Genes The basic unit of heredity Encode how to make a protein DNARNA proteins Proteins carry out most of life’s function. When altered causes dysfunction of a protein When there is a mutation in the gene, then it will change the codon, which will change which amino acid is called for which will change the conformation of the protein which will change the function of the protein. Genetic disorders result from mutations in the genome.
Gene Therapy Gene therapy is the process of inserting genes into cells to treat diseases. Gene Augmentation Therapy – a DNA is inserted into the genome to replace the missing gene product. Gene Inhibition Therapy - the antisense gene inhibits the expression of the dominant gene.
Approaches for Gene Therapy There are two approaches: Somatic cell gene therapy Modification of somatic cells, tissues etc Confined to the patient Germ-line gene therapy Modification of gametes, zygote or early embryo Permanent and transmissible Banned due to ethical issues
Types of Gene Therapy There are two types of gene therapies: Ex vivo Cells are removed from the patient, genetically modified and transplanted back into the patient In vivo Genetic material transferred directly into cells within a patient
Ex vivo Gene Therapy Ex vivo gene therapy can be applied to only selected tissues ( eg. Bone marrow) whose cells can be cultured in the lab. Technique involves the following steps: Isolate cells with genetic defect from a patient. Grow the cells in culture. Introduce the therapeutic gene to correct gene defect. Select the genetically corrected cells and grow. Transplant the modified cells to the patients. The procedure basically involves the use of patient’s own cells for culture and genetic correction, and then return back to the patients.
Vectors used in Gene Therapy The carrier particles or molecules used for deliver of gene to somatic cells are called vectors. Various vectors used in ex vivo therapy are: Viruses Human Artificial Chromosomes Bone Marrow Cells.
Vectors used in Gene Therapy Viruses: Retroviruses are frequently used. RNA – genetic material in retrovirus. Once inside cell DNA is synthesized by reverse transcription. This DNA is incorporated into the DNA of the host cell.
Vectors used in Gene Therapy Human Artificial Chromosome (HAC): HAC - developed in 1997 by H.Willard HAC – is a synthetically produced vector DNA, possessing the characteristics of human chromosome. It is a self-replicating micro-chromosome with the size ranging from 1/10th -1/5th of a human chromosome. It can carry long human gene and is used in gene therapy.
Vectors used in Gene Therapy Bone Marrow Cells: It contains totipotent embryonic stem cells which are capable of dividing and differentiating into various cell types.
The First Case –Example for Ex vivo Therapy The first gene therapy was performed on September 14th, 1990 Ashanti De Silva was treated for SCID Sever combined immunodeficiency Doctors removed her white blood cells, inserted the missing gene into the WBC, and then put them back into her blood stream. This strengthened her immune system Only worked for a few months
In vivo Gene Therapy In vivo gene therapy involves direct delivery of the therapeutic gene into target cells. Many tissues which are potential target for this therapy are – liver, muscle, lungs, spleen, brain and blood cells. Viral: Retro Adeno- Adeno-associated- Herpes simplex- Non-viral Naked DNA/Plasmid liposomes
Reference Book Biotechnology – By U. Sathyanarayanan