Genome complexity: mitochondrial DNA in nuclear DNA (Introduction)

by David Turell , Monday, October 24, 2022, 17:41 (761 days ago) @ David Turell

Ahttps://www.the-scientist.com/news-opinion/mitochondrial-dna-sneaks-into-nuclear-genom... new finding in a large population study

"...in 2018, a study challenged this simple picture of maternal mitochondrial inheritance, describing paternal mtDNA in 17 individuals and suggesting that the organelle might be inherited from either parent. “This was a really wild idea,” Patrick Chinnery, a neurologist at the University of Cambridge in the UK, tells The Scientist. “We had a healthy skepticism about the discovery and went looking for other explanations.”

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"Chinnery and his colleagues’ initial analysis of people testing positive for paternal mtDNA revealed that they hadn’t inherited the organelle itself from their fathers. Instead, pieces of paternal mtDNA had plastered themselves onto the nuclear genome. In the new study, the team scoured whole genome sequences from around 66,000 participants in Genomics England’s 100,000 Genomes Project. The researchers specifically searched for sections of DNA where one half could be mapped to the nucleus and the other half to the mitochondria.

"The search turned up a total of 1,637 mitochondrial fragments in the nuclear genome, with more than 99 percent of people harboring at least one. An average person possesses around five inserts that have not been previously described, suggesting they hopped onto the genome recently in human evolution, the team reports.

"The results suggest that “these transfers of genomic information from the mitochondria to the nucleus are still happening today,” says cell biologist Cole Haynes of the University of Massachusetts Chan Medical School, who was not involved in the study.

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"The study has broad implications for eukaryotic evolution, says Iain Johnston, a computational biologist at the University of Bergen in Norway who was not involved in the work. Instead of mitochondria being frozen in time, their information transfer with the nucleus is “continuous and dynamic,” he adds.

"Fragments of mtDNA were usually found next to binding sites for PRDM9, a protein involved in repairing double-stranded breaks in DNA. This suggests that mtDNA may integrate into the genome at sites where both DNA strands are severed, the authors write in their paper. “Bits of mitochondrial DNA preferentially stick in these holes and act as a kind of Band-Aid to repair the nuclear genome,” says Chinnery."

Comment: An early discovery and how it might affect evolution is an important issue.