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Type: Journal article
Title: ARX homeodomain mutations abolish DNA binding and lead to a loss of transcriptional repression
Author: Shoubridge, C.
Tan, M.
Seiboth, G.
Gecz, J.
Citation: Human Molecular Genetics, 2012; 21(7):1639-1647
Publisher: Oxford Univ Press
Issue Date: 2012
ISSN: 0964-6906
Statement of
Cheryl Shoubridge, May Huey Tan, Grace Seiboth, and Jozef Gécz
Abstract: Mutations in the Aristaless-related homeobox (ARX) gene are one of the most frequent causes of X-linked intellectual disability (ID). Several missense mutations, clustered in the paired-type homeodomain of ARX, have been identified. These mutations lead to a range of phenotypes from X-linked lissencephaly with abnormal genitalia to seizure disorders without brain malformations including X-linked infantile spasms with ID (ISSX-ID) and X-linked myoclonic epilepsy with spasticity and ID (XMESID). The effect of these mutations on the DNA-binding and transcriptional activity has been evaluated. Luciferase reporter assays showed altered repression activity of ARX by all mutations, causing brain malformations and ISSX-ID phenotypes, but not by the P353L mutation implicated in a milder phenotype of XMESID. Similarly, transient overexpression of wild-type ARX repressed endogenous expression of known ARX targets, LMO1 and SHOX2, when measured by real-time quantitative polymerase chain reaction. Overall, the molecular consequence of missense mutations correlated well with the severity of the clinical phenotype. In all mutations tested, except P353L, the DNA binding was abolished. Electrophoretic mobility shift assay results were validated using chromatin immunoprecipitation following overexpression of normal and selected missense mutations. Unlike wild-type ARX and clinically less severe mutations, the mutations leading to severe clinical phenotypes were not able to specifically bind to DNA upstream of known, endogenous ARX-regulated genes, LMO1 and SHOX2. In conclusion, the missense mutations in the ARX homeodomain represent loss-of-function mutations, which lead to a reduced or complete loss of DNA binding and as a consequence, a loss of transcriptional repression.
Keywords: Cell Nucleus
DNA-Binding Proteins
Homeodomain Proteins
Transcription Factors
Repressor Proteins
Transcription, Genetic
Protein Structure, Tertiary
Active Transport, Cell Nucleus
Mutation, Missense
HEK293 Cells
LIM Domain Proteins
Rights: © The Author 2011.
DOI: 10.1093/hmg/ddr601
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Paediatrics publications

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