中文摘要：

目的通过比较不同个体外周血DNA甲基化谱的差异，评估DNA甲基化在同卵双生子个体甄别中的应用价值。方法在知情同意基础上获得22对同卵双生子外周血样。抽提基因组DNA后进行重亚硫酸盐转化．采用Illuraina公司的人27k甲基化微珠芯片检测基因组27578个CpG位点的甲基化程度（启值）。依据常染色体CpG位点的序值，采用欧氏距离计算方法计算同卵双生子间以及同性男ll的无关个体间的表观遗传距离。比较同卵双生子对与无关个体对两组不同人群间的表观遗传距离差异。结果同卵双生子对人群以及无关个体对人群中的男性个体对与女性个体对的表观遗传距离差异均无统计学意义（P值分别为0．0695和0．4825）。同卵双生子对的表观遗传距离显著低于无关个体对人群（中位数：6．02νs7．20，P=0．0002）．但两组人群的表观遗传距离均显著大于4．00（P〈0．0001）。结论同卵双生子间的外周血DNA甲基化谱差异显著．DNA甲基化是进行同卵双生子个体甄别的有效生物学标记。

英文摘要：

Objective To evaluate the potential usefulness of DNA methylation in individual discrimination of Inonozygotic twins by investigating the differences of DNA methylation profiles in monozygotic twins＇ blood samples. Methods Blood samples from 22 pairs of monozygotic twins were obtained with informed consent. Genomic DNA extracts were bisulfite treated followed by detection with Infinium~ HumanMethyla- tion27 BeadChip Assays（Illumina, USA）. Epigenetic distances between each pair of monozygotic twins and each pair of unrelated individuals of same gender were calculated with Euclidean distance algorithms. Dis- tribution of epigenetic distance in monozygotic twin group was statistically compared with that in unrelated individuals. Results Difference of epigenetic distance between male and female pairs was not statistically significant in unrelated individual group or in monozygotic twin group（P=0.069 5 and 0.4825, respectively）. Epigenetic distance of monozygotic twins was significantly lower than that of unrelated individual pair of same gender （Median： 6.02 vs 7.20, P=0.0002）. However, all the epigenetic distance in monozygotic twin group or in unrelated individuals were significantly higher than 4.00（P〈0.000 1）. Conclusion DNA methy- lation profiles of monozygotic twin＇s blood samples were significantly different with each other, which was similar to that in unrelated individuals of same gender. These results indicated that DNA methylation was a useful biomarker in individual discrimination of monozwotic twins.