Mitochondrion is a critical organelle present in most of the
eukaryotic cells. Commonly known as
the “power house of the cell” it is not only responsible for the production of
ATP, but it is also involved in multiple cellular processes including oxidative
phosphorylation, apoptosis, organizing cell signaling pathways, and regulation
of cell cycle.
Human Mitochondrial DNA (mtDNA) consists of 16,569 bp in a double
stranded circular structure and encodes 37 genes. It is used to study human
migration and evolution. mtDNA is
inherited from the mother, and does not undergo recombination, providing a
molecular clock to study evolutionary changes. Mutations in mtDNA are implicated in
various diseases including metabolic disorders, neurodegenerative diseases, and
cancer. More than 200 different
mutations in the mtDNA have been associated with human diseases. Thus, sequencing the mitochondria can
provide clues to origins of diseases as well as help delineate changes due to
aging as well as somatic and germ-line mutations that might cause
disorders. In order to sequence the
mtDNA, it is important to isolate the mtDNA effectively without any nuclear DNA
contamination. Owing to the immense
size difference between human nuclear DNA (6 billion bp) and human mtDNA (16
kb), small amounts of nuclear DNA contamination can lead to most of the DNA
sequences being of nuclear origin.
All current methods of isolating mitochondrial DNA involve first
isolating the organelle and then purifying its DNA using standard protocols.
These methods involve steps that
lead to loss of material and destruction of the mtDNA and substantial nuclear
DNA contamination. The mtDNA has copies in the nuclear genome, so contamination
of the nuclear DNA will lead to erroneous conclusions on mtDNA variants.
Therefore, a way to isolate mitochondrial DNA without contamination from nuclear
DNA is needed to diagnose and study disease states.
Ravi Sachidanandam and his group at the Icahn School of Medicine at Mount Sinai
have devised a method to efficiently and rapidly isolate mitochondrial DNA in
high purity. This method has been
applied in a several cell types and validated by sequencing.
Patent Status: Patent