Aug 2026· Experimental Eye Research· Vol 272, pp.
111208
· 0 citations· 47 references
Medicine
TL;DR
The findings suggest that Piezo1/2 recruitment to the plasma membrane is developmentally regulated and associated with a key transitional stage of lens fiber cell maturation.
Abstract
It has been proposed that in the absence of a blood supply and any direct innervation, the lens utilizes a variety of mechanosensitive ion channels to transduce changes to its internal and external environments into the activation of signaling pathways that alter fiber cell structure and hence overall lens function. One such mechanosensitive channel is Piezo1, the activation of which has been shown to phosphorylate Myosin light chain kinase (MLCK) and increase the expression of Transglutaminase 2 in fiber cells. To complement these functional studies, we have conducted a comprehensive mapping of the distribution of Piezo1 and Piezo2, the other member of this protein family, throughout all regions of the mouse lens. Using Western blotting, we first show that in addition to Piezo1, the mouse lens also expresses Piezo2. Using immunohistochemistry, we then show that both proteins are present throughout all regions of the lens, but are more concentrated in a discrete zone of high intensity labelling in mature fiber cells in the inner cortical region of the adult mouse lens. Despite being localized to the same localized ring the two proteins exhibited distinctly different subcellular distributions. In the outer cortex Piezo1 was more localized to the membrane, while Piezo2 was predominantly located in the cytoplasm of differentiating fiber cells. To determine at what stage of development this prominent ring of Piezo1/2 labelling was formed, immunohistochemistry was performed at different stages of embryonic and postnatal development. We found Piezo1 and Piezo2 to be both first expressed in the lens vesicle at E10, with both proteins exhibiting a constant level of cytoplasmic labelling across the whole lens throughout embryonic development and up to P6. This pattern of localisation changed from cytoplasmic to membranous at around P15 when the tunica vasculosa lentis was almost fully regressed and eye opening occurred. Our findings suggest that Piezo1/2 recruitment to the plasma membrane is developmentally regulated and associated with a key transitional stage of lens fiber cell maturation.
Piezo1 and Piezo2 are mechanosensitive ion channels that transduce mechanical stimuli into intracellular biochemical signals in diverse tissues and organ systems. Their functions in odontoblast development are still not well understood. In this study, we showed that Piezo1 and Piezo2 displayed dynamic expression in odontoblasts during terminal cytodifferentiation, suggesting a functional role in this process. However, Piezo1 knockouts in odontoblasts using Wnt1-Cre (Piezo1 cKO) did not cause pronounced structural change in tooth development in a majority of the Piezo1 cKO mice. Piezo2 cKO did not show obvious tooth defect either. Therefore, we pursued a double knockout approach. A phenotype analysis of Wnt1-Cre mediated Piezo1 and Piezo2 double knockout (Piezo1/Piezo2 dKO) mice revealed impaired cytodifferentiation and morphological change in the odontoblasts. Specifically, the heights of odontoblast and ameloblast layers were lower in Piezo1/Piezo2 dKO mice than controls, and expression of markers for odontoblast terminal differentiation, including collagen type 1a and alkaline phosphatase, was delayed. Furthermore, levels of nuclear β-catenin and Wnt10a were remarkably decreased, indicative of compromised Wnt/β-catenin signaling. Notably, the application of the Wnt10a protein rescued the odontoblast phenotype of Piezo1/Piezo2 dKO teeth in an ex vivo organ culture system. Moreover, the intraperitoneal injection of Yoda1, a Piezo1 channel agonist, facilitated odontoblast cytodifferentiation and elevated Wnt/β-catenin signaling in dental pulp tissues at the newborn stage. Altogether, these data suggest that Piezo channels play a role in regulating the terminal differentiation of odontoblasts via modulation of Wnt/β-catenin signaling.
Xu-Guang Nie, Kelley Huang, Emily Y. Chu et al.· International Journal of Ora...· 0 citations
By explaining how a single amino acid change produces a hypomorphic PIEZO2 allele, the findings broaden the clinical spectrum of PIEZO2 disorders and offer structural insight into mechanotransduction.
Alec R. Nickolls, Eric M. Mulhall, Daniel J. Orlin et al.· Neuron· 0 citations
BACKGROUND
Nx3 (novex-3) is an exceptionally small isoform of the giant protein titin, whose structural and functional roles within the sarcomere remain poorly understood.
METHODS AND RESULTS
We used a comprehensive, multimodal approach to define the key properties of Nx3 in healthy and failing hearts, including its abundance relative to FLT (full-length titin), sarcomeric localization, protein interactions, and functional relevance in mouse and human cardiomyocytes under physiological and pathological conditions. Using Western blotting, quantitative polymerase chain reaction, total RNA sequencing, and ribosome profiling, we show that Nx3 is constitutively expressed from fetal development through adulthood. In adult mouse and human myocardium, Nx3 accounts for ≈20% to 25% of total titin protein, despite representing only ≈8% to 14% at the transcript level. Immunoelectron microscopy and binding studies reveal that Nx3 adopts a nonlinear configuration within the sarcomere: its N terminus is anchored at the Z-disk, although the proximal portion of its unique region encoded by Ttn exon 48, enriched in coiled-coil motifs, engages laterally with adjacent titin or Nx3 molecules at the Z-disk/I-band interface. Its monomeric C terminus extends toward the A-band but remains confined to the Z-/I-band region. This architecture confers enhanced stability and flexibility to the Z-disk under mechanical load. Protein interaction studies, including yeast 2-hybrid screening and coimmunoprecipitation, identified Pin1 (peptidyl-prolyl cis-trans isomerase NIMA-interacting 1) and TBC1D4 (TBC1 domain family member 4) as binding partners of the Nx3 C terminal region, suggesting participation in signaling networks regulating cardiomyocyte metabolism. Genetic ablation of Nx3 in mouse hearts and human induced pluripotent stem cell-derived cardiomyocytes indicates that, although dispensable for sarcomere assembly, Nx3 is required for optimal Z-disk organization and mechanical performance. In end-stage dilated cardiomyopathy, human hearts exhibit dysregulated Nx3 expression, with reduced protein abundance relative to nonfailing controls and focal Z-disk disruption, likely contributing to impaired contractile function.
CONCLUSIONS
Nx3 regulates Z-disk stability and modulates signaling pathways that optimize cardiac performance, and its dysregulation contributes to heart failure pathogenesis.
W. Linke, Lisa Kümper, A. Fomin et al.· Circulation Research· 0 citations
Within the neuronal classes of the retina, amacrine cells (ACs) exhibit the greatest neuronal diversity in morphology and function. We show that the selective expression of the transcription factor Gbx2 is required for dendritic stratification of an individual AC subtype in the mouse retina. We identify Robo1 and Robo2 as downstream effectors that when deleted, phenocopy the dendritic misprojections seen in Gbx2 mutants. Slit1 and Slit2, the ligands of Robo receptors, are localized to the upper layers of the inner plexiform layer where we observe the dendritic misprojections in both Gbx2 and Robo1/2 mutants. We show that Robo receptors also are required for the proper dendritic stratification of additional AC subtypes, such as Vglut3+ ACs. These results show both that Gbx2 regulates the terminal differentiation of a single AC subtype and identify Slit-Robo signaling as a developmental mechanism for dendrite stratification in the retina.
Labony Khandokar, Yessica Santana Agreda, Bridget M. Curran et al.· Developmental Biology· 0 citations
Summary The transcription factor ATOH1 is a master regulator of mechanosensory hair-cell (HC) development in the ear. Here, we report that its target gene Casz1 regulates the maturation of outer HCs (OHCs). Genetic deletion of Casz1 during (but not after) cochlear development in the mouse caused: hearing loss; disorganization of mechanosensory stereocilia bundles in OHCs; reduced F-actin density in OHC cuticular plates; progressive OHC loss; and mild morphological alterations in inner HCs. This deletion also altered gene expression, delaying downregulation of genes expressed in immature OHCs, including the actin regulator-encoding gene Coro2a, and accelerating upregulation of genes expressed in mature OHCs. Deleting Coro2a in Casz1 mutant mice restored F-actin density in cuticular plates but increased stereocilia bundle disorganization and hearing thresholds, revealing that CORO2A provides an overall beneficial effect. Our data indicate that CASZ1 regulates transcriptional and morphological maturation of OHCs, and that CASZ1 in maturing HCs is necessary for hearing.
Y. Nakano, E. C. Driver, Ning Hu et al.· iScience· 0 citations
Ependymal (E1) cells, with their tufts of ∼50 motile cilia, line the walls of the brain ventricles and help propel the cerebrospinal fluid (CSF). The CSF is rich in signaling molecules, but the cellular targets that detect these signals and their function remain unknown. Here, we describe a distinct population of ependymal cells (E2) in the forebrain of mice and humans, the majority having only 1 or 2 cilia. These cilia were motile, but unlike E1 cells’ cilia, their pattern of motility and high expression of Arl13b and Inpp5e suggest a sensory function. E2 cells were characterized by an enormous, donut-like basal body that contained an increased number and size of subdistal appendages. In mice, E2 cells were mostly born in the embryo, but completed their differentiation in juveniles and young adults; they were found at higher densities in regions of high CSF flow and neurogenesis. E2 cilia contained the G protein-coupled receptor Smoothened, which accumulated in their cilia upon exposure to Sonic Hedgehog (Shh). Together, these findings identify E2 cells as a novel CSF-sensing ependymal cell type and provide a cellular target for the CSF signaling.
A. Cebrian-Silla, Fiona Dale-Huang, Stephanie A. Redmond et al.· bioRxiv· 0 citations
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