Human Gene Therapy

Human Gene Therapy
Human beings suffer from more than 5000 different diseases caused by single gene mutations, e.g., cystic fibrosis acatalasis, hunting tons chorea, tay sachs disease, lisch nyhan syndrome, sickle cell anemia, mitral stenosis, hunter's syndrome, haemophilia, several forms of muscular dystrophy etc. In addition, many common disorders like cancer, hypertension, atherosclerosis and mental illness seem to have genetic components.

The term gene therapy can be defined as introduction of a normal functional gene into cells, which contain the defective allele of concerned gene with the objective of correcting a genetic disorder or an acquired disorder.
The first approach in gene therapy is: -

a) Identification of the gene that plays the key role in the development of a genetic disorder.

b) Determination of the role of its product in health and disease.

c) Isolation and cloning of the gene.

d) Development of an approach for gene therapy.

The genetic material may be transferred directly into cells within a patient, which is referred as in vivo gene therapy or else cells may be removed from the patient and the genetic material inserted into them, which is referred as invitro gene therapy. Apart from the two methods mentioned above there is one more method that is ex-vivo gene therapy in which genetic material is inserted into the cells just prior to transplanting the modified cells back into the patient.

Major disease classes under gene therapy include: -

a) Infectious diseases: - infection by a virus or bacterial pathogen

b) Cancers: - uncontrolled and enormous cell division and cell proliferation as a result of activation of an oncogene or inactivation of a tumors suppressor gene or an apoptosis gene.

c) Inherited disorders: - genetic deficiency of an individual gene product or genetically determined in appropriate expression of a gene.

d) Immune system disorders: - includes allergies, inflammation and also autoimmune diseases in which immune system cells appropriately destroy body cells.

Telomerase: A Cancer Therapeutic Target

Telomerase: A Cancer Therapeutic Target


Although Elizabeth Blackburn had identified telomerase in 1980, it took 29 years for her work to be truly recognised. In 2009, Blackburn and her esteemed colleagues were awarded the Nobel Prize in Physiology or Medicine based on the successful ‘discovery of how chromosomes are protected by telomeres and the enzyme telomerase’ (Nobelprize.org, 2012).


As a result of this initial discovery, many scientific studies and research projects have aimed to further understand telomerase and the way in which it is related to degenerative diseases, aging and cancer (Reece, 2011). One such study was conducted by Jian Hu from the Dana-Farber Cancer Institute, Boston, USA. Titled ‘Antitelomerase Therapy Provokes ALT and Mitochondrial Adaptive Mechanisms in Cancer’, the study looked at modeling telomerase reactivation through the use of an inducible telomerase reverse transcriptase allele (Hu, 2012).

The starting point for a mutation has been found to be related to a problem which can arise during cell division if the subject (mouse) has levels of the enzyme which are low or nonexistent. When this factor is married with conventional DNA polymerases exhibiting an end-replication problem a normal or premalignant cell can lose the essential telomere sequences and uncapping can occur (Hu, 2012). This leads to the activation of cellular checkpoints not unlike those caused by DNA double-stranded breaks and ultimately results in telomere dysfunction (Hu, 2012). Flow on effects of dysfunction can be seen with records of induced p53 (tumor suppressor protein), cellular senescence and apoptosis (Children’s Medical Research Institute, 2006). Mutational inactivation of the p53 protein allows for cell cycling to continue and provides a procarcinogenic mutator mechanism for cells with telomere dysfunction via translocations, amplification and deletions (Hu, 2012). However, continual dysfunction and uncontrolled chromosomal instability can restrict full malignant progression.

As a result, clinically derived inhibitors with oligonucleotide changes enable maintenance of telomeres through homologous recombination. The alternative lengthening of telomeres (ALT) mechanism is one such inhibitor. By engineering an allele, TERT (a reverse transcriptase catalytic subunit) which can be inserted into the genome, and using mice mutant for Atm, the development of high penetrance and T cell lymphomas was able to be modeled. Results showed that mice from either the parental or first generation with the allele 4-Hydroxytamoxifen (4-OHT)-inducible Telomerase Reverse Transcriptase-Estrogen Receptor (TERTER) developed T cell lymphomas at synonymous penetrance and latencies. In comparison, the third and fourth generation mice presented lymphomas with lower penetrance and longer latency (Hu, 2012), refer to Figure 2.

Several key genes including those that were regulated from a master regulator possessed deviant expression in relation to oxidative and mitochondria pathways. The PGC-1ß, believed to control mitochondrial oxidative energy metabolism by activating specific target transcription factors including estrogen-related receptors (Sonoda, 2007), was found to be a major driver of the adaptive response to telomere dysfunction (Hu, 2012), refer to Figure 3.


The pressure for a cell to maintain mitochondrial function is directly relatable to the ROS (reactive oxygen species) levels and may be of great importance to telomeres due to ROS destroying telomeric G-rich sequences. Thus confirming the PGC link (refer to Figure 4) between mitochondria, telomeres and carcinogenic cells (Hu, 2012).


Furthermore, rendering genetic modelling crucial in the desire to understand tumor cell response, and quite possibly providing the answer to curing cancer.

Genetic Testing

Genetic Testing

This last century has seen an escalation in advancement of technology. In about one hundred years, man has gone from the horse and buggy to super sonic flight. These advancements have also been implanted in the health industry as seen in the almost doubling of the life expectancy of man.It also appears as though this escalation will only continue. One field where these advancements are moving at a very high speed is the field of genetics and biotechnology. The last ten years have seen some of the greatest landmarks in genetic genealogy research. The pattern in this field indicates that the discoveries and applications of those discoveries will continue to grow at an exponential rate.

With the increase in genetic knowledge there has also been an increase in the variety and ease of genetic testing available. Genetic testing refers to any sort of test which involves the study of the genome. When genetics was in its infancy, tests were expensive and took a long period of time to perform. Recent advances have significantly decreased the costs and time needed to perform genetic testing. This decrease in cost and time has made genetic testing available to more of the general public.

Genetic testing has also been used for determining family relationships. The simplest relationship to determine with a genetic test is a paternal or a maternal relationship. Today, genetic testing can also be used to determine other, more distant relationships. Genetic testing is available for full siblings, half siblings, grandparents and cousins. This allows family relationships to be determined even if one or more of the family members is deceased. As research continues, the ability to dive deeper into your family tree is becoming possible. With the use of Y-chromosome and mtDNA (mitochondrial DNA) testing more can be learned. The use of these genetic tests has allowed genealogists to verify their family trees and in some cases discover new branches that were not previously known. Genetic testing is even being used to understand the roots of family trees. This includes the use of genetic tests to look for Native American ancestry, and ancestry from different parts of Europe and Asia.

As knowledge and research in the area of genetics and biotechnology continue to advance, genetic testing will become even more accessible. This increase in use of genetic tests will give people more access to information. This information can be used to help solve crimes, increase the quality of health care, and provide information into your personal or family history.

Gene Therapy - Viral Vectors

Gene Therapy - Viral Vectors

In both types of therapy, scientists need something to transport either the entire gene or a recombinant DNA to the cell's nucleus, where the chromosomes and DNA reside. In essence, vectors are molecular delivery trucks. One of the first and most popular vectors developed were viruses because they invade cells as part of the natural infection process. Viruses have the potential to be excellent vectors because they have a specific relationship with the host in that they colonize certain cell types and tissues in specific organs. As a result, vectors are chosen according to their attraction to certain cells and areas of the body.

One of the first vectors used was retroviruses. Because these viruses are easily cloned (artificially reproduced) in the laboratory, scientists have studied them extensively and learned a great deal about their biological action. They also have learned how to remove the genetic information that governs viral replication, thus reducing the chances of infection.

Retroviruses work best in actively dividing cells, but cells in the body are relatively stable and do not divide often. As a result, these cells are used primarily for ex vivo (outside the body) manipulation. First, the cells are removed from the patient's body, and the virus, or vector, carrying the gene is inserted into them. Next, the cells are placed into a nutrient culture where they grow and replicate. Once enough cells are gathered, they are returned to the body, usually by injection into the blood stream. Theoretically, as long as these cells survive, they will provide the desired therapy.

Another class of viruses, called the adenoviruses, also may prove to be good gene vectors. These viruses can effectively infect nondividing cells in the body, where the desired gene product then is expressed naturally. In addition to being a more efficient approach to gene transportation, these viruses, which cause respiratory infections, are more easily purified and made stable than retroviruses, resulting in less chance of an unwanted viral infection. However, these viruses live for several days in the body, and some concern surrounds the possibility of infecting others with the viruses through sneezing or coughing. Other viral vectors include influenza viruses, Sindbis virus, and a herpes virus that infects nerve cells.

Scientists also have delved into nonviral vectors. These vectors rely on the natural biological process in which cells uptake (or gather) macromolecules. One approach is to use liposomes, globules of fat produced by the body and taken up by cells. Scientists also are investigating the introduction of raw recombinant DNA by injecting it into the bloodstream or placing it on microscopic beads of gold shot into the skin with a "gene-gun." Another possible vector under development is based on dendrimer molecules. A class of polymers (naturally occurring or artificial substances that have a high molecular weight and formed by smaller molecules of the same or similar substances), is "constructed" in the laboratory by combining these smaller molecules. They have been used in manufacturing Styrofoam, polyethylene cartons, and Plexiglass. In the laboratory, dendrimers have shown the ability to transport genetic material into human cells. They also can be designed to form an affinity for particular cell membranes by attaching to certain sugars and protein groups.

Early migration of modern humans into Arabia.....but from where?

Early migration of modern humans into Arabia.....but from where?

TOOLS. Stone tools (hand axes) were unearthed in the Arabian peninsula in a rock shelter called Jebel Faya. These tools were dated as old as 127,000 years as it was presented in Science last January. The authors suggest that this early expansion of anatomically modern humans took place from Africa and then added that "It is likely that populations expanded and moved through the interior of Arabia, as well as via the coastline, and used adaptive strategies incorporating terrestrial resources" But, other researchers do not share this idea. John Shea of Stony Brook University in New York pointed out that "stone points from Jebel Faya are shorter, thicker and less pointy than those found throughout Africa beginning 100,000 years ago" Moreover, he proposes that the stone tools similarities of Jebel Faya to Indian finds could reflect a different migration, one that came from Asia. Now the debate is open and waiting for more evidence.