Genetic Diseases Current Affairs - 2019
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Scientists from The Broad Institute and Massachusetts Institute of Technology in US have developed RNA Editing for Programmable A to I Replacement (REPAIR), a new gene editing tool therapies that can reverse disease-causing mutations in humans.
REPAIR gene editing tool can tweak an individual RNA ‘letters’ in human cells without making changes to entire genome and can have profound potential as a tool for both research and disease treatment.
REPAIR is based on gene editing tool CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) that can be used to modify DNA in cells. The new tool can change single RNA nucleosides in mammalian cells in a programmable and precise fashion.
To create REPAIR, scientists had systematically profiled CRISPR-Cas13 enzyme family for potential editor candidates. They had selected enzyme called PspCas13b from Prevotella bacteria which was most effective at inactivating RNA.
Scientists had engineered deactivated variant of PspCas13b enzyme that binds to specific stretches of RNA but lacks its scissor-like activity and fused it to a protein called ADAR2, which changes nucleoside adenosine to inosine in RNA transcripts.
REPAIR has ability to reverse disease-causing mutations at RNA level, as well as other potential therapeutic and basic science applications. It paves way for therapies that can reverse mutations and has profound potential as tool for both research and disease treatment.
REPAIR has ability to target individual RNA letters or nucleosides, switching adenosines to inosines. These letters are involved in single-base changes which are known to regularly cause genetic disease in humans. For ex, in human disease, a mutation from G to A is extremely common and these alterations have been implicated in for cases of focal epilepsy, Parkinson’s disease and Duchenne muscular dystrophy.
Thus, it can reverse impact of any pathogenic G-to-A mutation regardless of its surrounding nucleotide sequence, with potential to operate in any cell type.
RNA editing using REPAIR offers safer, more flexible way to make corrections in cell unlike permanent changes to genome required for DNA editing using CRISPR-Cas9 gene editing technology. REPAIR can also fix mutations without tampering with genome as RNA naturally degrades making it potentially reversible fix.