Apodaca, G. | Search bioRxiv

bioRxiv2025

Conditional deletion of Tmem63b does not impact mouse voiding behavior

The proper function of the lower urinary tract depends on its ability to sense and react to mechanical forces as urine is produced, transported, stored, and eliminated; however, our current understanding of the mechanosensors involved in these events is limited. TMEM63 ion channels are reported to function as mechanosensors/osmosensors in other organs, and our studies revealed that the primary site of Tmem63a and Tmem63b gene expression and TMEM63B protein expression in the mouse bladder wall was the urothelium. Despite this localization, voiding behavior in conditional urothelial Tmem63b knockout mice, assessed using a video-monitored void-spot screening assay, was not significantly different from control mice, even when the urothelium was stressed by exposure to cyclophosphamide. We further observed that dorsal root ganglia sensory neurons, including those innervating the bladder, were also sites of Tmem63a, Tmem63b, and TMEM63B expression. Again, voiding behavior was not impacted in conditional sensory neuron Tmem63b knockout mice, treated or not with cyclophosphamide. Our studies reveal that the urothelium and dorsal root ganglia are sites of Tmem63a, Tmem63b, and TMEM63B expression, but deletion of Tmem63b alone in these tissues does not result in a demonstrable voiding phenotype.

physiology↗

bioRxiv2024

The umbrella cell keratin network: organization as a tile-like mesh, formation of a girded layer in response to bladder filling, and dependence on the plectin cytolinker

The keratin cytoskeleton and associated desmosomes contribute to the mechanical stability of epithelial tissues, but their organization in bladder umbrella cells and their responses to bladder filling are poorly understood. Using super-resolution confocal microscopy, along with 3D image reconstruction and platinum replica electron microscopy, we observed that the apical keratin network of umbrella cells was organized as a dense tile-like mesh comprised of tesserae bordered on their edges by cortical actin filaments, filled with woven keratin filaments, and crosslinked by plectin. A band of keratin was also observed at the cell periphery that was linked to the junction-associated actin ring by plectin. During bladder filling, the junction-localized desmosomal necklace expanded, and a subjacent girded layer was formed that linked the keratin network to desmosomes, including those at the umbrella cell-intermediate cell interface. Disruption of plectin led to focal keratin network dissolution, loss of the junction-associated band of keratin, perturbation of tight junction continuity, and loss of cell-cell cohesion. Our studies reveal a novel tile-like organization of the umbrella cell keratin cytoskeleton that is dependent on plectin, that reorganizes in response to bladder filling, and that likely serves to maintain umbrella cell continuity in the face of mechanical distension.

cell biology↗