Gene Therapy

Gene therapy is the technique in the genes from an individual’s cell are inserted, altered or removed. This is done mainly to treat various diseases. By this technique, the defective genes are corrected. Gene therapy process involves commonly inserting the functional genes into a genomic location that are not specified to replace a mutated gene. Chromosomes that carry genes are specific base sequences to encode instructions for making the proteins. Thus gene therapy can be considered as the efficient technique for correcting defective genes. There are various approaches that researchers use to correct faulty genes. They are discussed as below:

• By inserting a normal gene to a nonspecific location in the genome for replacing a nonfunctional gene.
• Swapping an abnormal gene with a normal gene through homologous recombination.
• Returning the gene to its normal function by repairing an abnormal gene through selective reverse mutation.
• Altering the regulation of a particular gene.

Working and uses of gene therapy

As you all have understood from the reading that in gene therapy we insert a normal gene in the genome to replace an abnormal gene. Vector is the carrier molecule used to deliver these therapeutic genes. The common vector used currently is the viruses which in a pathogenic manner encapsulates and delivers the genes. The vector unloads the therapeutic human gene into the target cell. Now let us see some of the different types of viruses which are commonly used as gene therapy vectors:

• Retroviruses
• Adenoviruses
• Adeno-associated viruses
• Herpes simplex viruses

Gene therapy can be used in several many ways. They can be as:

• To replace the missing or defective genes
• To deliver genes to destroy the cancer cells
• To supply genes that cause cancer cells to revert back to normal cells
• To deliver bacterial or viral genes as a form of vaccination
• To provide genes that promote or impede the growth of new tissue
• To deliver genes that stimulate the healing of damaged tissue.

Types of gene therapy

There are some types of Gene therapy which you need to know. They are classified into the following types:

·         Germ line gene therapy

In germ line gene therapy, the Germ cells are modified by the introducing functional genes. These functional genes are integrated into their genomes. Thus, the change due to the gene therapy would be heritable and passed on to upcoming generations. This approach would remove all the genetic disorders and hereditary diseases.

·         Somatic gene therapy

In somatic gene therapy, the somatic cells of a patient get the therapeutic genes. The modifications and effects happen only in that particular patient only. So there is no fear of these inherited to the later generations.

Applications of gene therapy

·         Treatment of cancer

The very common and important application of gene therapy is in treating cancer. Researchers use various approaches for this. The targeted healthy cells enhance the ability to fight cancer. Some approaches also target these cancer cells in destroying them to prevent their growth. Researchers also replace missing or altered genes with healthy genes in another approach.

·         Treating type I diabetes

To treat the diabetes patients, researchers used an adenovirus vector to provide the gene for hepatocyte growth factor (HGF) using gene therapy. This experiment was done in pancreatic islet cells removed from rats. After injecting these altered cells into diabetic rats they started controlling their blood glucose levels. Thus transplantation of islet cells in humans was successfully done.

·         Treating X-linked severe combined immunodeficiency (X-SCID)

Lack of both T and B cells of the immune system causing vulnerable infections in babies was overcome with the gene therapy. This disease was caused by a faulty gene on the X chromosome. Researchers replaced the faulty genes of various children upon which great improvement was shown in their immune system functions.