Transgenic models of brain diseases

Neuroscientist Dr. Doping tells about experimental animals, the genetic knockout and translational medicine. How does the method of genetic knockout? What are the theoretical approaches to identify the causes of schizophrenia? As transgenic models used in preclinical pharmacology?

The subjects, which I have been doing for many years, is associated with the development of new models of human diseases of the brain in experimental animals. In preclinical pharmacology it is important to reproduce the pathological processes that occur in diseases of the human brain, to try to understand these mechanisms and to find new targets for the development of drugs.

If we could combine all pluses of such drugs as Meldonium, Cogitum, Cortexin, Cerebrolisin and Phenylpiracetam and remove minuses and side effects it would be great.

In the history of drug researchers attempted to reproduce either upon administration of psychotropic substances, causing some change in neurotransmitter systems involved in the disease or administered any toxic substance. And until 1989, opportunities were limited only to either pharmacological or neurotoxic approaches. Directional target genetic changes or when a certain gene is switched off or its expression is increased or decreased by a certain amount or increased at times - However, the technique of so-called knock-out was developed in the 1989 year. That is, the possibility of genetic manipulation of the animal.

This has opened up a whole new world. And the scientists who discovered this approach, won the Nobel Prize in 2007: Oliver Smithies, and Sir Mario Capecchi Evans. These three great scientists have received well-deserved Nobel Prize, because it creates an opportunity for a large number of scientists involved in any problems (not only the brain, what you will), play pathology in animals.

What is the strength of this method and it gives us? You know, we all like mammals consists of about 20 000 proteins. If simplistic to perceive one gene - one protein, the approximately 20,000 protein molecules, which is now possible to study by genetic manipulations. And, removing one by one, or changing, we can finally understand the function of these proteins. The fact is that over the years, scientists have discovered the function, more or less imagining the role played by 6-7 thousand proteins. All the rest is unknown.

At present, it is believed that these 5000 proteins could be potential targets of action of psychotropic drugs, not only psychotropic - pharmacological agents. How to study the function of these genes? There consortia when off one gene at a time. They appeared in the United States, China, Australia. There were companies that are trying to study the function of these genes, shutting down one by one, trying to turn out patents and somehow discover and develop new medicines, totally unexpected. This is one application.

Second - as we know what the pathological process involved, we can just play it on the animal. And when we reproduce the disease process, we can try to find new mechanisms, any new target for therapeutic intervention.
In particular, I have been such a disease like schizophrenia, of which there are two main theories. Either enhanced dopaminergic transmission (dopamine - a transmitter, which is involved in the movement, psychotic reactions, drug addiction). One of the dominant theories that schizophrenia is associated with increased dopamine. The second theory is also global - so-called Hypo-glutamatergic theory, ie decreased glutamate transmission. Both we particularly reproduced animal in mice. In 2014, I have reproduced in rats. This new approach, which has become available recently - reproduction in rats. And in an attempt to study their behavior in an attempt to study their biochemistry, some molecular mechanisms of interaction between different proteins that we study, we think that we will find something very interesting, which will lead to the development of new drugs.

The third and most interesting from the point of view of medicine is an attempt to reproduce in animals exactly the mutation that is found in humans.
This reproduction of the so-called humanized mice (humanized animals). As a result of a large genetic screening, with some disease, schizophrenia, found dysbindin gene. And you just take the data obtained from the clinical analysis, and is literally play with mice, we can now rats. As a result, we conducted a study that unexpectedly led to the prediction of which drugs should be used in certain forms of depression.
Only in 2003 it was found enzyme responsible for the synthesis of the neurotransmitter serotonin in the brain. It was always considered that serotonin is synthesized in the brain and the periphery of the same enzyme - tryptophan. Suddenly, however, it became clear in 2003 that it has two isoforms, one isoform peripheral, another center.

We were very intrigued by this revelation. Such findings were to occur in the 1950-1960's, and this occurred in 2003 year. And we have tried to identify the gene. It so happened that we randomly allocated it from several species of mice. We sloppy attitude to this issue, and there were several breeds of mice in the same room. We have identified DNA, mixed, and suddenly found two isoforms. Again two isoforms that differ only by one amino acid. That is, we have found a point mutation. Naturally, this could be from the same species. We figured out. It was found that different breeds of mice have different versions of the gene. This gene is called tryptophan hydroxylase-2, which is responsible for neuronal.

It was found that the synthesis of serotonin fairly well controlled in the brain by these isoforms of the enzyme. In the future, we tried to find something similar in humans, in a small cohort of patients with depression who do not respond to classical antidepressants, mainly serotonin. When depression of essential drugs are serotonin reuptake inhibitors - SSRIs, serotonin reuptake inhibitors. These patients do not respond to medication, who based his action on the mechanism of serotonin.
In these patients, we found a mutation that was very similar to the one we found in mice. Moreover, the serotonin synthesis was reduced by 80%. That is, the functional effect of this mutation was quite serious.

We reproduced this in mice. Now we already have human mutation and exactly reproduced in mice. And when we reproduce it on mice they found the same 80% reduced synthesis of serotonin. And when we tried to introduce them to the selective serotonin reuptake inhibitor antidepressants such as "Prozac" and some others, we suddenly discovered (the synthesis of serotonin and is already 80% reduction), that when you give these blockers reuptake, the decline It goes even further. That is, it gets even worse, because the serotonin became even less going on so-called havoc, devastation of inner neuronal serotonin, which, of course, is not good, and patients with this mutation would not recommend to make such inhibitors.
We, in particular, have patented this idea. In principle, it would be nice before giving SSRIs to patients with depression - and depression are suffering in the world and 30% of the population over a lifetime, and SSRIs are widely used throughout the world, especially in America - to see if there is a mutation in these patients .

I think this is a pretty good example of translational medicine, when we started with the patient switched to an experimental animal, an animal found a mechanism that tells us how to treat or modulate treatment, or, conversely, prevents the treatment of certain medications. And now we hope that this will finally come back to the clinic.
The concept of translational very important today in biology, in medicine in general. Today translational biomedical centers are opened all over the world. And to some extent, I suppose, and so must be kept current research: start with the patient and the patient to complete. And already we molecular biologists, physiologists, pharmacologists, somewhere between these two poles.

The following application of transgenic models, which is fairly obvious - it is a pre-clinical pharmacology. This is a test of selectivity of action of drugs.

The fact is that when you open any guide, any tutorial, you will read: "This substance is a selective activator of this receptor antagonists" and "selective antagonist of another receptor." I am a pharmacist can tell you that this is true of interest on 85. All the same, there is some kind of target secondary, tertiary target. That is absolutely selective drugs not happen at all. There is always some kind of secondary and tertiary targets.

Any drug has a therapeutic effect and side effect. And it often happens that it is impossible to understand how receptors mediate the therapeutic effect or side effect. How do we check? For example, we are exploring some receptor. In particular, we have such a wonderful receptor - Tranexamic receptor-1, which we have recently taken a great interest. Just until recently, no selective drug substances that act on these receptors, it was not, but in 2009, "Hoffmann-La Roche" has developed the first substance to act on these compounds.

How to check it? We took the knockout animals lacking the gene, and tested for their effects of the substance. We see something, say, in the control animals. And on this knockout animals there is no effect. Thus we have proved that the substance, a completely new chemical structures, however cause certain physiological response, influencing it in the receptor that we investigated.
Prospects of development of this area are enormous, especially with regard to the fact that there were entirely new technologies for creating transgenic animals in recent years - CRISPR, TALEN-nuclease, ZFN-nucleases. This new technology, which now make it possible to do almost any genetic manipulation of any kind of animal. Now it can be, and rabbits, and rats, and monkeys, incredibly increases the translational value of this research. Many aspects, especially the psychological and cognitive, can not be studied in mice, for obvious reasons. And, perhaps, to more complex organisms it will develop very quickly and interesting.