Weizmann Institute scientists have discovered an essential mechanism for the normal development of nerve fibers. The discovery may lead, in the future, to the development of new treatments for nerve diseases
Prof. Elior Pels. growth
Multiple sclerosis and many other diseases that attack the nervous system are manifested by the destruction of the myelin sheath -
The fatty layer that wraps the nerve fibers. A group of scientists from the Weizmann Institute of Science recently identified the mechanism responsible for the formation of this envelope during the development of the nervous system. The discovery may, in the future, help develop ways to restore the myelin sheath after it has been damaged as a result of various diseases. Nerve cells have thin extensions
and long (axons), sometimes reaching a length of a meter or more. The myelin covers large sections of these extensions, with small spaces between the sections. The myelin layer is formed when certain cells, called glial cells,
are wrapped around the axon, and cover it in layers, forming a thick and well-closed envelope. The myelin covering protects the nerve fibers, and allows the electrical signals flowing through them to jump very quickly between the spaces between the segments of the "protective blankets". These electrical jumps allow the rapid and efficient transmission of nerve electrical signals along the nerve fibers. When the myelin covering is missing, or damaged, the signals are unable to jump along the axon - which causes damage to the normal function of the nerve fiber, and can gradually lead to its death.
Prof. Elior Pless, research student Ivo Spiegel, and other members of Prof. Pless's research group, from the department of molecular cell biology at the Weizmann Institute of Science, studied, in collaboration with American scientists, the nerve cells during their development and the formation of the myelin sheaths. They discovered a pair of proteins that transmit messages
from the axon to the glial cells. These proteins, called Necl, belong to a large family of "glue molecules", which connect and attach living cells to each other. The scientists discovered that these "glue molecules" (Necl1 and Necl4) perform another function: they transmit cellular signals that cause the glial cells to start the process of producing the myelin sheath.
It turns out that the production of Necl4 in the glial cells increases when they come into contact with an axon that lacks myelin, as well as at the beginning of the formation process of the myelin sheath. On the other hand, when the glial cells lack Necl4 or when the connection between 4 Necl and Necl1 is prevented, the myelination process is not carried out properly.
Prof. Peles: "We discovered a new system of communication between these cells of the nervous system. The drugs used today to treat multiple sclerosis and other diseases caused by damage to the myelin layer are able to slow down the disease - but not stop or cure it. Today, the damage caused to the nerve fibers in these diseases is irreversible. But if we manage to understand the mechanisms that control the process of wrapping the axons in the myelin covering, in the future we will be able to find a way to reproduce this process in patients." These findings were published in the online version of the scientific journal Nature Neuroscience
From the journal Nature.
A cross-section of a nerve cell extension wrapped in a glial cell, as seen in an electron microscope. The myelin sheath appears dark in color, with the nerve cell in the center. Around the myelin sheath you can see the cytoplasm of the glial cell
Transverse section of a peripheral nerve containing several nerve cell extensions, as seen under an electron microscope. The myelin sheaths are visible in black, and in the center are the nerve cells
