Scientists have found a gene associated with the development of unique features of the human brain
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- Scientists have found a gene associated with the development of unique features of the human brain
Scientists have discovered that one of the genes that appeared in the human evolutionary line can affect two types of brain cells at once — neurons and microglia. The researchers found that human microglia mature unusually slowly: it takes from four to eight years, whereas in mice the process takes about three weeks.
According to scientists, such a long period of development can help form complex neural connections and be associated with the peculiarities of human cognitive abilities. What is known about the SRGAP2 gene, why brain immune cells mature over the years and how this may be related to human evolution — in the Izvestia material.
A gene that turned out to be associated with two types of brain cells at once
Researchers from the Zuckerman Institute at Columbia University have been studying SRGAP2 for more than 15 years, one of several dozen genes whose copies appeared in humans. The work was published in the journal Neuron.
Previously, scientists have established that human copies of SRGAP2 affect the development of neurons. They increase the number of synapses — connections between nerve cells — and at the same time slow down their maturation. As a result, a denser network of neural connections is formed, which can help the brain process and store information.
A new study has brought an unexpected discovery. Scientists have found that human copies of SRGAP2 are almost ten times more active in microglia than in neurons. Experiments with human cells and mice have shown that human variants of SRGAP2 significantly slow down the development of microglia. In humans, these cells take about 4-8 years to mature, whereas in mice, microglia reach maturity in about three weeks.
Microglia are needed not only to protect the brain.
Microglia are the most common immune cells in the brain. They help protect the nervous tissue from harmful influences, remove damaged neurons and support the normal development of the brain. However, scientists gradually found out that the functions of these cells are much broader.
Microglia make up about 5-10% of brain cells and are involved in the organization of emerging neural circuits. During brain development, it helps determine which synapses between neurons should be preserved and which should be eliminated. In addition, microglia are able to make synapses more or less susceptible to signals, helping to set up communication within neural networks.
That is why the rate of maturation of microglia can be of great importance for the brain. If cells develop more slowly, they take longer to interact with the emerging neural circuits. Researchers believe that SRGAP2 can coordinate the development of neurons and microglia.
Carlos Diaz-Salazar is a researcher at the Medical Research Institute of the Hospital del Mar in Barcelona and the lead author of the study.
This gene helps control the rate of neuron development, and nature has also selected it to control the development of microglia, which is so important for the development of neurons so that they are synchronized during development.
Thus, the gene can link the development processes of two different cell types and maintain their synchronous maturation.
Why does the human brain take so long to develop
Compared to the brains of other mammals, the human brain takes an unusually long time to form. Scientists call this extended period of development neoteny. It is believed that it can play an important role in the emergence of complex human cognitive abilities.
A new study shows that unusually slow development may not be unique to neurons. Human microglia also take much longer to mature than similar cells in other animals. It turns out that brain development can follow a kind of slow-motion schedule at several levels at once. Neurons take longer to form and adjust their connections, and microglia take longer to develop and participate in the organization of these networks.
Scientists suggest that SRGAP2 may help to coordinate this pace. In their opinion, this synchronization of the development of different cells may be one of the features of the human brain. However, the authors do not claim that the found gene is directly responsible for intelligence. This is a possible mechanism that helps explain why the human brain develops differently than the brains of other animals.
Carlos Diaz-Salazar
This slow development may help human microglia influence the human brain in a way that allows us to develop powerful cognitive abilities.
Discovery may help to understand brain diseases
The study is interesting not only from the point of view of human evolution. Microglia are associated with the development of the nervous system and, as scientists note, may play a role in neurodevelopmental and neurodegenerative diseases. Therefore, understanding why human microglia mature so slowly and what role SRGAP2 plays in this may help to understand the features of the human brain and its disorders.
The next question to be explored by researchers is exactly how this gene promotes neoteny and affects other parts of the brain. Scientists want to understand the full range of mechanisms by which the human nervous system develops according to its unusual scenario.
Frank Polle, Doctor of Philosophy
We want to understand all the elements that make up the human brain in order to understand what makes us unique from an evolutionary point of view.
According to him, since scientists have recently discovered a link between microglia and neurodegenerative and neurodegenerative diseases, the new discovery brings researchers closer to understanding what makes human microglia special in the context of brain diseases.
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