What is gene therapy?


Every human being has around 20,000 to 25,000 genes, which provide the blueprint for our individual bodies and minds. — US Department of Energy Genome Programs (genomics.energy.gov)

I have heard about people using genes to treat diseases nowadays, but I am not sure what this gene therapy means.

Gene therapy involves trying to alter or modify the genes inside your body’s cells in order to treat or stop a disease.

Since 2017, the US Food and Drug Administration (FDA) has approved three different types of gene therapy.

Maybe we can start at the beginning: what are genes?

Genes are the basic physical and functional unit of heredity.

Our genes are made out of DNA (deoxyribonucleic acid).

Each person has two copies of each gene – one inherited from your mother and the other inherited from your father.

Each human being has around 20,000 to 25,000 genes.

These genes code for the way your body and mind are structured.

Some genes act as instructions (a blueprint) for your body to make various proteins, which in turn form your cells and organs, and the enzymes and hormones that regulate your body.

Other genes do not code for proteins.

Most genes are the same for all human beings, which is why we all look like human beings (and not a kangaroo, fish, bird or an alien)!

However, just under 1% of our genes vary slightly between each person.

That is why we have different races, heights, propensity for different diseases, curly or straight hair, etc.

These small differences also contribute to why we all look different from one another.

Genes that don’t work as they should also cause diseases in the human body.

What types of diseases are caused by faulty genes?

These are what we call genetic disorders.

A genetic disease is any type of disease caused by an abnormality in our genetic blueprint.

This abnormality can range from very minor to significantly major.

What we consider minor is, for example, a small mutation in the DNA of a single gene resulting in the change of a single base protein.

What we consider major is a gross chromosomal abnormality, such as the addition of a whole chromosome or the subtraction of one.

Some genetic disorders are inherited from our parents.

Others are caused by mutations due to our environment.

Examples of single gene disorders, which are caused by the alteration of just one gene in our bodies, are:

  • Cystic fibrosis
  • Thalassaemia
  • Sickle cell anaemia
  • Haemochromatosis

Examples of multifactorial inheritance, which are caused by a combination of environmental factors and mutations in many of our genes, are:

  • Breast cancer
  • Heart disease
  • High blood pressure
  • Alzheimer’s disease
  • Diabetes
  • Arthritis
  • Obesity
If we inherited these genes from our parents, then how can we possibly modify or alter them? This sounds terribly like science fiction.

We are rapidly approaching that era where what used to be science fiction could become part of our everyday life.

In gene therapy, scientists can:

  • Replace a gene that causes a medical problem with a new gene that doesn’t cause that problem.
  • Add genes to help our bodies fight or treat the disease.
  • Turn off the genes that are causing the disease or problems.
How do they do this? Do they have to “harvest” my cells? I’m scared just thinking about it!
Well, some gene therapies use a “vector” or vehicle that is engineered to deliver the gene into your body.

Many of the vectors are viruses, especially adenoviruses (not coronaviruses!).

Viruses have a natural ability to deliver genetic material into our cells.

After all, their main purpose is to attach themselves to cells and reproduce themselves.

Sometimes, the vector or virus is injected straight into our bodies, where they will deliver the gene that will modify our cells.

They are injected straight into the part of our body that has those defective cells.

Other times, we have to “harvest” healthy tissue from our body that needs to be modified.

These are usually tissues containing immune cells or stem cells, e.g. blood or bone marrow.

These tissue samples are then taken to the lab and specific cells are separated out.

The viral vector containing the corrective gene is then introduced to the harvested cells in the lab.

The modified cells are left to multiply, and then injected back into us.

Once inside our bodies, they will continue to multiply and eventually treat the disease or correct the defect within us.

Check out part two of this article below by clicking on "Using viruses as vectors in gene therapy".

Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health, computers and entertainment. For further information, email starhealth@thestar.com.my. The information contained in this column is for general educational purposes only. Neither The Star nor the author gives any warranty on accuracy, completeness, functionality, usefulness or other assurances as to such information. The Star and the author disclaim all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.

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Genetics , immunotherapy , gene therapy

   

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