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    Home / College Guide / :: OSEL.CZ :: – Sheep Dolly celebrates 25 years
     Posted on Thursday, July 22 @ 00:00:07 PDT
    College

    :: OSEL.CZ :: – Sheep Dolly celebrates 25 years July 22, 2021 by archynewsy Sir Ian Wilmut. His youthful desire was to become a naval officer. Due to his color blindness, he did not pass the entrance tests and the paths of fate led him to the path of embryologist at the Roslin Institute, University of Edinburgh. Credit: Darwin College, Cambridge. CC BY-SA 4.0 In July 1996, Dolly saw the light of day. At first glance, quite an ordinary sheep, but with an extraordinary origin. She was born by somatic cell nuclear transfer cloning under the hands of Ian Wilmut and Keith Campbell at the Roslin Institute in Scotland. In a few weeks, a single sheep turned the helm of history. Dolly – the first cloned mammal ever created from a single adult cell. Credit: University of Edinburgh. In fact, there was a mistake at the beginning: Campbell and Wilmut used somatic cell nuclear transfer (SCNT) cloning (see box 1 below) to study the pluripotency of cells, ie their “strain”. While embryonic and progenitor cells are almost undifferentiated and should playfully reprogram in an egg, terminally differentiated cells lack such ability. At least, Scottish researchers postulated in Edinburgh, and used an embryonic cell, a fetal fibroblast cell, and finally a mammary gland epithelial cell to test the hypothesis.

    In this order, the researchers assumed a descending ability to dedifferentiate and actually used the epithelial cell as a negative control. Therefore, it was very surprising that even after the transfer of the nucleus of such a differentiated cell into the egg, the nucleus was reprogrammed, an embryo began to develop, creating a transferable blastocyst, from which Dolly was born after another 150 days. The surprising result triggered a scientific fever over the search for the secret of cell stemming – after all, Dolly was living proof that every cell in our body has its potential for pluripotency. To begin with, it is necessary to define a clone: ​​an individual with the same genetic information as his model. The clone can be a plant propagated by cuttings, yeast propagating by budding, a monozygotic twin or a sheep produced by the transfer of a somatic cell nucleus. Outside of this somatic cell, however, eggs are needed – its cytoplasm can dedifferentiate a terminally differentiated cell – physiologically this happens to sperm. The result is a totipotent single-celled zygote and subsequently a multicellular pluripotent embryo. Therefore, the cytoplasm of the egg, which can be obtained by so-called enucleation, ie by removing the genetic information of the egg, would be suitable for the reprogramming of the somatic cell.

    Reconstruction of the egg and the formation of a totipotent zygote will be created after the introduction of the nucleus of any somatic cell, either by injection or electroporation. It should be noted that the transfer of somatic cell nuclei is not a 100% clone. Mitochondria are part of the cytoplasm of the egg and they carry their own mitochondrial DNA. When we consider the amount of mitochondria in the egg (about 100 thousand), it is a significant amount of genetic information (approximately comparable to the hapliodic genome of the egg), which does not come from the somatic cell of the master but from the donor’s egg. From the beginning, there are problems with cloning, technical, biological, ethical. While technical reserves address the progress of instruments (micromanipulators, injectors, electroporators), with biology it is worse. We cannot do there without the knowledge that is often still waiting for its discoverer. Thus, we face a generally very low success rate of embryo transfer and pregnancy, Large offspring syndrome, etc. It is certainly to blame for the perfectly tuned epigenetic regulation of gene expression during embryonic development, leading, among other things, to physiological silencing of genes depending on the origin.

    (from mom versus from dad) – gene imprinting. There is a massive reprogramming in the genetic information of the somatic cell inserted into the dedifferentiation “bath” of the ooplasm, and after imprinting there is neither sight nor hearing, which cannot be done without consequences. Another problem is the suitability of the egg for somatic cell nucleus transfer. Species compatibility is not very tolerant of concessions, which distances the possibilities for dinosaur cloning. African or Indian elephant eggs are offered for mammoths, but where to get them in sufficient numbers? Efforts to save species on the brink of extinction have been more noble, and zoologists and scientists have long sought to clone the white rhinoceros. In the case of man, all cloning, whether reproductive or therapeutic, is considered unethical, as man as a being is protected against this by the Convention on Human Rights and Biomedicine (the so-called Oviedo Declaration). Perhaps the creation of the Convention in 2001 was the result of increasing efforts and proclamations of human cloning. At present, however, we live with the knowledge that the human clone created by the transfer of the somatic cell nucleus on the planet Earth did not arise.

    See also China: Taiwan independence means war Ian Wilmut, holder of the Golden Plate Award from the American Academy of Sciences, holder of the Order of the British Empire (OBE), member of the Royal Society (FRS). member of the Academy of Medical Sciences, member of the Royal Society of Edinburgh. Promoted to aristocratic status (2008). In the picture, he is posing with his Dolly. The name Dolly was given to her by a team of scientists who were involved in creating the cloned sheep. The sheep was created from a mammary gland cell, and no one was able to recall more impressive breasts than the then popular singer Dolly Parton. Credit: University of Edinburgh. On the other hand, as is the case with scientific revolutions, Dolly also tore down an avalanche of conspiracies, fears and ethical questions. The scientists thus dispelled imaginary ideas that prophesied the cloning of Hitler and other bandits. It’s a nice example of how much people at the end of the millennium believed the genome as a kind of book of destiny. Today we know that the mere writing of genetic information means nothing without the regulation of gene expression, epigenetics, interaction with the external environment.

    In short, in the words of a classic: “maybe it would be a completely different Adolf, and maybe it wouldn’t be Adolf either…” Famous American country singer Dolly Parton in Nashville, Tennessee, 2005. (Free work). A little closer to the truth was Spilberg’s blockbuster Jurassic Park, which worked with the idea of ​​Mesolithic dinosaurs preserved in time and currently used for cloning. The closest ambitious plans are to clone mammoths, but so far we do not have to be afraid of such “success” (see box 2 below). On the other hand, cloning of cattle has been and is feasible, despite technical and biological difficulties, quite a number of cattle clones have been born. But cloning in cattle certainly did not happen – by cloning, ie creating an identical copy, the breeder deprives himself of the so-called genetic gain; it stems from the fact that offspring are always better (understand more efficient in the production of meat, milk) than parents. See also Two Norwegian sisters killed by lightning, third seriously injured So we don’t just laugh, so what was 1996 and Dolly’s birth so special that he moved the world? Although nuclear transfer cloning was not a hot new feature, it was revolutionary to find that a terminally differentiated cell has the potential to dedifferentiate, i.

    e., become a stem cell again. It’s like going back in time, because previous assumptions have claimed a one-way process of cell differentiation. The egg that is capable of this was suddenly viewed as the Philosopher’s Stone, thanks to which we create gold (stem cells) from plums (somatic cells). The tool of therapeutic cloning was born: ‘take any cell of your body, insert a donor into it, create your own clone (genetically and immune-free) and let it develop to the stage of a 5-day blastocyst in vitro ; isolate embryonic stem cells from it and use them where you need to find a remedy – Parkinson’s disease? Multiple sclerosis? Cirrhosis of the liver? No problem!’ In total, Dolly gave birth to six lambs in her lifetime. Pictured with triplets Lucy, Darcy and Cotton. Credit: Roslin Institute. True, this does not sound completely non-conflicting, so it is no wonder that therapeutic cloning has brought ethical pitfalls much more contemporary than a cloned dictator. And again, we surprised ourselves and asked ourselves whether “we can do whatever we can.” Creating an embryo and a potential being for the purpose of someone else’s therapy is unacceptable and has practically put a stop to this branch of regenerative medicine.

    However, crowds of scientists continued to search for other ways to reprogram somatic cells into stem-pluripotent cells, albeit without ova and embryos. See also The Šiauliai family has been stolen from bans: 17 imaginary accidents in two years Dolly the sheep was prepared after her death and today she is exhibited at the National Museum of Scottland. Photo: Maltesedog, free work. Extensive stem cell studies have narrowed to a handful of proteins known today as the lapidary “Yamanak’s factors.” If we induce the expression of these transcription factors in a differentiated somatic cell, lo, we get an induced pluripotent stem cell (iPSC)! Nor is it without losing a flower, because it is a gene manipulation, but it is a significant leap in knowledge and another way to obtain stem cells. In 25 turbulent years in the field of genetic engineering, we have calmed down a bit, sobered up and gained further epoch-making knowledge. Over the last 25 years, cloning by the transfer of somatic cell nuclei has resulted in an inexhaustible number of genetically modified organisms, from laboratory amphibians and rodents to livestock. It is clear that Dolly the sheep played a significant role in the rise of bioengineering and gene manipulation.

    However, she too was part of a continuum of constant and unceasing scientific work, not a work of fright. Perhaps that is why in 2012 he was decorated with the Nobel Prize by John B. Gurdon for the work he did in the 1960s, ie cloning frogs. Undoubtedly, Campbell and Wilmut also based their hypotheses on Gurdon’s results. As with the two, the second nobelist of 2012, Shinya Yamanaka, followed up with his knowledge of the key factors of pluripotency 20 years later. And we can look forward to what the next quarter century of the “after Dolly” era will bring. It is a pleasant realization that the engine of further knowledge and development is medicine and not the pursuit of sensation. Video: Commentary by the editor of Reproduction magazine Video: The Story of Dolly the Cloned Sheep | Retro Report Literature

     
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