Why do scientists need glowing pigs
Where are Piglet and I going
It seems that geneticists are only thinking about how to come up with the most exotic mockery of cats, dogs or pigs with public money. Of course, this is not the case: genetic manipulation of mammals is aimed at solving serious medical and agricultural problems. But what connection can there be between a glowing pig and a human disease?
The Green RevolutionPerhaps we should start by correcting an error that is not too significant, but is widespread in newspaper headlines.
Neither cats made in 2007, nor dogs received in 2009, nor pigs that flashed in the news recently, do not glow in the dark. Like dozens of other animals raised in laboratories over the past ten years, they all really glow green – but not in the dark, but when irradiated with blue light or ultraviolet.
This property is due to the fact that all these animals are injected with the green fluorescent protein (GFP) gene. It is the biochemical properties of the latter that determine the green glow of cats and pigs. In addition to GFP, there are fluorescent proteins and other colors – red, yellow, blue, etc. But GFP among them is certainly the main "celebrity".
The glowing green protein was isolated from the jellyfish Aequorea victoria in the sixties. But he made a real revolution in science in the nineties, when the gene encoding GFP was decoded. At that time, genetic engineering was just gaining momentum in biological laboratories around the world, and scientists did not immediately realize that a protein from an unremarkable deep-sea jellyfish could radically change the approach to biological experiment in various fields of science.
The central problem of almost any experiment related to the role of certain molecules in cells, organs or whole organisms is the need to somehow see these molecules in their "habitat". There are many methods of "observing" the molecular world, but the vast majority of these methods assume that a cell or, for example, a histological section is "fixed" before they can be analyzed. The fixation process may include formalin treatment, freezing, homogenization in a test tube, and so on. It is clear that after such manipulations, the experiment ends – it will no longer be possible to resurrect the cell after it has been dissolved in acid.
GFP and similar proteins have opened up the possibility of "spying" on the life of molecules without "arresting" whole cells and tissues in which these molecules live. It is enough to equip a microscope with a blue laser and a green light filter: the glow is safe for cells, but it can tell scientists a lot.
By linking GFP with other proteins by genetic methods, we can trace, for example, the dynamics of their work in different parts of the body. It is possible to determine exactly where they are inside the cell without disturbing the cell itself.
The possibilities are not limited to proteins. Certain sections of DNA, for example, can regulate the work of genes associated with cancer. By replacing the latter with the GFP gene and exposing the cell to various influences, we can, by observing the green glow, find out under what conditions the mechanisms that can cause cancer are activated.
These are just the simplest examples of using GFP. Today, almost every research in the field of cell biology uses one or another fluorescent protein. In 2008, the Nobel Prize in Chemistry was awarded for the discovery of GFP.
But why is it necessary to inject GFP into whole organisms?
The role of country music in the history of scienceTo understand this issue, we need to recall another scientific revolution of the nineties.
On July 5, 1996, the world's most famous sheep named Dolly was born. Her fame lay in the fact that Dolly's genome was obtained not as a result of the fusion of the "half" genomes of the sperm and egg – as happens in mammals normally – but by transplanting an "adult" nucleus with a "ready" genome into an "empty" egg.
The most interesting thing was that the nucleus used to "reproduce" Dolly was taken from a somatic (that is, not sexual, intended for reproduction) cell, namely– from a mammary gland cell. By the way, Dolly's name is also connected with this fact: taking into account such a source of genetic information, the sheep was named after the American country singer Dolly Parton, known for her curvy forms.
The method, first tested on Dolly, thus received the name "somatic cell nuclear transfer" (SCNT). The success of this method proved for the first time in practice that an entire mammalian organism can be reproduced only on the basis of genetic information from one adult cell.
Today, a successful SCNT will not surprise anyone. The procedure has been tested on domestic animals, cattle, and many other representatives of mammals. What is the use of such experiments?
Firstly, they allow you to clone existing animals. For example, in South Korea, with the help of cloning, dogs are bred to work at customs – according to experts, the cloning procedure in this case is more profitable than the traditional breeding and training of potentially incompetent puppies. The same method could potentially be used to "resurrect" extinct species.
Secondly, obtaining whole organisms from adult cells opens up the widest possibilities for genetic engineering. Methods of introducing new genes into isolated adult cells are numerous and well developed. If whole organisms can be obtained from such modified cells, then it means that the genome of dogs and sheep can be manipulated. It is this factor that dominates the constant interest of the scientific community in animal cloning.
Engineering savvy and genetic "fish"In principle, introducing genes into adult cells in order to further transplant the nucleus into an "empty" egg is a rather complicated and extremely inefficient process.
It is much easier to work with embryonic cells. In this case, they can be modified and "planted" in the embryo when it is already developing confidently.
As a result, "normal" and transgenic cells are randomly distributed throughout the embryo. A chimera is formed: part of the cells of an adult organism contains the introduced gene, part does not. But if you find an animal whose modified cells have formed a sexual system (including eggs or spermatozoa), then the offspring of such animals will already be fully genetically modified.
Unfortunately, this method is not available for all animals. Technical difficulties (for example, with the cultivation of embryonic cells) today allow the described operations to be carried out routinely only on mice. That is why mice are such a favorite object of biologists: we simply do not know how to genetically modify other mammals so easily.
In total, in most cases, the genetic modification of other mammals is limited to a core transplant. But, as already mentioned, this process is complicated, expensive and extremely inefficient. The transplantation of the nucleus by micromanipulators is not too simple in itself, but taking into account the fact that only every hundredth of the resulting cell develops into an adult animal, the process turns into Sisyphean labor altogether.
Therefore, there is a constant demand in science for new methods of genetic modification with subsequent core transplantation. Scientists are coming up with more and more effective schemes, connecting whole genetic modules that facilitate the embedding of genes and improve the "survival" of the modified nucleus in the egg.
For example, in the mentioned recent work on pigs, a proprietary commercial system of two genetic "probes" was used, one of which encoded an enzyme from the moth Trichoplusia ni, "cutting out" the desired gene and integrating it into the genome of the cell. In short, today genetic engineering is in no way inferior in the complexity of engineering in the traditional sense.
This is where the green fluorescent protein comes into play. If the purpose of your research is to optimize the method of "gene transplantation" (no matter what) into an adult organism, then there is nothing simpler, more proven and effective than GFP. In such studies, green protein plays the role of a "fish" in the layouts of websites and magazines. GFP is a genetic lorem ipsum (in the jargon of many professions, including designers, so called conditional, often meaningless text that fills the page layout – VM).
Modify itWhy do we need genetic modification of animals at all?
For scientists developing new SCNT methods, this question is not even worth it: the possibilities of the method are almost limitless. But in order not to be unfounded, it is worth giving at least a few examples of the potential application of genetic modification in practice.
1. Production of medicines. A huge number of medicinal proteins are contained in natural sources in such small quantities that it is not possible to isolate them from there. To date, most of these proteins are obtained with the help of genetically modified yeast and bacteria. But these organisms are very far from mammals and do not know how to accurately recreate human proteins. This can lead to both low efficacy of drugs and to more serious problems – for example, allergic reactions.
By injecting the genes of insulin, interferon, blood clotting factors and many other proteins we need, for example, into the mammary glands of cows, we can get a real drug factory, and of much higher quality. Such drugs already exist: for example, the anticoagulant ATryn, obtained from the milk of transgenic goats, is approved for medical use in Europe and the USA.
2. Xenotransplantation. Transplanting organs from animals to humans might have seemed like a crazy idea twenty years ago, but today it's a matter of solving several technical difficulties. In particular, of particular interest are all the same pigs, whose physiology is similar to human in many respects. Some of the problems of organ rejection and compatibility have already been solved by "disabling" some porcine genes. Some authors claim that it is possible to expect the appearance of artiodactyl organ donors for humans within ten years.
3. Modeling of diseases. Mice have helped scientists find thousands of drugs that are successfully used in practice. But rodents are very different from humans, and not all diseases can be modeled on mice. For example, mouse models are extremely ineffective in studies of myocardial infarction, Alzheimer's disease and multiple sclerosis. More effective methods of genetic manipulation of other animals can significantly make life easier for biologists, doctors and millions of patients.
4. Agriculture. Today's reputation of genetically modified products does not leave much hope for the imminent appearance of GM meat on the shelves. Nevertheless, in conditions of gradual depletion of soils and natural resources, the efficiency of food production per unit area of fertile land may become a dominant factor in the foreseeable future, especially in developing countries. In this situation, genetic modification will be indispensable: from increasing the resistance of livestock to pathogens and physical exertion to increasing milk yields and muscle mass. In addition, with the help of genetic engineering, it is possible to reduce the negative impact of livestock on the environment.
In other words, genetic engineering of animals is not just glowing pigs. This is a solution to many problems that simply cannot be solved in other ways. This is worth remembering, even if you are still afraid to eat genetically modified corn.
Portal "Eternal youth" http://vechnayamolodost.ru16.01.2014