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About genetic disease

The purpose of this site is to provide information to patients and caregivers about the field of gene therapy and how it is being investigated for use in haemophilia.

Watch this narrated video which demonstrates how gene therapy works using a 3D vector model, and how this could potentially be applied to haemophilia.

Read full video transcript +

Genes: the body’s instruction manual

The human body is made up of trillions of cells. At the centre of each cell is the nucleus, which contains all the instructions the body needs to function.

These instructions are stored on chromosomes, which are made up of DNA (deoxyribonucleic acid). DNA is organised into genes, which provide instructions to make proteins — molecules that build, regulate, and maintain the body. Clotting factors are an example of proteins.

Another way to think about this is like a reference library.

The library (nucleus) contains a bunch of “how to” encyclopaedias (chromosomes) that are written in their own special alphabet (DNA). The encyclopaedias (chromosomes) are organised into specific chapters (genes), which provide the instructions the body needs to build proteins.

 

Genes and haemophilia

Haemophilia is a rare genetic bleeding disorder that causes a delay in clot formation. In haemophilia, there is a mutation in the gene that contains the body’s instructions for creating one of several important blood-clotting proteins called “factors.” There are two main types of haemophilia: A and B.

  • Haemophilia A, or factor VIII deficiency, affects approximately 25 in 100,000 male births
  • Haemophilia B, or factor IX deficiency, affects approximately 5 in 100,000 male births

Expected

clot formation


Delayed or deficient

clot formation

Haemophilia is most often inherited, meaning it’s passed down through a mutation in the parents’ genes or DNA. However, in one-third of cases, haemophilia is caused by a new or spontaneous mutation. Because of how haemophilia is passed from parents to children, it primarily affects men. However, in rare cases, women can have haemophilia too.

Haemophilia severity is classified based on a person’s factor level in the blood:

  • Mild (>5% to 40%)
  • Moderate (1% to 5%)
  • Severe (<1%)

Individuals with haemophilia may bleed spontaneously (without a known cause) from an injury, inside or outside of the body, and longer than those without haemophilia. Common sites of internal bleeding are joints and muscles; bleeding in these locations can lead to joint damage and arthritis. External bleeding may also occur, including nose bleeds, prolonged bleeding from minor cuts and dental work, and unexplained bruising.

 

Understanding genetic disease

DNA has its own alphabet: A, C, G, T. The letters stand for the 4 nucleotides, which are the building blocks of DNA. Unique combinations of adenine (A), cytosine (C), guanine (G), and thymine (T) make up all of the genes in the body.

Original DNA sequence

gene mutation is a change in the sequence of DNA that makes up a gene. There are different types of gene mutations including:

Gene mutations can cause:

  • A protein to not work properly or stop working altogether
  • An insufficient amount of protein or no protein to be made at all

When a protein is missing or not working properly, the function in the body that protein controls will be affected, resulting in a genetic disease.