New gene editing technique may be helpful in treating inherited blindness

Los Angeles: A new technique that has the potential to treat inherited diseases has been shown for the first time to hinder retinal degeneration in rats with a type of inherited blindness, scientists say.

Researchers from the Cedars-Sinai Board of Governors Regenerative Medicine Institute in Los Angeles focused on inherited retinitis pigmentosa, a degenerative eye disease with no known cure that can lead to blindness.

They used a technique known as CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)/Cas9 to remove a genetic mutation that causes the blindness disease.

CRISPR/Cas9 is adapted from a strategy used by bacteria to fight invading viruses. Though the study involved rats, it is an important milestone because of its potential implications for humans. "Our data show that with further development, it may be possible to use this gene-editing technique to treat inherited retinitis pigmentosa in patients," said Shaomei Wang from the institute's Eye Programme.

Retinitis pigmentosa is a class of diseases in which patients experience night blindness in the early stages, along with atrophy and pigment changes in the retina, constriction of the visual field and eventual blindness.

CRISPR/Cas9 has been in use by genetic researchers for less than five years.
In that time, it has transformed the science of genome editing by making the process easier, more dependable and less expensive. The technique is adapted from a system that bacteria deploy to disable invading viruses.

The bacteria first copy part of the invader's genetic code into a special sequence of ribonucleic acid (RNA), which acts a messenger to carry out the code's instructions.

When the virus returns, the RNA binds to a protein called Cas9, guiding it to the matching gene in the virus. The protein disables the gene. For the study, the researchers designed a CRISPR/Cas9 system to remove a mutated gene that causes photoreceptor cell loss in the eye.

They injected this system into young laboratory rats that had been engineered to model a type of inherited retinitis pigmentosa known as autosomal dominant, which involves this mutated gene. After a single injection, the rats were able to see better compared with controls, as measured by optomotor reflex, which involves turning the head in response to moving stripes of varying degrees of brightness.

"This is the first time CRISPR/Cas9 gene editing has been used to prevent vision loss in a living animal. It is a truly remarkable result and paves the way for more exciting studies and translation to the clinic in the future," said Clive
Svendsen, director of the Board of Governors Regenerative Medicine Institute.
The findings were published in the journal Molecular Therapy.