V快讯：用光控制CRISPR/Cas9基因编辑

Biodog

一段时间以来，科学家们一直都在尝试操纵基因。最近，美国匹兹堡大学的Alexander Deiters就发现了一种方式，以更高的精度来控制这个过程。他采用的是光。Deiters及其研究团队首次实现了这一技术突破，他们将相关研究结果发表在最近的化学领域顶级期刊《美国化学学会杂志》（Journal of the American Chemical Society）。延伸阅读：3篇权威：光激活的CRISPR-Cas9系统。
自2013年以来，科学家开始使用一种叫做CRISPR/Cas9的基因编辑工具。该方法采用一种细菌来源的蛋白（Cas9）和一种合成的引导性RNA，在基因组的特定位置引起双链断裂。这使得研究人员能够切除一个基因，改变其功能，或引进所需的突变。
事实上，CRISPR（成簇的规律间隔的短回文重复DNA碱基序列）方法已经展示出极大的前景，使研究人员能够治疗囊胞性纤维症和镰状细胞性贫血，建立实验动物模型模拟人类疾病，以及培育抗白粉病的小麦品系。
匹茨堡大学Kenneth P. Dietrich艺术与科学学院的化学教授Deiters，以及北卡罗来纳大学教堂山分校的同事们，通过一系列的实验，发现了Cas9中的一个赖氨酸残基（赖氨酸是一种氨基酸），可以用光激活的类似物来替代它。
Deiters开发的这种方法，生成一个功能上无效的Cas9蛋白，所以称为“笼困”，直到通过曝光将“笼子”移除，激活酶，从而激活基因编辑。
Deiters说：“这种方法可以让人们用比以前更好的空间和时间控制，设计细胞或动物中的基因。以前，如果你想敲除一个基因，你对基因会在何时何地发生的控制有限。设计一个灯开关在Cas中，提供了一个更精确的编辑工具。你可以说，‘在这个细胞中，在这个时间点上，在我想修改基因组的区域’。”
Deiters指出，改进后，随时间推移在一个基因将被操纵的地点进行控制，可能有助于消除“脱靶效应”，并可能使遗传学研究达到前所未有的分辨率。（转自生物通）
CRISPR Gets Lit Up and Tuned

Scientists develop method for conditional control of the CRISPR/Cas9 system using light. [BlackJack3D/iStock]

• By now, most within the biomedical fields have likely at least heard mention of the gene-editing tool known as CRISPR/Cas9. Since 2013, this technique has created a veritable revolution within the disciplines of molecular biology and genetics and is already showing tremendous promise for treating such diseases a cystic fibrosis and sickle cycle, as well as being able to generate new animal models that better mimic human disease.
  The power of the CRISPR/Cas9 system lies not only in its powerful editing capabilities, but also its speed, simplicity, and compatibility for use within most organisms. However, there is one main drawback for which scientists at the University of Pittsburgh and University of North Carolina believe they may have just found a solution—conditional control, or making the system tunable, using light.      
  The findings from this study were published recently in the Journal of the American Chemical Society through an article entitled "Optical Control of CRISPR/Cas9 Gene Editing."
  Conventionally, this gene-editing technique uses the bacterially derived Cas9 protein along with a synthetic guide RNA to introduce a double-strand break at the desired location within the genome. This allows for the excision of a stretch of DNA or some alteration of gene function through the introduction of mutations within that region.
  The standard process is an all or nothing approach, where investigators select for the genotype or phenotype of interest after treating cells with the CRISPR/Cas9 assay. In the current study however, the researchers created a functional inactive Cas9 protein that can be turned on in the presence of a specific wavelength of light.     
  “In order to achieve conditional control of the CRISPR/Cas9 system, a genetically encoded light-activated Cas9 was engineered through the site-specific installation of a caged lysine amino acid,” stated the scientists. “Several potential lysine residues were identified as viable caging sites that can be modified to optically control Cas9 function, as demonstrated through optical activation and deactivation of both exogenous and endogenous gene function.”
  The research team noted that the improved control over the time and location at which a gene can be manipulated may offer a solution to off-target effects, as well as potentially enable genetic studies with unparalleled resolution.
  "This method may allow people to engineer genes in cells or animals with better spatial and temporal control than ever before," explained Alexander Deiters, Ph.D., professor of chemistry at the University of Pittsburgh and sensor author on the current study. "Previously, if you wanted to knock out a gene, you had limited control over where and when it would happen. Engineering a light switch into Cas9 provides a more precise editing tool. You can say, 'In this cell, at this time point, is where I want to modify the genome.'"