A high frequency of mtDNA polymorphisms in HeLa cell sublines

Area of Science:

• Genomics
• Mitochondrial Biology
• Human Evolution

Background:

• HeLa cells are a widely used human cell line with a complex genetic history.
• The original human mitochondrial DNA (mtDNA) Cambridge Reference Sequence (CRS) has known mosaic composition issues.
• Understanding HeLa mtDNA is crucial for cell line authentication and studying mtDNA dynamics.

Purpose of the Study:

• To determine the complete mitochondrial DNA (mtDNA) sequences of founder HeLa cells and derived sublines.
• To characterize the African origin and haplogroup of HeLa mtDNA.
• To investigate the rate of mtDNA sequence divergence and mutation accumulation in HeLa cells.

Main Methods:

• Whole mitochondrial genome sequencing of founder HeLa cells and five sublines.
• Comparative sequence analysis against the revised Cambridge Reference Sequence (CRS).
• Identification and characterization of single nucleotide polymorphisms (SNPs) and sequence alterations.

Main Results:

• HeLa mtDNA belongs to the African L3 haplogroup, featuring 38 core alterations from the CRS.
• Eight novel polymorphisms were identified in the mtDNA coding regions across different HeLa sublines.
• HeLa mtDNA exhibits a significantly higher divergence rate than typical human populations, suggesting relaxed negative selection.

Conclusions:

• HeLa mtDNA sequence provides a clearer reference than the mosaic CRS.
• The accelerated mutation rate in HeLa mtDNA may be linked to relaxed selection or processes similar to somatic mtDNA mutations in cancers.
• Evidence suggests a high number of mtDNA segregation units within HeLa cells, indicating potential for rapid genetic variation.