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Dataset ID
Description
Technology
Samples
EGAD00001008764
The single base substitution mutational signatures SBS2 and SBS13, likely caused by APOBEC cytosine deaminases, are common in many human cancer types. However, the stimulus activating APOBEC mutagenesis is unknown and understanding of when it occurs in the progression from normal to cancer cell is limited. Here, as part of a wider survey of human tissues, we whole genome sequenced 342 microdissected normal epithelial crypts from the small intestines of 39 individuals. SBS2/13 mutations were present in 17% normal small intestine crypts and were likely due to APOBEC3A activity. Localised clusters of SBS2/13 mutations (kataegis) were also commonly found. APOBEC mutation burdens were variable between individuals and between crypts from the same individual. Crypts with SBS2/13 often had immediate crypt neighbours without SBS2/13, suggesting that the underlying cause of SBS2/13 is cell-intrinsic rather than a widely distributed microenvironmental exposure, or needs to be permitted by cell-intrinsic conditions. APOBEC mutagenesis occurred throughout the human lifespan, including in young children, and was episodic with a small number of episodes occurring during the life history of a single cell. The results indicate that APOBEC mutagenesis is more common in the small intestine epithelium than in many other cell types, and is an episodic process in vivo initiated or permitted by cell intrinsic factors.
HiSeq X Ten
Illumina NovaSeq 6000
31
EGAD00001015828
Lifestyle, environmental and other exposures to exogenous mutagens generate somatic mutations in normal human cells in vivo and increase cancer risk. However, the global repertoire of exogenous mutagen exposures is uncertain. Using single-molecule duplex sequencing of normal kidney (n=319) and blood (n=272) samples from 10 countries, we show that kidney proximal tubule cells exhibit higher mutation rates than most normal cell types despite low cell division rates. Compared to cells from kidney glomeruli, medulla, distal tubules, or peripheral blood, proximal tubule cells show marked enrichment of mutational signatures due to the exogenous carcinogenic mutagens, aristolochic acids, and of several signatures of unknown causes. The results suggest the existence of multiple, common, systemically circulated mutagens affecting human populations and indicate that the genomes of kidney proximal tubule cells report such exposures with high sensitivity.
HiSeq X Ten
Illumina NovaSeq 6000
333
EGAD00001016809
Mutations accumulate in normal human cells over the course of an individual’s lifetime. Early studies have shown differences in mutation rates and mutational signatures between cell types, but the range of tissues investigated has been constrained by limitations of DNA sequencing technologies. Here, we employ genome-wide NanoSeq single molecule duplex sequencing to survey the mutation landscapes of 53 normal cell types and tissue structures purified by laser-capture microdissection and flow sorting. Single base substitution mutation rates ranged from ~3/year in spermatogonia and sperm contributing to the male germline, to ~20/year in postmitotic neurons, ~50/year in mitotically active colorectal epithelial cells, ~60/year in kidney proximal tubule cells and hepatocytes, 100s/year in ultraviolet light exposed skin epidermis and from 10-50/year across the other cell types. At least 18 single base substitution and 9 small insertion and deletion mutational signatures contribute to mutation burdens, some to all cell types, some to subsets of cell types and others to a single cell type. Known exogenous mutagen exposures and endogenous mutational processes account for some mutational signatures but the origins and mechanisms underlying many are uncertain. This comprehensive survey of mutagenesis provides a foundation for understanding somatic evolution in human cell populations in health and disease.
HiSeq X Ten
Illumina NovaSeq 6000
6
