Biology subjects

Sugioka, K.

Publications and source records attributed to Sugioka, K..

8 recordsLinked to original sources

bioRxiv2026

Combinatorial regulation of cellular rotation by CUL-3-actomyosin-dependent oriented division, eggshell geometry, and Ras–MAPK signaling during dorsal–ventral axis establishment in Caenorhabditis elegans

Cellular rotation is an understudied mechanism that regulates animal morphogenesis. In C. elegans, the dorsal-ventral axis is established when the two-cell-stage AB cell rotates within the eggshell as it divides, generating the diamond-shaped blastomere arrangement at the four-cell stage that enables distinct cell fate specification. Multiple mechanisms, including actomyosin-dependent oriented division, chiral cortical flow, and eggshell shape, have been proposed to regulate this arrangement, but whether these represent conflicting hypotheses or co-acting mechanisms remains unclear. Here, we show that CUL-3-actomyosin-dependent oriented division, eggshell geometry, and the Ras-MAPK signaling pathway regulate distinct steps of cellular rotation. AB cell rotation occurred in two distinct phases: Phase I during AB cytokinesis and Phase II during cytokinesis of the neighboring P1 cell. Quantitative analysis revealed that CUL-3-actomyosin-dependent oriented division is the only one of these three pathways that regulates the AB division axis before anaphase. Actomyosin-dependent oriented division and eggshell geometry were both required for Phase I rotation, whereas Phase II rotation was independent of eggshell geometry. We further identified the Ras-MAPK signaling pathway as a regulator of AB cell rotation that acts independently of eggshell geometry. Strikingly, the CUL-3-actomyosin-dependent pathway may have two distinct roles: first, specifying the AB division axis, and second, correcting the division axis in all cell types during cytokinesis. Together, these functions contribute significantly to cellular rotation and dorsal-ventral axis establishment.

Cell Biology↗

bioRxiv2026

DemuxHMM: Large-Scale Single-Cell Embryo Profiling via Recombination Barcoding

High-resolution developmental time-courses with single-cell RNA sequencing (scRNA-seq) increasingly target trajectory inference and other analyses in the study of development and disease [1-6]. These datasets are often generated by pooling individuals and inferring cell-to-individual mappings after sequencing, in a process called demultiplexing. Existing demultiplexing methods are limited in the number of timepoints they can support, due to either the need for individual-by-individual processing or reduced accuracy at large numbers of individuals. To address these limitations, we introduce a combined experimental and computational framework for creating large-scale, individual-resolved datasets. Our framework couples a simple breeding scheme that creates contiguous SNP patterns (recombination barcodes) with a recombination-aware demultiplexing method, DemuxHMM, that explicitly models this structure with a Hidden Markov Model (HMM). We demonstrate substantial performance and scalability gains from this combined approach on simulated data, highlighting its potential to enable the creation of large-scale single-cell time series.

bioinformatics↗

bioRxiv2025

Cell cycle oscillations in a polarity network facilitate state switching by morphogenetic cues

The proper establishment of cell form, fate, and function during morphogenesis requires precise coordination between cell polarity and developmental cues. To achieve this, cells must establish polarity domains that are stable yet sensitive to guiding cues. Here we show that C. elegans germline blastomeres resolve this trade-off by creating a time-varying polarization landscape. Specifically, coupling the PAR polarity network to the cell-cycle kinase CDK-1 ensures that newborn cells operate in a low-feedback regime that lowers barriers to polarity state switching, allowing spatial cues to induce and orient PAR protein asymmetries. As CDK-1 activity rises at mitotic entry, increasing molecular feedback reinforces cue-induced asymmetries to yield robust and stable patterning of PAR domains. Consistent with this model, optogenetic and chemical perturbations show that low-CDK/low-feedback regimes destabilize PAR domains but are required for both de novo polarization and the reorientation of polarity in response to inductive cues. We propose that mitotic oscillations in cell polarity circuits dynamically optimize the polarization landscape to enable coordination of polarity with morphogenesis. Such temporal control of developmental networks is likely a general mechanism to balance robustness of cellular states with sensitivity to signal-induced state switching. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/681824v1_ufig1.gif" ALT="Figure 1"> View larger version (58K): org.highwire.dtl.DTLVardef@18b39f3org.highwire.dtl.DTLVardef@1898670org.highwire.dtl.DTLVardef@1d95517org.highwire.dtl.DTLVardef@1615f14_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Identification of Genes Required for Spatial Control and Mechanical Resilience of Cytokinesis during Caenorhabditis elegans Embryogenesis

Cytokinesis is the final step of cell division, in which the dividing cell is physically separated into two daughter cells by the contractile ring. The contractile ring is a highly resilient molecular machine that can function properly under mechanical stress. Additionally, its function, position, and orientation are spatially modulated in developing animals to regulate morphogenesis. Although essential regulators of cytokinesis have been identified through previous genetic screens, the molecular mechanisms underlying these spatial controls and the mechanical resilience of cytokinesis remain elusive. To identify cytokinesis regulators involved in these processes, we performed a high-throughput RNAi screen using a gain-of-function mutant of actin that exhibits ectopic cortical contraction and abnormal spatial control of cytokinesis in Caenorhabditis elegans embryos. We obtained a list of early embryonic genes that suppress embryonic lethality in an act-2 mutant background. Two parallel secondary screens of candidate genes were conducted. The first secondary screen in a wild-type background identified 69 candidate genes regulating spatial cytokinesis control--asymmetric ring closure, positioning, and rotation--during early embryogenesis. The second secondary screen in the act-2(or295) background identified four genes required for cytokinesis in this background, including microtubule regulators, evl-20/ARL2, and lpin-1/Lipin1. This study will serve as a useful resource for the development of future hypotheses and provide insights into the precise regulation of cytokinesis in tissues.

cell biology↗

bioRxiv2024

Cytokinesis-dependent twisting of HMR-1/Cadherin regulates the first left-right symmetry-breaking event in Caenorhabditis elegans

Diverse mechanisms for establishing cellular- and organismal-level left-right (L-R) asymmetry emerged during the evolution of bilateral animals, including cilia-based and actomyosin-dependent mechanisms. In pond snails and Caenorhabditis elegans, cell division plays a critical role in regulating both levels of L-R asymmetries. However, the precise mechanism by which cell division breaks cellular-level L-R symmetry remains elusive. Here, we show that cytokinesis-induced cortical flow twists the cell-cell adhesion pattern, which in turn controls the L-R asymmetrical constriction of the contractile ring, thereby breaking the first L-R body symmetry in C. elegans. During the second mitosis of C. elegans embryos, we discovered the twisting of the HMR-1/cadherin patch at the cell-cell contact site. The HMR-1 patch twisting occurs within a few minutes upon cytokinesis onset, with individual cadherin foci within the patch exhibits directional flow and coalescence. This cell type exhibits chiral cortical flow, characterized by counter-rotational surface flows in the two halves of the dividing cell. We found that this chiral cortical flow plays a critical role in regulating HMR-1 patch twisting by inducing cadherin flow. As the HMR-1 patch twists, the contractile ring preferentially associates with HMR-1 on the right side of the embryo. We demonstrate that HMR-1 patch twisting regulates the L-R asymmetric ring closure. This study uncovers an interplay between three fundamental cellular processes--cell-cell adhesion, cytokinesis, and cell polarity-- mediated by cadherin flow, shedding light on cadherin flows role in cellular patterning during development.

cell biology↗

bioRxiv2022

Intrinsic and extrinsic inhibition of cortical flow underlies symmetry breaking during unilateral cytokinesis

The contractile ring plays crucial roles in animal morphogenesis. Previous studies have explored how tissue mechanics controls the contractile ring; however, the mechanisms by which the ring senses tissue mechanics remain largely unknown. Here, we demonstrate the mechanism of contractile ring mechanosensation and its tuning during asymmetric ring closure of Caenorhabditis elegans embryos. High-resolution imaging of cortical flow revealed that local suppression of the ring-directed cortical flow is associated with a delay in furrowing. This suppression of cortical flow results from cortical compression. We found that the artificial inhibition of ring-directed cortical flow was sufficient to induce asymmetric ring closure in symmetrically dividing cells. Moreover, genetic analysis suggests that the positive feedback loop among ring-directed cortical flow, myosin enrichment, and ring constriction constitutes the anillin-dependent, mechanosensitive engine driving asymmetric ring closure. Our results suggest that the balance between RhoA-dependent and cortical flow-dependent myosin enrichment fine-tunes the rings mechanosensitivity in tissues.

cell biology↗

bioRxiv2017

Cell-nonautonomously tunable actomyosin flowsorient distinct cell division axes

Cell division axes during animal development are arranged in diverse orientations, but the molecular mechanisms underlying this diversity remain unclear. By focusing on oriented divisions that are independent of known microtubule/dynein pathways, we show here that the non-muscle myosin II motor is an extrinsically tunable force generator that orients cell division axes through cortical actomyosin flows. We identified three extracellular cues that generate different actomyosin flows. A single contact site locally inhibited myosin activity in a mechanosensitive manner to generate local flow asymmetry, while size asymmetry of two contact sites and Wnt signaling both polarized myosin activity and actomyosin flow, with the latter overriding mechanosensitive effects. These intracellular actomyosin flow anisotropies specify distinct division axes to establish the geometries of not only Caenorhabditis elegans 4-, 6-, and 7-cell stage but also mouse 4-cell stage embryos. Tunable actomyosin flows together with microtubule/dynein pathways may specify diverse division axes across species.

cell biology↗

bioRxiv2017

The tumor suppressor APC is an attenuator of spindle-pulling forces during C. elegans asymmetric cell division

The adenomatous polyposis coli (APC) tumor suppressor has dual functions in Wnt/{beta}-catenin signaling and accurate chromosome segregation, and is frequently mutated in colorectal cancers. Although APC contributes to proper cell division, the underlying mechanisms remain poorly understood. Here we show that C. elegans APR-1/APC is an attenuator of the pulling forces acting on the mitotic spindle. During asymmetric cell division of the C. elegans zygote, a LIN-5/NuMA protein complex localizes dynein to the cell cortex to generate pulling forces on astral microtubules that position the mitotic spindle. We found that APR-1 localizes to the anterior cell cortex in a Par-aPKC polarity-dependent manner and suppresses anterior centrosome movements. Our combined cell biological and mathematical analyses support the conclusion that cortical APR-1 reduces force generation by stabilizing microtubule plus ends at the cell cortex. Furthermore, APR-1 functions in coordination with LIN-5 phosphorylation to attenuate spindle pulling forces. Our results document a physical basis for spindle-pulling force attenuation, which may be generally used in asymmetric cell division, and when disrupted potentially contributes to division defects in cancer.\n\nSignificance StatementAPC (adenomatous polyposis coli) is a Wnt signaling component as well as a microtubule-associated protein, and its mutations are frequently associated with colorectal cancers in humans. Although APC stabilizes microtubules (MTs), its mechanical role during cell division is largely unknown. Here we show that APC is an attenuator of forces acting on the mitotic spindle during asymmetric cell division of the C. elegans zygote. We performed live-imaging, laser-microsurgery, and numerical simulation to show how APC suppresses spindle pulling force generation by stabilizing microtubule plus-ends and reducing microtubule catastrophe frequency at the cell cortex. Our study is the first to document a mechanical role for the APC protein, and provides a physical basis for spindle-pulling force attenuation.

cell biology↗