Abstract
The mitochondrial DNA (mtDNA) sequences of two commonly used human cell lines, HepaRG and SJCRH30, were determined. HepaRG originates from a liver tumor obtained from a patient with hepatocarcinoma and hepatitis C while SJCRH30 originates from a rhabdomyosarcoma patient tumor. In comparison to the revised Cambridge Reference Sequence, HepaRG and SJCRH30 mtDNA each contain 14 nucleotide variations. In addition to an insertion of a cytosine at position 315 (315insC), the mtDNA sequences from both cell types share six common polymorphisms. Heteroplasmic variants were identified in both cell types and included the identification of the 315insC mtDNA variant at 42 and 75% heteroplasmy in HepaRG and SJCRH30, respectively. Additionally, a novel heteroplasmic G13633A substitution in the HepaRG ND5 gene was detected at 33%. Previously reported cancer-associated mtDNA variants T195C and T16519C were identified in SJCRH30, both at homoplasmy (100%), while HepaRG mtDNA harbors a known prostate cancer-associated T6253C substitution at near homoplasmy, 95%. Based on our sequencing analysis, HepaRG mtDNA is predicted to lie within haplogroup branch H15a1 while SJCRH30 mtDNA is predicted to localize to H27c. The catalog of polymorphisms and heteroplasmy reported here should prove useful for future investigations of mtDNA maintenance in HepaRG and SJCRH30 cell lines.
Highlights
More than 1000 human mitochondrial proteins are encoded by the nuclear genome and must be imported into mitochondria following translation on cytoplasmic ribosomes [1]
Mitochondrial fusion and fission allow for complementation of heteroplasmic mitochondrial DNA (mtDNA) genes in trans; as the proportion of wild-type to mutant mtDNA decreases, the ability of a cell to produce energy via oxidative phosphorylation (OXPHOS) can decline [15]
Enrichment of mtDNA heteroplasmic variants have been reported in certain cancers [16,17], and heteroplasmic variants have been identified in human peripheral blood mononuclear cells, 501T fibroblast cell lines, and cancer-derived cell lines [14,18]
Summary
More than 1000 human mitochondrial proteins are encoded by the nuclear genome and must be imported into mitochondria following translation on cytoplasmic ribosomes [1]. A single human cell can contain several thousand copies of mtDNA that are distributed within hundreds of individual mitochondria or throughout an elaborate mitochondrial reticular network [10,11,12]. Mitochondrial fusion and fission allow for complementation of heteroplasmic mtDNA genes in trans (e.g., a wild-type gene product complementing a mutant gene product); as the proportion of wild-type to mutant mtDNA decreases, the ability of a cell to produce energy via oxidative phosphorylation (OXPHOS) can decline [15]. Enrichment of mtDNA heteroplasmic variants have been reported in certain cancers [16,17], and heteroplasmic variants have been identified in human peripheral blood mononuclear cells, 501T fibroblast cell lines, and cancer-derived cell lines [14,18]
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