First DNA Sequence From a Single Mitochondria


Source: Perelman School of Medicine at the University of Pennsylvania

Summary: Researchers have found that that DNA sequences between mitochondria within a single cell are vastly different.


Mitochondria are semi-autonomous organelles which participate in a wide range of cellular functions such as ATP production, oxidant stress and calcium signaling. The thing which makes them unique is that they contain their genome in multiple copies called as mitochondrial DNA (mtDNA) which has the ability to encode a subset of proteins required for mitochondrial function. Single mitochondria can contain 10 or more different genomes with hundred to thousands of mitochondria residing in each cell. Mutations accumulating in mtDNA give rise to numerous mitochondrial diseases. These mutations have been found in colorectal, ovarian, breast, bladder, kidney, lung and pancreatic tumors. Researchers from the Perelman School of Medicine at the University of Pennsylvania found that DNA sequences between mitochondria within a single cell are vastly different. The study findings were published in the journal Cell Reports.

Sequencing of Mitochondria

Manual isolation of a single live mitochondrion. The mitochondria can be seen under a microscope where a thin glass tube can be used to isolate the mitochondria from the dendrite region of the mouse neuron. Credit: Jacqueline Morris and Jaehee Lee, Perelman School of Medicine, University of Pennsylvania

The researchers extracted single mitochondrion and then extracted its mtDNA. When the mutations present in a single mitochondrion of an individual mouse and human cells were compared, they found that mouse cells had more accumulated mutations compared to human cells. The process of mtDNA mutations accruing over a lifetime generally happens somewhat differently in each person. The study reported similarities and differences in separate mtDNA in the same cell and also between different cell types such as neurons and astrocytes in the brain. This data helps in improving diagnosis of neurological diseases and pinpointing patients who may develop certain conditions especially the elderly in which mtDNA mutations have been found to accumulate with age.

Senior author James Eberwine said, “This roadmap of the location and number of mutations within the DNA of a mitochondrion and across all of a cell’s mitochondria is where we need to start.”


More Information: Jacqueline Morris et al, “Pervasive within-Mitochondrion Single-Nucleotide Variant Heteroplasmy as Revealed by Single-Mitochondrion Sequencing”, Cell Reports (2017). DOI: http://dx.doi.org/10.1016/j.celrep.2017.11.031


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