Genetics

What is Gene Therapy, and what are its advantages ?

Gene therapy is a novel approach to deal with various diseases. A simple explanation of Gene Therapy: Introduction of the functional gene into the effective cell which produces sufficient amount of appropriate protein encoded by transferred gene. The field of Gene Therapy is still a developing field in the world of medical science.

Three main strategies in gene therapy:-
1. Gene addition
2. Usage of antisense nucleotide or ribozymes
3. Control of gene expression

Why gene therapy over drug therapy?
• Reinstate dysfunctional gene with functional gene
• Continuous secretion of therapeutic protein
• Cell specific

Types of gene therapy:-
Somatic cells:-
When a morbid somatic cell is cured by changing the gene expression. The genetical changes that take place do not get transferred into the succeeding generation.
Germ Cells:-
The aim of the Germ line gene therapy is to transfer the genomic changes to the offspring.

Although plans of conducting it on larger animals and humans has not been executed. There is a misconception that it has already been put into practice widely but actually the genetic information are just being used for selection of eggs/sperms, no alteration has taken place.

Two main approaches:-
• Ex-Vivo Approach is used for the cells that can be re-implanted. They are taken out of the human body, transgened and introduced into the cell which is reset in the body.eg: lymphocytes, fibroblasts, myoblasts, umbilical cord blood, stem-cells etc.
• In-Vivo Approach in which transgene is commenced into the objective cell to comprehend the working of the gene therapy and help reassess the facts about human genes and gene delivery technique.

Fundamentals of gene therapy are:-
1. Identification of disease causing gene
2. Cloning of the gene
3. Gene mutation identification
4. Detection of gene expression and protein function
5. Gene transfer efficacy and safety testing system. It makes sure transgenes have all the components mandatory for transcription, translation and RNA polyadenylation.

Methods of gene Therapy:

The vector that is introduced should be non immunogenic and safe. The following methods are used :-
- PHYSICAL:- Parental injections, micro-injections, aerosol, electroporation (high voltage current passed to the target cell to produce pores through which transgene enters the cell) and gene guns.
- CHEMICAL:- Calcium phosphate, DEAE-dextran, liposomes and lipoplexes (for oral delivery of gene), surfactants and perflurochemical liquids for aerosol delivery of gene.
- VIRAL VECTORS:- advantageous over the other two:-
a) More specific
b) Single dose is sufficient
DISADVANTAGES:-
a) limited packaging capacity
b) unknown long term physiological effects
c) risk of immunological activation
d) regeneration of wild type of virus
examples of vectors:- retro virus, adeno-virus, herpes simplex virus etc.

Other advancements:-

- NEW ORGAN TRANSPLANT OR TISSUE IMPLANT:-
Used in the treatment of lysosomal storage disease
- HUMAN ARTIFICIAL CHROMOSOME:-
Laboratory engineered chromosome consisting of all mandatory information
- RECEPTOR MEDIATED DELIVERY
DNA of particular size is transferred to a specific receptor cell as ligand to deliver transgene
- VIRALLY DIRECTED ENZYME PRODRUG THERAPY:-
Vector is expressed only in tumour cells not in normal cells.
- THERAPEUTIC ANTISENSE AND RIBOZYMES:-
Consisting of the use of oligonucleotide sequences that are complimentary to a gene that has to be inhibited by forming triplex with the regulatory component of chromosomal DNA or by complexing a region of mRNA.

Gene vaccines:-
DNA vaccine can stimulate cell mediated and humoral immunity. However there are risks of provocation of autoimmune response and insertional metagenesis.
We hope that clinical trials of 20th century may become a clinical reality in 21st century and we can fight fatal genetic disorders in a better way.

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Research – Genes responsible for some amount of High Blood Pressure cases ?

In recent years, there has been an increasing trend towards looking for gene based causes of a number of diseases and afflictions. With progress being made towards an increased trend of mapping the entire genome structure of the human body, and more research towards linkage of some genes (or mutations / defects in the genes) with afflictions and diseases, there are more links being found between genes and diseases. Consider the case of High Blood Pressure, which is a disease that causes harm to the cardio-vascular system of the body with long term damage, and which is also known as a modern disease, caused due to a more sedate lifestyle.
Research (news article) is isolating a genetic cause in around 5 – 10% of cases where genetic mutations can cause hypertension, and if this research goes on, it can eventually lead to genetic screening for this form of hypertension.

Scientists at Yale University have found two new genetic mutations that can cause hypertension in up to a third of patients suffering from a common cause of severe high blood pressure.
Five to ten percent of patients with severe hypertension have tumours of the adrenal gland that produce a hormone called aldosterone. Removing these tumours can cure this form of hypertension.
Sifting for clues by sequencing all of the genes from these tumours, and comparing their sequences to the patients” normal DNA, the researchers found that either one of two mutations of a single gene were found in 8 of 22 tumours studied.
The investigators discovered that these mutations cause both aldosterone release and tumour formation by allowing the encoded protein, a potassium channel, to conduct sodium rather than only allowing potassium to pass through the channel.

As additional attention is paid to decoding the human genome, it becomes more and more clear that a large number of diseases will be linked to genes (mutations / defects) in some way, which in turn can help to screen for these diseases before the disease becomes apparent.

Causes and Symptoms of Prostate Cancer

Prostate cancer is a disease which only affects men. Cancer begins to grow in the prostate – a gland in the male reproductive system. The prostate is so called because of its position – it is at the base of the bladder. The exact causes of prostate cancer are unknown.

Causes of Prostate Cancer

- Prostate cancer is caused by changes in the DNA of a prostate cancer cell. DNA makes up our genes, which control how cells behave.
- Prostate cancer may also be linked to higher levels of certain hormones. High levels of male hormones (androgens) may play a part in prostate cancer risk in some men.
- The risk (predisposing) factors for prostate cancer include advancing age, genetics (heredity), hormonal influences, and such environmental factors as toxins, chemicals, and industrial products.
- It develops in the outer part of the gland as distinct from Benign Prostatic Hyperplasia (BPH), which develops in the centre of the gland. Therefore, it is possible to get prostatic cancer even after one has had a prostatectomy for BPH.

Symptoms of Prostate Cancer

Levels of a substance called prostate specific antigen (PSA) is often high in men with prostate cancer. However, PSA can also be high with other prostate conditions. Since the PSA test became common, most prostate cancers are found before they cause symptoms. In the later stages, prostate cancer can spread locally into the surrounding tissue or the nearby lymph nodes, called the pelvic nodes. The cancer then can spread even farther (metastasize) to other areas of the body. Symptoms of prostate cancer may include :

- A need to urinate frequently, especially at night.
- Difficulty in starting urination or inability to urinate.
- Weak or interrupted flow of urine.
- Painful or burning urination.
- Difficulty in having an erection.
- Pain during ejaculation.
- Blood in the urine or semen.
- Pain or stiffness in the lower back, hips, or thighs.
- Pain with bowel movement.
- Unintentional weight loss.
- Lethargy.
It is advised to consult a doctor immediately if you have experienced any of the above symptoms. Men aged 50 and above have the chances of developing prostate cancer.