(ORDO NEWS) — Human nerve cells develop much more slowly than those of other mammals. New experiments have shown that this rate is determined by the activity of mitochondria.
By stimulating or suppressing it, scientists were able to accelerate the growth of human neurons and slow down the growth of mice.
The human nervous system grows extremely slowly, the maturation of neurons stretches for years.
At the same time, in most other animals, it takes much less time: for example, several weeks are enough for mouse neurons.
This difference is considered important for the development of a particularly complex brain.
However, the mechanisms that create it lie in the basic processes of cellular metabolism and are associated with the activity of mitochondria.
The reasons for differences in the rate of neuronal growth have remained a mystery for decades.
Ten years ago, Pierre Vanderhaeghen and his colleagues at the Free University of Brussels tried to place human nerve cells in the brain of a mouse.
However, it turned out that even in the new environment they developed at the same slow pace. This forced scientists to look deeper into the roots of the problem, within the neurons themselves.
To begin with, they had to find an indicator that allows them to determine and track the age of nerve cells.
A suitable marker turned out to be the NeuroD1 transcription factor, a region of the genome that “turns on” when a cell moves from a stem state to the path of development of a mature neuron.
Therefore, biologists have created protein labels that allow fixing the activation of NeuroD1.
Next, they determined the activity of mitochondria before and after this moment.
Recall that mitochondria are organelles that carry out the oxidation of glucose, producing ATP molecules, which serve as the main source of energy for all other processes inside the cell.
To monitor their activity, the scientists tracked their oxygen consumption. Such work showed that by two weeks after birth, mitochondria in mouse neurons utilize about ten times more oxygen than in humans.
The hypothesis about their influence on the growth rate of neurons should be tested.
Therefore, Vanderhagen and his colleagues chemically accelerated the mitochondrial metabolism of human nerve cells in vitro, “in vitro.” Indeed, their maturation was much faster than usual.
Additional confirmation was given by the repetition of experiments with the transplantation of human neurons in mice.
If mitochondria in such cells were stimulated in advance, then these cells matured at a “mouse” speed, over weeks.
Conversely, slowing down the activity of mitochondria in mouse neurons caused them to grow at the same leisurely pace as human neurons.
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