High resolution methylation analysis of the FMR1 gene trinucleotide repeat region in fragile X syndrome.
High resolution methylation analysis of the FMR1 gene trinucleotide repeat region in fragile X syndrome.
复制标题
脆性 X 综合征中 FMR1 基因三核苷酸重复区域的高分辨率甲基化分析。
DOI：
10.1093/hmg/2.10.1659
复制
发表时间：
1993
影响因子：
3.5
通讯作者：
Yang,TP
中科院分区：
文献类型：
--
作者：
Hornstra,IK;Nelson,DL;Warren,ST;Yang,TP
脆性X综合征是人类最常见的遗传性智力低下，与FMR 1基因5′端非翻译区CGG三核苷酸重复序列数目的扩增有关。传播男性，个人谁是不受影响的疾病携带者，显示了适度增加的重复单位的数量，而完全渗透男性显示了一个重大的扩展重复数。受影响男性中重复序列的主要扩增与这些患者中含有三核苷酸重复序列的5′ CpG岛中某些限制性内切酶识别位点的甲基化相关。突变的表型表达似乎是由于FMR 1基因的转录沉默。我们现在报告直接高分辨率甲基化分析的三核苷酸重复序列及其侧翼区使用连接介导的PCR基因组测序。我们发现，在正常男性白细胞和传递男性淋巴母细胞的DNA中，FMR 1三核苷酸重复序列内和周围的所有CpG二核苷酸的胞嘧啶残基均未甲基化;这些相同的胞嘧啶在受影响的男性淋巴母细胞中、在含有来自受影响男性的脆性X染色体的体细胞杂交体细胞中以及在含有正常非活性X染色体的体细胞杂交体细胞中甲基化。通过基因组测序确定的受累患者FMR 1 5′ CpG岛的甲基化模式与非活性人类X染色体上X连锁人类磷酸甘油酸激酶和次黄嘌呤磷酸核糖基转移酶基因5′ CpG岛的甲基化模式非常相似。这些结果表明，失活X染色体上基因沉默的机制也可能参与脆性X患者FMR 1基因表达的抑制。
Fragile X syndrome is the most common form of inherited mental retardation in man. The disease is associated with expansion in the number of tandem CGG trinucleotide repeats in the 5′ untranslated region of the human FMR1 gene. Transmitting males, individuals who are unaffected carriers of the disease, show a moderate increase in the number of repeat units, while fully penetrant males show a major expansion in repeat number. Major expansion of the repeat in affected males is correlated with methylation of certain restriction enzyme recognition sites in the 5′ CpG Island containing the trinucleotide repeat in these patients. Phenotypic expression of the mutation appears to be due to transcriptional silencing of the FMR1 gene. We now report direct high resolution methylation analysis of the trinucleotide repeat and its flanking regions using ligation-mediated PCR genomic sequencing. We find the cytosine residue of all CpG dinucleotides examined within and surrounding the FMR1 trlnucleotide repeat to be unmethylated in the DNA of normal male leukocytes and transmitting male lymphoblasts; these same cytosines are methylated in affected male lymphoblasts, in a somatic cell hybrid containing a fragile X chromosome from an affected male, and in a somatic cell hybrid containing a normal inactive X chromosome. The methylation pattern of the FMR1 5′ CpG Island in affected patients as determined by genomic sequencing is remarkably similar to that seen for the X-linked human phosphoglycerate kinase and hypoxanthine phospho ribosyitransferase gene 5′ CpG Islands on the Inactive human X chromosome. These results suggest the mechanism(s) silencing genes on the Inactive X chromosome may also be involved in repression of FMR1 gene expression in fragile X patients.