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Mammalian cells keep algal DNA for 95 generations without selection

Cultured mammalian cells retained large portions of an algal genome, with substantial foreign DNA surviving for 95 generations after selection was withdrawn in one lineage. The peer-reviewed experiment followed transfer from a red alga into hamster and human cell lines. Most algal genes remained silent, while tests involving DNA methylation examined how recipient cells accommodate the material.

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Glass flasks of blue-green culture of the single-celled red alga Cyanidioschyzon merolae stand in a symmetrical row on a sunlit university laboratory windowsill.

Foreign DNA survives repeated cell division

Large stretches of DNA from Cyanidioschyzon merolae, a single-celled red alga, persisted inside mammalian cells in a peer-reviewed laboratory study. Researchers introduced algal material into Chinese hamster ovary cells and a human cancer cell line. The experiments compared cell fusion with engulfment of algal cells; the stable lines examined most closely came from fusion.[1], [2]

Some hamster-derived lines held almost the whole algal genome, whereas human lines retained less. In one selected lineage, substantial transferred DNA remained through 95 generations after researchers removed selection pressure. These findings concern cultured cell models.[1]

The collaboration brought together Japanese universities. Its researchers include Sachihiro Matsunaga at the University of Tokyo, Hiroshi Kimura and Tomokatsu Ikawa at Tokyo University of Science, Hidenori Nishihara at Kinki University, Takuya Sakamoto at Kanagawa University and Yuko Sato at Shizuoka University. The group is investigating ways to introduce genetic information from plants and other organisms into animal cells.[2]

Most transferred genes stay silent

Foreign DNA inside recipient nuclei formed compact, distinct regions. Approximately 96 percent of the algal genes examined had no detectable expression. DNA methylation, a chemical marking process, and chromatin features associated with gene repression accompanied this widespread silence. Retention therefore concerned genetic material rather than demonstrated acquisition of photosynthesis.[1]

Methylation experiment separates entry from persistence

The methylation enzyme Dnmt3a was disabled, reducing the formation of stable colonies. The initial amount of algal DNA reaching nuclei did not fall to the same extent. The researchers thus examined distinct stages of foreign-genome accommodation: early entry into the nucleus and subsequent maintenance across cell generations.[1]

The university announcement places the work within a longer-term synthetic-biology programme, which seeks to build or modify biological systems. Introducing gene clusters for oxygen-producing photosynthesis, nitrogen fixation or useful-substance production remains a future technological aim. The programme envisages using such functions in cultured animal cells. The current experiment follows the persistence and regulation of transferred genetic material, including how an animal-cell nucleus accommodates DNA originating in an evolutionarily distant organism.[1], [2]

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References

  1. News sourceNature CommunicationsMammalian cells retain large stretches of algal DNA across generations↩1↩2↩3↩4↩5
  2. News sourceThe University of TokyoMammalian cells retain large fragments of algal DNA↩1↩2↩3
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