[Effects of ICAM-1 gene K469E, K56M polymorphisms on plasma sICAM-1 expression levels in Chinese Yugur, Tibetan and Han nationalities].

Abstract

This study was purposed to investigate the intercellular cell adhesion molecule-1 (ICAM-1) gene K469E (A/G) (rs5498) and K56M (A/T) (rs5491) single nucleotide polymorphisms (SNP) and soluble ICAM-1 (sICAM-1) levels in plasma in three Chinese populations of Yugur, Tibetan and Han nationalities, to analyze comparatively the genotypes and allele frequencies distribution in different ethnic groups, and to explore the effects of ICAM-1 K469E and K56M polymorphism and sICAM-1 levels in plasma. EDTA-anticoagulant venous blood from Yugur(327 cases), Tibetan (400 cases) and Han (126 cases) people was collected, the DNA was extracted by using whole blood genomic DNA extraction kit, DNA SNP were analyzed by PCR-RFLP, genotype was judged by gel scan imaging system after agarose gel electrophoresis, the gene sequence was determined and the distribution of ICAM-1 genotypes and allele frequencies were compared among different ethnic groups, besides, the group representativeness was tested via the Hardy-Weinberg genetic equilibrium. Finally, the human sICAM-1 plasma levels were detected by using human ICAM-1 ELISA kit. The results showed that DNA sequencing result was consistent with PCR-RFLP analysis. In Yugur, Tibetan and Han nationalities, the KK, KE and EE three genotypes at ICAM-1 K469E gene locus were detected, the genotype distribution was not statistically significantly different, while the K, E allele frequency distribution was statistically significantly different (P < 0.05). Both of genotype and allele frequency distribution between Yugur, Tibetan and Han nationalities were statistically significantly different (P < 0.05). In K56M site only KK, KM two genotypes were detected, but the MM genotype was not detected in the three ethnic groups; the difference of two genotypes and K, M allele frequencies between Yugur and Han population was statistically significantly different (P < 0.05). Among three ethnic groups, the sex ratio and age distribution of K469E, K56M genotypes and allele frequencies of ICAM-1 gene were not significantly different, and distribution was in accordance with Hardy-Weinberg genetic equilibrium (P > 0.05). The plasma sICAM-1 level at ICAM-1 K469E allele locus in K individuals [(253 ± 122), (185 ± 97) μg/L] was higher than that at non-K allele [(145 ± 110) μg/L, P < 0.01]; the plasma sICAM-1 level of ICAM-1 K56M sites with KK genotype [(253 ± 122) μg/L] was higher than that of the KM genotypes [(168 ± 103) μg/L, P < 0.01]. In Yugur and Tibetan groups, the plasma sICAM-1 levels [(224 ± 80), (214 ± 111) μg/L] were higher than that in the Han group [(175 ± 125)μg/L, P < 0.05]. Pairwise comparison indicated that the plasma sICAM-1 levels between Yugur and Han group were statistically significantly different (P < 0.01), that was significantly different between Tibetan and Han group (P < 0.05). It is concluded that in Yugur, Tibetan and Han population, the genotypes and gene frequencies of two amino acid sites K469E and K56M in ICAM-1 were KK/KE-type, KK-type and K allele, moreover, the ratio of them in Yugur and Tibetan group was higher than that in Han, while there is not significant difference in sex ratio and age distribution, therefore, ICAM-1 genotype and allele frequency distribution in this study had ethnic representativeness. ICAM-1 gene K469E and K56M polymorphisms were likely to affect the plasma sICAM-1 expression level. K469E gene K allele may be a genetic risk factor, while K56M gene M allele a may be genetic protective factor for some diseases.