What is gene therapy?

Gene therapy is the use of genetic instructions to produce a protein to treat a disorder or deficiency. It can aid in a disease even if the therapy is not directly targeting a gene defect that causes the disease. In amyotrophic lateral sclerosis (ALS), gene therapy may help if it can deliver a beneficial protein, to salvage dying nerve cells. The gene therapy simply is a means to boost on site production of a trophic (growth enhancing) factor, at places where nerve cells are in trouble.

Genes are the molecules in all cells of our bodies that carry the instructions to make all of the materials that comprise the body. In the 1950s, scientists determined that genes code precisely for proteins, with a sequence that specifies the order of the building blocks of proteins, the amino acids. Each gene corresponds to a protein. Each base in a gene codes for an amino acid. The order of bases in a gene produces the ordered chain of amino acids that produce a working protein.

At the turn of the current century, scientists determined, in rough draft form, the sequence of all of the human genes. By this time, they also knew how to create a gene construct, and move that construct into cells, to get the cells to make the corresponding protein.

In some diseases, researchers already know that a defective gene is not able to work. They have the potential means to cure the disease, by replacing the defective gene with a correct, working copy. In ALS, only a few percent of patients have a known gene defect. For the rest, it may be one undiscovered gene that is the problem, or it may be several. But gene therapy can still be designed to aid patients with ALS by providing supportive proteins for nerve cells.

Vectors deliver genes Genes normally reside in the nucleus, the core of a cell, separated from the surrounding materials by a membrane. The chromosomes are the structures within the cell nucleus that contain the DNA that comprises the genes. It is very challenging to get a gene made in the lab to cross both the outer envelope of a cell, and the nuclear membrane as well, to reach the chromosomes.

Scientists studying viruses have discovered natures own solution to the problem of moving genes. Viruses are essentially genes that have evolved to hijack cells, instead of forming cells for themselves. So viruses have strategies to enter cells and take over the protein production process, to produce instead, the virus. Researchers have figured out how to use viruses as Trojan horses, to bring in genes that can then carry out genetic repairs, replacing defective DNA.

For many viruses, researchers can disarm the genes responsible for the damaging properties and put in, instead, genetic instructions to make therapeutic proteins. These viruses, redesigned by researchers, are called vectors. They are simply a means to smuggle in therapeutic genes.

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Gene Therapy - The ALS Association

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