2016年1月19日 訊 /生物谷BIOON/ --突變體小鼠模型為我們研究個別基因對發育、生理以及疾病發生等科學問題提供了極大的便利。然而,傳統的小鼠突變體模型構建是一項十分耗時耗力的工程。最近的CRISPR-Cas9系統對於動物體的遺傳修飾是一項革命性的突破。
CRISPR系統首先被發現於細菌抗病毒侵染的免疫系統,通過一類sgRNA的介導,核酸內切酶Cas9能夠被引導到特定的基因序列區域,Cas9的切割會造成基因的雙鏈斷裂,而在基因損傷修復過程中,由於常常會發生錯誤,有可能會造成鹼基的增減突變。額外的鹼基增加或減少會使得該基因密碼子提前終止,造成蛋白的突變。這一特點使得CRISPR系統能夠用於個體水平的基因編輯。更進一步,如果編輯對象是動物的受精卵或早期胚胎幹細胞,就能夠得到全身性基因敲除的動物。然而,該技術的缺點在於很多基因全身性的敲除都會導致致死的表型。目前利用CRISPR技術對動物進行組織特異性遺傳修飾技術還不夠成熟。
最近,來自西南醫學中心再生醫學研究中心的Eric N. Olson研究組構建了在心肌細胞中特異性表達Cas9的小鼠,之後利用腺病毒介導的針對Myh6基因的sgRNA的感染,成功得到了心肌細胞特異性Myh6基因敲除的小鼠。相關結果發表在最近一期的《PNAs》雜誌上。
首先,作者介紹了他們構建Myh6基因條件性敲除小鼠的過程,方法已經在上述內容中介紹過了。之後他們通過生化與成像的方法證明該小鼠在心肌細胞內Myh6基因得到了敲除。
進一步,作者發現這一突變體小鼠患有心臟衰竭與異常肥大症。相比野生小鼠,突變體小鼠心肌縮短率有明顯的降低。之後,作者從小鼠體內分離出Cas9陽性的心肌細胞,進行體外sgRNA刺激。結果顯示,Myh6特異性的sgRNA誘導能夠造成心肌細胞的增大與延長。
綜上,作者利用心肌細胞特異性CRISPR-cas9基因編輯技術構建了小鼠心臟疾病模型,該技術對於後續的組織特異性基因修飾具有重要的指導意義。(生物谷Bioon.com)
doi: 10.1073/pnas.1523918113
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A mouse model for adult cardiac-specific gene deletion with CRISPR/Cas9
Kelli J. Carroll, Catherine A. Makarewich, John McAnally, Douglas M. Anderson, Lorena Zentilin, Ning Liu, Mauro Giacca, Rhonda Bassel-Duby, and Eric N. Olson
Clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas)9 genomic editing has revolutionized the generation of mutant animals by simplifying the creation of null alleles in virtually any organism. However, most current approaches with this method require zygote injection, making it difficult to assess the adult, tissue-specific functions of genes that are widely expressed or which cause embryonic lethality when mutated. Here, we describe the generation of cardiac-specific Cas9 transgenic mice, which express high levels of Cas9 in the heart, but display no overt defects. In proof-of-concept experiments, we used Adeno-Associated Virus 9 (AAV9) to deliver single-guide RNA (sgRNA) that targets the Myh6 locus exclusively in cardiomyocytes. Intraperitoneal injection of postnatal cardiac-Cas9 transgenic mice with AAV9 encoding sgRNA against Myh6 resulted in robust editing of the Myh6 locus. These mice displayed severe cardiomyopathy and loss of cardiac function, with elevation of several markers of heart failure, confirming the effectiveness of this method of adult cardiac gene deletion. Mice with cardiac-specific expression of Cas9 provide a tool that will allow rapid and accurate deletion of genes following a single injection of AAV9-sgRNAs, thereby circumventing embryonic lethality. This method will be useful for disease modeling and provides a means of rapidly editing genes of interest in the heart.