The long-term goal of this proposal is to determine whether aging is associated with perturbations in the balance of double strand break (DSB) repair by homologous recombination (HR). DSBs accumulate in aging and senescent cells, and homozygous mutations in HR genes such as those causing Bloom's syndrome, Werner syndrome or Fanconi anemia are associated with premature aging, age-related disease and cancer predisposition. However, it is not known whether the accumulation of genetic aberrations and DNA breaks in normal aging cells is caused by a primary defect in DSB repair or whether it reflects secondary changes associated with aging. A small number of studies in model organisms suggest that aging destabilizes HR control at the expense of error-free short tract gene conversion and in favor of error-prone long tract gene conversion, but aging mammalian cells have not yet been studied in this regard. To address this question, we have developed a mouse strain carrying a new HR reporter that allows rapid flow cytometric analysis of short- and long-tract gene conversion in living cells. We will use this new tool to determine whether aging in mice is associated with skewing of HR in favor of error-prone pathways such as long tract gene conversion.
Our Specific Aims are:
Aim 1. Determine the impact of aging on the quality of HR in freshly explanted primary mouse fibroblasts.
Aim 2. Determine the impact of aging on the quality of HR in freshly explanted erythroid progenitors. Success in the work described in this proposal will reveal new mechanisms underlying phenotypes associated with aging.
Aging is associated with increased levels of DNA breakage and chromosome rearrangements, which may contribute to age-related ailments including increased cancer risk and 'anemia of the aged'. One possible explanation for this as yet unexplained age-related phenomenon is that the cell's systems for repairing DNA breaks may become less efficient with increasing age. Our experiments will address this long-standing and important question, the answer to which will have wide ramifications for our understanding of age-related disease.
| Willis, Nicholas A; Frock, Richard L; Menghi, Francesca et al. (2017) Mechanism of tandem duplication formation in BRCA1-mutant cells. Nature 551:590-595 |
| Willis, Nicholas A; Rass, Emilie; Scully, Ralph (2015) Deciphering the Code of the Cancer Genome: Mechanisms of Chromosome Rearrangement. Trends Cancer 1:217-230 |
