To "turn" mutant proteins into healthy proteins, Liu Ruqian's team's latest "Nature" brings new breakthroughs in gene therapy

▎Editor of WuXi AppTec's content team Today, the latest batch of "Nature" papers is online as scheduled.
One of the papers from the team of Professor David Liu, a big cow in the CRISPR field, has attracted the attention of the pharmaceutical industry.

Using the single-base editing method, the team provides a new idea for gene therapy, which is expected to open up a whole new world of rare genetic disease treatment.

This study is aimed at sickle cell disease (SCD).

This is an autosomal dominant genetic disease, the cause is quite clear-due to genetic mutations, the patient's body cannot produce normal hemoglobin.

At present, many biopharmaceutical companies are developing gene therapies to treat this disease: some companies want to introduce genes encoding normal hemoglobin into patients to reshape the patient’s ability to make these hemoglobins; other companies are taking a different approach and want to recover.
The body's ability to produce fetal hemoglobin.

This hemoglobin also has the ability to transport oxygen, but often stops production in infancy.

No matter which method is used, good results have been achieved in clinical trials, and a functional cure for SCD can be achieved.

However, these methods either use lentivirus as a gene carrier or use CRISPR technology.
These theoretically may bring potential therapeutic risks, such as inserting genes into random positions on chromosomes, disrupting the function of tumor suppressor genes, or causing DNA double Strand breaks, leading to unexpected chromosomal rearrangements.

At present, scientists have not observed these phenomena in clinical trials, but there are theoretical hidden dangers after all.

▲Professor Liu Ruqian, one of the leaders of this research (photo source: Broad Institute official website; Credit: Casey Atkins Photography, courtesy of Broad Institute) This paper provides a brand new idea.

SCD is a disease caused by a single base mutation.
The cause is the mutation of adenine (A) to thymine (T).

As early as a few years ago, Liu Ruqian's team had developed a single-base editing technology to accurately edit bases without breaking the DNA double helix.

Unfortunately, this tool still has limitations.
You can't do the opposite and change T back to A.

From a rare hemoglobin variant in Indonesia, researchers have found new ideas.

This variant has adenine mutated to cytosine (C), but it can still maintain the normal function of hemoglobin.

The modification of T to C can be achieved through single-base editing.

In human cells, the researchers conducted a proof-of-concept.

They isolated hematopoietic stem cells and progenitor cells from SCD patients, performed single-base editing, and found that 80% of mutant hemoglobin can be turned into functional mutant hemoglobin.

The researchers also transplanted these stem cells into immunodeficient mice.

After 16 weeks, functional variant hemoglobin still accounted for 68%, and the corresponding symptoms of mice were reduced by 5 times, indicating that single-base editing has achieved long-lasting therapeutic effects.

▲Single-base editing of mouse hematopoietic stem cells can reverse their symptoms (picture source: reference [1]) In another experiment, researchers isolated hematopoietic stem cells from a humanized SCD mouse model And progenitor cells, perform single-base editing, and then enter these cells into irradiated mice.

Also after 16 weeks, 79% of the blood of these mice was variant hemoglobin with normal functions.

Similarly, the symptoms of these mice were reduced by a factor of three.

Taken together, the hematological parameters of these mice are also close to normal.

"It is a simpler and more direct method to convert disease-causing gene mutations into gene mutations that are known to keep people healthy.

" Professor Liu Ruqian said.

At the end of the abstract, the researchers pointed out that it is possible to eliminate the disease-causing hemoglobin through single-base editing and produce healthy and functional hemoglobin.

This can circumvent the potential problems caused by the CRISPR/Cas9 system and minimize the risk.

Some other gene therapy experts also pointed out that the research is novel compared with other technologies and has great potential.

Reference materials: [1] Newby, GA, Yen, JS, Woodard, KJ et al.
Base editing of haematopoietic stem cells rescues sickle cell disease in mice.
Nature (2021).
https://doi.
org/10.
1038/s41586- 021-03609-w[2] Relying on an ultra-rare variant, David Liu unveils a new approach to editing sickle cell, Retrieved June 2, 2021, from https://endpts.
com/relying-on-an-obscure- variant-david-liu-unveils-a-new-approach-to-editing-sickle-cell/