Ardui Simon, Race Valerie, Zablotskaya Alena, Hestand Matthew S, Van Esch Hilde, Devriendt Koenraad, Matthijs Gert, Vermeesch Joris R
Department of Human Genetics, KU Leuven, Leuven, Belgium.
Hum Mutat. 2017 Mar;38(3):324-331. doi: 10.1002/humu.23150. Epub 2017 Jan 17.
The FMR1 gene contains an unstable CGG repeat in its 5' untranslated region. Premutation alleles range between 55 and 200 repeat units and confer a risk for developing fragile X-associated tremor/ataxia syndrome or fragile X-associated primary ovarian insufficiency. Furthermore, the premutation allele often expands to a full mutation during female germline transmission giving rise to the fragile X syndrome. The risk for a premutation to expand depends mainly on the number of CGG units and the presence of AGG interruptions in the CGG repeat. Unfortunately, the detection of AGG interruptions is hampered by technical difficulties. Here, we demonstrate that single-molecule sequencing enables the determination of not only the repeat size, but also the complete repeat sequence including AGG interruptions in male and female alleles with repeats ranging from 45 to 100 CGG units. We envision this method will facilitate research and diagnostic analysis of the FMR1 repeat expansion.
FMR1基因在其5'非翻译区含有一个不稳定的CGG重复序列。前突变等位基因的重复单元数在55至200之间，并会增加患脆性X相关震颤/共济失调综合征或脆性X相关原发性卵巢功能不全的风险。此外，前突变等位基因在女性种系传递过程中常常会扩展为全突变，从而导致脆性X综合征。前突变发生扩展的风险主要取决于CGG单元的数量以及CGG重复序列中AGG中断的存在情况。遗憾的是，由于技术难题，AGG中断的检测受到了阻碍。在此，我们证明单分子测序不仅能够确定重复序列的大小，还能够确定包括AGG中断在内的完整重复序列，该重复序列存在于重复单元数在45至100个CGG之间的男性和女性等位基因中。我们设想这种方法将有助于FMR1重复序列扩展的研究和诊断分析。
