RNA Trans-Splicing

One RNA Trans-splicing therapeutic could address 97% of all Rett Syndrome mutations.

Levels of MECP2 protein matter. Too little or too much protein can cause neurological problems. Complicating the situation is the fact that different types of brain cells produce varying levels of MeCP2. Furthermore, due to X chromosome inactivation about half of all cells in females with Rett already make normal amounts of MECP2.

Strategies that fix the underlying errors restore the normal levels of MeCP2 without the possibility of introducing too much protein. Gene editing, RNA editing and RNA trans-splicing fall into this category. Gene replacement does not as it is not possible to control how many copies of a gene enter into any given cell.

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What it is

RNA carries the genetic instructions to make protein. Before the protein can be made certain unnecessary portions of the RNA must be removed. RNA Trans-splicing is a technology that hijacks this naturally occurring phenomenon in order to remove the mutated sections of the MeCP2 RNA and replace it with healthy versions.

Why it matters

RNA trans-splicing is attractive for two main reasons. Firstly, a single RNA trans-splicing therapeutic could treat 97% of all Rett patients. And secondly, it avoids any possibility of producing too much of the MeCP2 protein.

Status

This program is being pursued by Stuart Cobb and Chris Sibley, both from the University of Edinburgh.

One Therapeutic For
Many Mutations

Once RNA is copied from DNA various portions of the RNA are unnecessary and need to be removed. A specialized cellular machine called a splicesome removes the unnecessary regions and splices the remaining sections together to create the final processed RNA that is ready for translating into protein.

Stuart Cobb is pursuing Spliceosome-Mediated RNA Trans-splicing (SMaRT) technology which leverages the normal regulatory mechanisms within cells and should therefore produce the appropriate amount of MeCP2 protein in each brain cell.

SMaRT works by providing an engineered healthy RNA molecule (RNA Trans-splicing Molecule or RTM) and hijacking the spliceosome to ensure that it gets spliced into the RNA in lieu of the diseased sections. The RTM encompasses a large enough section of the RNA to address 97% of all mutations.

Mutations not addressed are those found in exon 1 of the protein. If SMaRT is proven successful a separate RTM could be engineered for the remaining 3%.

RSRT’s support has enabled us to drive forward an innovative form of gene therapy for Rett Syndrome. We are optimistic that a genetic therapy for Rett syndrome will become a reality in the years ahead.

Stuart Cobb, PhD
University of Edinburgh

SMaRT should restore MeCP2 protein to normal levels without the possibility of elevating the protein to toxic thresholds. Importantly, this approach would selectively raise levels of MeCP2 only in the cells where the mutant protein is being made, leaving cells expressing the healthy copy of MECP2 unchanged.

Stuart Cobb has recently recruited a collaborator, Chris Sibley, at the University of Edinburgh, with deep expertise in RNA biology and regulation to help speed this project forward.

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