ABSTRACT
Accumulation of somatic mutations over the lifetime of an individual can be facilitated by genetic factors like impaired DNA repair pathways, and by exogenous DNA damaging agents.  The large-scale cancer genome sequencing projects have demonstrated that mutation load and spectra in cancer genomes are characteristic of the cell and type tissue, location in the body, and environmental exposures.  However, accurate measurements of lifetime accumulation of genetic changes attributable to these factors in healthy human cells are lacking.  Previously, we demonstrated that mutation loads and spectra in the genomes of single skin fibroblast-derived clonal lineages from two healthy individuals resemble cancers.  We showed that while, all samples carry CàT changes at CpG dinucleotides (the aging-associated mutation signature), cells from sun-exposed body sites carry a higher mutation burden with a predominant UV–induced mutation signature as compared to unexposed sites.  Somatic mutation load also can be used as a measure of the ability of the cells to repair lesions.  As such, we hypothesize that individuals with potentially deleterious polymorphisms in DNA repair genes, would have higher mutation loads and different mutational spectra than carriers of functional alleles.  We have obtained DNA from >3000 individuals via the NIEHS Environmental Polymorphisms Registry.  Amplification of potential DNA repair genes with asymmetric barcodes, and sequencing via the Pacific Biosciences single molecule real-time sequencing technology is used for identifying healthy individuals with common and rare deleterious alleles in the given gene.  Sequencing single cell-derived clones from these individuals provides the range of mutation loads, and predominant mutation signatures attributable to defects in DNA repair pathways across a population.

Host: Kirill Lobachev, Ph.D.