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Title: The mismatch repair system protects against intergenerational GAA repeat instability in a Friedreich ataxia mouse model
Authors: Ezzatizadeh, V
Pinto, RM
Sandi, C
Sandi, M
Al-Mahdawi, S
Te Riele, H
Pook, MA
Keywords: Friedreich ataxia;FRDA;Frataxin;GAA trinucleotide repeat;Transgenic mouse model;Mismatch repair;MMR;Msh2;Msh3;Msh6;Pms2
Issue Date: 2012
Publisher: Elsevier
Citation: Neurobiology of Disease, 46(1): 165 - 171, Apr 2012
Abstract: Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a dynamic GAA repeat expansion mutation within intron 1 of the FXN gene. Studies of mouse models for other trinucleotide repeat (TNR) disorders have revealed an important role of mismatch repair (MMR) proteins in TNR instability. To explore the potential role of MMR proteins on intergenerational GAA repeat instability in FRDA, we have analyzed the transmission of unstable GAA repeat expansions from FXN transgenic mice which have been crossed with mice that are deficient for Msh2, Msh3, Msh6 or Pms2. We find in all cases that absence of parental MMR protein not only maintains transmission of GAA expansions and contractions, but also increases GAA repeat mutability (expansions and/or contractions) in the offspring. This indicates that Msh2, Msh3, Msh6 and Pms2 proteins are not the cause of intergenerational GAA expansions or contractions, but act in their canonical MMR capacity to protect against GAA repeat instability. We further identified differential modes of action for the four MMR proteins. Thus, Msh2 and Msh3 protect against GAA repeat contractions, while Msh6 protects against both GAA repeat expansions and contractions, and Pms2 protects against GAA repeat expansions and also promotes contractions. Furthermore, we detected enhanced occupancy of Msh2 and Msh3 proteins downstream of the FXN expanded GAA repeat, suggesting a model in which Msh2/3 dimers are recruited to this region to repair mismatches that would otherwise produce intergenerational GAA contractions. These findings reveal substantial differences in the intergenerational dynamics of expanded GAA repeat sequences compared with expanded CAG/CTG repeats, where Msh2 and Msh3 are thought to actively promote repeat expansions.
Description: Copyright @ 2012 Elsevier. The article can be accessed from the link below.
This article has been made available through the Brunel Open Access Publishing Fund.
ISSN: 0969-9961
Appears in Collections:Biological Sciences
Brunel OA Publishing Fund
Dept of Life Sciences Research Papers

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