Somatic Gene Therapy vs. Germline Gene Therapy

Gene therapy is technique in which we deliver nucleic acid polymers into a patient’s cell. This technique is used to treat diseases just like drugs that’s why gene used in gene therapy are called as gene drug. Gene therapy can be either somatic gene therapy or germline gene therapy. In somatic gene therapy, the drug genes are introduced in the somatic cells of the body. When drug genes are introduced in the germ cell or zygotes it is called germline gene therapy. Changes in somatic gene therapy are not heritable while in germline gene therapy changes are heritable.

What is Somatic Therapy?

When genes are introduced into the somatic cells it is known as somatic therapy. In somatic gene therapy any modifications due to transfer of new genes affect only the individual patient only and are not inherited by their off springs. In somatic gene therapy, therapeutic DNA is either integrated in the genome or as an external episome or plasmid and helps in treating the disease. Genes used are tissue specified in most instances but the location of the gene are not specified and it may not be possible to reconstruct normal level and distribution of the tissue. No ethical issues have been attached to somatic gene therapy. Somatic gene therapy involves insertion of a normal and healthy gene into the appropriate cells of the individual which is affected by a genetic disease, this technique permanently corrects the disorder. Genes are carried to the person’s cell either by viruses (by replacing their own gene by human genome) or liposomes (fat-like cells which carry DNA into a cell). These genes become inserted into the chromosomes in the nucleus. The target cells might be of bone marrow or muscles or lungs. In bone marrow the cells are easily isolated and re-implanted. Cells of bone marrow that are implanted into the person’s cell can divide for his whole life to produce blood cells.

What is Germline Therapy?

When germ cells or gamete is modified by the insertion of functional gene it is known germline gene therapy. All the cells of the organism gets modified by just introducing a modified gene into the germ cell.  So the changes are heritable and passed on to their next generations. The main advantage of this technique is that all the cells are easily accessible because they are outside the body and the delivery of the gene is less problematic. And the gene that is inserted into the germ cell will be transmitted to progeny cells during growth and development and helps by treating the disease. The disadvantage of this technique is that it raises lot of ethical questions because it impacts the inheritance patterns of humans. Also high frequency of insertional mutations are observed in this technique which cause teratogenic consequences.

Key Differences between Somatic Gene Therapy and Germline Gene Therapy

  1. In somatic therapy, functional genes are introduced into the somatic cells while in germline therapy, genes are introduced into the germ cell or gametocyte.
  2. Changes in somatic therapy affects only the individual patient only and they are not inherited by their offspring while changes in germline therapy are heritable and passed on to person’s future generations.
  3. There is no ethical issues in somatic therapy while germline therapy have many ethical issues which are yet to be answered.
  4. Most of the time it is impossible to obtain normal level of expression similar to that of normal gene while in germline therapy high frequency of mutations are observed which causes teratogenic consequences.