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Mechanosensation in the Upper Gastrointestinal Tract
Mechanosensation in the Upper Gastrointestinal Tract
Ingestion and digestion are driven by coordinated mechanosensory signals in the gastrointestinal (GI) tract. The GI tract is innervated by two major afferents - the vagal afferents and the DRG neurons, which relay different mechanosensory signals to the brain.
The sense of fullness and hunger is tightly mediated by chemical signals, such as leptin, and ghrelin, which are well-studied. However, for the longest time, mechanical signals which may also play a role in mediating the sense of satiety and hunger have been ignored, even though mechanical coordination plays an important role in digestion right from the moment the food is ingested. The GI tract undergoes a series of contractions and distentions to propel and accommodate the food.
I am interested in learning how these mechanical forces in the upper GI tract coordinate peristalsis and digestion, and relay satiety or hunger signals to the brain. I hope to further identify their molecular and cellular identities.
FM1-43 labels PIEZO2 activity in the skin
FM1-43 labels PIEZO2 activity in the skin
The PIEZO ion channels are critical for sensing mechanical force (like stretch, pressure) and mediate exteroceptive processes such as touch and proprioception. Interestingly, recently, it has been shown to play a critical role in interoceptive processes such as sensing bladder fullness, and lung expansion. However, their role in interoception has not been fully explored, partially due to the lack of robust tools.
We discovered that the dye FM1-43, traditionally used to study vesicular recycling can specifically label PIEZO2 activity in the neuronal endings. The dye is uptaken by the nerve endings that express PIEZO2 and makes its way to the cell body. For example, when the skin is touched, the hair in that area gets deflected activating the PIEZO2 positive neurons in the lanceolate endings. I generated a touch-dependent activity map of the mouse skin, using FM1-43, where the fluorescence gave a direct read-out of areas of skin that received a touch stimulus. This experiment helped confirm that FM1-43 only labels active mechanosensory neurons, and this discovery is a vital step that will now allow us to study PIEZO2 positive mechanosensory neurons in internal organs. (Villarino, et al. Neuron, 2023)
FM1-43 labelled lanceolate endings
Void Spot Assay Analysis in Cystitis Model
Void Spot Assay Analysis in Cystitis Model
Marshall et al, 2020 delineated the role of Piezo2 in sensing low threshold bladder stretch. In certain conditions affecting bladder filling, patients report not being able to sense bladder filling and having to time themselves to relieve their bladder to avoid accidents. Mice lacking PIEZO2 also show different urination patterns than the wild-type mice, which is validated using the void spot assay. In the void spot assay, the base of the cage is covered with filter paper, and the urination spots are later quantified to understand their bladder voiding patterns.
I wrote a macro in FIJI to automate the quantification of the void spot assay. I used the code to analyze the differences in urination patterns in diseased and healthy states.
I have written a code to correlate the void spots with the time spent at those coordinates via video analysis. This is to sparse out each voiding events, so that events that overlap in space are not ignored.
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