Biology subjects

Kawanishi, T.

Publications and source records attributed to Kawanishi, T..

6 recordsLinked to original sources

bioRxiv2025

A single-cell transcriptomic atlas of inner ear morphogenesis in zebrafish

The inner ear constitutes different cell types next to one another: the sensory patches whose hair cells synapse with neurons, the thin channels of three semicircular canals whose perpendicular organization enables detection of directional head rotation, and the endolymphatic duct and sac whose conditional epithelial barrier relieves excess pressure and promotes fluid pressure homeostasis. How the ears component cell states are established during development has remained unknown. We use single-cell RNA sequencing to distinguish cell states within the developing ear with wild-type zebrafish embryos and lmx1bb mutants that exhibit defects in canal and sac morphogenesis. We identify the earliest marker for the semicircular canal-genesis zone (ccn1l1), unexpected genes in the endolymphatic sac that suggest a role for tissue contraction in its function (smtnb), parallel gene sets for sensory patches in the neuromast and ear, and a conserved role for cell-cycle pausing (cdkn1bb expression in the canals and sac as previously observed in the developing mouse ear). This atlas provides the most comprehensive transcriptional profiling of the developing inner ear, identifying new molecular leads to understand ear morphogenesis. Summary statementSingle-cell transcriptomic analysis of developing wild-type and lmx1bb mutant zebrafish reveals cell-states and effectors that distinguish the inner ears sensory patches, semicircular canals, endolymphatic duct and sac, and periotic mesenchyme.

developmental biology↗

bioRxiv2025

Differential spreading behaviors of Nodal signalling molecules in the extracellular space cooperatively shape left-right asymmetry

Left-right (LR) patterning of vertebrate embryos is mediated by diffusive proteins secreted mainly from the left-right organizer (LRO), such as TGF-{beta} superfamily ligands Nodal and Gdf1, as well as their inhibitors Dand5 and Lefty. However, precise modes of action for these proteins remain unclear due to difficulties in visualizing and manipulating their extracellular behaviors. Here we visualize and manipulate the extracellular dynamics of these proteins employing novel transgenic zebrafish lines and extracellular trapping molecules including the morphotrap. We demonstrate that the heterodimer of Nodal and Gdf1, which is the major signal transducer in vertebrate Nodal signalling, spreads from the LRO through the extracellular space in the paraxial mesoderm (PM) to its target tissue, the lateral plate mesoderm (LPM), in a free-diffusion-like manner. By contrast, Dand5 is highly enriched in the right PM, where it is immobilized through interaction with heparan sulfate proteoglycans and asymmetrically suppresses Nodal signalling. Our study uncovers diverse modes of action for LR-related secreted proteins in the extracellular space, providing a new framework for understanding how spatially organized Nodal signalling molecules shape embryonic LR asymmetry.

developmental biology↗

bioRxiv2024

Species-specific oxygen sensing governs the initiation of vertebrate limb regeneration

Why mammals cannot regenerate limbs, unlike amphibians, presents a longstanding puzzle in biology. We show that exposing ex vivo amputated embryonic mouse limbs to subatmospheric oxygen environment, or stabilizing oxygen-sensitive HIF1A enables not only rapid wound healing, but alters cellular mechanics, and reshapes the histone landscape to prime regenerative fates. Conversely, regenerative Xenopus tadpole limbs display low oxygen-sensing capacity, robust wound healing, a regenerative histone landscape, and glycolytic programs even under high oxygen. This reduced oxygen-sensing capacity, in stark contrast to mammals, associates with decreased HIF1A-regulating gene expressions. Our findings thus uncover species-specific oxygen sensing as a unifying mechanism for limb regeneration initiation across vertebrates, reveal how aquatic subatmospheric habitats may enhance regenerative capabilities, and identify targetable barriers to unlock latent limb regenerative programs in adult mammals.

developmental biology↗

bioRxiv2021

Reemployment of Kupffer's vesicle cells into axial and paraxial mesoderm via transdifferentiation

Kupffers vesicle (KV) in the teleost embryo is a fluid-filled vesicle surrounded by a layer of epithelial cells with rotating primary cilia. KV transiently acts as the left-right organizer but degenerates after the establishment of left-right asymmetric gene expression. Previous labelling experiments indicated that descendants of KV-epithelial cells are incorporated into mesodermal tissues after KV collapses (KV-collapse) in zebrafish embryos. However, the overall picture of their differentiation potency had been unclear due to the lack of suitable genetic tools and molecular analyses. In the present study, we established a novel zebrafish transgenic line with a promoter of charon, in which all KV-epithelial cells and their descendants are specifically labelled until the larval stage. We found that KV-epithelial cells underwent epithelial-mesenchymal transition upon KV-collapse and infiltrate into adjacent mesodermal progenitors, the presomitic mesoderm and chordoneural hinge. Once incorporated, the descendants of KV-epithelial cells expressed distinct mesodermal differentiation markers and contributed to the mature populations such as the axial muscles and notochordal sheath through normal developmental process. These results indicate that fully differentiated KV-epithelial cells possess unique plasticity in that they are reemployed into mesodermal lineages through transdifferentiation after they complete their initial role in KV.

developmental biology↗

bioRxiv2021

Zic1 advances epaxial myotome morphogenesis to cover the neural tube via Wnt11r

The dorsal axial muscles, or epaxial muscles, are a fundamental structure covering the spinal cord and vertebrae, as well as mobilizing the vertebrate trunk. To date, mechanisms underlying the morphogenetic process shaping the epaxial myotome are largely unknown. To address this, we used the medaka zic1/zic4-enhancer mutant Double anal fin (Da), which exhibits ventralized dorsal trunk structures resulting in impaired epaxial myotome morphology and incomplete coverage over the neural tube. In wild type, dorsal dermomyotome (DM) cells, progenitors of myotomal cells, reduce their proliferative activity after somitogenesis and subsequently form unique large protrusions extending dorsally, potentially guiding the epaxial myotome dorsally. In Da, by contrast, DM cells maintain the high proliferative activity and form mainly small protrusions. By combining RNA- and ChIP-sequencing analyses, we revealed direct targets of Zic1 which are specifically expressed in dorsal somites and involved in various aspects of development, such as cell migration, extracellular matrix organization and cell-cell communication. Among these, we identified wnt11r as a crucial factor regulating both cell proliferation and protrusive activity of DM cells. We propose that the dorsal movement of the epaxial myotome is guided by DM cells and that Zic1 empowers this activity via Wnt11r to achieve the neural tube coverage.

developmental biology↗

bioRxiv2021

Mechanically Sensitive HSF1 is a Key Regulator of Left-Right Symmetry Breaking in Zebrafish Embryos

The left-right symmetry breaking of vertebrate embryos requires fluid flow (called nodal flow in zebrafish). However, the molecular mechanisms that mediate the asymmetric gene expression regulation under nodal flow remain elusive. In this paper, we report that heat shock factor 1 (HSF1) is asymmetrically activated in the Kuppfers vesicle at the early stage of zebrafish embryos in the presence of nodal flow. Deficiency in HSF1 expression caused a significant situs inversus and disrupted gene expression asymmetry of nodal signaling proteins in zebrafish embryos. Further studies demonstrated that HSF1 could be immediately activated by fluid shear stress. The mechanical sensation ability of HSF1 is conserved in a variety of mechanical stimuli in different cell types. Moreover, cilia and the Ca2+-Akt signaling axis are essential for the activation of HSF1 under mechanical stress in vitro and in vivo. Considering the conserved expression of HSF1 in organisms, these findings unveil a fundamental mechanism of gene expression regulation triggered by mechanical clues during embryonic development and other physiological and pathological transformations.

developmental biology↗