CRISPR Tool Reactivates Silenced FMR1 Gene of Fragile X Syndrome in Human Stem Cells

Using a gene editing tool, researchers successfully reactivated the FMR1 gene — which is silenced in fragile X syndrome patients — in human stem cells. This news was reported on August 16, 2018 in an article in Fragile X News Today written by Diogo Pinto. The open-access scientific article, “Targeted Reactivation of FMR1 Transcription In Fragile X Syndrome Embryonic Stem Cells,” was published online on August 15, 2018 in Frontiers in Molecular Neuroscience. Fragile X syndrome (FXS) is caused by a mutation in the FMR1 gene that results from the addition of three extra nucleotides — the building blocks of DNA — to its sequence. This is called a CGG repeat, which varies in number from 5 to 55 in healthy individuals. The more repeats, the higher the risk of developing the disease. This mutation results in the loss of the fragile X mental retardation protein (FMRP), the protein that is produced by the FMR1 gene. Treatments tested so far attempt to compensate for the loss of the FMRP protein and usually target only one of the protein’s functions. However, they have proven insufficient to treat the disease. Researchers believe one potential explanation for the lack of success in human clinical trials to date is that the different functions played by FMRP in nerve cells and other cell types may be difficult to correct with any treatment targeting only one dysregulated molecular pathway. In the newly reported therapeutic approach, researchers from the University of Michigan and the VA Ann Arbor Healthcare System used the CRISPR/Cas9 gene editing technology to target the CGG repeat that causes the mutation, and reactivates transcription of the silenced FMR1 gene. The CRISPR/Cas9 system is a genome editing tool that can edit parts of the genome by removing, adding, or altering sections of the DNA sequence.
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