Sickle Cell Disease 2016: Scientists Use CRISPR In Mice To Show Gene-Editing May Someday Treat Blood Disorder
Researchers have moved a substantial step forward toward treating an intractable blood disorder, and it’s all thanks to the revolutionary gene-editing technique known as CRISPR/Cas 9.
As explained in the video above, released by the University of California, Berkeley, a coalition of scientists teamed up to use the technique on lab mice. They selectively edited both copies of the gene that gives rise to sickle cell disease in human hematopoietic stem cells — the earliest stage of what eventually becomes red blood cells — and transplanted them into mice. Four months later, they found that 2 percent of the cells left behind in the mice’s bone marrow had retained the editing. Though that percentage may seem miniscule, it would almost certainly provide some degree of relief for people with the condition, and likely only represents the bare minimum of CRISPR's capabilities.
The team’s findings were published in Science Translational Medicine.
“I’m extremely excited, because we haven’t been trying this for very long. You know, we will get better,” said lead author Mark Dewitt, a researcher at UC Berkeley’s Innovative Genomics Initiative, in the video above. “And what we have right now is already — if we can scale it up and make sure it works well — good enough to form the basis of a clinical trial to cure sickle cell with gene editing.
In addition to UC Berkeley, the study team included scientists from the University of California San Francisco Benioff Children’s Hospital Oakland Research Institute (CHORI) and the University of Utah School of Medicine.
CRISPR stands for “Clustered Regularly Interspaced Short Palindromic Repeats.” The term describes a section of repeating DNA that contains unique DNA bits nestled within its open spaces. Certain microorganisms, like bacteria, use CRISPR as a type of immune system, with the bits made out of past viral foes. When the bacteria comes across that virus again, its Cas (CRISPR-associated protein) attacks the hapless invader, slicing its DNA into ribbons. Scientists discovered they could rejig the CRISPR/Cas system using guide RNA to target most any piece of DNA, allowing them to precisely edit the genes of a cell with much more ease and affordability than previous techniques.
The gene responsible for sickle cell makes someone’s body produce defective hemoglobin, which in turn creates abnormally shaped red blood cells. Usually shaped like a crescent, these cells often get stuck in the bloodstream or quickly die off, depriving the body of oxygen and causing fits of pain, fatigue, and other chronic issues. But people with just one healthy copy of the gene produce relatively healthy hemoglobin and experience few, if any symptoms. So even a partial fix in stem cells could amount to a lasting virtual cure.
Aside from sickle cell, researchers elsewhere have provided evidence that CRISPR could help treat genetic disorders like muscular dystrophy. And earlier this July, the world’s first human clinical trial involving the technique (to treat lung cancer) was approved in China. A similar U.S. trial is close to fruition, pending further approval, and may begin as early as the end of this year.
It seems no matter where you go, CRISPR is poised to make a far-reaching impact on our health, and sooner than any of us may have imagined.
Source: Dewitt M, Magis W, Bray N, et al. Selection-free genome editing of the sickle mutation in human adult hematopoietic stem/progenitor cells. Science Translational Medicine. 2016.