Biology subjects

Carattino, M. D.

Publications and source records attributed to Carattino, M. D..

3 recordsLinked to original sources

bioRxiv2026

Subtypes of Bladder-Innervating Sensory Neurons revealed by Immuno-Fluorescence In Situ Hybridization

Sensory neurons that innervate the urinary bladder are critical for triggering voiding and mediating pain perception under pathological conditions. Despite functional and immunohistochemical evidence indicating the existence of several bladder afferent populations, the subtypes of dorsal root ganglion (DRG) neurons that innervate this organ are poorly defined and specific markers to study them have not been described. Here, we combined retrograde tracing with the cholera toxin {beta} subunit and immunofluorescence in situ hybridization with markers defined by transcriptomic analysis of C and A{delta} afferents to classify the lumbosacral DRG neurons that innervate the urinary bladder. Four lumbosacral (L6-S2) bladder-innervating DRG neuron populations were identified: three Calca+ peptidergic populations that express Adra2a/Th, Th/Ntrk2, or Ntrk2, and one non-peptidergic population that expresses Ntrk2. Among the whole population of peptidergic lumbosacral sensory neurons, Adra2a+/Th+, Th+/Ntrk2+ and Ntrk2+ neurons were rare. Thus, our studies identified multiple populations of bladder-innervating DRG neurons, revealing unappreciated diversity among the sensory neuron subtypes present at the lumbosacral level that innervate visceral and somatic tissues.

neuroscience↗

bioRxiv2026

Functional characterization and classification of mechanosensitive bladder afferents

Normal urinary bladder function relies on afferent fibers that detect and integrate mechanical and chemical cues related to bladder distension. Though, the molecular identity and function of the various sensory neuron types involved in bladder function have yet to be fully elucidated. Here, we introduce a novel framework for the functional classification of mechanosensitive bladder afferents based on their differential responses to physiological (15 l/min) and noxious filling (30 s at intravesical pressures of 10, 20, 30, 40, 50, and 60 cmH2O). Our data reveal the presence of three distinct types of mechanosensitive bladder afferents, two that respond to physiological distension (type I and II) and one that is activated by noxious stimulation (type III). Of the two populations that respond to physiological filling, one displays a linear increase in firing with bladder filling (type I), while the firing of the other plateaus as intravesical pressure increases (type II). Fast filling (130 l/min) increases the discharge of all three afferent types, with the effect being most pronounced in those responding to noxious stimulation (type III). Corroborating the existence of three functionally distinct bladder afferent populations, Yoda1, a selective PIEZO1 channel activator, significantly increased the firing rate of types I and III during slow filling and of type III during noxious stimulation. In summary, we present a reliable and reproducible method for studying and classifying bladder afferents, while providing compelling evidence for the existence of functionally distinct populations of mechanosensitive afferents, each activated and regulated by distinct mechanisms. New & NoteworthyUsing a novel approach, we identify three types of mechanosensitive afferents innervating the urinary bladder, two that respond to slow filling and one that is activated only by noxious distension. The three afferent types display distinct firing patterns during rapid filling and in response to the PIEZO1 channel agonist Yoda1.

physiology↗

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↗