Glowing Monkeys: to be continued
Primates lit up with other people's genes
Pyotr Smirnov, "Newspaper.Ru»Photo: E.Sasaki et al.
The first transgenic primates were created. GM igrunki and their offspring are just glowing green for now, but scientists hope to model human diseases on them soon, which monkeys cannot have, and test new medicines for them. However, the pioneer of cloning monkeys, Shukhrat Mitalipov, doubts that "primitive" igrunki are suitable for this purpose.
After it was proved in the middle of the XX century that DNA is the material basis of heredity, scientists began to make purposeful attempts to influence the genome. However, more than a decade has passed before the advent of practical genetic engineering. First, scientists needed to completely decipher the genetic code: it was necessary to figure out what to insert into the genome. Then it took some more time to create the first carrier vector, which became the SV40 virus. The first test subjects were bacteria, and after a few years it was possible to achieve results with the culture of eukaryotic cells, but a clear demonstration of the power of transgenic technologies is still the production of healthy animals with an embedded gene.
What could be better suited for this purpose than the green fluorescent protein once isolated from jellyfish? It is not difficult to detect it in tissues, and it is always easier to deal with boring skeptics by showing them a disco porosya or a glowing cat. Thanks to the work of Erica Sasaki from the Central Institute of Experimental Animals in Kawasaki, Japan, and her colleagues, the first primates joined the list of animals glowing under the influence of ultraviolet light this week. They became ordinary igrunki (Callithrix jacchus).
Moreover, the authors of the publication in Nature managed to raise five glowing monkeys at once and even get glowing offspring from one of them. That is, to fix the embedded gene in the genome.
Despite the fact that the first transgenic mice were created more than ten years ago, and in recent years similar manipulations with the genome of rats, rabbits, dogs, cats, pigs and even cows have been successful, it has not been possible to obtain similar results on primates for a long time. The problem of the "fragility" of monkey embryos seems to have been solved a year and a half ago: then Shukhrat Mitalipov's group received a line of embryonic stem cells from a cloned zygote. The key to success was quite unexpectedly the process of cell visualization – scientists abandoned the damaging dye, working only in polarized light, and cloning succeeded.
Sasaki and her colleagues also had to look for ways to optimize: Japanese scientists attacked SV40 zygotes obtained as a result of not artificial, but natural fertilization. Instead of mixing sperm and eggs in a test tube, and then transfecting the zygote, the researchers waited for the usual fertilization, then caught the "offspring" at the unicellular stage from the genital tract of animals and embedded the gene of the green fluorescent protein already in it. This increased the frequency of embedding into the genome from 80% to almost 100%. And only then the zygote was hooked to the surrogate mother for further development.
In total, the Japanese transplanted 80 embryos to 50 monkeys, achieving 7 pregnancies with the birth of 5 healthy cubs.
The five first transgenic monkeys created by Japanese scientists:
Hisui (a), Wakaba (b), Banko (c), Kei (d on the left) and Kou (d on the right).
Under ultraviolet irradiation, the skin on the soles of monkeys glows green.
The success rate is not as low as it may seem at first glance. Firstly, surrogacy affects the "survival rate" of transplanted zygotes, and secondly, staying in a test tube has an unpredictable effect on the cell. Even with the proven technology of in vitro fertilization in humans, when eggs are taken from the same mother, who is then planted as many as 3 embryos, the probability of pregnancy is about 20%.
But the main topic for discussion was not the effectiveness at all, but the applicability of the resulting model in practice. Of course, the green protein in this case is just a visual demonstration of the possibilities, instead of it, you can easily embed a defective gene and, conversely, a gene that is normally absent in this species. Usually, by the way, these genes are still connected to the green protein gene to make it easier to track the effectiveness of embedding: where the tissues have turned green, there is, therefore, the main product. So the transition from illustrativeness to functionality is not even a matter of time. But is there a need for this?
Mitalipov and his colleague Gerald Shatten, leading experts in the field of cloning, in a comment to this article in Nature, note that the "primacy" of this model may not correspond to its name. Despite the fact that igrunki are already primates, and the progress of technology in comparison with the same mice is certainly evident, it is not much more effective to study the processes in the human body on igrunki.
The fact is that the igrunkovs belong to the broad-nosed monkeys of the New World, quite far from humans. Unlike the same monkeys, they are difficult to infect with our viruses. And the small size of the brain, the structures of which are difficult to distinguish during tomography, coupled with relatively low intellectual abilities make these monkeys unsuitable for studying higher nervous activity.
In addition, in her work, Sasaki used a virus that embeds its genome into a random section (and sometimes several sections) of the monkey genome. And here, the first place in importance is not even viral DNA, potentially capable of influencing genetic rearrangements in the zygote, but the randomness of the whole process. On the one hand, the green protein gene can be embedded in the "passive part" of the genome, on the other, on the contrary, three to five embedded copies can saturate the cell with the synthesis product.
In mice, scientists have long changed viral vectors to homologous recombination, in which the injected DNA exchanges places with the host site due to the partial similarity of the "sticking ends". Since the sequence of nucleotides is unique, then you can choose a section of the genome to your taste.
All of the above does not in any way prevent admiring the technological genius of Japanese researchers, who, hopefully, will soon find a way to repeat their success on species closer to humans. The next step in this direction has been taken.
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