title: Trinucleotide expansion in disease: why is there a length threshold?
abstract: Trinucleotide repeats (TNRs) expansion disorders are severe neurodegenerative and neuromuscular disorders that arise from inheriting a long tract (30-50 copies) of a trinucleotide unit within or near an expressed gene (Figure 1a). The mutation is referred to as 'trinucleotide expansion' since the number of triplet units in a mutated gene is greater than the number found in the normal gene. Expansion becomes obvious once the number of repeating units passes a critical threshold length, but what happens at the threshold to render the repeating tract unstable? Here we discuss DNA-dependent and RNA-dependent models by which a particular DNA length permits a rapid transition to an unstable state.
authors.affiliation: Department of Bio and Fermentation Convergence Technology, Kookmin University, 136-702, Republic of Korea.
authors.forename: Do-Yup
authors.initials: DY
authors.lastname: Lee
authors.affiliation: Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA. Electronic address: ctmcmurray@lbl.gov.
authors.forename: Cynthia T
authors.initials: CT
authors.lastname: McMurray
mesh_terms: D004247:DNA / Q000235:genetics / Q000378:metabolism; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008957:Models, Genetic; D019636:Neurodegenerative Diseases / Q000235:genetics*; D009468:Neuromuscular Diseases / Q000235:genetics*; D012313:RNA / Q000235:genetics / Q000378:metabolism; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: D012313:RNA; D004247:DNA