Genome surgery restores retinal function in mice: study

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Researchers from Columbia University have developed a new technique with a powerful gene editing tool to restore retinal function in mice afflicted by a degenerative retinal disease.

This is the first time researchers have successfully applied CRISPR technology to retinitis pigmentosa, which can lead to loss of sight, according to a paper published in Ophthalmology, the journal of the American Academy of Ophthalmology.

Stephen H. Tsang, a clinical geneticist, and his colleagues sought to create a more agile CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) tool so it can treat more patients, regardless of their individual genetic profile.

They called the technique "genome surgery" because it cuts out the bad gene and replaces it with a normal, functioning gene.

Retinitis pigmentosa is a group of rare inherited genetic disorders caused by one of more than 70 genes. It involves the breakdown and loss of cells in the retina, the light-sensitive tissue that lines the back of the eye

The disease typically starts in childhood and progresses slowly, affecting peripheral vision and the ability to see at night. Most will lose much of their sight by early adulthood and become legally blind by age 40. It is estimated to affect roughly one in 4,000 people worldwide and there is almost no cure for it.

CRISPR has revolutionized the speed and scope with which scientists can modify the DNA of living cells.

Scientists have used it on a wide range of applications, from engineering plants to producing animals. But CRISPR has some flaws to overcome before it can live up to its hype of curing diseases in humans by simply cutting out bad genes and sewing in good ones.

People with autosomal recessive disorders inherit two copies of the mutant gene. When two copies of the gene are mutated, treatment involves a more straightforward, one-step approach of simply replacing the defective gene.

However, in autosomal dominant disorders like retinitis pigmentosa, the person inherits only one copy of a mutated gene from their parents and one normal gene on a pair of autosomal chromosomes. So, the challenge for CRISPR-wielding scientists is to edit only the mutant copy without altering the healthy one.

Tsang and colleagues have come up with an "ablate-and-replace" strategy that can be used to develop CRISPR toolsets for all types of mutations that reside in the same gene and is not exclusive for one type of mutation.

Because Tsang's technique can be applied in a mutation-independent manner, it represents a faster and less expensive strategy for overcoming the difficulty of treating dominant disorders with genome surgery.

Source(s): Xinhua News Agency