Human's Playground: Genetic Engineering - Uses - Medicine

Gene Therapy

Gene therapy is the treatment of medical disorders by introducing specific engineered genes into a patient's cells.

The first attempted trial of gene therapy took place in 1990. A research team at the National Institutes of Health were trying to treat a 4-year-old girl suffering from severe combined immunodeficiency disease (SCID), which made her extremely susceptible to infections. The disease was caused by a single defective gene that encodes for the enzyme adenosine deaminase (ADA). This mutation caused toxic levels of these chemicals to destroy B and T cells (white blood cells).

Scientists at NIH used a virus to insert the normal ADA gene into a batch of the girl’s own T-cells removed from her body. Every 3 months for the next two years she received transfusions of the modified T-cells, which synthesized normal ADA. Her body’s immune system improved and she started to live a normal life. The trial was successful.

However, one problem with this experiment was that the modified T-cells have a finite life span and eventually die. Scientists are concentrating on genetically modifying bone-marrow stem cells, which produce all types of blood cells.

How do scientists identify genes that cause complex diseases?

At this time, scientists “guess” a certain gene based on information that they’ve collected. They verify that the gene causes disease by conducting a statistical analysis of a pool of patients on the correlation between changes in the gene and a particular disorder. In one or two more years, according to Dr. Koustubh Ranade, a contemporary genetic researcher, we will not have to make these guesses. Due to the completion of the Human Genome Project and advances in genotyping technology, “we can just look at all the genes in the genome and we won’t have to make any guesses.”

How successful has gene therapy been?

“Gene therapy so far has failed in most cases,” states Dr. Ranade. “It has not worked,” he goes on to say, because of largely unknown reasons. After they insert a gene, it stops being expressed after a short period of time. Also, people have died because the human immune system overreacts to the vector (inserts the DNA into a cell’s nucleus, usually a virus).

There are two types of gene therapy: somatic cell and germ line.

Somatic Cell	Germ Line
This method contrasts from germ line therapy, another type of gene therapy, in that attempts to modify cells focus on nonreproductive (somatic), existing cells. This method only affects the treated individual and is not inherited by their children. Somatic cell gene therapy attempts to insert a gene into millions of existing cells in the human body, or at least a good portion of those. Molecular biologist Lee M. Silver says: “In practice, though, it is very difficult to get those genes into a large number of cells.”	Germ line therapy, a process by which the DNA of an organism is modified at an early stage of development so all subsequent cells carry the modified DNA, can be used to remove genes that have been shown to cause diseases such as cystic fibrosis and muscular dystrophy. Molecular biologist Lee M. Silver say that “Germ line therapy is relatively easy. since 1980’s, it has become commonplace and easy to do.” Many scientists are able to alter animal embryos at birth. Graduate students can learn it in their first year of class. However, this method used on humans is underdeveloped and raises serious ethical issues, which spurred the American Association for the Advancement of Science (AAAS) to temporarily ban human germ line therapy in 2000. In the future, this process even may allow parents to select the desired traits of their children prior to birth. Cystic fibrosis is a condition where the lungs become clogged with music, and muscular dystrophy is a crippling muscle disease. These genetically inherited diseases are among the most common and can lead to early deaths.

Somatic Cell

Germ Line

This method contrasts from germ line therapy, another type of gene therapy, in that attempts to modify cells focus on nonreproductive (somatic), existing cells. This method only affects the treated individual and is not inherited by their children. Somatic cell gene therapy attempts to insert a gene into millions of existing cells in the human body, or at least a good portion of those. Molecular biologist Lee M. Silver says: “In practice, though, it is very difficult to get those genes into a large number of cells.”

Germ line therapy, a process by which the DNA of an organism is modified at an early stage of development so all subsequent cells carry the modified DNA, can be used to remove genes that have been shown to cause diseases such as cystic fibrosis and muscular dystrophy.

Molecular biologist Lee M. Silver say that “Germ line therapy is relatively easy. since 1980’s, it has become commonplace and easy to do.” Many scientists are able to alter animal embryos at birth. Graduate students can learn it in their first year of class.

However, this method used on humans is underdeveloped and raises serious ethical issues, which spurred the American Association for the Advancement of Science (AAAS) to temporarily ban human germ line therapy in 2000. In the future, this process even may allow parents to select the desired traits of their children prior to birth.

Cystic fibrosis is a condition where the lungs become clogged with music, and muscular dystrophy is a crippling muscle disease. These genetically inherited diseases are among the most common and can lead to early deaths.