 was positively associated with the formation of IAA and IA2 antibodies considered individually or in combination (odds ratio [OR], 95% CI, Pc: [IAA+ versus IAA-]: 4.94, 2.09-11.62, <0.0005; [IA2+ versus IA2-]: 2.65, 1.52-4.59, 0.0015; [IAA and/or IA2+ versus rest]: 9.83, 2.37-40.78, <0.0015; [IAA and IA2+ versus rest]: 3.51, 2.01-6.15, <0.0015). Also, -5.1/5.1 was increased in IAA+ patients compared to IAA- patients (2.82, 1.64-4.83, <0.0005). All patients positive for -5/5 developed at least one of the three antibodies. Frequency of MICA5.1 was decreased in IAA+ (0.54, 0.36-0.81, 0.017), in IA2A+ (0.63, 0.45-0.88, 0.04), in IAA and/or IA2A+ (0.52, 0.33-0.84, 0.044), and in IAA and IA2A+ (0.55, 0.39-0.78, 0.0055) patients when compared with patients negative for corresponding antibodies. Frequency of MICA9, 5/5.1, and 5.1/9 was decreased in IAA+ compared to IAA- patients (0.51, 0.32-0.79, 0.021; 0.22, 0.11-0.44, <0.005; and 0.39, 0.22-0.69, 0.026, respectively). Frequency of MICA9 and -5.1/9 was also decreased in IAA and/or IA2 antibody-positive patients while MICA5/5.1 decreased in patients positive for IAA and IA2 antibody both together. IAA and IA2 antibodies are believed to appear early during the autoimmune reaction against beta cells. Thus, according to our data, MICA-5/5 and -5.1/5.1 is associated with early autoimmunity in T1DM patients. Our study suggests that MICA gene polymorphism is associated with autoantibody formation and that the polymorphism especially MICA5/5 and -5.1/5.1 are important in early events of autoimmune reaction.

MHC class I chain-related gene A-A5·1 allele is associated with ulcerative colitis in Chinese population

The human MHC class I chain-related gene A (MICA) plays a role in regulating protective responses by intestinal epithelial Vdelta1 gamma delta T cells and the polymorphism of MICA were reported to be related to several autoimmune diseases. The present study aimed to investigate the association of the microsatellite polymorphisms of TM region of MICA gene with the susceptibility to ulcerative colitis (UC) in Chinese population. The microsatellite polymorphisms of the MICA were genotyped in unrelated 86 Chinese patients with UC and 172 ethnically matched healthy controls by a semiautomatic fluorenscently labelled PCR method. All the subjects were the Chinese with Han nationality. The frequency of MICA-A5.1 homozygous genotype and A5.1 allele were significantly increased in UC patients compared with healthy controls (22.1%versus 7%, P = 0.0009, Pc = 0.0126, OR = 3.781, 95%CI: 1.738-8.225 and 30.2%versus 17.4%, P = 0.0014, Pc = 0.007, OR = 2.051, 95%CI: 1.336-3.148, respectively). Adjusted the effects of gender and age at onset, MICA-A5.1 homozygous genotype and A5.1 allele were also increased in the UC patients. Moreover MICA-A5.1 allele was significantly increased in frequency in the female UC patients (38.2%versus 21.0%, P = 0.0095, Pc = 0.0475, OR = 2.326, 95%CI: 1.234-4.382). Logistic regression analysis also revealed that gender was independently associated with UC patients carried MICA-A5.1 allele (P = 0.046, OR (male) = 0.511, 95% CI: 0.264-0.987). Although the UC patients with extensive colitis (32.5%versus 17.4% in the healthy controls, P = 0.005, Pc = 0.025) and the UC patients with extraintestinal manifestations (36%versus 17.4% in the healthy controls, P = 0.0039, Pc = 0.0195) were more likely to carry the MICA-A5.1 allele, EIMs was associated with extent of disease (P < 0.0001, OR (with EIMs) = 3.511, 95% CI 1.747-7.056) and MICA-A5.1 allele was not associated with UC patients with extensive colitis or with EIMs in the logistic regression analysis. Therefore, the MICA-A5.1 homozygous genotype and A5.1 allele were closely associated with UC and the MICA-A5.1 allele was positively associated with the female UC patients in Chinese population.

MHC class I chain-related antigen A in mono- and polyglandular autoimmunity

We have evaluated whether the MHC-class-I-chain-related gene A (MICA), being closely located to HLA-B, predisposes for endocrine autoimmunity. It encodes a cell surface protein. The gene shows in its transmembrane segment a GCT repeat encoding 4, 5, 6, or 9 alanine residues (alleles A4, A5, A6, A9), and A5.1 has an additional 1-bp-insertion (GGCT, A5.1). We determined the polymorphism in 48 patients with Graves' disease (GD), 59 with Hashimoto's thyroiditis (HT) and 206 healthy unrelated controls. 43 patients had one endocrinopathy (monoglandular autoimmunity, MGA) and 64 at least two endocrinopathies (polyglandular autoimmunity, PGA). After extraction of genomic DNA from whole blood, the MICA microsatellites were amplified by PCR, and fragment sizes were determined with an automatic DNA sequencer (ABI PRISM 310). The exact test of Fisher and Odds ratios (OR) were applied for group comparisons. We identified the MICA alleles A4, A5, A5.1, A6, and A9 in either homozygous or heterozygous form in 21.5%, 25.2%, 70.1%, 21.5%, 22.4% of patients versus 24.8%, 27.2%, 62.1%, 36.9%, 23.8% of controls, respectively. Patients with GD (14.6%, 33.3%, 70.8%, 18.8%, 22.9%) and HT (27.1%, 18.6%, 69.5%, 23.7%, 22.0%) did not differ in their frequencies. Allele A6 was less frequent in patients (21.5%) than controls (36.9%; OR=0.468, 95%CI=0.273–0.805); this was more pronounced in patients with PGA (18.8%; OR=0.395, 0.198–0.786 vs. controls) than MGA (25.6%; OR=0.671, 0.265–1.700 vs. controls). Allele A5.1 was more frequent in patients with PGA (78.1%) than MGA (58%; OR=2.571, 1.102–6.001) or controls (62.1%; OR=2.176, 1.129–4.195). No significant relationships were observed between thyroid antibodies against TPO and TSH receptor and MICA frequencies. Allele A5.1 creates a frameshift resulting in a premature termination codon in the transmembrane region of the MICA protein, lacking for its cytoplasmatic domain. This truncated protein is regarded as a soluble, secreted form of MICA. These results indicate that the MICA gene influences susceptibility to endocrine autoimmunity.

Distribution of MICA alleles and haplotypes associated with HLA in the Korean population

The MICA (MHC class I chain-related gene A) is a polymorphic gene located 46 kb centromeric of the HLA-B gene, and is preferentially expressed in epithelial cells and intestinal mucosa. The MICA gene, similar to human leukocyte antigen (HLA) class I, displays a high degree of genetic polymorphism in exons 2, 3, 4, and 5, amounting to 54 alleles. In this study, we investigated the polymorphisms at exons coding for extracellular domains (exons 2, 3, and 4), and the GCT repeat polymorphism at the transmembrane (exon 5) of MICA in 199 unrelated healthy Koreans. Eight alleles were observed in the Korean population, with allele frequencies for MICA*010, MICA*00201, MICA*027, MICA*004, MICA*012, MICA*00801, MICA*00901, and MICA*00701 being 18.3%, 17.8%, 13.6%, 12.3%, 11.1%, 10.8%, 10.6%, and 3.3%, respectively. Strong linkage disequilibria were also observed between the MICA and HLA-B gene—MICA*00201-B58, MICA*004-B44, MICA*00701-B27, MICA*00801-B60, MICA*00901-B51, MICA*010-B62, MICA*012-B54, and MICA*027-B61. In the analysis of the haplotypes of HLA class I genes (HLA-A, B, and C) and the MICA, the most common haplotype was MICA*004-A33-B44-Cw*07, followed by MICA*00201-A2-B58-Cw*0302 and MICA*012-A2-B54-Cw*0102. The MICA null haplotype might be identified in the HLA-B48 homozygous individual. These results will provide an understanding of the role of MICA in transplantation, disease association, and population analyses in Koreans.

Polymorphism in transmembrane region of MICA gene and cholelithiasis.

To study the significance of polymorphism of MHC class I chain-related gene A (MICA) gene in patients with cholelithiasis. Subjects included 170 unrelated adults (83 males) with cholelithiasis and 245 randomly selected unrelated adults (130 males) as controls. DNA was extracted from peripheral leukocytes and analyzed for polymorphism of 5 alleles (A4, A5, A5.1, A6 and A9) of the MICA gene. There was no significant difference in phenotype, allele, and genotype frequencies of any of the 5 alleles between cholelithiasis patients and controls. This study demonstrates that MICA alleles studied bear no relation to cholelithiasis.

The increase in the frequency of MICA gene A6 allele in oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) was reported to be associated with immune function. The MICA (MHC class I chain-related gene A) is expressed by keratinocytes and other epithelial cells, and its encoded protein interacts with gamma/delta T cells localized in submucosa. The MICA also influences the heat shock protein function. We speculated that the alterations of MICA might influence the pathogenesis of OSCC through the aberration in presenting tumor antigens or heat shock protein. MICA gene has a triplet repeat (GCT) polymorphism in the transmembrane domain, resulting in five distinctive allelic patterns. We analysed this MICA polymorphism in 67 OSCC patients and 351 randomly selected unrelated controls. By using the ABI Prism 377-18 DNA sequencer (Applied Biosystems, Foster City, CA, USA) to analyse the sample DNA PCR products. The number of micro-satellite repeats was estimated with Genescan 672 software (Applied Biosystems) with a standard size marker of GS-350 TAMRA (N,N,N,N-tetramethyl-6-carbohydroxyl rhodamine; Applied Biosystems). The phenotype frequency of allele A6 of MICA in subjects with OSCC was significantly higher than that in controls (RR = 3.46, 95% CI = 1.73-6.94, P = 0.0002), as was the frequency of allele (RR = 2.64, 95% CI = 1.39-5.02, P = 0.002). The results suggest that allele A6 in MICA might confer the risk of OSCC.

Identification of MICA alleles with a long Leu-repeat in the transmembrane region and no cytoplasmic tail due to a frameshift-deletion in exon 4.

MHC class I chain-related gene A (MICA) is located close to HLA-B gene and expressed in epithelial cells. The MICA gene is reported to be highly polymorphic as are the classical class I genes. To further assess the polymorphism in the MICA gene, we analyzed a total of 60 HLA-homozygous cells for the sequences spanning exons 2-6. In the analysis, four new MICA alleles were identified and six variations were recognized in exon 6. MICA*017, which was identified in three HLA-B57 homozygous cells (DBB, DEM and WIN), differed from MICA*002 in exon 3 and had a guanine deletion at the 3' end of exon 4. MICA*015 identified in an HLA-B45 homozygous cell (OMW) also had the same deletion that causes a frameshift mutation resulting in complete change of the transmembrane region and premature termination in the cytoplasmic tail; these alleles have a long hydrophobic leucine-rich region instead of the alanine repeat in the transmembrane region and terminate at the second position in the cytoplasmic domain. The frameshift deletion was found only in HLA-B45- or -B57-positive panels tested, suggesting a strong linkage disequilibrium between the deletion and B45 or B57. MICA*048, which was different in exon 5 from MICA*008, was identified in an HLA-B61 homozygous cell (TA21), while MICA*00901 identified in HLA-B51 homozygous cells (LUY and KT2) was distinguished from MICA*009 by exon 6.

Polymorphism of Transmembrane Region of MICA Gene and Kawasaki Disease

Kawasaki disease is a febrile disease of children complicated with vasculitis of the coronary arteries and potential aneurysm formation. It has been recognized worldwide and appears to be increasing in frequency. Studies have found that Kawasaki disease is associated with major histocompatibility complex (MHC) class I B antigens. The MHC-class-I-chain-related gene A (MICA) is located near HLA-B. It has a triplet repeat microsatellite polymorphism in the transmembrane region. We investigated the microsatellite polymorphism in children with Kawasaki disease and controls. Seventy children (46 boys), age at diagnosis 1.68 ± 1.69 years, with Kawasaki who were treated with aspirin as well as intravenous gamma-globulin were enrolled. Control subjects consisted of 154 children (87 boys), age 2.81 ± 2.12 years. Phenotype frequency of allele A4 in patients with aneurysm formation was significantly lower than in patients without aneurysms [relative risk (RR) = 0.06, 95% confidence interval (CI) = 0.01–0.48, p = 0.00469, pc = 0.0232] and showed a similar tendency when compared with controls. Gene frequency of allele A4 was also significantly lower in patients who developed aneurysms than in patients who did not (RR = 0.07, 95% CI = 0.01–0.57, p = 0.0057, pc = 0.0282). Gene frequency of allele A5 showed a tendency to be higher in patients who developed aneurysms than in controls (RR = 2.35, 95% CI = 0.98–5.63, p = 0.0486, pc = 0.220). Allele A5.1 tended to be negatively associated with Kawasaki disease (RR = 0.57, 95% CI = 0.35–0.93, p = 0.022, pc = 0.105). Our study showed that allele A4 was negatively associated with coronary aneurysm formation in Kawasaki disease. This suggests that allele A4 protects the children with Kawasaki disease from developing coronary aneurysms after aspirin and gamma globulin therapy.

Age-related association of MHC class I chain-related gene A (MICA) with type 1 (insulin-dependent) diabetes mellitus

To assess the contribution of the HLA class I region to susceptibility to and heterogeneity of type 1 diabetes, we investigated the association of polymorphism of MHC class I chain-related gene A (MICA) with age-at-onset as well as susceptibility to type 1 diabetes. One hundred one Japanese patients and 110 healthy control subjects were studied. The frequency of A4 allele was significantly higher and that of A6 allele was significantly lower in patients than in control subjects. The frequency of A5.1 allele was highest in early-onset patients (23.0%), intermediate in intermediate-onset patients (9.2%) and lowest in late-onset patients (7.7%) (trend chi-squared test, p = 0.0098). A5.1 allele was strongly associated with HLA-B7 and Cw7, suggesting that MICA∗A5.1-B7-Cw7 haplotype contains a gene responsible for age-at-onset. A4 allele was associated with a susceptible haplotype, DR4-DQB1∗0401, and A6 allele was associated with a protective haplotype, DR2-DQB1∗0601, suggesting that the association of MICA with type 1 diabetes susceptibility may be due to linkage disequilibrium with class II haplotypes. These data suggest that MICA gene is associated with age-at-onset and that a gene (or genes) responsible for age-at-onset of type 1 diabetes is located in the HLA class I region, probably near the region of MICA-B-C.

Polymorphism in the transmembrane region of the MICA gene and type 1 diabetes.

Although MHC class II genes have a stronger association with type 1 diabetes than MHC class I genes, studies have shown that MHC class I molecules play an independent role in the etiology of type 1 diabetes, and the existence of susceptibility genes within a segment of MHC between the HLA-B and TNF genes has been predicted, where MHC class I chain-related gene A (MICA) resides. MICA has a triplet repeat polymorphism in the transmembrane region consisting of five alleles. We analyzed this polymorphism in 162 unrelated children (82 boys) with type 1 diabetes (age at diagnosis 7.01 +/- 3.76 yr) and 154 randomly selected unrelated children (87 boys), age 2.81 +/- 2.12 yr. Phenotype frequency of allele A9 in children with type 1 diabetes was significantly higher than in controls (RR = 2.42, 95% CI = 1.52-3.85, p = 0.000162, pc = 0.00081). Gene frequency of allele A9 was also significantly higher in children with type 1 diabetes when compared with control children (RR = 2.73, 95% CI = 1.85-4.03, p = 2.62 x 10(-7), pc = 1.31 x 10(-6)). This study demonstrates that MICA allele A9 confers risk of type 1 diabetes.

MICA gene polymorphism and the risk to develop cervical intraepithelial neoplasia

Cervical intraepithelial neoplasia (CIN) is associated with human papillomaviruses (HPV) and the HLA genes. The MICA (MHC class I chain-related gene A) is expressed by keratinocytes and epithelial cells and interacts with gamma delta T cells. It is therefore possible that MICA might influence the pathogenesis of CIN and cervical cancer through presentation of viral or tumor antigens. To investigate this, we determined the MICA transmembrane allele frequencies in a prospective population-based cohort study from the Västerbotten County in northern Sweden. 74 women developed CIN. 153 control women who remained healthy during follow up were matched for age. Five polymorphic microsatellite alleles of MICA were identified by a polymerase chain reaction-based (PCR) technique using fluorescent-labeled primers. MICA A5 and A5.1 were the most common alleles in this population. None of the alleles of MICA were associated with disease. The frequency of MICA allele A5 was higher among HPV 18 seropositive than HPV 18 seronegative patients but this difference was not significant after the correction of p value. In conclusion, microsatellite allele polymorphism of MICA transmembrane part is not associated with cervical intraepithelial neoplasia.

Molecular genetics (HLA) of Behçet's disease.

Behçet's disease (BD) has been known to be strongly associated with the human leukocyte antigen (HLA) B51. This B51 association has been confirmed in many different ethnic groups between the Middle East and Japan, and it has been proposed that BD is prevalent in those ethnic groups along the old Silk Route. The hypothesis could be made that B51 molecules are primarily involved in BD development through specific antigen presentation. However, polymorphic analyses of the TNFB gene and Tau-a microsatellite between the HLA-B and TNF genes indicate that the pathogenic gene of BD is not the HLA-B51 gene itself but another gene located around the HLA-B gene. HLA-C genotyping by the PCR-SSP method also suggests that the BD pathogenic gene is not the HLA-C gene itself but other gene located near the HLA-B gene. Recently we sequenced a single contig of 236,822 bp from the MICA gene (58.2 kb centromeric of HLA-B) to 90.8 kb telomeric of HLA-C and identified 8 novel genes designated NOB1-8 (NOB: new organization associated with HLA-B). During the course of the genomic sequence analysis we clarified the genetic structure of the MICA (MHC class I chain-related gene A) gene and found a triplet repeat microsatellite polymorphism of (GCT/AGC)n in the transmebrane (TM) region. Furthermore, the microsatellite allele consisting of 6 repetitions of GCT/AGC (MICA A6 allele) was present at a significantly higher frequency in the BD patient group than in the control group and a significant fraction of B51-negative patients were positive for this MICA A6 allele. These results suggest the possibility of a primary association of BD with MICA rather than HLA-B.