Medgadget

New Techique for Faster, Easier Genome Engineering in Human Cells

Last year, a new technique for cutting the DNA of  bacteria to insert genes was described in journal Science. It offers researchers a relatively easy way to remove precise sections of a bacterial genome and should accelerate research in the field of genetic modification.

For the clinical readers of this site, it’s exciting to know that new research has verified this technique in human cells. The findings foreshadow a brighter future for genetic medicine that is cheaper, safer, and more reliable than the options available today. The researchers are even comparing the revolutionary nature of the new method to how PCR changed the science of genetics.

From UC Berkeley:

Two developments – zinc-finger nucleases and TALEN (Transcription Activator-Like Effector Nucleases) proteins – have gotten a lot of attention recently, including being together named one of the top 10 scientific breakthroughs of 2012 by Science magazine. The magazine labeled them “cruise missiles” because both techniques allow researchers to home in on a particular part of a genome and snip the double-stranded DNA there and there only.

Researchers can use these methods to make two precise cuts to remove a piece of DNA and, if an alternative piece of DNA is supplied, the cell will plug it into the cut instead. In this way, doctors can excise a defective or mutated gene and replace it with a normal copy. Sangamo Biosciences, a clinical stage biospharmaceutical company, has already shown that replacing one specific gene in a person infected with HIV can make him or her resistant to AIDS.

Both the zinc finger and TALEN techniques require synthesizing a large new gene encoding a specific protein for each new site in the DNA that is to be changed. By contrast, the new technique uses a single protein that requires only a short RNA molecule to program it for site-specific DNA recognition, Doudna said.

In the new Science Express paper, [George Church, professor of genetics at Harvard Medical School] compared the new technique, which involves an enzyme called Cas9, with the TALEN method for inserting a gene into a mammalian cell and found it five times more efficient.

“It (the Cas9-RNA complex) is easier to make than TALEN proteins, and it’s smaller,” making it easier to slip into cells and even to program hundreds of snips simultaneously, he said. The complex also has lower toxicity in mammalian cells than other techniques, he added.

“It’s too early to declare total victory” over TALENs and zinc-fingers, Church said, “but it looks promising.”

Press release: Cheap and easy technique to snip DNA could revolutionize gene therapy

Article abstracts in Science Express: RNA-Guided Human Genome Engineering via Cas9; Multiplex Genome Engineering Using CRISPR/Cas Systems

Original paper in Science describing the technique: A Programmable Dual-RNA–Guided DNA Endonuclease in Adaptive Bacterial Immunity