Transcription defects induced by repeat expansion: fragile X syndrome, FRAXE mental retardation, progressive myoclonus epilepsy type 1, and Friedreich ataxia

Abstract
Fragile X mental retardation syndrome, FRAXE mental retardation, Progressive myoclonus epilepsy Type I, and Friedreich ataxia are members of a larger group of genetic disorders known as the Repeat Expansion Diseases. Unlike other members of this group, these four disorders all result from a primary defect in the initiation or elongation of transcription. In this review, we discuss current models for the relationship between the expanded repeat and the disease symptoms.