Physics PhD Dissertation Defense: Jiazhang Chen: "Mechanosensation of Sensory Neurons in Drosophila Larvae"

Abstract: 

Mechanosensation, a ubiquitous phenomenon, is fundamental to the survival and evolution of organisms. This intricate process, which has been refined over eons, encompasses a broad spectrum of sensory experiences. These range from auditory perception, the delicate discernment of tactile stimuli, to the detection of potentially damaging forces. The majority of these mechanosensory processes are mediated by specialized neurons or neuron-associated structures within the organism. These structures have evolved to adeptly convert mechanical stimuli into electrochemical signals, thereby enabling the organism to interact with and adapt to its environment.

In Drosophila larvae, the perception of nociceptive touch instigates a defensive response, a process mediated by Class IV dendritic arborization (C4da) sensory neurons. The precise mechanisms enabling these larvae to perceive mechanical nociception, particularly in response to intense mechanical stimuli, remain elusive. The specific nature of the mechanical stimuli that activate larval nociceptors, as well as the mechanisms through which sensory neurons mediate the perception of mechanical pain, are yet to be fully elucidated. To investigate these intriguing questions, we have utilized microfluidic devices, enabling us to specifically examine the mechanosensitivity of C4da neurons and understand the molecular mechanisms.

In contrast to nociceptive responses, gentle touch in Drosophila larvae triggers behaviors such as hesitation, turning, or retreating, mediated by Class III dendritic arborization (C3da) sensory neurons. These neurons, located subcutaneously, possess long, microtubule-rich dendritic shafts and short, actin-rich filopodia. Previous research has identified the nompC channel, a member of the transient receptor potential (TRP) family, as a touch-sensitive channel in C3da neurons. The intracellular N-terminal of the nompC channel forms a spring-like structure linked to microtubules, and touch-induced compression of this structure is hypothesized to gate the channel. However, the presence of actin, not microtubules, in C3da neuron filopodia raises questions about the role of the nompC channel in these structures. The mechanistic differences between primary dendrites and filopodia also remain unclear. To investigate these, we utilized atomic force microscopy (AFM) to examine filopodia mechanosensitivity and the molecular mechanisms involved.

Committee members:

Qi Wen - WPI, Physics - WPI, Physics

Nancy Burnham - WPI, Physics

Kun-Ta Wu - WPI, Physics

Yang Xiang - University of Massachusetts Chan Medical School, Neurobiology