Upgrade of paws

Mouse paw has been improved genetically

Additional neural communication channels between the brain and the paw gave the animals the opportunity to perform more complex movements

Kirill Stasevich, "Science and Life", based on materials MedicalXpress

A primate's brush looks like a more perfect tool than a rodent's brush: we can do a lot of complex manipulations with our hands, whereas for a mouse, even just grabbing something in a fist already turns out to be quite a difficult task. 

Of course, rodents, and many other animals, the ability to make some complex movements with their paws seems to be unnecessary. But we are talking about something else in this case: it is quite obvious that the neural mechanism that allows you to control the brush has made a rather noticeable evolutionary leap in humans and monkeys. 

The work of the muscles is controlled by special zones in the brain that generate a motor impulse, sending it along special pathways in the spinal cord to the corresponding muscles. These pathways are neural circuits in which cells contact each other with the help of axons – very, very long processes. 

When the neural "wire" is just beginning to form, it is very important that the neural processes grow to the right place. Debugging of the pathways occurs after birth, when the cub literally gets on its feet. And here the main role is played by two kinds of proteins: semaphorins and receptors for semaphorins, called plexins.

Semaphorins forbid neural processes to grow where they should not: if a neuron tried to germinate in some place and suddenly felt a semaphore signal, the neural process will immediately change direction. In mice, one of the semaphorins forms conducting pathways that control the movement of limbs; since mice mostly just run on their four paws, signaling proteins suppress the formation of neural pathways that would allow more complex movements. 

Researchers from Cincinnati Children's Medical Center, together with colleagues from Yale and some other scientific centers, have found out exactly which receptor protein works in mice when they form motor pathways. 

An article in Science says that if this protein called PlexA1 (that is, plexin A1) is turned off, then the brushes begin to work better in animals: in particular, mutant mice cope better with spaghetti and other food that had to be grabbed and held in a fist. But in tests for general coordination, in which it was just necessary to walk on a particularly difficult surface, there was no difference between normal animals and animals with the receptor turned off. In other words, without the receptor protein, motor neurons were able to lay additional "wires" to the paws, and additional neural control allowed the mice to perform quite complex manipulations. 

Finally, if we compare the genes in mice and primates, we can see that in primates, the PlexA1 gene has an additional controller – a special regulatory sequence in DNA. A special protein binds to the regulatory sequence, which affects the activity of the PlexA1 gene located next to it. Obviously, it was thanks to such additional molecular genetic controls that primates were able to move their brush like no other animal. 

Most likely, the following is happening here: due to the additional regulation in the system of semaphore genes and proteins, the brain receives additional channels of communication with the hand and therefore can control more complex actions - although the molecular details of how and when regulatory proteins and DNA fragments work have yet to be clarified. 

The authors of the work believe that their results will also be useful in clinical studies; for example, it can be imagined that by acting through a system of semaphorins and their receptors, it is possible to improve the condition of patients with congenital or acquired defects associated with the motor system. 

Portal "Eternal youth" http://vechnayamolodost.ru  25.08.2017