Nichol Edamura K, Pearson C E
Program of Genetics & Genomic Biology, The Hospital for Sick Children, 55 University Avenue, Elm Wing 11-135, Toronto, Ontario, M5G 1X8, Canada.
Hum Genet. 2005 Nov;118(2):301-4. doi: 10.1007/s00439-005-0037-5. Epub 2005 Nov 15.
Expansion and hyper-methylation of a CGG repeat tract are the main causes of fragile X syndrome (FRAXA). In some rare instances, FRAXA patients harbor not only an expanded CGG tract, but a deletion encompassing the CGG repeat and flanking sequences as well. Through the use of an SV40 primate replication system, it was possible to determine that CpG methylation and DNA replication may actually mediate the formation of these rare events. Also, the genetically stabilizing AGG interruptions can be lost by replication-mediated CGG deletions.
CGG重复序列的扩增和高甲基化是脆性X综合征（FRAXA）的主要病因。在一些罕见情况下，FRAXA患者不仅有扩增的CGG序列，还存在包含CGG重复序列及其侧翼序列的缺失。通过使用SV40灵长类动物复制系统，有可能确定CpG甲基化和DNA复制实际上可能介导了这些罕见事件的形成。此外，具有基因稳定作用的AGG中断序列可能会因复制介导的CGG缺失而丢失。
