Cloning extinct animals: dreams and reality
At first – a modest, but real achievement:Scientists have created a cloned embryo of an extinct frog
Alexander Khramov, Infox.ruBioengineers managed to obtain a cloned embryo of a frog that became extinct 30 years ago.
This gives hope that in the future scientists will be able to "resurrect" extinct species.
Cloning was carried out by Australian specialists from the University of New South Wales under the supervision of Professor Mike Archer (see the press release UNSW Scientists produce cloned embryos of extinct frog - VM).
The experiment used tissue samples of the Australian frog Rheobatrachus silus, frozen back in the 1970s. This amphibian, the last representatives of which were met in 1983, was distinguished by unusual reproductive behavior. The female frogs swallowed the fertilized eggs and then carried them in their stomach, so that the frogs were born from their mother's mouth.
To "resurrect" these unusual creatures, experts decided to use the eggs of frogs of a similar species Mixophyes fasciolatus. After inactivating their own nuclei, they replaced them with nuclei from the frozen tissues of R. silus. As a result, some of the eggs began to divide spontaneously and reached the blastula stage – the first stage of embryonic development, when a ball of germ cells is formed.
It turned out that all germ cells contain the genetic material of an extinct species. Despite the fact that the embryos did not last even a few days, scientists regard their creation as a significant success on the way to cloning extinct organisms. "Lazarus has risen from the dead before our eyes, the genome of an extinct frog has started working," Professor Archer stressed.
According to the researchers, the experiment showed that the technique of deep freezing of biological material can be used to save endangered amphibians: by freezing tissue samples of such species, they can be brought back to life in the future. Recall that currently there are projects for cloning such extinct species as the woolly mammoth and the dodo bird.
And here is another project of cloning an extinct bird
What should we do to resurrect the wandering pigeon?
Dmitry Tselikov, CompulentaTwelve birds lie belly up in a wooden box at the Museum of Vertebrate Zoology in Berkeley (USA).
Their stuffed reddish-brown breasts resemble sweet potatoes. The bluish heads and thin white tails are perfectly aligned, only one bird turned its beak towards its neighbor. Instead of an eye, she has a ball of cotton. A piece of paper tied to the leg reads: "Ectopistes migratorius. Manitoba. 1884". This is a wandering pigeon, which was one of the most common birds of North America by the time the Europeans landed. By 1914, it had completely disappeared.
An engraving of a painting by John James Audubon (1824)But scientists are seriously discussing the possibility of bringing him (and others) back to life.
What difficulties can they face?
About one and a half thousand wandering pigeons "live" in museum collections. This is all that remains of a seemingly inexhaustible resource. The birds were shipped by boxcars, sold by the ton at 31 cents a dozen for meat and feathers for mattresses. In just 25 years, their number has decreased from billions to thousands. Marta, the last of the birds, took her place under the museum glass in 1914.
Aviary with wandering pigeons. Photo of 1896Ben Novak does not believe that this is the end of the story.
The 26-year-old geneticist is convinced that new technologies make it possible to bring wandering pigeons back to life. He has been struggling for five years to decipher the genome of a bird and even left graduate school to make his dream come true.
He is not alone. The organization Revive and Restore ("Revive and Restore") sponsors scientists who want to bring extinct species back to life, and has made Mr. Novak the head of the project to revive the wandering pigeon.
The bird lying in a box from Berkeley did not fly over Manitoba alone in 1884. These pigeons roamed the eastern part of North America in flocks of several hundred million individuals. To feed on their way, they pecked whole forests, leaving behind a layer of droppings more than a couple of centimeters thick.
The habit of pack life ruined them. Pigeon nests in the northeastern United States were "packed" extremely tightly - one hundred pieces per tree (each with an egg or a helpless lump of fat), and therefore they were a banquet table for predators. The helpless chicks weighed about the same as their parents, but they could not yet get into the air and, to top it all off, they often fell out of the nest.
Even before the arrival of Europeans, local hunters shot pigeons with bows or knocked them down with sticks. But in the middle of the XIX century, the railway and the telegraph turned birds into a commodity of national importance. Professional hunters followed the flocks and robbed their nests, driving the parents away with the smoke of burning birch bark. In one day, a simple shooting in the air allowed thousands of pigeons to be shot down. By the end of the 1850s, the number of the species had significantly decreased, and by 1889 there were only a few thousand birds.
Shooting of wandering pigeons (1875 drawing)The pigeon from Manitoba is a whole genetic library.
In each cell of his fleshy toe, 1.5 billion DNA base pairs are stored, determining everything from the color of an eggshell to the sound of a bird's voice. Unfortunately, the best days of these DNA are long gone. They are broken down by enzymes, oxygen and ultraviolet radiation, as well as polluted by other organisms. Every time a person touches his foot, his DNA gets into the sample. Birds are lying nearby: their DNA also penetrates into the sample.
But, fortunately, in the last decade, a number of methods have appeared that allow working with imperfect DNA. The new machines can analyze hundreds of thousands of short fragments simultaneously, speeding up the tedious process and reducing its cost. In ten years, the sequencing efficiency has increased by about 500 thousand times.
With the help of new technologies, scientists have found the closest relative of the wandering pigeon. It turned out to be a striped-tailed pigeon (Patagioenas fasciata) from western North America, widely distributed to this day. Short, mutilated fragments of DNA from museum exhibits do not intersect so often, and a computer is not able to put the genome together, but the DNA of a striped-tailed pigeon can serve as a template.
In an effort to restore the pigeon genome, Mr. Novak sent requests to 30 museums, but all refused him samples. He reconciled himself to the need to write a dissertation about mastodons, but in his spare time he was engaged in his favorite bird. In 2011, the Field Museum of Natural History (Chicago, USA) still provided him with a piece of leg, which immediately went to the genetic laboratory in Toronto (Canada) for $2.5 thousand, which the researcher borrowed from a friend.
Meanwhile, the biotech revolution began to attract more and more attention from the general public. Writer Stuart Brand, who became famous in the late 1960s for campaigning for a NASA satellite to photograph the entire Earth, founded the Long Now Foundation, whose purpose is to find "a counterpoint to modern accelerating culture for the spread of far-sightedness." The aforementioned organization Revive and Restore is a branch of this foundation, established by the writer and his wife Ryan Phelan, the founder of DNA Direct, which sequences genomes to order. They chose a wandering pigeon as their first experiment. In February 2012, Revive and Restore held a conference at Harvard University, and Mr. Novak could not help but respond. There he was elected project coordinator.
So, here is Mr. Novak's plan in general terms. To sequence the genomes of striped-tailed and wandering pigeons and find significant differences between them. Change the DNA of the germ cell of the striped-tailed pigeon so that it matches the DNA of the wandering pigeon. To transplant this cell to some other pigeon, with which it is convenient to work in the laboratory (yes, at least a blue one). Hope that the cell will get into the gonads of the embryo of this pigeon. To grow a pair of such embryos and make them mate. Their descendant will be a wandering pigeon.
The first point of the plan is already being implemented. In March 2013, Mr. Novak started working in the Beth Shapiro laboratory at the University of California, Santa Cruz (USA), where the initial goal is planned to be achieved within a year. But the second point raises doubts. The last common ancestor of the two species lived about 30 million years ago, so their genomes are likely to differ in millions of locations. We will have to find out which gene mutations are responsible for meaningful physical differences. Ms. Shapiro notes that this will take a lot of time and work and that it is not worth it. Even mapping gene mutations in humans is extremely time–consuming.
But the most difficult thing is not even that, but making all the necessary changes to the genome of a living cell. Steven Salzberg from Johns Hopkins University (USA) notes that George Church from Harvard (USA) and his colleagues have developed a technology for multichannel automated genome engineering (Multiplex Automated Genome Engineering), which allows for small-scale changes in bacterial genomes. But the animal genome is much more complex than the bacterial one...
In addition, specialists have learned how to extract specialized germ cells from chicken embryos, but no one has worked with pigeons yet. Mr. Novak intends to circumvent this difficulty by taking up pigeon stem cells and forcing them to become sexual. But it should be noted that no one has done this with bird stem cells either...
At the same time, the pace of the biotechnological revolution inspires optimism. Who knows – maybe in a couple of years all this will become commonplace...
After the first wandering pigeons are raised, new problems will begin, because they need to be somehow accustomed to their natural habitat and old migration routes. David Blockstein of the US National Council for Science and the Environment is confident that at this stage the experiment will certainly fail. And if it doesn't fail, then agriculture will get another pest. Hank Greeley of Stanford University (USA) thinks the same way: the reborn pigeon will return to the same geographical region, but in a completely different ecological environment.
Today there is no authority that has the authority to make decisions on the revival of extinct species. Perhaps the work on the wandering pigeon will serve as a reason for its creation. And it is better if this work is carried out by responsible scientists, and not by unknown people. Mr. Brand fears that genomics will soon come out of laboratories and will be as easy to use as children's constructors. To prevent this from happening, it is necessary to start a dialogue between science, society and the government right now to develop an appropriate legal framework.
Even Ms. Shapiro, who does not believe in the success of the project and did not undertake it, only provided her laboratory to Mr. Novak, because she considers him useful, because he can combine various fields of science and promote them all at once...
Prepared by Wired: The Plan to Bring the Iconic Passenger Pigeon Back From ExtinctionPortal "Eternal youth" http://vechnayamolodost.ru