Genetic Engineering Is A Miracle CRISPR-Cas9 Engineering Tool
February 15, 2021 at 8:16 p.m.
By Max [email protected]
And with the newest and arguably most effective genetic engineering tool, CRISPR-Cas9 (CRISPR for short), the genome – an organism’s entire DNA content, including all its genes – has become almost as editable as a simple piece of text. As long as the genetic code for a particular trait is known, scientists can use CRISPR techique to insert, edit or delete the associated gene in virtually any living plant’s or animal’s genome. In essence, CRISPR allows its users to snap a stretch of DNA and then either disable the affected sequence or replace it with a new one.
CRISPR stands for “clustered regularly interspaced short palindromic repeats.” Those repeats are found in bacteria’s DNA. They are actually copies of small pieces of viruses. Bacteria use them like collections of mug shots to identify bad viruses. Cas9 is an enzyme that can cut apart DNA.
Bacteria fight off viruses by sending the Cas9 enzyme to chop up viruses that have a mug shot in the collection. Scientists recently figured out how bacteria do this. Now, in the lab, researchers use a similar approach to turn the microbe’s virus-fighting system into the hottest new lab tool.
History
The process had its start in 1992, when Professor Francisco Mojica was working on his thesis at the University of Alicante in Spain. A keen microbiologist, he was studying microorganisms belonging to the Archaea family, a group of prokaryotes (cells without a nucleus) that he brands "quite peculiar."
These microorganisms are halophiles, meaning they require high-salt conditions to survive. Mojica and colleagues were interested in understanding how Archaea are able to grow in high salinity and, when required, adapt to changes in such salinity. They opted to sequence their DNA to look for clues in the genome.
In a pre-Human Genome Project era, this was quite the task. The scientists didn't have the luxury of sequencing data being at their disposal.
Nevertheless, Mojica and the team's efforts were successful. They discovered that the halophiles' DNA possessed a series of regularly spaced repeats, which they labelled tandem repeats (or TREPS). "We saw that these repeated regions in the halophiles were transcribed, meaning they were active.”
According to Dr. Mojica, the cell was reading this information in each of the growing conditions that we tested, and so we knew that they had to be important for the cell. This was followed by seminal work demonstrating that by targeting genes in mouse embryonic stem cells and then injecting those modified stem cells back into mouse embryos, scientists could create live mice with designer changes. The breakthroughs by Capecchi, Smithies and Evans were eventually recognized with the 2007 Nobel Prize in Physiology or Medicine.
Recent Work
From Dr Mojica’s initial work, CRISPR has, for the past eight years, shown great promise for treating a number of diseases because of its precision and versatility something like a pair of genetic scissors and the letter-by-letter editing capabilities of word-processing software.
Beginning in 2012, two researchers, Jennifer Doudna and Emmanuelle Charpentier, did much of the pioneering work to turn molecules made by microbes into a tool for customizing genes, whether in microbes, plants, animals or even humans. Both women are Nobel laureates.
No longer hypothetical, CRISPR-Cas9 is producing exciting results for medical teams to use the gene-editing technology to achieve a remarkable level of functional correction of the disease phenotype in two transfusion-dependent patients with either β-thalassemia or sickle cell disease by alleviating the severe anemia. It has also been used as a cure for hereditary blindness.
Plant scientists are using it to create new crops. Some researchers are even trying to use CRISPR to bring species back from extinction. Along with these high profile experiments, other scientists are using CRISPR to ask fundamental questions about life such as which genes are essential to a cell’s survival.
The basic idea that cells could contain repeating DNA sequences was not itself a surprise; more than 50% of the human genome – well over one billion letters of DNA – comprises different types of repetitive arrays, some of which are copied millions of times.
CRISPRs have been found in almost half of all the bacterial genomes that had been sequenced to date and in nearly every archaeal genome. In fact, they appeared to be the most widely shared family of repeating DNA sequences in all prokaryotes.
Final Thoughts
Today CRISPR has been developed as a preventative strategy to combat coronaviruses. Using CRISPR technique it is possible to effectively degrade SARS-CoV-2 sequences in human lung epithelial cells and reduce the viral replication. This approach is potentially helpful in dealing with emerging pandemic strains.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns. He can be reached by email at [email protected].
And with the newest and arguably most effective genetic engineering tool, CRISPR-Cas9 (CRISPR for short), the genome – an organism’s entire DNA content, including all its genes – has become almost as editable as a simple piece of text. As long as the genetic code for a particular trait is known, scientists can use CRISPR techique to insert, edit or delete the associated gene in virtually any living plant’s or animal’s genome. In essence, CRISPR allows its users to snap a stretch of DNA and then either disable the affected sequence or replace it with a new one.
CRISPR stands for “clustered regularly interspaced short palindromic repeats.” Those repeats are found in bacteria’s DNA. They are actually copies of small pieces of viruses. Bacteria use them like collections of mug shots to identify bad viruses. Cas9 is an enzyme that can cut apart DNA.
Bacteria fight off viruses by sending the Cas9 enzyme to chop up viruses that have a mug shot in the collection. Scientists recently figured out how bacteria do this. Now, in the lab, researchers use a similar approach to turn the microbe’s virus-fighting system into the hottest new lab tool.
History
The process had its start in 1992, when Professor Francisco Mojica was working on his thesis at the University of Alicante in Spain. A keen microbiologist, he was studying microorganisms belonging to the Archaea family, a group of prokaryotes (cells without a nucleus) that he brands "quite peculiar."
These microorganisms are halophiles, meaning they require high-salt conditions to survive. Mojica and colleagues were interested in understanding how Archaea are able to grow in high salinity and, when required, adapt to changes in such salinity. They opted to sequence their DNA to look for clues in the genome.
In a pre-Human Genome Project era, this was quite the task. The scientists didn't have the luxury of sequencing data being at their disposal.
Nevertheless, Mojica and the team's efforts were successful. They discovered that the halophiles' DNA possessed a series of regularly spaced repeats, which they labelled tandem repeats (or TREPS). "We saw that these repeated regions in the halophiles were transcribed, meaning they were active.”
According to Dr. Mojica, the cell was reading this information in each of the growing conditions that we tested, and so we knew that they had to be important for the cell. This was followed by seminal work demonstrating that by targeting genes in mouse embryonic stem cells and then injecting those modified stem cells back into mouse embryos, scientists could create live mice with designer changes. The breakthroughs by Capecchi, Smithies and Evans were eventually recognized with the 2007 Nobel Prize in Physiology or Medicine.
Recent Work
From Dr Mojica’s initial work, CRISPR has, for the past eight years, shown great promise for treating a number of diseases because of its precision and versatility something like a pair of genetic scissors and the letter-by-letter editing capabilities of word-processing software.
Beginning in 2012, two researchers, Jennifer Doudna and Emmanuelle Charpentier, did much of the pioneering work to turn molecules made by microbes into a tool for customizing genes, whether in microbes, plants, animals or even humans. Both women are Nobel laureates.
No longer hypothetical, CRISPR-Cas9 is producing exciting results for medical teams to use the gene-editing technology to achieve a remarkable level of functional correction of the disease phenotype in two transfusion-dependent patients with either β-thalassemia or sickle cell disease by alleviating the severe anemia. It has also been used as a cure for hereditary blindness.
Plant scientists are using it to create new crops. Some researchers are even trying to use CRISPR to bring species back from extinction. Along with these high profile experiments, other scientists are using CRISPR to ask fundamental questions about life such as which genes are essential to a cell’s survival.
The basic idea that cells could contain repeating DNA sequences was not itself a surprise; more than 50% of the human genome – well over one billion letters of DNA – comprises different types of repetitive arrays, some of which are copied millions of times.
CRISPRs have been found in almost half of all the bacterial genomes that had been sequenced to date and in nearly every archaeal genome. In fact, they appeared to be the most widely shared family of repeating DNA sequences in all prokaryotes.
Final Thoughts
Today CRISPR has been developed as a preventative strategy to combat coronaviruses. Using CRISPR technique it is possible to effectively degrade SARS-CoV-2 sequences in human lung epithelial cells and reduce the viral replication. This approach is potentially helpful in dealing with emerging pandemic strains.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns. He can be reached by email at [email protected].
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