Researchers Analyze Neuronal Regeneration Based on Nervous Cell Design

Neuronal Regeneration Based on Nervous Cell Design

A research team from the University of Michigan, in the United States, reveals that both halves of our nervous cells are controlled by a single gene. Their discovery, recently published in the online journal PLOS Biology, suggests that in order to be able to develop novel regeneration therapies for nervous cells, this design must be taken into consideration. The research team from the Life Sciences Institute at U-M, led by assistant professor Bing Ye, discovered that when they tried to manipulate the genes of the Drosophila fly to increase the growth of only one part of the neuron, the other part had its growth simultaneously stunted.

According to professor Ye, their observation plays an important role for scientists that are trying to create new therapies for spinal cord injuries, neurodegenerative disorders and other diseases of the nervous system. Professor Ye compares the nervous cells to a tree. The branches of the nervous cells are called dendrites. The dendrites are responsible for the input of nervous impulses from other neurons. The trunk of the nervous cells is called an axon. The axon is responsible for transmitting the nervous impulses to the next nervous cell.

Neuron

“If you want to regenerate an axon to repair an injury, you have to take care of the other end, too”, reports Ye. Even though this axon-dendrite separation of the neuron is considered to be a doctrine among researchers, the mechanism that regulates and maintains their individual functionality is not yet fully understood. During the growth of the human body, the nervous system develops rapidly. However, nervous cells do not divide and replicate. Precedent studies have shown that when a nervous cell reaches its adult form, it no longer has the ability to grow or replicate, thus, any damage caused by neurodegenerative disorders or injury is permanent.

The current study reveals the bi-modal nature of nervous cells and explains how an enzyme, specifically a kinase, can have a different effect on the two parts of the cell. The growth effect that the kinase has on the axon is opposite to the growth impairment that the same kinase has on the dendrites. During their study, the researchers were able to identify the genes that are responsible for this effect. The reason why axon studies are easier than studies performed on dendrites is a technical reason: under the microscope, axons are easier to track and study. Ye’s research team managed to circumvent this technical difficulty by using Drosophila models. In order to study both the axon and dendrites, they labeled them both and observed the effects of various genetic mutations induced on genes shared between humans and Drosophila flies.

One gene that is common between humans and Drosophila flies is known as MAP3K12, which is responsible for coding a protein named DLK (Dual Leucine-Zipper Kinase). The DLK protein is responsible for the growth of the axons. According to the study, longer axons meant higher values of DLK. The nervous cells that had no DLK present showed no regenerative capabilities after injury. On the other hand, high values of DLK also meant that dendrites were less developed. “If we use this kinase, DLK, as a drug target for axon growth, we’ll have to figure out a way to block its effect on dendrites”, concludes professor Ye.