A revolutionary gene-editing technology was lately used to cure living adult animals, making small changes to the immense DNA molecule database with accuracy and precision.
Researchers used the genome-editing system and corrected a "letter" of the genetic alphabet to cure laboratory mice with an inherited liver disease. The letter was mutated in a vital gene linked to liver metabolism. The same mutation in a similar gene causes the inherited liver disease counterpart in humans and successfully repairing the genetic defect in mice could mean that clinical trials on humans might start in a couple of years.
"What's exciting about this approach is that we can actually correct a defective gene in a living adult animal," senior author of the study Daniel Anderson said. Anderson is a Samuel A. Goldblith Associate Professor of Chemical Engineering at MIT and a Koch Institute for Integrative Cancer Research member.
The latest technology in genome editing is called Crispr, which allows scientists to change DNA on animal and plant chromosomes with pinpoint precision. It was discovered in 1987 as the bacteria's immune defense against invasive viruses. The gene-editing potential was fully realized in higher animals and humans in 2012 and 2013 when researchers learned that the technology can be combined with Cas9, a DNA breaking enzyme used to edit human genome. The DNA molecule database has 3 billion "base pairs" and the simple method changes with such accuracy equivalent to correcting one misspelt word in a 23-volume encyclopedia.
Scientists copied the Crispr system to make complex gene-editing tests with Cas9 bound to a short RNA guide strand programmed to link to a certain genome sequence, instructing Cas9 exactly where to cut. They also delivered a DNA template strand. When Cas9 repairs the cell damage, it copies the template and introduces new genetic material to the genome. This process could possibly treat Huntington's disease, hemophilia and other diseases caused by single mutations.
"This work shows that CRISPR can be used successfully in adults, and also identifies several of the challenges that will need to be addressed moving forward to the development of human therapies," biomedical engineering assistant professor at Duke University Charles Gersbach said. "In particular, the authors note that the efficiency of gene editing will need to improve significantly to be relevant for most diseases and other delivery methods need to be explored to extend the approach to humans. Nevertheless, this work is an exciting first step to using modern gene-editing tools to correct the devastating genetic diseases for which there are currently no options for affected patients."
