Alternatives to CRISPR-cas9: the new genetic editing tools, more precise and safer

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Talk about CRISPR-cas9 is to refer to one of the greatest advances in genetic technology, in what to edition, reconfiguration and cell manipulation is concerned.

The editing system of genes CRISPR-Cas9 has shown great promise due to its ability to act in the correction and eradication of some diseases caused by genetic disorders, such as Huntington’s disease. But there is now a growing fear due to nonspecific effects in the genome that threaten its future development.

Scientists at the University of Texas at Austin raise his voice to propose the substitution of Cas9 with a different protein, known as Cas12a, because it has proved to be a better alternative in addressing the shortcomings of CRISPR-cas9.

In order to thar, why choose Cas12a? The response that the team at the University of Texas gives is that its main difference lies in the type of coupling that develop Cas9 and Cas12a. 

CAas9 is fixed in the first few letters of its genomic destination, not reading the rest of positions that should be to bind, thus ignoring the rest of genetics code. As a result, due to subsequent discrepancies in the DNA structure, the enzyme could potentially ignore them and edit erroneously a different section of the genome and affect the health of the body.

However, Cas12a proceeds in such a way that checks every couple of genetic basepairs in its target site and then continues to advance, reading and ensuring the identity of each position, allowing the correction of errors that may arise. This fact has been demonstrated by researchers at the University of Texas at Austin and his research was published in the journal Molecular Cell.

CRISPR-cas9 acts as a molecular scissors with the ability to split and cut all types of DNA sequences in the genome. Its activity is developed through Cas9, an endonuclease enzyme of DNA and  that contains a RNA guide, that transports them to the complementary DNA sequence and that is associated with a adaptative system or beacterial immune system. This process is done in a specific way, that allows to insert changes and create new configurations thus generating a whole new structure, so that the potential of CRISPR-cas9, is in its enormous capacity for the treatment of diseases product of genetic irregularities.

This process consists of two steps, being the first stage that linked to the RNA guide, which binds and complements the area of DNA that is wanted to be changed through the work of the enzime Cas9 and genetic cell repair mechanisms.

In this way, in the second stage are activated endogenous mechanisms of DNA repair, which has been fragmented by Cas9, and as a result, in not a few cases occurs the appearance of insertion or deletion mutations, that when they are located within a gene there is the potential loss in protein production that is reconfigured.

The Cas9 enzyme cuts the DNA strands of the genes to serve as a guide to the CRISPR editing systems , but the fear of the nonspecific effects is growing.

The toxicity of CRISPR: a growing concern

The panorama of CRISPR in the future of the genetic edition is presented with the question of whether its benefits are so promising as their faults, that is why the concern about security in the gene therapy with CRISPR  motivated scientists from around the world to propose new methods to improve the effectiveness of this technology.

In the middle of the spring of this year, a multidisciplinary team comprised of scientists at Stanford University and the National Institute of Standards and Technology announced that they had succeeded in developing a new system for editing of genes baptized as MAGESTIC, which has been designed to enhance the process by which DNA is repaired.

Also, at the beginning of this year, scientists from Poland stated that they were designing an improved version of CRISPR through the use of a variant of Cas9 that divides one of the DNA secuences instead of two, minimizing the potential risk to generate  nonspecific deletions of genetic material.

Nevertheless, concerns about the safety continue in spite of the fact that genetic editing industry through CRISPR is on the rise.

A blow to the industry of gene therapy

In a investigation published in Nature Biotechnology, which suggested that Cas9 have the potential to cause undetectable genetic disorders caused the stock prices of major companies in the industry of genetic therapies through CRISPR edition will experience declines, among them CRISPR TherapeuticsIntellia Therapeutics and Sangamo, suffering from severe drops in the price of their actions. 

These new publications that expose the potential detrimental of CRISPR evidencing the occurrence of unexpected changes in genes, threaten to delay human trials using CRISPR, which were referred to start the first phases of clinical trials at the end of this year.

Cas12a: a more viable and safe alternative 

To say that Cas12a is a new discovery, it is not at all true because in fact other teams in subsequent investigations have suggested that has the potential to be more efficient than Cas9, but due to the fact that the evidence in these investigations were not entirely conclusive results did not acquire a character of relevance.

In this respect, for the team from the University of Texas, due to new developments on Cas12a, it is possible to perform tests that verify their effectiveness, so that it can be created a new concept in the genetics.

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“Broadly, Cas12a is a safer alternative, but there are still areas where Cas12a shows surprisingly blind to certain mispairing between its RNA and its genomics target”. Ilya Finkelstein, assistant professor of molecular biosciences at the University of Texas.

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Thus, before using Cas12a as the last genetic editing tool, does not have to be proven its complete precision and specificity?

Present and future of the genetic editing

Currently, the genetic technology has produced great advances and improved the quality of life of countless patients who suffered from a wide variety of pathologies like cancer. These results are so positive, and are the ones that have motivated institutions such as the Broad Institute of MIT and Harvard, Cambridge, USA, to create initiatives such as the Zhang Lab research institute dedicated to the study of genomics for the biomedical sciences. In this way they invest a good part of its economic resources for the recruitment of new talent, support in research and the empowerment of genetic science.

Zhang lab researchers have recently published in Science their results about a variant of Cas9 that have been created with an  expanded space of detection and verification of genetics targets, to which they have called SpCas9-NG. In addition,this variant can recognize relaxed NG PAMs .

It is for this reason that its future is equally encouraging as its present, and it is expected that genetic diseases and immunological will be part of the past to future generations.

However, there are still many unresolved doubts about its real usefulness and ethical implications for application in human beings, that is why the way of genetic engineering is long and with bumps that stand in their way.

What is your opinion on the processing capacity of the enzymes CRISPR-cas9 or Cas12a? Have you had any experience in the lab? Leave your comment about what do you think in concerns to the potential of genetic editing and its current state.

Image credits: Anusorn Nakdee, Soleil Nordic / shutterstock.com

References

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  2. Arlene Weintraub. To CRISPR cure for Huntington’s? https://www.fiercebiotech.com/research/a-crispr-cure-for-huntington-s
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  4. The indexes in the United States close to the low; the Dow Jones Industrial Average fell 0.35% https://es.investing.com/news/stock-market-news/los-indices-de-estados-unidos-cierran-a-la-baja-el-dow-jones-industrial-average-cae-un-035-343770
  5. Keith Noonan. Why the actions of Intellia Therapeutics, Inc. lost a 19.2% in March. https://www.fool.com/investing/2018/04/13/why-intellia-therapeutics-inc-stock-lost-192-in-ma.aspx
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  8.  Tomberg Kosicki M, K, Bradley A. Repair of double-strand breaks induced by crispr-Cas9 leads to large deletions and complex rearrangements. NATURE BIOTECHNOLOGY. 2018.
  9. Chen J, Ma , Harrington L, Costa MD. CRISPR-Cas12a target binding unleashes indiscriminate single-stranded DNase activity. Science. 2018; 360(6387): p. 436-439.
  10. DARCIA SCHWEITZER. Conflict, CRISPR and the Scientific Method. https://www.promegaconnections.com/conflict-crispr-and-the-scientific-method/
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  14. How to Make the Gene-Editing Tool CRISPR Work Even Better. https://news.utexas.edu/2018/08/02/how-to-make-the-gene-editing-tool-crispr-work-even-better
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