An unusual type of genetic mutation-trinucleotide repeat expansion-causes Huntington's disease and 14 other neurodegenerative disorders. The first disease-causing TNR expansions were reported only in 1991, so there is still much to learn about their mechanistic roots. In addition to their medical relevance, the genetics of trinucleotide repeats (TNRs) are unique and complex. It is now clear that TNR expansions and contractions occur by multiple genetic mechanisms, including aberrant DNA replication, repair, and possibly gene conversion. The goal of this work is to define more thoroughly how DNA replication and repair contribute to TNR instability in yeast and in primate (human and simian) cells. Mechanistic similarities between yeast and primate cells will help delineate important fundamental properties that govern triplet repeat alterations. For example, the identification of yeast genetic pathways affecting TNRs should help clarify the roles of homologous human pathways. Differences between yeast and primate cells may help resolve certain issues, such as the strong tendency towards expansions in humans which has not been recapitulated in model systems. One unique facet of our proposal is to better understand thresholds. The threshold is a distinctive but enigmatic feature of TNRs where instability changes dramatically over a narrow range of tract lengths. We detected thresholds in both yeast and primate cells, and we propose to dissect them genetically. To help achieve our goal, we developed genetic assays for the direct selection of TNR expansions or contractions. Repeats are inserted into a promoter-reporter construct such that the TNR length determines reporter gene expression. Variations in TNR length are revealed as changes in the reporter phenotype. These selective assays provide several major advantages, including sensitivity, quantitation, and flexibility. We believe the innovative nature of our genetic assays, and our application of those assays to important model systems, will continue to help advance the field of TNR genetics.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM061961-05
Application #
6830491
Study Section
Special Emphasis Panel (ZRG1-CDF-2 (90))
Program Officer
Carter, Anthony D
Project Start
2000-07-01
Project End
2008-06-30
Budget Start
2004-07-01
Budget End
2005-06-30
Support Year
5
Fiscal Year
2004
Total Cost
$286,650
Indirect Cost
Name
University of Nebraska Medical Center
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
168559177
City
Omaha
State
NE
Country
United States
Zip Code
68198
Gellon, Lionel; Razidlo, David F; Gleeson, Olive et al. (2011) New functions of Ctf18-RFC in preserving genome stability outside its role in sister chromatid cohesion. PLoS Genet 7:e1001298
Sommer, Debbie; Stith, Carrie M; Burgers, Peter M J et al. (2008) Partial reconstitution of DNA large loop repair with purified proteins from Saccharomyces cerevisiae. Nucleic Acids Res 36:4699-707
Razidlo, David F; Lahue, Robert S (2008) Mrc1, Tof1 and Csm3 inhibit CAG.CTG repeat instability by at least two mechanisms. DNA Repair (Amst) 7:633-40
Dhar, Alok; Lahue, Robert S (2008) Rapid unwinding of triplet repeat hairpins by Srs2 helicase of Saccharomyces cerevisiae. Nucleic Acids Res 36:3366-73
Claassen, David A; Lahue, Robert S (2007) Expansions of CAG.CTG repeats in immortalized human astrocytes. Hum Mol Genet 16:3088-96
Collins, Natasha S; Bhattacharyya, Saumitri; Lahue, Robert S (2007) Rev1 enhances CAG.CTG repeat stability in Saccharomyces cerevisiae. DNA Repair (Amst) 6:38-44
Daee, Danielle L; Mertz, Tony; Lahue, Robert S (2007) Postreplication repair inhibits CAG.CTG repeat expansions in Saccharomyces cerevisiae. Mol Cell Biol 27:102-10
Farrell, Brian T; Lahue, Robert S (2006) CAG*CTG repeat instability in cultured human astrocytes. Nucleic Acids Res 34:4495-505
Pelletier, Richard; Farrell, Brian T; Miret, Juan Jose et al. (2005) Mechanistic features of CAG*CTG repeat contractions in cultured cells revealed by a novel genetic assay. Nucleic Acids Res 33:5667-76
Bhattacharyya, Saumitri; Lahue, Robert S (2005) Srs2 helicase of Saccharomyces cerevisiae selectively unwinds triplet repeat DNA. J Biol Chem 280:33311-7

Showing the most recent 10 out of 19 publications