Motor neurons direct the muscles to move in response to stimuli. They are the longest cells in the body, with some extending from the spinal cord to the toes. New motor neurons are continuously generated throughout life from specialised cells in the spinal cord.
During development, motor neurons must first establish connections with the correct muscles, which they do by growing long processes (or axons) towards them. This process is guided by a “love-hate relationship” with the blood vessels that surround them.
Initially, motor neurons are attracted to the blood vessels by a protein called semaphorin 3A. This protein is produced by the motor neurons themselves and attracts the growth cones of the motor neurons towards the blood vessels.
However, once the motor neurons make contact with the blood vessels, they are repelled by another protein called netrin-1. This protein is produced by the blood vessels and keeps the motor neurons from getting too close.
The motor neurons “tug” on the blood vessels in response to the netrin-1 protein, causing the blood vessels to remodel and move away from the motor neurons. This “tugging” provides the motor neurons with the guidance they need to grow towards their target muscles.
This love-hate relationship between motor neurons and blood vessels is essential for the proper development of the nervous system.
A “love-hate relationship” may be the key to understanding how motor neurons grow, according to a new study. This finding could have implications for the treatment of motor neuron diseases such as ALS.
Motor neurons are the nerve cells that control muscle movement. They are some of the largest neurons in the body, and they are unique in that they extend from the spinal cord all the way to the muscles they innervate.
In order for motor neurons to reach their target muscles, they must first grow long processes (called axons) that can extend for over a meter. This process is guided by special “growth cones” at the tips of the axons.
Growth cones are sensitive to a variety of signals in the surrounding environment, and they use these signals to determine which way to grow. One of the most important signals for motor neuron growth cones is provided by blood vessels.
Blood vessels secrete a variety of growth factors that can promote or inhibit the growth of motor neurons. However, the precise role of blood vessels in motor neuron development has been difficult to study.
Now, in a new study published in the journal Nature Neuroscience, researchers have used a novel approach to investigate the role of blood vessels in motor neuron development.
First, the researchers used a genetic approach tolabel blood vessels in the developing spinal cord. This allowed them to track the movement of blood vessels in real-time.
Next, the researchers used a mathematical model to simulate the growth of motor neurons in the presence or absence of blood vessels.
This allowed the researchers to see how blood vessels influenced the growth of motor neurons in a way that couldn’t be seen with traditional methods.
The researchers found that blood vessels have a complex and dynamic relationship with motor neurons. Sometimes they promoted the growth of motor neurons, while other times they inhibited it.
This “love-hate relationship” between blood vessels and motor neurons is thought to be important for the proper development of the nervous system.
The findings of this study could have important implications for the treatment of motor neuron diseases such as ALS. Currently, there is no effective treatment for ALS, and the disease is nearly always fatal.
The new study provides insight into how motor neurons grow, and how this process can be disrupted in diseases like ALS. This knowledge could one day be used to develop better treatments for these devastating disorders.
