CRISPR,小鼠癌症模型 z-bo 2021-11-05 407

　　Genome sequencing of tumor cells has revealed thousands of cancer-related mutations. Breeding strains of mice with genetic defects is one way to reveal the effects of these mutations, but breeding such mice is a costly and time-consuming process.

　　Now, researchers at the Massachusetts Institute of Technology have found an alternative: They have shown that a gene editing system called CRISPR can introduce cancer-causing mutations into the livers of adult mice, allowing scientists to screen more quickly. Check these mutations.

　　In a paper published in the journal Nature, researchers created liver tumors in adult mice by destroying the tumor suppressor genes p53 and pten. They are now working on finding ways to deliver the necessary CRISPR components to other organs, allowing them to investigate mutations in other cancer types.

　　The author of the paper, Professor Phillip Sharp of the David H. Koch Institute of MIT, said: "Human tumor sequencing has revealed hundreds of different combinations of oncogenes and tumor suppressor genes. In the future, as delivery methods improve, this Flexible technology will provide you with a way to test these combinations fairly quickly."

　　Tyler Jacks, director of the Koch Institute at MIT and professor of biology, is the senior author of this paper. Wen Xue, Sidi Chen, and Hao Yin, postdoctoral fellows at the Koch Institute, are the main authors of this paper.

　　gene destruction

　　CRISPR relies on the cellular machinery that bacteria use to protect themselves against viral infections. The researchers replicated this bacterial system to create a gene editing complex, which includes a DNA-cutting enzyme called Cas9, and a short guide chain programmed to bind to a specific genome sequence and tell Cas9 to cut it.

　　In some cases, researchers just cut part of a gene to disrupt its function. In other cases, they also introduced a DNA template strand encoding a new sequence to replace the deleted DNA.

　　In order to explore the potential use of CRISPR in the construction of mouse cancer models, researchers first used it to knock out p53 and pten. p53 and pten can protect cells from cancer by regulating cell growth. Previous studies have confirmed that transgenic mice with two gene mutations will develop cancer within a few months.

　　Such research on genetically modified mice has produced many important research findings, but because some mutations need to be introduced into embryonic stem cells, this process takes more than a year and thousands of dollars. Jacks said: "This is a very long process. The more genes you need to study, the longer and more complicated it will be."

　　Using Cas enzyme to target cut p53 and pten gene fragments, the researchers destroyed these two genes in about 3% of liver cells, resulting in liver tumors within 3 months.

　　Many possible models

　　Researchers also used CRISPR to construct a mouse model carrying the β-catenin oncogene, which can make cells more likely to become cancerous when other mutations subsequently occur. To build this model, researchers must delete the normal version of the β-catenin gene and replace it with an overactive form. They succeeded in 0.5% of liver cells.

　　Jacks said: "Not only can genes be deleted, but they can also be replaced with modified versions. When you consider the type of gene you want to mutate in the future, this opens up all kinds of new possibilities for you. Loss of function and It’s possible to get functions.

　　Using CRISPR to generate tumors can enable scientists to more quickly study the mechanisms by which different genetic mutations interact to produce cancer, as well as the effects of some potential drugs on tumors with specific genetic profiles.

　　In this study, the researchers injected some genes necessary for CRISPR into the tail vein of mice. Although this is an effective method of delivering genetic material to the liver, it has no effect on other target organs. Sharp said that researchers are now developing nanoparticles and other DNA and RNA delivery methods that can target other organs more effectively.