Sexual Dimorphism in the Structure of a Single Neuron, with a Role in Sexual Behavior in C. elegans

What is it about?

We discovered that a highly branched neuron called PVD, previously characterized in hermaphrodites, forms a different structure in males. Moreover, while in hermaphrodites PVD functions primarily in pain sensing, in males, it has an additional role during mating; when its development is disrupted, males are slower and less coordinated. This discovery provides a unique example of sexual dimorphism in the structure of a single neuron, which is linked to behavioral differences.

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Photo by Stefano Bucciarelli on Unsplash

Photo by Stefano Bucciarelli on Unsplash

Why is it important?

It has long been established that men and women have different susceptibilities to various neurological disorders. For example, women are more prone to depression, while men have a higher risk of Parkinson’s disease. Could these differences be linked to the structure of individual neurons in the brain? This is difficult to determine due to the sheer number of neurons in the human brain—approximately 75 billion. Even if a difference were found between the sexes in just one neuron, pinpointing its exact contribution would be challenging, as even the simplest tasks require a multitude of intricately interconnected neurons. To explore the significance of a single neuron's spatial structure, researchers have turned to the nematode C. elegans, just one millimeter long. A unique feature of this organism is that the identity of all 302 neurons in the hermaphrodite is invariant, allowing scientists to fully map their placement, spatial structure and connections. Furthermore, within the nematode population, there are also male individuals with distinct anatomy, additional neurons, and different behavior. This makes for a remarkably simple system where we can directly ask: What determines the structure of each neuron in the nervous system? Are there sex-specific differences, and do they affect behavior?” This discovery of sexual dimorphism in the structure of a single sensory neuron, which also relates to male-specific behavior—provides a unique example in C. elegans and opens new avenues for studying sex-based neural differences. The discovery is expected to enhance our understanding of how such sexual dimorphisms alter responses both at the single-cell level and, the behavior of the whole organism.

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