Monday, November 13, 2023

Study Connects Neuron Gene Expressions to Differing Functional Distinctions

 Long, thin, bumpy extensions of two neurons extend from upper left to bottom right across a black background. One is light green, the other is magenta. The light green one features patches of darker green amid little bumps along its length.

In a new study in Neuron, neurobiologists at the Picower Institute for Learning and Memory found that two closely related neuron subtypes in drosophila differed from each other in how they expressed more than 800 genes, about 5% of the total amount of genes in the fly genome. The two neuron types studied were both from what could be considered the spinal cord of the fruit fly. These neuron types control the muscles by releasing the neurotransmitter, glutamate. The main functional differences of the two subtypes are that the “phasic” neurons connect to a lot of muscles and emit big, occasional bursts of glutamate, and the “tonic” neurons connect to only one muscle and emit a constant, small amount of glutamate. Phasic neurons make fewer synapses on an individual muscle than tonic ones do, but make about 4 times as many synapses in total because they innervate so many more muscles. Tonic neurons have more inputs from other neurons due to it having more widely branching dendrites. Of the expressed genes of the neuron types, a significant amount helped with the growth of the axon branches, some helped with the structure and function of synapses, and others played a role in the types of chemicals the neurons were sensitive to as inputs. Researchers disrupted the functions of some genes to see which were the most different between the two subtypes. By disrupting the Wnt4 gene, a gene expressed 40 times more by the tonic neurons, the synaptic growth decreased significantly in the tonic neurons. By mutating a calcium ion buffering gene found 30 times more in phasic neurons, the phasic neurons had higher resting calcium levels similar to tonic neurons.

This study holds a lot of significance in not only discovering how different genes can overlap and differ in different cell types, but also specifically in how neuron subtypes can differ. The research presented in this article is exciting because figuring out how different kinds of neurons develop from their expression of different genes helps in advancing how a brain works. It could also help in understanding what can change or go wrong in disease. The study compares two similar cells in a very detailed manner and shows that even similar cells can have a lot of differences in gene expression to develop specific, distinct functions.,spring%20the%20muscles%20into%20action

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