Posts belonging to Category CRISPR



How To Correct Genes That Cause High Cholesterol

U.S. researchers have used nanotechnology plus the powerful CRISPR-Cas9 gene-editing tool to turn off a key cholesterol-related gene in mouse liver cells, an advance that could lead to new ways to correct genes that cause high cholesterol and other liver diseasesNanotechnology is the design and manipulation of materials thousands of times smaller than the width of a human hair.

We’ve shown you can make a nanoparticle that can be used to permanently and specifically edit the DNA in the liver of an adult animal,” said study author Daniel Anderson, an associate professor in chemical engineering at the Massachusetts Institute of Technology.

The study, published  in Nature Biotechnology, holds promise for permanently editing genes such as PCSK9, a cholesterol-regulating gene that is already the target of two drugs made by the biotechnology companies Regeneron Pharmaceuticals and Amgen.

In the study, the scientists were trying to develop a safe and efficient way to deliver the components needed for CRISPR-Cas9, a type of molecular scissors that can selectively trim away defective genes and replace them with new stretches of DNA.

The system consists of a DNA-cutting enzyme called Cas9 and a stretch of RNA that guides the cutting enzyme to the correct spot in the genome. Most teams currently use viruses to deliver CRISPR into cells, an approach that is limited because the immune system can develop antibodies to viruses.

To overcome this, the team chemically modified the CRISPR components to protect them from enzymes in the body that would normally break them down. They then inserted this material into nano-scale fat particles and injected them into mice, where they made their way to liver cells.

In tests targeting the PCSK9 gene, the system proved highly effective, . The PCSK9 protein made by this gene was undetectable in the treated mice, eliminating the gene in more than 80 percent of liver cells, which also experienced a 35 percent drop in total cholesterol, the researchers reported.

High levels of cholesterol can clog arteries, causing reduced blood flow that can lead to a heart attack or stroke.

Source: http://news.mit.edu/

Editing Genes In Human Embryos

Two new CRISPR tools overcome the scariest parts of gene editing.The ability to edit RNA and individual DNA base pairs will make gene editing much more precise. Several years ago, scientists discovered a technique known as CRISPR/Cas9, which allowed them to edit DNA more efficiently than ever before.
Since then, CRISPR science has exploded; it’s become one of the most exciting and fast-moving areas of research, transforming everything from medicine to agriculture and energy. In 2017 alone, more than 14,000 CRISPR studies were published.

But here’s the thing: CRISPR, while a major leap forward in gene editing, can still be a blunt instrument. There have been problems with CRISPR modifying unintended gene targets and making worrisome, and permanent, edits to an organism’s genome. These changes could be passed down through generations, which has raised the stakes of CRISPR experiments — and the twin specters of “designer babies” and genetic performance enhancers — particularly when it comes to editing genes in human embryos.
So while CRISPR science is advancing quickly, scientists are still very much in the throes of tweaking and refining their toolkit. And on Wednesday, researchers at the Broad Institute of MIT and Harvard launched a coordinated blitz with two big reports that move CRISPR in that safer and more precise direction.
In a paper published in Science, researchers described an entirely new CRISPR-based gene editing tool that targets RNA, DNA’s sister, allowing for transient changes to genetic material. In Nature, scientists described how a more refined type of CRISPR gene editing can alter a single bit of DNA without cutting it — increasing the tool’s precision and efficiency.

The first paper, out Wednesday in Science, describes a new gene editing system. This one, from researchers at MIT and Harvard, focuses on tweaking human RNA instead of DNA.

Our cells contain chromosomes made up of chemical strands called DNA, which carry genetic information. Those genes have recipes for proteins that lead to a bunch of different traits. But to carry out the instructions in any one recipe, DNA needs another type of genetic material called RNA to get involved.

RNA is ephemeral: It acts like a middleman, or a messenger. For a gene to become a protein, that gene has to be transcribed into RNA in the cell, and the RNA is then read to make the protein. If the DNA is permanent — the family recipe book passed down through generations — the RNA is like your aunt’s scribbled-out recipe on a Post-It note, turning up only when it’s needed and disappearing again.

With the CRISPR/Cas9 system, researchers are focused on editing DNA. (For more on how that system works, read this Vox explainer.) But the new Science paper describes a novel gene editing tool called REPAIR that’s focused on using a different enzyme, Cas13, to edit that transient genetic material, the RNA, in cells. REPAIR can target specific RNA letters, or nucleosides, that are involved in single-base changes that regularly cause disease in humans.

This is hugely appealing for one big reason: With CRISPR/Cas9, the changes to the genome, or the cell’s recipe book, are permanent. You can’t undo them. With REPAIR, since researchers can target single bits of ephemeral RNA, the changes they make are transient, even reversible. So this system could fix genetic mutations without actually touching the genome (like throwing away your aunt’s Post-It note recipe without adding it to the family recipe book).

Source: https://www.vox.com/