title: Ups and Downs: Mechanisms of Repeat Instability in the Fragile X-Related Disorders.
abstract: The Fragile X-related disorders (FXDs) are a group of clinical conditions resulting from the expansion of a CGG/CCG-repeat tract in exon 1 of the Fragile X mental retardation 1 (FMR1) gene. While expansions of the repeat tract predominate, contractions are also seen with the net result being that individuals can show extensive repeat length heterogeneity in different tissues. The mechanisms responsible for expansion and contraction are still not well understood. This review will discuss what is known about these processes and current evidence that supports a model in which expansion arises from the interaction of components of the base excision repair, mismatch repair and transcription coupled repair pathways.
authors.affiliation: Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, Building 8, Room 2A19, National Institutes of Health, 8 Center Drive MSC 0830, Bethesda, MD 20892-0830, USA. xiaonan.zhao@nih.gov.
authors.forename: Xiao-Nan
authors.initials: XN
authors.lastname: Zhao
authors.affiliation: Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, Building 8, Room 2A19, National Institutes of Health, 8 Center Drive MSC 0830, Bethesda, MD 20892-0830, USA. ku@helix.nih.gov.
authors.forename: Karen
authors.initials: K
authors.lastname: Usdin
keywords: Fragile X syndrome; Fragile X-related disorders; base excision repair; mismatch repair; repeat expansion; transcription coupled repair