PDF(Pubmed)
Abstract：
The Repeat Expansion Diseases (REDs) arise from the expansion of a disease-specific short tandem repeat (STR). Different REDs differ with respect to the repeat involved, the cells that are most expansion prone and the extent of expansion. Furthermore, whether these diseases share a common expansion mechanism is unclear. To date, expansion has only been studied in a limited number of REDs. Here we report the first studies of the expansion mechanism in induced pluripotent stem cells derived from a patient with a form of the glutaminase deficiency disorder known as Global Developmental Delay, Progressive Ataxia, And Elevated Glutamine (GDPAG; OMIM# 618412) caused by the expansion of a CAG-STR in the 5\' UTR of the glutaminase (GLS) gene. We show that alleles with as few as ~120 repeats show detectable expansions in culture despite relatively low levels of R-loops formed at this locus. Additionally, using a CRISPR-Cas9 knockout approach we show that PMS2 and MLH3, the constituents of MutLα and MutLγ, the 2 mammalian MutL complexes known to be involved in mismatch repair (MMR), are essential for expansion. Furthermore, PMS1, a component of a less well understood MutL complex, MutLβ, is also important, if not essential, for repeat expansion in these cells. Our results provide insights into the factors important for expansion and lend weight to the idea that, despite some differences, the same mechanism is responsible for expansion in many, if not all, REDs.
摘要：
重复扩增疾病(RED)起因于疾病特异性短串联重复序列(STR)的扩增。不同的RED在涉及的重复方面有所不同，最容易扩增的细胞和扩增的程度以及这些疾病是否具有共同的扩增机制尚不清楚。迄今为止,仅在有限数量的RED中研究了扩张。在这里，我们报道了诱导多能干细胞的扩增机制的第一个研究，该干细胞来源于一种称为全球发育延迟的谷氨酰胺酶缺乏症的患者。进行性共济失调,以及谷氨酰胺酶(GLS)基因的5'UTR中CAG-STR的扩增引起的谷氨酰胺(GDPAG;OMIM#618412)升高。我们表明，具有少至100重复序列的等位基因在培养物中显示出可检测的扩增，尽管在该基因座上形成的R环水平相对较低。此外,使用CRISPR-cas9敲除方法，我们显示PMS2和MLH3，MutLα和MutLü的成分，已知参与错配修复（MMR）的2种哺乳动物MutL复合物，对扩张至关重要。此外，PMS1是一种不太了解的MutL复合物的组成部分，MutLβ,也很重要,如果不是必需的,在这些细胞中重复扩增。我们的结果提供了对扩张重要因素的见解，并赋予了这样的想法，尽管有一些差异，许多,如果不是全部,REDs可能会以非常相似的方式扩展。
