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Cell Rep. 2015 Oct 13;13(2):234-41. doi: 10.1016/j.celrep.2015.08.084. Epub 2015 Oct 1.

Reversion of FMR1 Methylation and Silencing by Editing the Triplet Repeats in Fragile X iPSC-Derived Neurons.

Author information

1
Department of Physiology and Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea.
2
The Azrieli Center for Stem Cells and Genetic Research, Department of Genetics, Institute of Life Sciences, the Hebrew University, Givat-Ram, Jerusalem 91904, Israel.
3
The Azrieli Center for Stem Cells and Genetic Research, Department of Genetics, Institute of Life Sciences, the Hebrew University, Givat-Ram, Jerusalem 91904, Israel. Electronic address: nissimb@cc.huji.ac.il.
4
Department of Physiology and Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea. Electronic address: dwkim2@yuhs.ac.

Abstract

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability, resulting from a CGG repeat expansion in the fragile X mental retardation 1 (FMR1) gene. Here, we report a strategy for CGG repeat correction using CRISPR/Cas9 for targeted deletion in both embryonic stem cells and induced pluripotent stem cells derived from FXS patients. Following gene correction in FXS induced pluripotent stem cells, FMR1 expression was restored and sustained in neural precursor cells and mature neurons. Strikingly, after removal of the CGG repeats, the upstream CpG island of the FMR1 promoter showed extensive demethylation, an open chromatin state, and transcription initiation. These results suggest a silencing maintenance mechanism for the FMR1 promoter that is dependent on the existence of the CGG repeat expansion. Our strategy for deletion of trinucleotide repeats provides further insights into the molecular mechanisms of FXS and future therapies of trinucleotide repeat disorders.

PMID:
26440889
DOI:
10.1016/j.celrep.2015.08.084
[Indexed for MEDLINE]
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