Xian Hu

• Haga, Jens Ådne Rekkedal; Vestli, Live Lislerud; Jakobsen, Kjetill Sigurd; Resseguier, Julien Alain Andre; Margadant, Felix & Bakke, Oddmund [Vis alle 7 forfattere av denne artikkelen] (2026). Morphology and autofluorescence of the thallus of the golden-brown alga <i>Hydrurus foetidus</i> by optical and fluorescence-lifetime imaging. Biology Open. doi: 10.1242/bio.062873. Fulltekst i vitenarkiv Vis sammendrag

  The chrysophyte Hydrurus foetidus belongs to the psychrophilic, rheophilic algae of cold, fast-flowing glacial and alpine streams but remains poorly characterised at the cellular level. We present a systematic optical-microscopy study of field-collected material of this organism, combining confocal imaging, quantitative morphometry, three-dimensional volumetry and fluorescence-lifetime imaging (FLIM). Confocal imaging revealed a pseudoparenchymatous architecture: elongated, longitudinally aligned cells dominate the central axis, whereas round cells occupy the peripheral branches, and the two populations differ in volume. High-magnification imaging showed a consistent apical bias in nuclear position along the cell files of the central axis. FLIM of endogenous autofluorescence yielded reproducible lifetime signatures across the green, orange and far-red emission channels; in the far-red the chlorophyll a signal resolved into a two-component mixture, and the round-cell population was bimodal in lifetime whereas the elongated population was not. All material derives from a single winter collection; the whole-thallus spatial analyses come from one intact thallus, while morphometry, volumetry and FLIM sampled cells from multiple thalli of that collection, and the data are analysed accordingly. Together, these data provide a morphological and photophysical foundation, and a label-free autofluorescence reference, for future cell-biological study of H. foetidus and of multicellular organisation among the chrysophytes.

• Livia, Bajelan,; Bjarne, Bogen,; Ranveig, Braathen,; Prabhu, Gopalakrishnan, Ramakrishna; Victor, Greiff, & Hu, Xian [Vis alle 10 forfattere av denne artikkelen] (2026). Idiotype-specific CD4+ T cells chronically stimulate autoreactive B cells to develop into B lymphomas in mice | Nature Communications. Nature Communications. doi: 10.1038/s41467-026-69916-w. Fulltekst i vitenarkiv Vis sammendrag

  The molecular mechanism linking autoimmunity to the development of lymphoma remains unexplained. Here, the authors develop a mouse model and show that chronic Id-driven T-B collaboration initiates autoreactive B cell responses and drives malignant transformation into lymphoma.

• Vo, Nicole; Oñate, Lorena de; Frank, Maximillian; Hu, Xian; Blackburn, Sophie M. & Foss, Dana V. [Vis alle 13 forfattere av denne artikkelen] (2026). Calcium Shock Enables Efficient and Programmable Particle Delivery for Genome Editing Applications. Advanced Science. 13(21). doi: 10.1002/advs.202510441. Vis sammendrag

  ABSTRACT Classical intracellular delivery methods such as transfection and transduction are inefficient, particularly with confluent cells and organoids, and lack cell type‐specific programmability. We demonstrate that an innovative methodology called calcium shock (CaSh) dramatically improves particle delivery into single cells, colonies, and organoids, and enables programmable delivery (CaSh‐Pro) into specific cell types within heterocellular populations. Calcium shock works by increasing endocytotic uptake while simultaneously disarming cell‐cell junctions. CaSh‐Pro further incorporates specific molecular targeting agents and amphiphilic peptides for preferential editing of different cell types. Calcium shock improves expression of plasmid, ribonucleoprotein, or adeno‐associated viral vectors with minimal toxicity in intact organoids representing diverse lineages. CaSh and CaSh‐Pro provide simple, versatile protocols for genome editing in complex systems, to enable biological discovery and therapeutic development.

• Ho, Richard David Jun-Geet; Mossige, Joachim; Ponomartcev, Sergei; Natalia, Smirnova,; Sunny, Dai, Keqing & Hu, Xian [Vis alle 9 forfattere av denne artikkelen] (2025). [2509.08929] Spontaneous elongation of 3D gastruloids from local cell polarity alignment. arXiv. doi: https:/arxiv.org/abs/2509.08929. Fulltekst i vitenarkiv Vis sammendrag

  Gastruloids are 3D stem cell aggregate models for early embryogenesis that provide a unique platform to study how collective cell dynamics drive tissue symmetry breaking and axial elongation. Using 3D light sheet imaging, we show that a pulse of Chiron, a Wnt activator, induces coherent alignment of cell polarity during elongation. While nuclear elongation occurs with or without treatment, only Chiron-treated gastruloids exhibit quasi-long-range alignment of nuclear axes, linking cell polarity coherence to tissue-scale remodeling. A minimal physical model of polarized cells, incorporating alignment-dependent torques and polarity-mediated adhesion, reproduces symmetry breaking and elongation, demonstrating that local cell polarity alignment alone can drive tissue-scale convergence-extension flows.

• Hu, Xian; Jalal, Salma; Yao, Mingxi; Bakke, Oddmund; Margadant, Felix Martin & Sheetz, Michael P. (2024). Differential Talin cleavage in transformed and non-transformed cells and its consequences. Frontiers in Cell and Developmental Biology. 12. doi: 10.3389/fcell.2024.1430728. Fulltekst i vitenarkiv Vis sammendrag

  This study investigates differences in focal adhesion (FA) morphology and Talin cleavage levels between transformed and non-transformed cell lines. Utilizing fluorescently tagged wild-type Talin and Talin mutants with calpain cleavage site mutations, FA structures were visualized. Mutations in different Talin cleavage sites showed varying impacts on FA morphology and distribution across melanoma cell lines (Meljuso, A375P, A2058) and a non-transformed cell line (HFF). Western blot analysis, ratiometric fluorescence intensity-based measurements, and FRAP experiments revealed higher Talin cleavage levels within FAs of transformed cell lines compared to non-transformed cells. Additionally, growth assays indicated that reducing calpain cleavage levels attenuated transformed cell growth. These findings suggest that Talin cleavage level is crucial for FA morphology and assembly, with higher levels observed in transformed cells, influencing their growth dynamics.

• Reint, Ganna; Li, Zhuokun; Labun, Kornel; Keskitalo, Salla; Soppa, Inkeri & Mamia, Katariina Aino Inkeri [Vis alle 19 forfattere av denne artikkelen] (2021). Rapid genome editing by CRISPR-Cas9-POLD3 fusion. eLIFE. 11. doi: 10.7554/eLife.75415. Fulltekst i vitenarkiv Vis sammendrag

  Precision CRISPR gene editing relies on the cellular homology-directed DNA repair (HDR) to introduce custom DNA sequences to target sites. The HDR editing efficiency varies between cell types and genomic sites, and the sources of this variation are incompletely understood. Here, we have studied the effect of 450 DNA repair protein - Cas9 fusions on CRISPR genome editing outcomes. We find the majority of fusions to improve precision genome editing only modestly in a locus- and cell-type specific manner. We identify Cas9-POLD3 fusion that enhances editing by speeding up the initiation of DNA repair. We conclude that while DNA repair protein fusions to Cas9 can improve HDR CRISPR editing, most need to be optimized to the cell type and genomic site, highlighting the diversity of factors contributing to locus-specific genome editing outcomes.

• Skjeldal, Frode Miltzow; Haugen, Linda Hofstad; Mateus, Duarte Nunes De C; Frei, Dominik Michael; Rødseth, Anna Vik & Hu, Xian [Vis alle 7 forfattere av denne artikkelen] (2021). De novo formation of early endosomes during Rab5-to-Rab7a transition. Journal of Cell Science. ISSN 0021-9533. 134(8). doi: 10.1242/jcs.254185. Fulltekst i vitenarkiv Vis sammendrag

  Rab5 and Rab7a are the main determinants of early and late endosomes and are important regulators of endosomal progression. The transport from early endosomes to late endosome seems to be regulated through an endosomal maturation switch, where Rab5 is gradually exchanged by Rab7a on the same endosome. Here, we provide new insight into the mechanism of endosomal maturation, for which we have discovered a stepwise Rab5 detachment, sequentially regulated by Rab7a. The initial detachment of Rab5 is Rab7a independent and demonstrates a diffusion-like first-phase exchange between the cytosol and the endosomal membrane, and a second phase, in which Rab5 converges into specific domains that detach as a Rab5 indigenous endosome. Consequently, we show that early endosomal maturation regulated through the Rab5-to-Rab7a switch induces the formation of new fully functional Rab5-positive early endosomes. Progression through stepwise early endosomal maturation regulates the direction of transport and, concomitantly, the homeostasis of early endosomes.

• Guadagno, Noemi Antonella; Margiotta, Azzurra; Bjørnestad, Synne Arstad; Haugen, Linda Hofstad; Kjos, Ingrid & Xiaochun, Xu [Vis alle 10 forfattere av denne artikkelen] (2020). Rab18 regulates focal adhesion dynamics by interacting with kinectin-1 at the endoplasmic reticulum. Journal of Cell Biology. ISSN 0021-9525. 219(7), s. 1–23. doi: 10.1083/JCB.201809020. Fulltekst i vitenarkiv Vis sammendrag

  The members of the Rab family of small GTPases are molecular switches that regulate distinct steps in different membrane traffic pathways. In addition to this canonical function, Rabs can play a role in other processes, such as cell adhesion and motility. Here, we reveal the role of the small GTPase Rab18 as a positive regulator of directional migration in chemotaxis, and the underlying mechanism. We show that knockdown of Rab18 reduces the size of focal adhesions (FAs) and influences their dynamics. Furthermore, we found that Rab18, by directly interacting with the endoplasmic reticulum (ER)-resident protein kinectin-1, controls the anterograde kinesin-1–dependent transport of the ER required for the maturation of nascent FAs and protrusion orientation toward a chemoattractant. Altogether, our data support a model in which Rab18 regulates kinectin-1 transport toward the cell surface to form ER–FA contacts, thus promoting FA growth and cell migration during chemotaxis

• Wu, Hua; Chen, Yuyuan; Li, Bin; Li, Chun; Guo, Jun & You, Jia [Vis alle 12 forfattere av denne artikkelen] (2020). Targeting ROCK1/2 blocks cell division and induces mitotic catastrophe in hepatocellular carcinoma. Biochemical Pharmacology. ISSN 0006-2952. 184, s. 1–11. doi: 10.1016/j.bcp.2020.114353. Fulltekst i vitenarkiv Vis sammendrag

  Background Rho-Associated kinases ROCK1 and ROCK2 have been extensively investigated in the pathogenesis of cardiovascular disease. However, their roles are not fully understood in carcinogenesis. In this study, we investigated whether ROCK1 or ROCK2 is required for the survival and growth of hepatocellular carcinoma (HCC) cells and underlying mechanism. Methods ROCKs expression was determined in human HCC tissue and cell lines using qRT-PCR, western blotting, and immunohistochemistry (IHC). Cell growth and proliferation were assayed using cell counting kit-8 (CCK-8) and EdU incorporation assay. Cell cycle and apoptosis analysis were performed using flow cytometry. HCC cell division or mitosis was observed using a confocal microscope and a time relapse fluorescence microscope. Inhibitory role of targeting ROCK1/2 on HCC was assayed in both xenograft and primary HCC mouse models. Results Both ROCK1 and ROCK2 are over-expressed in human HCC tissues and cell lines. Knockdown of ROCK1 or ROCK2 inhibited HCC cell growth. Pharmacological inactivation of ROCK1/2 with Fasudil further blocked the growth and survival of HCC both in vitro and in vivo. Mechanically, Fasudil induces cell cycle arrest in HCC cells, but not apoptosis. Instead, Fasudil treatment led to mitotic catastrophe in HCC cells, characterized with the multipolar and asymmetric mitosis, and disassociated stress fibers. Knockdown of cofilin restored the cell morphology and division, and reduced the mitotic catastrophe induced by Fasudil. Conclusions Both ROCK1 and ROCK2 are required for HCC cell division and growth. Targeting ROCK1 or ROCK2 rather than both can serve as a potential approach for HCC treatment and may reduce the side effects.

• Hu, Xian; Jalal, Salma; Sheetz, Michael; Bakke, Oddmund & Margadant, Felix Martin (2020). Micro-stepping extended focus reduces photobleaching and preserves structured illumination super-resolution features. Journal of Cell Science. ISSN 0021-9533. 133, s. 1–12. doi: 10.1242/jcs.240796. Fulltekst i vitenarkiv Vis sammendrag

  Despite progress made in confocal microscopy, even fast systems still have insufficient temporal resolution for detailed live-cell volume imaging, such as tracking rapid movement of membrane vesicles in three-dimensional space. Depending on the shortfall, this may result in undersampling and/or motion artifacts that ultimately limit the quality of the imaging data. By sacrificing detailed information in the Z-direction, we propose a new imaging modality that involves capturing fast ‘projections’ from the field of depth and shortens imaging time by approximately an order of magnitude as compared to standard volumetric confocal imaging. With faster imaging, radiation exposure to the sample is reduced, resulting in less fluorophore photobleaching and potential photodamage. The implementation minimally requires two synchronized control signals that drive a piezo stage and trigger the camera exposure. The device generating the signals has been tested on spinning disk confocal and instant structured-illumination-microscopy (iSIM) microscopes. Our calibration images show that the approach provides highly repeatable and stable imaging conditions that enable photometric measurements of the acquired data, in both standard live imaging and super-resolution modes.

• Hu, Xian; Margadant, Felix Martin; Yao, Mingxi & Sheetz, Michael Patrick (2017). Molecular stretching modulates mechanosensing pathways. Protein Science. ISSN 0961-8368. 26(7), s. 1337–1351. doi: 10.1002/pro.3188. Fulltekst i vitenarkiv
• Le, Shimin; Hu, Xian; Yao, Mingxi; Chen, Hu; Yu, Miao & Xu, Xiaochun [Vis alle 10 forfattere av denne artikkelen] (2017). Mechanotransmission and Mechanosensing of Human alpha-Actinin 1. Cell reports. 21(10), s. 2714–2723. doi: 10.1016/j.celrep.2017.11.040. Fulltekst i vitenarkiv
• Mingxi, Yao; Goult, Benjamin T.; Klapholz, Benjamin; Hu, Xian; Toseland, Christopher P. & Yingjiang, Guo [Vis alle 9 forfattere av denne artikkelen] (2016). The Mechanical Response of Talin. Nature Communications. doi: 10.1038/ncomms11966. Fulltekst i vitenarkiv Vis sammendrag

  Talin, a force-bearing cytoplasmic adapter essential for integrin-mediated cell adhesion, links the actin cytoskeleton to integrin-based cell–extracellular matrix adhesions at the plasma membrane. Its C-terminal rod domain, which contains 13 helical bundles, plays important roles in mechanosensing during cell adhesion and spreading. However, how the structural stability and transition kinetics of the 13 helical bundles of talin are utilized in the diverse talin-dependent mechanosensing processes remains poorly understood. Here we report the force-dependent unfolding and refolding kinetics of all talin rod domains. Using experimentally determined kinetics parameters, we determined the dynamics of force fluctuation during stretching of talin under physiologically relevant pulling speeds and experimentally measured extension fluctuation trajectories. Our results reveal that force-dependent stochastic unfolding and refolding of talin rod domains make talin a very effective force buffer that sets a physiological force range of only a few pNs in the talin-mediated force transmission pathway.

• Hu, Xian; Jing, Chaoran; Xiaochun, Xu; Nakazawa, Naotaka; Cornish, Virginia W. & Margadant, Felix Martin [Vis alle 7 forfattere av denne artikkelen] (2016). Cooperative Vinculin Binding to Talin Mapped by Time-Resolved Super Resolution MIcorscopy. Nano Letters. ISSN 1530-6984. doi: 10.1021/acs.nanolett.6b00650. Fulltekst i vitenarkiv Vis sammendrag

  The dimeric focal adhesion protein talin contains up to 22 cryptic vinculin binding sites that are exposed by unfolding. Using a novel method to monitor the in situ dynamics of the talin dimer stretch, we find that in contrast to several prevalent talin dimer models the integrin-binding talin N-termini are separated by 162 ± 44 nm on average whereas as expected the C-terminal dimerization domains colocalize and are mobile. Using vinculin tagged by DHFR-TMP Atto655 label, we found that optimal vinculin and vinculin head binding occurred when talin was stretched to 180 nm, while the controls did not bind to talin. Surprisingly, multiple vinculins bound within a single second in narrowly localized regions of the talin rod during stretching. We suggest that talin stretches as an antiparallel dimer and that activates vinculin binding in a cooperative manner, consistent with the stabilization of folded talin by other binding proteins.

• Margadant, Felix; Brugge, Joan Siefert; Chew, Li Li; Hu, Xian; Yu, Hanry & Bate, Neil [Vis alle 8 forfattere av denne artikkelen] (2011). Mechanotransduction In Vivo by Repeated Talin Stretch-Relaxation Events Depends upon Vinculin. PLoS Biology. ISSN 1544-9173. 9(12), s. 1001223–1001223. doi: 10.1371/journal.pbio.1001223. Fulltekst i vitenarkiv
• Schvartzman, Mark; Palma, Matteo; Sable, Julia; Abramson, Justin; Hu, Xian & Sheetz, Michael Patrick [Vis alle 7 forfattere av denne artikkelen] (2011). Nanolithographic Control of the Spatial Organization of Cellular Adhesion Receptors at the Single- Molecule Level. Nano Letters. ISSN 1530-6984. doi: 10.1021/nl104378f. Fulltekst i vitenarkiv
• Zhang, Xin; Tee, YH; Heng, JK; Zhu, Y; Hu, Xian & Margadant, F [Vis alle 10 forfattere av denne artikkelen] (2010). Kinectin-mediated endoplasmic reticulum dynamics supports focal adhesion growth in the cellular lamella. Journal of Cell Science. ISSN 0021-9533. 123(22), s. 3901–3912. doi: 10.1242/jcs.069153. Fulltekst i vitenarkiv

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• Hu, Xian; Margadant, Felix & Bakke, Oddmund (2026). Micro-stepping extended focus reduces photobleaching and preserves structured illumination super-resolution features. Vis sammendrag

  Despite the progress made in fast scan units, confocal systems still have insufficient temporal resolution for many volume imaging requirements, such as tracking movement of membrane vesicles in live cells. Researchers might sacrifice certain imaging modalities to achieve better performance in temporal resolution. This may result in imaging artifacts such as undersampling artifacts and limit the amount of analyzable data. We propose a imaging modality producing fast projections from the field of depth which will shorten the imaging time by approximately an order of magnitude compared to volume imaging. The implementation requires merely a minimum two synchronized control signals that drive a piezo stage and trigger the camera exposure, a third, optional signal, blanks the laser output when the stage is in motion which mildly improves the stability and repeatability of the exposure. The device generating the signals has been tested on spinning disk confocal as well as on instant structured- illumination-microscopy (iSIM) microscopes. Our calibration images show that the approach provides highly repeatable and stable imaging conditions and does enable photometric measurements of the acquired data, in both the regular spinning disk setup as well as in the iSIM configuration.While light sheet microscopes can provide even faster projections of the same volume, the presented method provides more homogeneous optical sectioning and maintains the structured illumination characteristics.

• Mierke, Claudia Tanja; Hu, Xian; Yao, Mingxi; Schink, Kay Oliver & Sheetz, Michael (2024). Editorial: Tumor cell mechanosensitivity: molecular basis. Frontiers in Cell and Developmental Biology. 12. doi: 10.3389/fcell.2024.1484725. Fulltekst i vitenarkiv
• Reint, Ganna; Li, Zhuokun; Labun, Kornel; Keskitalo, Salla; Soppa, Inkeri & Mamia, Katariina Aino Inkeri [Vis alle 19 forfattere av denne artikkelen] (2022). Rapid genome editing by CRISPR-Cas9-POLD3 fusion. Fulltekst i vitenarkiv
• Hu, Xian (2020). First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Xian Hu is first author on ‘Micro-stepping extended focus reduces photobleaching and preserves structured illumination super-resolution features’, published in JCS. Xian is a Postdoc in the lab of Oddmund Bakke at the Department of Biosciences University of Oslo, Norway, investigating the link betw. [Journal]. Journal of Cell Science. doi: 10.1242/jcs.247320. Fulltekst i vitenarkiv
• Xiaochun, Xu; Hu, Xian; Sheetz, Michael Patrick & Margadant, Felix Martin (2017). Distortion Correction for Pillar Tracking Caused by Specimen and Devices. Fulltekst i vitenarkiv
• Fatima, Nazeefa; Bösl, Korbinian Michael; Bianchini, Federico; Fritz-Wallace, Katarina; Gade, Alexandra & Hu, Xian [Vis alle 8 forfattere av denne artikkelen] (2024). BioMedData Deliverable D3.4 Determining Best Practices and Specific Solutions for Data Handling. Zenodo. Fulltekst i vitenarkiv Vis sammendrag

  Data management practices across Research Infrastructures (RIs) play a critical role in the production of streamlined Findable, Accessible, Interoperable and Reusable (FAIR) data. It is important to assess how Research Data Management (RDM) practices are implemented to understand the strengths and weaknesses of data management services across facilities and organisations. The Norwegian landscape of life science research infrastructures involves a large number of data producers providing services to research users. The BioMedData project, an infrastructure established in 2020, brings together the RIs within the Life Sciences in Norway and aims at improving their data management practices. In 2021, BioMedData together with the partner RIs, initiated the assessment of the data management routines at the RIs to bridge gaps across the data life cycle. The assessment was performed through a questionnaire designed in Data Stewardship Wizard, addressed by the RIs, covering FAIR data principles as well as international requirements (Science Europe, Horizon2020) – the findings included a lack of community-recognised metadata standards within specific domains, and the need to apply and improve responsibilities for data management implementation within the RIs. Here, we provide a follow-up assessment that allows us to assess which RDM practices have been newly implemented or have improved over the past two years across five RIs. This report provides domain-specific findings as well as a direction towards understanding the need to streamline the processes of data production, sharing, and storage in a FAIR and cost-efficient way.

• Bianchini, Federico; Birkeland, Even; Bösl, Korbinian; Gade, Alexandra; Holmen, Oddgeir Lingaas & Hu, Xian [Vis alle 14 forfattere av denne artikkelen] (2021). BioMedData Deliverable D2.1 - Report on data management plan needs/gaps. Zenodo. Fulltekst i vitenarkiv Vis sammendrag

  The BioMedData project was established in 2020 to connect the largest research infrastructures within the Life Sciences in Norway with the scope of improving their data management practices, aiming at the production of findable, accessible, interoperable and reusable (FAIR) data. This report marks the conclusion of the first phase within the project, aimed at assessing the data management routines at these infrastructures and the gap with respect to the FAIR data principles. This study is supported by a questionnaire, compiled by all the infrastructures involved, covering international requirements (Science Europe, Horizon2020) as well as the FAIR data principles. The investigation revealed a lack of internationally recognised metadata standards and repositories within specific domains. In other cases, the international metadata standards lack attributes representing provenance information of steps prior to data generation. On top of this, the main responsibility for data management implementation is found to often lie with individual researchers and not infrastructures. A more systematic organisation of data management duties and associated budgeting by the research projects would allow the infrastructures to operate a cost recovering support model.

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