What is Genome Editing and how is it useful?

Genome Editing
Have you ever wondered how organisms develop in specific ways and organisms of the same species look alike? This happens because all organisms hold all the information needed for their growth within themselves, as a blueprint. DNA is the master molecule in our cells that holds this blueprint. The amount of DNA varies among different species and it is organized as separate chromosomes. Each chromosome is a long piece of DNA that has regions called genes. Genes act as blueprints for making proteins, the best characterised functional molecules in cells.

Ever since scientists discovered the role of genes in regulating life of cells and organisms, they have tried to alter genes. One reason to do that is to study the role of genes in causing diseases - making specific changes in genes of organisms like mice or bacteria will help to identify their role in these disease processes. Genetic changes are important for developing economically important strains of organisms. Plants that make the diabetic drug insulin and bacteria that make plastic are examples of successes of biotechnology.

Over the years molecular biologists have developed several techniques to tinker with the genome of cells or organisms. Scientists have techniques to disrupt a gene (called a gene knockout) or to transfer an altered gene (called a knock in) so that cells or organisms will have altered genomes. However these techniques are cumbersome and difficult and often take very long time to execute.

Moreover, making very small changes in a gene in its own natural context (with the rest of the gene and chromosome intact) is still a daunting task for scientists. However it is very important to do such studies in biology diseases ranging from cancer to allergy are often results of changes in gene. Genetic studies help not only to identify the reasons and mechanisms of these disease processes but help to develop better therapeutic approaches as well.

Genome editing is a relatively new technique in molecular biology that promises to make specific changes in the DNA of cells, in its own context. Here scientists transfer proteins into cells that can make these changes. These proteins are nucleases enzymes that cut DNA and are engineered to target specific regions of DNA in the cells. The technique utilizes ability of these enzymes to make specific cuts in the genome and the ability of the cells to repair them.

Different techniques have been developed to carry out genome editing. Some techniques use bacterial enzymes called meganucleases that bind long regions of DNA and cut them. Other techniques using engineered enzymes called zinc finger domains (ZFN) or transcription factor-like effector nuclease (TALEN) have also been developed more recently. Another exciting technique that is becoming more popular in genome editing is CRISPR; it utilizes a process used by bacteria to prevent recurring infections of viral or other foreign DNA.

Genome editing promises enormous potential in the fields of medicine and biotechnology. Ability to make small and precise changes in the DNA in its natural context is important for therapeutics (imagine repairing a faulty gene in a stem cell) and biotechnology (changing the stability or specificity of enzymes). Scientists predict that it will be used for different purposes like making specific mutations in cells, changing chromosome structure, making animals having precise changes in their DNA, and altering and studying stem cells.

There are some caveats though - as in many other cases, more problems lie in execution of an interesting idea than in designing it. The specificity and safety of genome editing has not reached a level stringent enough to make their use widespread. Scientists are trying to make sure only the designed changes are occurring in the genome and the so called "off-target effects" are absent. Even a single change happening in a region of DNA where it is not intended can have deleterious effects on the application of this technology. Furthermore, success rate of genome editing is less than other more established techniques. However steady progress is being made and we can expect genome editing to become a popular technique in the field of molecular biology, medicine and biotechnology.

Written By: Sujatha S., Canada (PHD Life Sciences)

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Edited by: Rajesh Bihani ( Find me on Google+ )

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