Molecular Genetics Laboratory UILDM, Santa Lucia Foundation, IRCCS, Rome, Italy.
S. Pietro Fatebenefratelli Hospital, UOSD Medical Genetics, Rome, Italy.
Prenat Diagn. 2018 Dec;38(13):1096-1102. doi: 10.1002/pd.5369. Epub 2018 Nov 20.
The Duchenne/Becker muscular dystrophy (DMD) carrier screening includes the evaluation of mutations in DMD gene, and the most widely used analysis is the multiplex ligation-dependent probe amplification (MLPA) for the DMD deletions/duplications detection. The high frequency of de novo mutations permits to estimate a risk up to 20% of mosaicisms for mothers of sporadic DMD children. The purpose of this study is to evaluate alternative analytical strategy for the detection of mosaics carrier women, in order to improve the recurrence risk estimation.
Different DNA and RNA analyses were conducted on samples from a woman that conceived a DMD fetus without previous family history of dystrophynopathy.
Standard MLPA analysis failed to identify mosaicism, even if MLPA doses suggested it. Electrophoresis and direct sequencing conducted on RNA permitted to detect two different amplicons of cDNAs, demonstrating the presence of somatic mosaicism. Subsequent detection of a second affected fetus confirmed the mosaic status on the mother.
The implementation of RNA analysis in diagnostic algorithm can increase the sensitivity of carrier test for mothers of sporadic affected patients, permitting detection of mosaic status. A revision of analytical guidelines is needed in order to improve the recurrence risk estimation and support prenatal genetic counseling.
杜氏肌营养不良症/贝克肌营养不良症（DMD）携带者筛查包括对 DMD 基因突变的评估，最广泛使用的分析方法是多重连接依赖性探针扩增（MLPA）检测 DMD 缺失/重复。由于新生突变的高频性，可估计散发性 DMD 患儿母亲的嵌合体风险高达 20%。本研究旨在评估用于检测嵌合体携带者女性的替代分析策略，以提高复发风险估计。
对一名无家族性肌营养不良病史但怀 DMD 胎儿的女性的样本进行了不同的 DNA 和 RNA 分析。
标准 MLPA 分析未能确定嵌合体，即使 MLPA 剂量表明存在嵌合体。对 RNA 进行电泳和直接测序，证明存在体细胞嵌合体，检测到两个不同的 cDNA 扩增子。随后对第二个受累胎儿的检测证实了母亲的嵌合体状态。
在诊断算法中实施 RNA 分析可以提高对散发性受累患者母亲的携带者检测的灵敏度，从而可以检测嵌合体状态。需要修订分析指南，以提高复发风险估计，并为产前遗传咨询提供支持。
