educational videos below to help you discuss inherited retinal diseases, how they happen, how
they’re passed down in families, and how a genetic test can help uncover more answers to help
your patients move forward in their future.
How do inherited retinal diseases happen?
Genetic counselor Elena breaks down what genes are and
how gene variants can impact vision.
Hi, I’m Elena the genetic counselor, here to help you find more answers. You might be wondering,
“How do inherited retinal diseases happen?” To find the answer, let’s take a closer look at our
genes. Genes are often called the great blueprint for life. As the body's instruction manual,
our genes tell all parts of our body, including our eyes, how to grow and function. Humans have
approximately 25,000 genes. Genes are stored in nearly every cell of our body, housed in small
threadlike structures called chromosomes. We have 23 pairs of chromosomes. For each pair, we
inherit one chromosome from our mother and one from our father. Within each of our chromosomes
are strands of deoxyribonucleic acid, commonly known as DNA. If genes are the blueprint for
life, think of DNA as the instructions within those blueprints. They carry very specific
instructions for how tall we can grow, the color of our hair, and the many characteristics that
makes us unique. Each DNA sequence is made up of thousands of building blocks that are
abbreviated as As, Cs, Gs, and Ts. These letters are strung together in long strands. The order
of these letters provides specific instructions to our body. When the inherited DNA sequence
contains a slight change—like a missing letter, or a letter is replaced by another, or there are
a few added letters—that's when we inherit a gene variant from our parents and can potentially
pass it to future generations. Most gene variants are considered benign, which means they aren’t
believed to have a serious impact on our health. However, some gene variants can affect how our
bodies function, including our eyes. This could result in vision loss or impairment from an
inherited retinal disease. A genetic test is the only way to precisely identify the genetic
cause of vision loss or impairment. With the evolution of genetic testing comes the ability to
potentially find the genetic cause of inherited retinal diseases in even more people. Just in
the past 10 years alone, nearly 100 new genes related to inherited retinal diseases have been
discovered, bringing the total identified to over 270 genes. And science continues to advance.
So, if you’ve never had a genetic test, or a prior test showed negative or inconclusive results,
talk to your eye specialist or genetic counselor about genetic testing or retesting. Move
forward with more answers, and stay tuned for my next video about the different ways retinal
diseases can be inherited at EyesOnGenes.com.
© Janssen Pharmaceuticals, Inc. 2021 10/21 cp-259572v2
How are retinal diseases inherited?
Narrated by genetic counselor Elena, this animated video
brings to life autosomal dominant, autosomal recessive, and X-linked inheritances.
Hi, I’m Elena. As a genetic counselor, I’m often asked about how changes within our genes, or
“gene variants,” can be inherited. Understanding key information about inherited retinal
diseases is how we can start to take control. Today, I’m going to walk us through 3 different
ways retinal diseases can be passed down from our parents. The first is autosomal dominant
inheritance. Whoa, that’s a mouthful! Here’s what it means: You might remember from the Genes
101 video that our genes are housed inside our chromosomes. We have 23 pairs of chromosomes. For
each pair, we receive one chromosome from each parent. To explain how this inheritance pattern
works, it helps to imagine two butterflies—one representing a mother, and one representing a
father. In this case, the butterfly with the gene variant has an added spot. This spot
represents inherited retinal disease in humans. For autosomal dominant inheritance, the child
would only need to inherit a single gene variant to be affected by the condition. So, in the
case where a single parent has the gene variant, there’s a 50% chance that the child will
inherit that parent’s retinal disease. This is represented by the added spot. Next, we have
autosomal recessive inheritance. Here, even if our parents don’t have an inherited retinal
disease, they can still be “carriers.” A carrier is someone who carries the gene variant, but
most of the time does not have symptoms. In rare cases, a “carrier” may experience symptoms. In
either case, carriers can pass down the gene variant to their children. Unlike autosomal
dominant inheritance, the child would have to inherit 2 copies of a gene variant, 1 from their
mother and 1 from their father, to be affected by the condition. What that means is, in the
cases where both parents are carriers but are not affected by the condition, there’s a 25%
chance that the child will inherit both copies of the gene variant and inherit a retinal
disease, and a 50% chance that the child will inherit a single copy and only be a carrier. Now
let’s examine X-linked recessive inheritance. For X-linked conditions, we need to take a closer
look into the chromosomes of each parent because in this pattern, gene variants are passed
through the X chromosome. Females have 2 X chromosomes, and males have 1 X and 1 Y. So, if a
female were to inherit an X chromosome with a gene variant, she still has another healthy X
chromosome that could act as a backup and function properly. However, males only inherit 1 X
chromosome, and if that happens to have a variant, he doesn’t have that backup healthy
chromosome. This leaves them more at risk of being affected by an X-linked recessive condition.
In the case where the mother is a carrier, and the father is unaffected by the condition, if
they have a son, there’s a 50% chance that he will be affected. However, if they have a
daughter, there’s a 50% chance that she will be a carrier of the gene variant. It's important to
remember that these outcomes can change depending on which parent possesses the gene variant.
Now, we know that’s a whole lot to take in. Understanding inheritance patterns plays a big role
in understanding how these conditions are passed down. It’s important to know that family
history is only one of the pieces we use to solve the diagnosis puzzle. You can still inherit
genes that cause retinal diseases with no known family history of these diseases. A genetic
test, along with the correct eye exams, may give us more answers. Move forward with more answers
and stay tuned for more episodes at EyesOnGenes.com.
© Janssen Pharmaceuticals, Inc. 2021 10/21 cp-259571v1