The Genetic Analysis Of 437817,445861/446216 SNP Loci On MICB Gene In Liaoning Han And Their Forensic Medicine Application

ForewordMHC classⅠchain-related B gene(MICB) as PerB11.2, which is non-typical HLA classⅠgene, was found that it has the function for proteins coding. MICB has 12.9 kb nucleotide in sequence, located 141.2 kb centromeric of the HLA-B locus. Being the NKG2D receptor, MICB is not associated withβ2 microglobulin and does not bind to peptides. MICB is combined with NKG2D/DAP 10. Up regulation has been suggested to signal cell stress to the immune system via an interaction withγδT cell,CD8+cell,NK cell. Constitutive expression is limited to gut epithelium in normal tissue.The MICB gene was first reported by Bahrain et al. in 1994. The hereditary variation of the MICB gene was studied by Hitoshi Ando et al in 1997, and the MICB gene shows to be polymorphic. Up to 2007, 264 SNPs in MICB gene has been confirmed by NCBI.There are a few reports about SNP polymorphisms on MICB gene at present. In this study, we investigate the frequencies of 437817 locus at exon 3 and 445861/446216 loci at promoter region in Liaoning Han population in order to provide a basic data for forensic identification.Materials and Methods1,Peripheral blood samples were obtained from 228 unrelated healthy individuals of Liaoning Han nationality. The samples of known parentage relationship from forty families were provided by department of Forensic Serology.2,The genotype frequencies of 437817 locus at exon 3 and 445861/446216 loci at promoter region were studied by the method of PCR-RFLR The technique for three loci was also applied to parentage testing.3,The gene and genotype frequencies of 437817, 445861/446216 loci were calculated by the direct count method. The Hardy-Weinberg equilibrium test and linkage equilibrium test were performed. DP and EPP values were calculated according to the Fisher's method and the Odelberg method. The chi-square test was performed using SPSS 13.0 software to analyze the distribution differences of allele frequencies between different populations.Results1,Two SNP alleles and two of three genotypes at 437817 locus were defined in Liaoning Han population. The frequencies of the two alleles, C and G, were 0.933 and 0.067 respectively. Two genotypes detected were C/C(n=197) and C/G(n=31), and the frequencies of C/C and C/G were 86.4％and 13.6％respectively. G/G genotype was not found in this population.2,There are four types of allelic combination in 445861/446216 loci in theory. Three of them were detected in tested population, GC,GG and CC with the frequencies of 55.0％, 28.3％, 16.7％respectively. The CG type was not found in the study. There are also 10 combined genotypes in 445861/446216 loci theoretically. Six of the ten were found, they are GG/GC, GC/GC, CC/GC, CC/GG, GG/GG and CC/CC, with the frequencies of 32.9％, 28.9％, 19.3％, 8.8％, 7.5％and 2.6％respectively.3,Forty father-child-mother trios for paternity identity were analyzed by the method used in the study for 445861/446216 allele combination types. The 36 of forty cases were not excluded from the paternity while the other four shown to be excluded.DiscussionMICB gene shows highly polymorphism like MICA and HLA-Ⅰ. More and more SNPs of MICB gene have been found with the deep studies in genome research. 264 SNPs were defined by NCBI thus far. Being a functional gene, variants of MICB gene are associated with immunogenic diseases. The 437817 and 445861/446216 variations were probably correlated with some of the diseases.The sequencing of PCR amplified products of 445861/446216 loci was carried out for the correct determination. And it is consistent with the goal sequence.At present, there is no any data report about the frequency of 437817 SNP locus on MICB gene. Only one about the frequencies of the 445861/446216 loci on MICB was presented in Spanish population. By comparison of our results with the Spanish data, there is a significant difference in the allelic frequency between Liaoning Han and Spanish population (using SPSS 13.0 software).The detection of combined genotypes of 445861/446216 loci on MICB gene is the useful method for forensic identification because of its higher soluble capability. The power of discrimination of unrelated individuals is 0.756 and excluding probability of paternity is 0.3437. Paternity testing using this system was carried out on forty cases of trios. The exclusive results were obtained in 4 cases, but not in other 36. These indicated that the system can be used in forensic analysis.Conclusion1,The 437817, 445861 and 446216 SNPs on MICB gene are polymorphic in Liaoning Han population. Their inheritance fits in Hardy-Weinberg equilibrium.2,The distributions of 445861/446216 allelic combination types on MICB gene are statistically differential in different populations.3,The 445861/446216 allelic combination types has a higher capability of resolving the problems in the fields of forensics. It can be a valuable genetic marker for forensic usage.