Molecular Consequences of Myotonic Dystrophy Type 2-causing CCTG DNA Repeats

Project Summary Myotonic dystrophy type 2 is a genetic disorder characterized by progressive muscle wasting and weakness that is caused by long CCTG DNA repeats. Individuals can have up to 11,000 CCTG repeats within the CNBP gene responsible for disease. The proposed project will elucidate the molecular

mechanisms of CCTG repeat instability with a specific focus on large-scale contractions and DNA breakage using budding yeast S. cerevisiae as a model organism. Understanding the molecular mechanisms of contractions is important to evaluate whether manipulating this process would be a viable approach to treat repeat expansion disease. We will evaluate the role of genes involved in the

mismatch repair pathway on large-scale contractions. We will carry out genetic analysis of double mutants and specific point mutants that are candidates for study because of their role in protein binding domains or implications from human genome wide association studies. Recently, my lab showed that

disease-associated lengths of CCTG repeats cause chromosomal fragility in vivo. This project will elucidate how variables such as genomic location and DNA replication dynamics affect CCTG DNA fragility, which has important implications for understanding the mechanisms of expansions and chromosomal translocations. Finally, we will investigate CCTG repeat-associated gene expression from

a distinct angle by characterizing differential effects of repeat length and orientation on steady-state transcript levels and RNA splicing. Altogether, the proposed studies will provide fundamental insights into the molecular mechanisms of DNA replication, repair, and transcription that underlie the etiology of

the tetranucleotide expansion disease DM2.