汉族人群4q亚端粒区等位片段4qA和4qB的结构特征

目的研究中国人4q35亚端粒区等位片段4qA和4qB的结构特征,探讨其与面肩肱型肌营养不良症（facioscapulohumeral muscular dystrophy,FSHD）的内在联系。方法研究对象包括80名无血缘关系的健康成年人。低熔点胶包埋法抽提基因组DNA。同一样品分别进行EcoRⅠ酶切、EcoRⅠ/BlnⅠ双酶切和HindⅢ酶切,脉冲电场电泳分离,p13E-11、4qA和4qB探针Southern印迹,计算4qA/4qB的频率、基因型频率及各型EcoRⅠ片段的长度,SPSS13.0统计软件分析数据。结果4q亚端粒区4qA的频率（46.9%）与4qB（53.1%）基本相等（χ2=1.250,P〉0.05）,4qA/4qB杂合型频率明显高于纯合型频率（P〈0.05）,4qA型和4qB型EcoRⅠ片段长度分别为（115.8±11.9）kb和（98.3±8.6）kb,两者差异有统计学意义（t=23.04,P〈0.001）。8.8%（7/80）的个体检测到易位构型。2名个体出现4qB型短EcoRⅠ片段。结论正常中国人4q亚端粒区4qA和4qB的频率基本相等,杂合型频率明显高于纯合型频率。4qB型D4Z4缺失不致病。4qA和4qB型EcoRⅠ片段具有动态性变化特征。

Analysis of alleles 4qA and 4qB of the chromosome 4q subtelomere in Chinese Han population

OBJECTIVE: To analyze two alleles (4qA and 4qB) distal to D4Z4 of the 4q subtelomere in Chinese population, and to elucidate the interrelationship between these variants of 4qter and facioscapulohumeral muscular dystrophy (FSHD). METHODS: Eighty unrelated healthy individuals from a random Chinese Han population were investigated. The genomic DNA was extracted from peripheral blood lymphocytes according to the specific procedure designed to minimize DNA shearing, then digested with EcoRI, HindIII or double digested with EcoRI and BlnI. The cleaved DNA was separated by pulsed field gel electrophoresis (PFGE) and Southern blotting with the probes p13E-11, 4qA and 4qB. The sizes of 4q35 EcoRI/4qA and EcoRI/4qB arrays were obtained by "curve fitting", and the frequencies of alleles and genotypes were calculated. Data were analyzed using a commercially available statistical package (Version 13.0 SPSS). RESULTS: In normal individuals, frequencies of 4qA and 4qB alleles (46.9% and 53.1%) were observed of no significant difference (chi(2) = 1.250, P>0.05). The frequency of 4qA/4qB heterozygote was much higher than that of homozygote (P<0.05). The means of EcoRI/4qA and EcoRI/ 4qB arrays (115.8+/-11.9 kb and 98.3+/-8.6 kb) were of significant difference (t=23.04, P<0.001). 8.8% (7/80) of the individuals displayed a translocation repeat array configuration. 4qB-type EcoRI arrays smaller than 35 kb were found in two individuals. CONCLUSION: The structural polymorphism of 4qA/4qB alleles within 4q35 and 10q26 is confirmed using PFGE in normal Chinese Han population. Although both alleles are almost equally common, shorten 4qB-type EcoRI fragment is not pathogenic. The frequency of 4qA/4qB heterozygote is significantly higher than that of homozygote.