Hello!
Thank you for watching this video on mitochondrial disorders.
I am a member of the GenomeConnect and ClinGen Patient Data Sharing Program team.
Each one of us has more than a trillion cells that make up our bodies.
Our cells contain our genetic material, called DNA.
DNA acts as our body s instruction manual.
Most of our genetic material is tightly wound up into structures called chromosomes and
stored in the part of the cell called the nucleus.
This genetic material is called our nuclear DNA.
Our DNA is our body s instruction manual, telling our bodies how to develop and function.
Each instruction is called a gene.
In addition to our nucleus that contains most of our DNA (represented by the blue in the
inner circle), our cells also contain other structures, called organelles.
These structures have other jobs in our cells.
One of those structures is called a mitochondrion, or mitochondria if we are talking about more
than one.
The mitochondria are represented by the green ovals.
Mitochondria are the energy factory of our cells.
They take the oxygen and food we eat and turn it into energy that our cells can use.
Aside from our nuclear DNA we already talked about, mitochondria also have their own genetic
material.
We call this mitochondrial DNA.
This mitochondrial DNA or mtDNA also makes proteins that are needed for mitochondria
function.
Some of our nuclear DNA codes for proteins that are important for our mitochondria.
There are thousands of mitochondria in most of our cells, all creating the energy they
need to function properly.
When mitochondria do not make enough energy for our cells, it may impact one or several
organs throughout the body like the heart, brain, or muscles.
We call this a mitochondrial disorder.
Mitochondrial disorders can be present at birth or develop at any time in an individual
s life.
Mitochondrial disorders are often genetic, meaning they are a result of certain changes
in our genetic material, called variants, that impact how the gene works in our body.
It is estimated that 1 out of every 5,000 individuals has a genetic mitochondrial disorder,
making mitochondrial disorders rare.
There are two main ways that genetic variants can affect how our mitochondria work: variants
in our mitochondrial DNA or variants in our nuclear DNA.
First, we will talk more about how genetic variants in our mitochondrial DNA can cause
mitochondrial disorders.
During fertilization, an egg and sperm cell come together.
The egg cell is much larger than the sperm and carries mitochondria.
Both the sperm and egg carry nuclear DNA.
Sometimes the mitochondria passed from the parent in their egg cell might have a variant
that affects mitochondrial function.
In other cases, variants in mitochondrial DNA might occur by chance and be new to the
individual.
Since each mitochondrion contains its own DNA, the number of mitochondria affected by
a variant may vary.
If some mitochondria have the variant, we call this heteroplasmy, represented by the
cell with both green and black mitochondria.
Whereas, if all of the mitochondria have the variant, we call this homoplasmy, represented
by the cell with all black mitochondria.
The number of mitochondria affected and the type of cells they are in can contribute to
an individual s symptoms.
In addition to variants in the mitochondrial DNA, sometimes variants in nuclear DNA can
affect how mitochondrial proteins are made and how mitochondria work in the body.
One important difference about nuclear DNA compared to mtDNA is it is passed down from
both parents.
Variants in nuclear DNA can also occur by chance and be new to the individual.
Mitochondria play an important role in our organs that require a lot of energy, therefore,
mitochondrial disorders can affect one or more systems in the body.
While symptoms of mitochondrial disorders may vary, some common symptoms include neurological
issues including seizures, migraines, and strokes, developmental delays, visual or hearing
problems.
Some examples of mitochondrial disorders include Leigh Syndrome, Mitochondrial Encephalopathy,
Lactic Acidosis and Stroke-Like Episodes (MELAS) Syndrome, and Leber Hereditary Optic Neuropathy
(LHON).
Thank you for watching our Mitochondrial Disorders video!
If you have general questions about mitochondrial disorders or other genetics-related topics,
you can reach us at info@genomeconnect.org or by calling 570-214-1721 or toll free 855-322-7683
If you have questions about your genetic test results, we encourage you to reach out to
your doctor or genetic counselor.
We hope you join us for our other videos!