Summary: Researchers have developed a new protein that can alter DNA in living cells with much higher precision than current methods.
Source: Nanyang Technological University.
Finding could lead to new therapeutics for diseases.
Researchers in Singapore have developed a new protein that can alter DNA in living cells with much higher precision than current methods.
The ability to alter DNA accurately will open more doors in the development of personalised medicine that could help to tackle human diseases that currently have few treatment options. Examples of diseases that have unmet therapeutic needs include neurodegenerative diseases like Huntington’s disease, muscular dystrophies, and blood disorders like sickle cell anaemia.
This new protein, named iCas, can be easily controlled by an external chemical input and thus solves some of the problems with CRISPR-Cas*, the existing gold-standard for DNA altering. For example, existing Cas enzymes may sometimes alter places in the DNA that result in dire consequences. With iCas, users now have the ability to control enzyme activity and thus minimize unintended DNA modifications in the cell.
Developed by a collaboration between A*STAR’s Genome Institute of Singapore (GIS) and Nanyang Technological University, Singapore (NTU Singapore), iCas was published in the peer reviewed scientific journal Nature Chemical Biology this week.
Leading the joint research team is Dr Tan Meng How, Senior Research Scientist of Stem Cell & Regenerative Biology at the GIS, and Assistant Professor at NTU’s School of Chemical and Biomedical Engineering.
“DNA is like an instruction manual that tells living cells how to behave, so if we can rewrite the instructions in this manual, we will be able to gain control over what the cells are supposed to do,” explained Dr Tan. “Our engineered iCas protein is like a light switch that can be readily turned on and off as desired. It also outperforms other existing methods in terms of response time and reliability.”
How DNA altering works
To ensure that DNA is precisely altered, which is required in many biomedical and biotechnological applications, the activity of the Cas protein must be tightly regulated.
The chemical that switches the iCas protein on or off is tamoxifen, a drug commonly used to treat and prevent breast cancer. In its absence, iCas is switched off with no changes made to the DNA. When switched on with tamoxifen, iCas will then edit the target DNA site.
In the study, iCas was found to outperform other chemical-inducible CRISPR-Cas technologies, with a much faster response time and an ability to be switched on and off repeatedly.
The higher speed at which iCas reacts will enable tighter control over exactly where and when DNA editing takes place. This is useful in research or applications that demand precise control of DNA editing.
For example, in studies of cell signalling pathways or vertebrate development, iCas can precisely target a subset of cells within a tissue (spatial control) or to edit the DNA at a particular developmental stage (temporal control).
“The iCas technology developed by Dr Tan is an exciting addition to the growing CRISPR toolbox. It enables genome editing in a precisely controlled manner, thus opening new doors for applications of the CRISPR technology in basic and applied biological research,” said Dr Huimin Zhao, the Steven L. Miller Chair Professor of the Chemical and Biomolecular Engineering faculty at the University of Illinois at Urbana-Champaign (UIUC).
GIS Executive Director Prof Ng Huck Hui added, “This development allows the researchers to have precision control for more accurate DNA editing, and it can help researchers engineer cells with new properties or repair diseased cells with mutated DNA.”
Prof Teoh Swee Hin, Chair of NTU’s School of Chemical and Biomedical Engineering, said, “DNA editing is an exciting field with many potential uses in the treatment of diseases. NTU has been active in research in the area of gene sequencing and bioengineering over the past years and this work by Dr Tan and his Singapore team will add to the growing body of knowledge in cell engineering for medicine.”
The CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins) system is a powerful technology that can be used to manipulate the DNA in living cells. For instance, it can be used to correct disease-causing mutations in humans or to engineer improved agricultural crops with desirable traits to ensure food security.
Source: Lester Kok – Nanyang Technological University
Image Source: This NeuroscienceNews.com image is credited to A*STAR’s Genome Institute of Singapore.
Original Research: Abstract for “A chemical-inducible CRISPR–Cas9 system for rapid control of genome editing” by Kaiwen Ivy Liu, Muhammad Nadzim Bin Ramli, Cheok Wei Ariel Woo, Yuanming Wang, Tianyun Zhao, Xiujun Zhang, Guo Rong Daniel Yim, Bao Yi Chong, Ali Gowher, Mervyn Zi Hao Chua, Jonathan Jung, Jia Hui Jane Lee and Meng How Tan in Nature Chemical Biology. Published online September 12 2016 doi:10.1038/nchembio.2179
[cbtabs][cbtab title=”MLA”]Nanyang Technological University. “DNA Altering Technology Could Help Tackle Diseases.” NeuroscienceNews. NeuroscienceNews, 13 September 2016.
<https://neurosciencenews.com/genetics-dna-disease-5037/>.[/cbtab][cbtab title=”APA”]Nanyang Technological University. (2016, September 13). DNA Altering Technology Could Help Tackle Diseases. NeuroscienceNews. Retrieved September 13, 2016 from https://neurosciencenews.com/genetics-dna-disease-5037/[/cbtab][cbtab title=”Chicago”]Nanyang Technological University. “DNA Altering Technology Could Help Tackle Diseases.” https://neurosciencenews.com/genetics-dna-disease-5037/ (accessed September 13, 2016).[/cbtab][/cbtabs]
Abstract
A chemical-inducible CRISPR–Cas9 system for rapid control of genome editing
CRISPR–Cas9 has emerged as a powerful technology that enables ready modification of the mammalian genome. The ability to modulate Cas9 activity can reduce off-target cleavage and facilitate precise genome engineering. Here we report the development of a Cas9 variant whose activity can be switched on and off in human cells with 4-hydroxytamoxifen (4-HT) by fusing the Cas9 enzyme with the hormone-binding domain of the estrogen receptor (ERT2). The final optimized variant, termed iCas, showed low endonuclease activity without 4-HT but high editing efficiency at multiple loci with the chemical. We also tuned the duration and concentration of 4-HT treatment to reduce off-target genome modification. Additionally, we benchmarked iCas against other chemical-inducible methods and found that it had the fastest on rate and that its activity could be toggled on and off repeatedly. Collectively, these results highlight the utility of iCas for rapid and reversible control of genome-editing function.
“A chemical-inducible CRISPR–Cas9 system for rapid control of genome editing” by Kaiwen Ivy Liu, Muhammad Nadzim Bin Ramli, Cheok Wei Ariel Woo, Yuanming Wang, Tianyun Zhao, Xiujun Zhang, Guo Rong Daniel Yim, Bao Yi Chong, Ali Gowher, Mervyn Zi Hao Chua, Jonathan Jung, Jia Hui Jane Lee and Meng How Tan in Nature Chemical Biology. Published online September 12 2016 doi:10.1038/nchembio.2179
