New Gene Editing Tool Reduces Accidental Mutations by Over 70%

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New Gene Editing Tool Reduces Accidental Mutations by Over 70%

Researchers have discovered that by splitting the gene editor used in traditional CRISPR technology, they can create a more precise tool capable of toggling on and off, significantly reducing the chances of unintended genomic mutations.

They say their new tool holds the potential to correct approximately half of disease-causing mutations.

CRISPR, a term now part of everyday vocabulary, represents one of the most significant discoveries of the 21st century, revolutionizing research and treatment of both genetic and non-genetic diseases.

However, a major concern associated with CRISPR technology is “off-target editing,” which refers to unintended, unnecessary, or adverse changes occurring at locations outside the intended genomic target site.

Now, researchers at Rice University have developed a new CRISPR-based gene editing tool that is more precise and dramatically reduces the likelihood of off-target editing.

“Our team embarked on creating an improved version of the gene editing tool that can be toggled on or off as needed, providing unparalleled safety and accuracy,” said the study’s lead author, Hongzhi Zeng. “This tool has the potential to correct approximately half of disease-causing point mutations in our genome. Currently, adenine base editors remain in a continuous ‘on’ state, which may lead to unnecessary genomic changes while achieving the desired corrections in the host genome.”

DNA consists of two intertwined strands, forming a double helix resembling a twisted ladder. The “rungs” of the ladder are made up of base pairs, which consist of two complementary nucleotide bases bound together by hydrogen bonds: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).

New Gene Editing Tool Reduces Accidental Mutations by Over 70%

Base pair mutations, also known as “point mutations,” are the culprits behind thousands of diseases. Traditional CRISPR utilizes adenine base editors (ABE) or cytosine base editors (CBE) to create point mutations at desired sites. In this case, researchers modified ABE.

They split ABE into two independent proteins that remained inactive until the addition of a molecule called sirolimus, also known as rapamycin, a drug with anti-tumor and immunosuppressive properties used to prevent rejection in organ transplants and treat certain cancers.

“After introducing this small molecule, the two independent inactive fragments of the adenine base editor are fused together, becoming active,” explained Zeng. “When the body metabolizes rapamycin, these two fragments separate, rendering the system inactive.”

Researchers found that besides having a shorter active duration compared to the original, intact ABE, their novel split gene editing tool offered additional advantages.

Zeng stated, “Compared to the complete [base] editor, our version reduced off-target editing by over 70% and improved on-target editing accuracy.”

They tested their approach by targeting the PCSK9 gene in the livers of mice. The PCSK9 gene produces a protein that helps regulate cholesterol levels in the blood, making it therapeutically relevant to humans. They packaged the split ABE activated by rapamycin into an adeno-associated virus (AAV) vector and found that it could convert single A●T base pairs on the gene into G●C base pairs. This conversion is particularly useful since G●C mutations to A●T base pairs account for nearly 50% of point mutations associated with human genetic diseases.

The study’s corresponding author, Xue Gao, said, “We hope to see our split genome editing tool eventually applied with higher precision to address human health-related issues.”

The study was published in the journal “Nature Communications.”