80 Chinese scholar Feng Zhang in recent years, frequently won the award, appeared in the major media magazine, this is because he as a genomic editing technology CRISPR one of the pioneers, in CRISPR / Cas applied to human cells played The key role. Last year, the MIT MIT announced that five of the latest professors of the latest professors, Zhang Feng ranked among them, according to reports in the history of MIT, Qian Xuesen was promoted to a lifetime professor at the age of 35, and for a long time Is the holder of the record of the youngest Chinese professor of life at the Massachusetts Institute of Technology, and Professor Zhang Feng, who was only 34 years old last year, refreshed the record.
In addition, this year Zhang Feng also became the first MIT James and Patricia Poitras professor, he said, "I am very honored to be appointed as the first neurological James and Professor Patricia Poitras .Poitras family and I love "The title is an important recognition of our study group in the study of mental illness in genomics and molecular tools."
Recently, Professor Zhang Feng and two other scholars in the Cell magazine published entitled "SnapShot: Class 2 CRISPR-Cas Systems" close-up article, introduced a new generation of CRISPR genome editing system: Class 2 CRISPR-Cas Systems.
In 2015, Zhang Feng and his colleagues reported that they found a different CRISPR system with the potential to achieve simpler and more accurate genomic engineering operations. The new system is based on searching for hundreds of thousands of CRISPR systems in different types of bacteria to find enzymes with useful properties. As a result, Cpf1 enzymes from the acidaminococcus and Lachnospiraceae are new Of the candidate.
Cpf1 system is simpler, it only needs one RNA. Cpf1 is also smaller than standard SpCas9, making it easier to deliver to cells and tissues; Cpf1 cleaves DNA in a way that differs from Cas9. When the Cas9 complex cleaves the DNA, it cuts the two strands of the same site, leaving the "blunt ends" often mutated when reconnecting. The two strands of inclusions formed with the Cpf1 complex are offset and leave overhang on the bare end. This is expected to help in precise insertion, allowing researchers to more efficiently and accurately integrate a DNA; the Cpf1 incision is far from the recognition site, which means that even if the target gene mutation at the cleavage site can still be re-cut, Chances to correct editing; the Cpf1 system provides new flexibility for selecting target sites. Like Cas9, the Cpf1 complex must be preferred to attach PAM, a short sequence, and the selected target is close to the naturally occurring PAM sequence. The PAM sequence identified by the Cpf1 system is distinct from Cas9. This may be an advantage when targeting certain genomes such as malaria parasites and the human genome.
It is pointed out that the second type of CRISPR-Cas system is based on different family of effect proteins and can be divided into three types and nine subtypes, such as Cas9 and Cas12a (Cpf1), which have been successfully used in genome engineering. In the previous study, Zhang Feng's research group also used a new bioinformatics approach to discover new proteins that were temporarily named C2c1, C2c2 and C2c3, and they developed a series of computational methods to search the NIH genome database, New CRISPR-Cas system.
In addition, the Zhang Feng research group also made some new attempts, such as they constructed 32 with a single point mutation of the Cas9 mutant, by means of verification of mismatch with the wizard to target them EMX1 gene. Zhang Feng will be these specific enhanced type of Cas9 protein called "eSpCas9 variant". Testing a large number of wizard RNAs with eSpCas9 with single point mutations and eSpCas9 with three point mutations, they found that both eSpCas9 were able to edit target sites with similar efficiencies.
Zhang Feng research group has also developed a number of based on the availability of CRISPR screening method. Using the new tool based on CRISPR to activate the SAM gene, his team confirmed that the tool could activate 12 different genes that were difficult to open with the old method. "There are many genes that can not be activated with the old system, and this new system can activate transcription up to 100 times or 1000 times," Zhang said.
At the end of last year, Zhang Feng found that Cpf1 was able to process its own CRISPR RNA (crRNA). And Cpf1-mediated pre-crRNA processing is independent of DNA cleavage. This ability can be used to simplify multiple genome editing. They designed the CRISPR array on this basis, edited four genes in mammalian cells with one vector, and edited the three genes in the mouse brain. This is based on CRISPR-Cpf1 to create a multiplexed gene editing system.
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