Format

Send to

Choose Destination
Int J Mol Sci. 2019 Jun 8;20(11). pii: E2813. doi: 10.3390/ijms20112813.

Immortalization of Different Breast Epithelial Cell Types Results in Distinct Mitochondrial Mutagenesis.

Author information

1
Department of Pathology, University of Washington, Seattle, WA 98195, USA. kwonsu17@uw.edu.
2
Department of Biochemistry, University of Washington, Seattle, WA 98195, USA. ssk773@uw.edu.
3
Department of Pathology, University of Washington, Seattle, WA 98195, USA. henebeck@uw.edu.
4
Department of Pathology, University of Washington, Seattle, WA 98195, USA. ahneun@uw.edu.
5
Institute of Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98109, USA. ahneun@uw.edu.

Abstract

Different phenotypes of normal cells might influence genetic profiles, epigenetic profiles, and tumorigenicities of their transformed derivatives. In this study, we investigate whether the whole mitochondrial genome of immortalized cells can be attributed to the different phenotypes (stem vs. non-stem) of their normal epithelial cell originators. To accurately determine mutations, we employed Duplex Sequencing, which exhibits the lowest error rates among currently-available DNA sequencing methods. Our results indicate that the vast majority of the observed mutations of the whole mitochondrial DNA occur at low-frequency (rare mutations). The most prevalent rare mutation types are C→T/G→A and A→G/T→C transitions. Frequencies and spectra of homoplasmic point mutations are virtually identical between stem cell-derived immortalized (SV1) cells and non-stem cell-derived immortalized (SV22) cells, verifying that both cell types were derived from the same woman. However, frequencies of rare point mutations are significantly lower in SV1 cells (5.79 × 10-5) than in SV22 cells (1.16 × 10-4). The significantly lower frequencies of rare mutations are aligned with a finding of longer average distances to adjacent mutations in SV1 cells than in SV22 cells. Additionally, the predicted pathogenicity for rare mutations in the mitochondrial tRNA genes tends to be lower (by 2.5-fold) in SV1 cells than in SV22 cells. While four known/confirmed pathogenic mt-tRNA mutations (m.5650 G>A, m.5521 G>A, m.5690 A>G, m.1630 A>G) were identified in SV22 cells, no such mutations were observed in SV1 cells. Our findings suggest that the immortalization of normal cells with stem cell features leads to decreased mitochondrial mutagenesis, particularly in RNA gene regions. The mutation spectra and mutations specific to stem cell-derived immortalized cells (vs. non-stem cell derived) have implications in characterizing the heterogeneity of tumors and understanding the role of mitochondrial mutations in the immortalization and transformation of human cells.

KEYWORDS:

breast cancer; duplex sequencing; mitochondrial DNA; mitochondrial tRNA; next generation sequencing; rare mutation; stem cells

PMID:
31181796
DOI:
10.3390/ijms20112813
Free full text

Supplemental Content

Full text links

Icon for Multidisciplinary Digital Publishing Institute (MDPI)
Loading ...
Support Center