Biology subjects

Hammond, C. L.

Publications and source records attributed to Hammond, C. L..

At least 19 recordsLinked to original sources

bioRxiv2026

NSAIDs impair fracture healing by disrupting neutrophil-mediated repair

Neutrophils are among the first immune cells recruited to fractures, yet their contribution to bone repair remains poorly understood. Using live imaging and neutrophil perturbation in adult zebrafish, we show that neutrophils establish the early fracture microenvironment. Neutrophils rapidly accumulated at fractures, underwent NETosis, and exhibited transcriptional programmes associated with matrix remodelling. Compromising neutrophil recruitment, via ibuprofen treatment or orthogonal perturbations, increased fracture non-union, delayed osteoblast differentiation, impaired mineralisation, and altered callus architecture. Mechanistically, neutrophils actively interacted with extracellular matrix proteins, including laminin, fibronectin, and collagen I, through uptake, trafficking and secretion-associated pathways. Together, our findings reveal that neutrophils establish a provisional emergency fracture matrix that templates subsequent bone repair, providing a mechanistic link between early non-steroidal anti-inflammatory drug (NSAID) exposure and impaired skeletal regeneration.

immunology↗

bioRxiv2026

Nanovibrational stimulation preferentially enhances osteogenic responses in zebrafish

Mechanical cues are key regulators of bone formation, yet their potential as therapeutic stimuli remains incompletely explored in vivo. Nanovibrational stimulation, which delivers low-amplitude, high-frequency mechanical input, has been shown to promote osteogenic differentiation in vitro, and rodent studies have similarly demonstrated osteogenic effects. However, its impact on other cellular systems at the whole-organism level remains poorly understood. Here, we demonstrate that nanovibrational stimulation enhances myogenic differentiation in vitro before investigating its effects on skeletal development and tissue specificity in zebrafish. Larval zebrafish exposed to nanovibrational stimulation exhibited increased osteoblast numbers and enhanced bone formation relative to controls. In adult zebrafish, nanovibration increased the osteoblast response to a fracture-like injury, indicating enhanced osteogenic activity during repair. To assess tissue specificity, we examined additional cell types and systems relevant to skeletal regeneration, including cartilage, muscle, vasculature and innate immune cells. Although nanovibrational stimulation promoted myogenic differentiation of C2C12 cells in vitro, its effects on muscle and other non-skeletal tissues in zebrafish larvae were comparatively limited. These findings suggest that nanovibrational stimulation exerts a preferential effect on osteogenic processes in vivo. These findings demonstrate that nanovibrational stimulation preferentially enhances osteoblast-mediated bone formation and skeletal injury responses in zebrafish, without causing significant perturbations in other tissues. Our results establish zebrafish as a tractable in vivo model for investigating vibration-induced mechanobiological processes, providing a more physiologically relevant representation of tissue-level mechanotransduction than conventional two-dimensional culture systems. Furthermore, these findings highlight the potential of nanovibrational stimulation as a non-invasive strategy to promote bone regeneration and fracture repair.

physiology↗

bioRxiv2026

Loss of lmx1ba drives premature osteoarthritis through disruption of skeletal homeostasis

Osteoarthritis is increasingly recognised as a disease of failed integration across the whole joint unit; however, the mechanisms that co-ordinate tissue integrity from development through to adult homeostasis remain largely unresolved. The LIM-homeodomain transcription factor LMX1B is a key determinant of embryonic skeletal patterning, but how it functions to regulate skeletal integrity in the mature skeleton is unknown. Recently, LMX1B was identified as a key driver of osteoarthritis. Here we show that loss of lmx1ba in zebrafish causes premature and progressive severe osteoarthritic pathology in adult spines and jaws, despite largely normal early skeletal patterning, revealing a conserved and continuous requirement for lmx1ba in joint maintenance beyond development. At a cellular level, loss of lmx1ba decouples osteoblast and osteoclast-mediated remodelling leading to bone overgrowth, heterogeneity of bone properties causing increased incidence of spontaneous fractures, and progressive abnormalities in spine morphology. In parallel, we observe degeneration of the intervertebral disc and dysregulation of the proteome and glycosaminoglycans indicative of disrupted extracellular matrix and a breakdown of the coordinated regulation of hard and soft tissue interfaces, which at the organismal level leads to altered joint performance. Notably, degeneration is restricted to mobile joints, and is not observed in cranial sutures, demonstrating a selective requirement for lmx1ba in mechanically active tissues. These changes are consistent with a model of spatially disrupted matrix properties that, under cyclic loading, promote progressive tissue damage. Our findings support a model in which continued expression of LMX1B in adulthood is required to maintain joint structures throughout life.

physiology↗

bioRxiv2026

Distinct roles for TANGO1S domains in maintaining ER-Golgi architecture

The endoplasmic reticulum (ER)-Golgi interface is a dynamic trafficking hub maintained in part by TANGO1, a scaffolding protein that coordinates proteins and membranes at ER exit sites (ERES). TANGO1 has two isoforms: TANGO1L, which has a lumenal SH3 domain, and TANGO1S, which lacks this domain but retains the transmembrane and cytoplasmic coiled coil (CC), TEER, and PRD domains common to both forms. We showed previously that loss of both isoforms disrupts ER - Golgi organization more severely than TANGO1L loss alone, indicating TANGO1S is functional and can compensate. Here we dissect the role of each TANGO1 cytoplasmic domain in maintaining secretory pathway organisation by expressing TANGO1S domain-deletion mutants in TANGO1L-/S- knockout cells. We show that TANGO1 loss causes cis-Golgi vesiculation that cannot be rescued by TANGO1S. TANGO1S re-expression also failed to rescue COPII and Sec16 recruitment in this cell line. Meanwhile, the TEER domain is essential for the organisation of the ER, and the TEER, CC2 and PRD domain are required for a defined ERGIC. This study represents an advance towards a domain-level resolution of TANGO1S function.

cell biology↗

bioRxiv2025

Deep learning methods for automated bone segmentation and biomechanical modelling in zebrafish

Automated segmentation of three-dimensional micro-computed tomography (CT) scan data is a critical bottleneck in computational morphometrics and biomechanical modelling across musculoskeletal biology. Although advances in imaging have generated increasingly large and complex datasets, manual segmentation remains prohibitively time-consuming, while existing deep learning solutions are often application-specific and rarely validated for their impact on downstream analyses. Here we present a generalisable computational framework for automated segmentation and biomechanical validation of skeletal structures, implemented using an attention-augmented 3D U-Net architecture. Using the adult zebrafish (Danio rerio) mandible as a representative case study, the network was trained on 47 manually segmented specimens and evaluated using a combined Dice-Hausdorff metric that integrates both volumetric and surface accuracy to capture biologically relevant morphology better than Dice score alone. To assess performance in a downstream biomechanical context, we directly compared automated segmentations with those produced by three expert human annotators and constructed finite element models from each. Quantitative comparisons of segmentation accuracy and statistical analyses of finite element outputs demonstrate that automated segmentations perform within the range of expert human annotations, with no systematic bias in mechanical predictions. By explicitly linking geometric accuracy to biomechanical outcomes, this work establishes an end-to-end pipeline for validating automated segmentation in computational biology. The framework will be applicable to a wide range of musculoskeletal and palaeobiological contexts, including comparative anatomy, ageing and disease studies, and fossil or incomplete specimens, where scalable and mechanically faithful segmentation is essential. Author summaryMany studies now use CT scanning to build computer models of bones and test how they perform under load. However, these analyses usually start with manual segmentation, where an expert traces the bone in thousands of image slices to create a 3D surface. This step is time-consuming and introduces uncertainty because experts do not always agree exactly on where boundaries lie. If segmentation changes the model shape, it may also change predicted biomechanics. In this work, we test whether deep learning can automate segmentation while preserving biomechanical outcomes. We train an attention augmented 3D U-Net to segment the adult zebrafish lower jaw and compare its outputs directly to three expert manual segmentations. We assess similarity using complementary measures that reflect both overall overlap and boundary differences. We then build finite element models from each segmentation and compare predicted stress, strain, and displacement distributions. We show that automated segmentations are as consistent as human experts and generate indistinguishable biomechanical predictions, without systematic bias. This supports scalable, repeatable pipelines for linking anatomy to function, and provides a general approach for validating automated segmentation in studies where downstream modelling is the goal.

bioengineering↗

bioRxiv2025

Characterisation of lmx1b paralogues in zebrafish reveals divergent roles in skeletal, kidney, and muscle development

LMX1B, a LIM-homeodomain family transcription factor, plays critical roles in the development of multiple tissues, including limbs, eyes, kidneys, brain, and spinal cord. Mutations in the human LMX1B gene cause the rare autosomal-dominant disorder, Nail-patella syndrome which affects development of limbs, eyes, brain, and kidneys. In zebrafish, lmx1b has two paralogues: lmx1ba and lmx1bb. While lmx1b morpholino data exists, stable mutants were previously lacking. Here we describe the characterisation of lmx1b stable mutant lines, with a focus on development of tissues which are affected in Nail-patella syndrome. We demonstrate that the lmx1b paralogues have divergent developmental roles in zebrafish, with lmx1ba affecting skeletal and neuronal development, and lmx1bb affecting renal development. The double mutant, representing loss of both paralogues (lmx1b dKO) showed a stronger phenotype which included additional defects to trunk muscle patterning, and a failure to fully inflate the notochord leading to a dramatic reduction in body length. Overall, these mutant lines demonstrate the utility of zebrafish for modelling Nail- patella syndrome and describe a previously undescribed role for lmx1b in notochord cell inflation. SUMMARY STATEMENTZebrafish lmx1ba and lmx1bb knockout lines exhibit paralogue-specific roles in cartilage, renal, muscle, and notochord development, establishing zebrafish as a viable model for dissecting LMX1B- related pathologies such as Nail-patella syndrome.

developmental biology↗

bioRxiv2025

The growth-promoting protein TMEM263 is an ER resident that controls early stages of lipid droplet biogenesis

Cell and organismal growth is controlled not only by the availability of nutrients, but also the ability to dynamically sense and respond to changes in metabolic demand. We have identified a protein, TMEM263 (also known as C12orf23) as a new mechanistic link between growth and lipid metabolism. TMEM263 was discovered in a screen as an ER-resident protein, and we have characterised its role as both necessary and sufficient for lipid droplet formation. TMEM263 has two transmembrane domains that fold into a hairpin structure which are essential for its localisation to the ER and to lipid droplets. Functionally, we propose that TMEM263 can interact with and support the condensation of neutral lipids in a bilayer to promote lipid droplet formation and growth. Consistently, loss of TMEM263 in cells and in zebrafish significantly impairs lipid droplet formation. Loss of TMEM263 protein function in vivo is associated with organismal growth defects and proportional dwarfism and our study provides a mechanistic understanding linking these phenotypes to impaired lipid droplet biology.

cell biology↗

bioRxiv2024

Tuning Collective Behaviour in Zebrafish with Genetic Modification

Zebrafish collective behaviour is widely used to assess their physical and mental state, serving as a valuable tool to assess the impact of ageing, disease genetics, and the effect of drugs. The essence of these macroscopic phenomena can be represented by active matter models, where the individuals are abstracted as interactive self-propelling agents. The behaviour of these agents depends on a set of parameters in a manner reminiscent of those between the constituents of physical systems. In a few cases, the system may be controlled at the level of the individual constituents such as the interactions between colloidal particles, or the enzymatic behaviour of de novo proteins. Usually, however, while the collective behaviour may be influenced by environmental factors, it typically cannot be changed at will. Here, we challenge this scenario in a biological context by genetically modifying zebrafish. We thus demonstrate the potential of genetic modification in the context of controlling the collective behaviour of biological active matter systems at the level of the constituents, rather than externally. In particular, we probe the effect of the lack of col11a2 gene in zebrafish, which causes the early onset of osteoarthritis. The resulting col11a2 -/- zebrafish exhibited compromised vertebral column properties, bent their body less while swimming, and took longer to change their orientations. Surprisingly, a group of 25 mutant fish exhibited more orderly collective motion than the wildtype. We show that the collective behaviour of wildtype and col11a2 -/- zebrafish are captured with a simple active matter model, in which the mutant fish are modelled by self-propelling agents with a higher orientational noise on average. In this way, we demonstrate the possibility of tuning a biological system, changing the state space it occupies when interpreted with a simple active matter model.

animal behavior and cognition↗

bioRxiv2023

Cyclical compression loading is the dominant mechanoregulator of synovial joint morphogenesis

Mechanical stimuli arising from fetal movements are critical factors underlying joint growth. Abnormal fetal movements negatively affect joint shape features with important implications for joint function and health, but the mechanisms by which mechanical forces due to fetal movements influence joint growth are still unclear. In this research, we integrated cell-level data into a novel mechanobiological model of zebrafish jaw joint morphogenesis to identify links between the mechanical stimuli arising from movement and patterns of growth. Larval zebrafish jaw joint growth patterns were quantified from tracked cell-data at several successive developmental stages in the presence or absence of movements. Pharmacological immobilisation, prior to the onset of jaw movements, resulted in growth rate decreases which were stronger along the ventrodorsal axis. Simulations of joint morphogenesis, based on the quantified cell-level data and which integrated mechanical stimuli arising from simulated jaw movements, were used to test hypotheses relating specific mechanical stimuli with the local changes in size and shape. Different types of mechanical stimulation were incorporated into the simulation to provide the mechanoregulated component on growth in addition to the baseline (non mechanoregulated) growth which occurs in the immobilised animals. We found that the magnitude of compression experienced during joint motion when included as the stimulus for mechanoregulated growth could not predict the real, normally loaded shaped joints. However, when the dynamic changes caused by the application of cyclical compression was implemented as the stimulus for mechanoregulated growth, the sizes and shapes of joints were correctly simulated. We conclude therefore that the cyclical application of compression loading due to the dynamic nature of fetal movements underlies the mechanoregulation of prenatal joint morphogenesis. Our results provide a fundamental advance in our understanding of mechanoregulation of the developing joint and increase our understanding of the origins of conditions such as hip dysplasia and arthrogryposis. Author summaryThe mechanical forces caused by fetal movements are important for normal development of the skeleton, and in particular for joint shape. Several common developmental musculoskeletal conditions such as developmental dysplasia of the hip and arthrogryposis are associated with reduced or restricted fetal movements. Paediatric joint malformations impair joint function and can be debilitating. To understand the origins of such conditions, it is essential to understand how the mechanical forces arising from movements influence joint growth and shape. In this research, we used a computational model of joint growth applied to the zebrafish jaw joint to study the impact of fetal movements on joint growth and shape. We find that the cyclical application of compression loading is critical to the normal growth and shape of the developing joint. Our findings implicate that dynamic compression must be targeted when developing strategies for the treatment of musculoskeletal conditions through targeted physiotherapy.

developmental biology↗

bioRxiv2022

Growth orientations, rather than heterogeneous growth rates, dominate jaw joint morphogenesis in the larval zebrafish

In early limb embryogenesis, synovial joints acquire specific shapes which determine joint motion and function. The process by which the opposing cartilaginous joint surfaces are moulded into reciprocal and interlocking shapes, called joint morphogenesis, is one of the least understood aspect of joint formation and the cell-level dynamics underlying it are yet to be unravelled. In this research, we quantified key cellular dynamics involved in growth and morphogenesis of the zebrafish jaw joint and synthesised them in a predictive computational simulation of joint development. Cells in larval zebrafish jaw joints labelled with cartilage markers were tracked over a forty-eight hour time window using confocal imaging. Changes in distance and angle between adjacent cell centroids resulting from cell rearrangement, volume expansion and extracellular matrix (ECM) deposition were measured and used to calculate the rate and direction of local tissue deformations. We observed spatially and temporally heterogeneous growth patterns with marked anisotropy over the developmental period assessed. There was notably elevated growth at the level of the retroarticular process of the Meckels cartilage, a feature known to undergo pronounced shape changes during zebrafish development. Analysis of cell dynamics indicated a dominant role for cell volume expansion in growth, with minor influences from ECM volume increases and cell intercalation. Cell proliferation in the joint was minimal over the timeframe of interest. Synthesising the dynamic cell data into a finite element model of jaw joint development resulted in accurate shape predictions. Our biofidelic computational simulation demonstrated that zebrafish jaw joint growth can be reasonably approximated based on cell positional information over time, where cell positional information derives mainly from cell orientation and cell volume expansion. By modifying the input parameters of the simulation, we were able to assess the relative contributions of heterogeneous growth rates and of growth orientation. The use of uniform rather than heterogeneous growth rates only minorly impacted the shape predictions whereas isotropic growth fields resulted in altered shape predictions. The simulation results suggest that growth anisotropy is the dominant influence on joint growth and morphogenesis. This study addresses the gap of the cellular processes underlying joint morphogenesis, with implications for understanding the aetiology of developmental joint disorders such as developmental dysplasia of the hip and arthrogryposis.

developmental biology↗

bioRxiv2021

Dominating Lengthscales of Zebrafish Collective Behaviour

Collective behaviour in living systems is observed across many scales, from bacteria to insects, to fish shoals. Zebrafish have emerged as a model system amenable to laboratory study. Here we report a three-dimensional study of the collective dynamics of fifty Zebrafish. We observed the emergence of collective behaviour changing between polarised to randomised, upon adaption to new environmental conditions. We quantify the spatial and temporal correlation functions of the fish and identify two length scales, the persistence length and the nearest neighbour distance, that capture the essence of the behavioural changes. The ratio of the two length scales correlates robustly with the polarisation of collective motion that we explain with a reductionist model of self-propelled particles with alignment interactions.

animal behavior and cognition↗

bioRxiv2021

Autophagy coordinates chondrocyte development and early joint formation in zebrafish

Autophagy is a catabolic process responsible for the removal of waste and damaged cellular components by lysosomal degradation. It plays a key role in fundamental cell processes, including ER stress mitigation, control of cell metabolism, and cell differentiation and proliferation, all of which are essential for cartilage cell (chondrocyte) development and survival, and for the formation of cartilage. Correspondingly, autophagy dysregulation has been implicated in several skeletal disorders such as osteoarthritis and osteoporosis. To test the requirement for autophagy during skeletal development in zebrafish, we generated an atg13 CRISPR knockout zebrafish line. This line showed a complete loss of atg13 expression, and restricted autophagic activity in vivo. In the absence of autophagy, chondrocyte maturation was accelerated, with chondrocytes exhibiting signs of premature hypertrophy. Focussing on the jaw element, autophagy disruption affected joint articulation causing restricted mouth opening. This gross behavioural phenotype corresponded with a failure to thrive, and death in homozygote atg13 nulls within 17 days. Taken together, our results are consistent with autophagy contributing to the timely regulation of chondrocyte maturation and for extracellular matrix formation.

developmental biology↗

bioRxiv2020

Transformed notochordal cells trigger chronic wounds destabilizing the vertebral column and bone homeostasis

Notochordal cells play a pivotal role in vertebral column patterning, contributing to the formation of the inner architecture of intervertebral discs (IVDs). Their disappearance during development has been associated with reduced repair capacity and IVD degeneration. Notochordal remnants are known to cause chordomas, a highly invasive bone cancer associated with late diagnosis. Understanding the impact of neoplastic cells during development and on the surrounding vertebral column could open avenues for earlier intervention and therapeutics. We investigated the impact of transformed notochord cells in the zebrafish skeleton using a RAS expressing line in the notochord under the control of the Kita promoter, with the advantage of adulthood endurance. Transformed cells caused damage in the notochord and destabilised the sheath layer triggering a wound repair mechanism, with enrolment of sheath cells (col9a2+) and expression of wt1b, similar to induced notochord wounds. Moreover, increased recruitment of neutrophils and macrophages, displaying abnormal behaviour in proximity to the notochord sheath and transformed cells, supported parallels between chordomas, wound and inflammation. Cancerous notochordal cells interfere with differentiation of sheath cells to form chordacentra domains leading to fusions and vertebral clefts during development. Adults displayed IVD irregularities reminiscent of degeneration; reduced bone mineral density, increased osteoclast activity; while disorganised osteoblasts and collagen indicate impaired bone homeostasis. By depleting inflammatory cells, we abrogated chordoma development and rescued the skeletal features of the vertebral column. Therefore, we showed that transformed notochord cells alter the skeleton during life, causing a wound-like phenotype and activating chronic wound response, suggesting parallels between chordoma, wound, IVD degeneration and inflammation, highlighting inflammation as a promising target for future therapeutics.

developmental biology↗

bioRxiv2020

The transcriptome of regenerating zebrafish scales identifies genes involved in human bone disease

Zebrafish scales are mineralised plates that can regenerate involving de novo bone formation. This presents an opportunity to uncover genes and pathways relevant to human musculoskeletal disease relevant to impaired bone formation. To investigate this hypothesis, we defined transcriptomic profiles of ontogenetic and regenerating scales, and identified 604 differentially expressed genes (DEGs) that were enriched for extracellular matrix, ossification, and cell adhesion pathways. Next, we showed that human orthologues of DEGs were 2.8 times more likely to cause human monogenic skeletal diseases (P<8x10-11), and they showed enrichment for human orthologues associated with polygenetic disease traits including stature, bone density and osteoarthritis (P<0.005). Finally, zebrafish mutants of two human orthologues that were robustly associated with height and osteoarthritis (COL11A2) or bone density only (SPP1) developed skeletal abnormalities consistent with our genetic association studies. Col11a2Y228X/Y228X mutants showed endoskeletal features consistent with abnormal growth and osteoarthritis, whereas spp1P160X/P160X mutants had elevated bone density (P<0.05). In summary, we show that transcriptomic studies of regenerating zebrafish scales have potential to identify new genes and pathways relevant to human skeletal disease.

genetics↗

bioRxiv2020

NCOA3 identified as a new candidate to explain autosomal dominant progressive hearing loss

Hearing loss is a frequent sensory impairment in humans and genetic factors account for an elevated fraction of the cases. We have investigated a large family of five generations, with 15 reported individuals presenting non-syndromic, sensorineural, bilateral and progressive hearing loss, segregating as an autosomal dominant condition. Linkage analysis, using SNP-array and selected microsatellites, identified a region of 13cM in chromosome 20 as the best candidate to harbour the causative mutation. After exome sequencing and filtering of variants, only one predicted deleterious variant in the NCOA3 gene (NM_181659, c.2810C>G; p.Ser937Cys) fit in with our linkage data. RT-PCR, immunostaining and in situ hybridization showed expression of ncoa3 in the inner ear of mice and zebrafish. We generated a stable homozygous zebrafish mutant line using the CRISPR/Cas9 system. ncoa3-/- did not display any major morphological abnormalities in the ear, however, anterior macular hair cells showed altered orientation. Surprisingly, chondrocytes forming the ear cartilage showed abnormal behaviour in ncoa3-/-, detaching from their location, invading the ear canal and blocking the cristae. Adult mutants displayed accumulation of denser material wrapping the otoliths of ncoa3-/- and increased bone mineral density. Altered zebrafish swimming behaviour corroborates a potential role of ncoa3 in hearing loss. In conclusion, we identified a potential candidate gene to explain hereditary hearing loss, and our functional analyses suggest subtle and abnormal skeletal behaviour as mechanisms involved in the pathogenesis of progressive sensory function impairment.

genetics↗

bioRxiv2020

Exposure to hypergravity during development leads to altered cartilage material properties and strain distribution in zebrafish.

Terrestrial vertebrates have adapted to life on Earth and its constant gravitational field, which exerts load on the body and influences the structure and function of tissues. While the effects of microgravity on muscle and bone homeostasis are well described, the effects of shorter exposures to increased gravitational fields are less well characterized. Here, we exposed zebrafish to 3 and 6g hypergravity from 3-5 days post fertilisation, when key events in jaw cartilage morphogenesis occur. We did not observe changes to growth, or morphology of cartilage or muscle. However, we observed altered mechanical properties of jaw cartilages. We model the impact of these material property changes using Finite Element Analysis and show strain distribution in the jaw is altered following hypergravity. In regions of predicted altered strain we observed local changes to chondrocyte morphology, suggesting altered gravity affects chondrocyte maturation, ultimately leading to changes to cartilage structure and function.

physiology↗

bioRxiv2020

Giantin is required for 1 intracellular N-terminal processing of type I procollagen

Knockout of the golgin giantin leads to skeletal and craniofacial defects driven by poorly studied changes in glycosylation and extracellular matrix deposition. Here, we sought to determine how giantin impacts the production of healthy bone tissue by focussing on the main protein component of the osteoid, type I collagen. Giantin mutant zebrafish accumulate multiple spontaneous fractures in their caudal fin, suggesting their bones may be more brittle. Inducing new experimental fractures revealed defects in the mineralisation of newly deposited collagen as well as diminished procollagen reporter expression in mutant fish. Analysis of giantin knockout cells expressing a GFP-tagged procollagen showed that procollagen trafficking is independent of giantin. However, our data show that intracellular N-propeptide processing of pro-1(I) is defective in the absence of giantin. These data demonstrate a conserved role for giantin in collagen biosynthesis and extracellular matrix assembly. Our work also provides evidence of a giantin-dependent pathway for intracellular procollagen processing.

cell biology↗

bioRxiv2020

Wnt16 Elicits a Protective Effect Against Fractures and Supports Bone Repair in Zebrafish

Bone homeostasis is a dynamic, multicellular process which is required throughout life to maintain bone integrity, prevent fracture and respond to skeletal damage. WNT16 has been linked to bone fragility and osteoporosis in humans, as well as functional haematopoiesis of leukocytes in vivo, but the mechanisms by which it promotes bone health and repair are not fully understood. We used CRISPR-Cas9 to generate mutant zebrafish lacking Wnt16 (wnt16-/-) to study its effect on bone dynamically. wnt16 mutants displayed variable tissue mineral density and were susceptible to spontaneous fractures and the accumulation of bone calluses at an early age. Fractures were induced in the lepidotrichia of the caudal fins of wnt16-/- and wild type (WT) zebrafish; this model was used to probe the mechanisms by which Wnt16 regulates skeletal and immune cell-dynamics in vivo. wnt16 mutants repaired fractures more slowly compared to WT zebrafish. Osteoblast cell number was reduced at the fracture site 4 days post-injury in wnt16 mutants, coinciding with prolonged activation of the canonical Wnt signalling pathway. Surprisingly, we found no evidence that the recruitment of innate immune cells to fractures was altered in wnt16 mutants. This study highlights zebrafish as an emerging model for functionally validating osteoporosis-associated genes and investigating fracture repair dynamically in vivo. Using this model, we demonstrate that Wnt16 protects against fracture and is likely to support bone repair by attenuating the activation of the canonical Wnt signalling pathway to facilitate osteoblast recruitment and bone matrix deposition.

cell biology↗