Vivarium on the air

Transgenic mice became the heroes of an online show

Olga Kolesova, "Search"

Recently, mice susceptible to the SARS-CoV-2 virus were born in the vivarium of the Federal Research Center "Institute of Cytology and Genetics SB RAS" (FIT ICiG SB RAS). It is difficult to overestimate the importance of this event for science. The fact is that the mouse, due to the excellent knowledge of its genome, the rapid reproduction cycle and the relative cheapness of maintenance, is an ideal animal for modeling human ailments, including CoViD-19.

But laboratory mice, unlike their flying counterparts, do not suffer from a new coronavirus infection – the ACE-2 receptor (a protein on the cell surface through which the virus penetrates there) they are somewhat different from the human. To infect a mouse with coronavirus, it is necessary to breed a generation of transgenic mice with an edited genome.

The experiment of the Laboratory of Developmental Genetics of FITZ ICiG SB RAS has turned into a reality show: having decided to show YouTube users real science, scientists step by step remove all stages of genetic manipulation. In the first series, for example, laboratory employee Alexey Korablev performed vasectomy on males – using a homemade anesthesia machine on a homemade operating table. The peculiarities of rodent reproduction require real contact with the male before planting a gene-modified embryo to the female. The audience of the film is the most suitable for the popularization of science – schoolchildren and students.

"We are tired of requests from federal TV channels to "put on a white coat and put something colored in a test tube," Nariman Battulin, head of the Laboratory of Developmental Genetics, Candidate of Biological Sciences, comments. – Real science looks different. In the SPF (Specified Pathogen Free) vivarium, of course, we work in special protective suits, almost like doctors in the "red zone". There are very high standards of keeping laboratory animals: cages with an isolated ventilation system, maintaining constant lighting and temperature in order to avoid the death of specially bred genetic lines from "mouse epidemics" and to provide conditions for the repeatability of the experiment."

The history of genetic modification of animals began at the Institute of Cytology and Genetics SB RAS back in the 1990s. At that time, the idea of developing valuable human proteins necessary for the production of medicines in the so-called "milk bioreactors" was popular. Oleg Leonidovich Serov, the head of our laboratory, tested the mechanism for the corresponding genome change in laboratory mice. Then work on the genetic modification of mice was carried out for other studies.

So, together with the Research Institute of Medical Genetics (Tomsk) we have bred a line of mice with chromosomal disorders that lead to mental retardation in humans. There are animal models in which we have removed parts of the genome responsible for the regulation of genes associated with the development of tumors. Such experiments make it possible to understand the genetics of the development of oncological diseases and find new targets for their therapy.

The events of recent years have contributed to the development of experiments with transgenic animals. Firstly, the SPF-vivarium was put into operation in 2010. Secondly, wonderful genome editing systems have appeared, one of which is in FITZ ICiG. Thirdly, graduate student A.Korablev came to the laboratory of developmental genetics, who, according to N.Battulin, became one of the best specialists in genetic modifications in Russia and the world.

"The laboratory has incredible opportunities for very precise intervention in the genome," N. Battulin continues. "And with the beginning of the pandemic, we realized that we could implement all these skills quickly and effectively, as they say, for the benefit of society."

And the directorate in the person of Alexey Vladimirovich Kochetov pushed us to this. In April, after studying the relevant literature, we found out that since the time of SARS (2003), four models of laboratory mice susceptible to coronavirus have been bred in the world. Three were in China, there was no access to them, one was in the American Jackson Laboratory, theoretically animals could be ordered there, but we would not have received them before autumn. It became clear: we need to breed mice with the modified ACE-2 gene ourselves. Together with Boris Scriabin from the University of Munster (A.Korablev trained with him at one time) we have developed three scenarios for obtaining models. The first one – the most clumsy, but the fastest one – has already been launched. We just take the ACE-2 human gene and embed it into the mouse genome.

The gene is injected once – to embryos, the next generations of mice inherit it. Therefore, we are especially happy when transgenic males are born, they can give much more offspring. The first mice will be sent to the State Scientific Center of Virology and Bacteriology "Vector" at the end of August, where they will be infected with coronavirus and will study the effectiveness of vaccines. For the first steps, this "rough" model is suitable: the fact is that with this method of genome modification, the ACE-2 protein works in all cells of the mouse organism, and in humans – not in all. While we are taking part in the race, similar mice have already been born at the Institute of Gene Biology in Moscow. However, there is no competition here – mice are important and necessary to gain solid knowledge about CoViD-19. For example, the story of the loss of sense of smell is insanely interesting for scientists. Olfactory receptors are supported by precisely those cells in which the ACE-2 gene works.

Or a cytokine storm triggered by the immune system's response to a coronavirus infection. To study the course of the disease, it is necessary to accurately reproduce the work of ACE-2. And here the following two plans come into effect. One of them involves switching off the mouse gene and inserting the coding part of the human gene. The regulatory part remains – the mechanism will work as usual. The second, the most refined, involves the replacement of only a few different amino acids in the gene. But this is a very difficult job, we will be able to get such mice only by February. However, for the fundamental study of the disease, later models derived in a filigree way will be ideal.

The pandemic revealed the unwillingness of our science to respond quickly to such challenges, and for purely financial reasons. According to N. Battulin, special reserve funds are needed. The availability of the necessary funds in the director's fund made it possible to launch an experiment on the breeding of mice in a fire-fighting manner. In addition, the RFBR promptly responded by announcing an appropriate competition, for which ICIG specialists submitted an application. Recall that the whole story takes place in Novosibirsk Akademgorodok, where, fortunately, Vector is not far away, and there is an established system of cooperation between institutes – proteins for genome editing are produced by the Institute of Chemical Biology and Fundamental Medicine, the International Tomographic Center helped with other consumables. The extreme relevance of the work is emphasized by the fact that not only Siberian colleagues, but also scientists from the University of Munster expressed interest in a new line of mice.

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