Biology subjects

Irons, Z. H.

Publications and source records attributed to Irons, Z. H..

3 recordsLinked to original sources

bioRxiv2025

Motile cilia spin the Reissner fiber, a tensioned and anchored extracellular thread essential for body morphogenesis

The Reissner fiber (RF) is an extracellular thread composed of the glycoprotein SCO-spondin (Sspo) that forms within cerebrospinal fluid (CSF) in the brain ventricles and central canal (CC) of vertebrates. Its assembly depends on motile cilia, yet how cilia and CSF flow transform secreted Sspo into a fiber that spans the length of the body axis has remained unknown. Using live imaging in zebrafish, we show that globular Sspo is remodeled into thin fibrils that anchor to the floor plate (FP), elongate, and spin together into a tensioned, posteriorly translocating RF. Fiber assembly draws on a shared CSF pool of Sspo but requires local ciliary activity for globule-to-fibril remodeling. Once assembled, the RF is anchored by dynamic fibrils that stabilize the fiber and preserve its tension. Perturbations that locally disrupt ciliary motility and RF integrity along the CC result in region-specific defects in axial morphogenesis. These findings identify the RF as a flow-responsive extracellular system that converts ciliary beating into mechanical structure, linking fluid dynamics to the large-scale shaping of the vertebrate body. HighlightsO_LIMotile cilia remodel Sspo globules into FP-anchored fibrils that bundle into RF. C_LIO_LIRF assembly draws on a shared CSF Sspo pool but requires local cilia activity. C_LIO_LILaser ablation reveals patterned RF tension constrained by dynamic FP anchors. C_LIO_LIRegional cilia defects cause local RF loss and corresponding body shape defects. C_LI

developmental biology↗

bioRxiv2022

Urotensin II-Related Peptides, Urp1 and Urp2, Control Zebrafish Spine Morphology

The spine provides structure and support to the body, yet how it develops its characteristic morphology as the organism grows is little understood. This is underscored by the commonality of conditions in which the spine curves abnormally such as scoliosis, kyphosis and lordosis. Understanding the origin of such spinal curves has been challenging in part due to the lack of appropriate animal models. Recently, zebrafish have emerged as promising tools with which to understand the origin of spinal curves. Using zebrafish, we demonstrate that the Urotensin II-related peptides (URPs), Urp1 and Urp2, are essential for maintaining spine morphology. Urp1 and Urp2 are 10-amino acid cyclic peptides expressed by neurons lining the central canal of the spinal cord. Upon combined genetic loss of Urp1 and Urp2, adolescent-onset planar curves manifested in the caudal region of the spine, akin to a lordosis-like condition. Highly similar curves were caused by mutation of Uts2r3, an URP receptor. Quantitative comparisons revealed that Urotensin-associated curves were distinct from other zebrafish spinal curve mutants that more closely reflected idiopathic scoliosis or kyphosis. Last, we found that the Reissner fiber, a proteinaceous thread that sits in the central canal and has been implicated in the control of spine morphology, breaks down prior to curve formation in an idiopathic scoliosis model but was unperturbed by loss of Uts2r3. This suggests a Reissner fiber-independent mechanism of curvature in Urotensin-deficient mutants. Overall, our results show that Urp1 and Urp2 control zebrafish spine morphology and establish new animal models of lordosis-like curves.

developmental biology↗

bioRxiv2021

Building the cytokinetic contractile ring in an early embryo: initiation as clusters of myosin II, anillin and septin, and visualization of a septin filament network

The cytokinetic contractile ring (CR) was first described some 50 years ago, however our understanding of the assembly and structure of the animal cell CR remains incomplete. We recently reported that mature CRs in sea urchin embryos contain myosin II mini-filaments organized into aligned concatenated arrays, and that in early CRs myosin II formed discrete clusters that transformed into the linearized structure over time. The present study extends our previous work by addressing the hypothesis that these myosin II clusters also contain the crucial scaffolding proteins anillin and septin, known to help link actin, myosin II, RhoA, and the membrane during cytokinesis. Super-resolution imaging of cortices from dividing embryos indicates that within each cluster, anillin and septin2 occupy a centralized position relative to the myosin II mini-filaments. As CR formation progresses, the myosin II, septin and anillin containing clusters enlarge and coalesce into patchy and faintly linear patterns. Our super-resolution images provide the initial visualization of anillin and septin nanostructure within an animal cell CR, including evidence of a septin filament network. Furthermore, Latrunculin-treated embryos indicated that the localization of septin or anillin to the myosin II clusters in the early CR was not dependent on actin filaments. These results highlight the structural progression of the CR in sea urchin embryos from an array of clusters to a linearized purse string, the association of anillin and septin with this process, and provide, for the first time, the visualization of septin filament higher order structure in an animal cell CR.

cell biology↗