Gene editing fixes mutation behind blood disease


Hope for sickle cell disease patients, with blood stem cells altered using CRISPR-Cas9 technique and implanted in mice. Amy Middleton reports.


Sickle cell disease is marked by malformed red blood cells, severely shortening the life of patients.
Omikrom / Getty Images

Patients living with sickle cell disease may one day find respite in gene editing, a new study from the US reveals.

Sickle cell disease (SCD) is a genetic disorder that affects the haemoglobin – oxygen-carrying molecules in our blood – of hundreds of thousands of people worldwide. The disease can lead to anaemia, pain, organ failure and stroke, and SCD patients have a lifespan of just 40 to 60 years.

Now, a potential new treatment could be in the works, thanks to a development in genetic editing.

Mark DeWitt from the University of California, Berkeley, and colleagues used a precise technique in genetic modification called CRISPR-Cas9 to alter the problem cells that cause SCD.

CRISPR is a process that allows researchers to slice, add and remove genes from a cell’s genome, using a bacterially derived protein called Cas9 and ‘molecular scissors’ that effectively cut DNA into pieces.

In SCD patients, haemoglobin molecules sometimes stick together to distort red blood cells into sickle-like shapes, which can get stuck in blood vessels, causing serious damage.

Gene editing offers a way to treat the precursors to red blood cells known as haematopoietic stem cells.

Using CRISPR-Cas9, the team successfully altered these problem precursor cells in a sample of blood lifted from SCD sufferers, and, for the first time, edited enough stem cells to have a significant effect on symptoms.

Next, researchers implanted the edited cells into mice to ensure they had the longevity to make an impact. The stem cells stayed put four months which the researchers say is a benchmark time-frame for potential benefits to patients.

“We’re very excited about the promise of this technology,” says Jacob Corn, senior author on the study.

“There is still a lot of work to be done before this approach might be used in the clinic, but we’re hopeful that it will pave the way for new kinds of treatment for patients with sickle cell disease.”

Before the stem cells can be applied clinically, the researchers emphasise larger-scale studies on mice are essential, as well as comprehensive safety checks and optimisations.

If the research continues, the researchers say this method could have benefits for a host of other blood-based conditions, potentially even HIV.

“Sickle cell disease is just one of many blood disorders caused by a single mutation in the genome,” explains Corn.

“It’s very possible that other researchers and clinicians could use this type of gene editing to explore ways to cure a large number of diseases.”

The study was published in Science Translational Medicine.

  1. http://stm.sciencemag.org/lookup/doi/10.1126/scitranslmed.aaf9336
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