Biology subjects

Lim, Y.-W.

Publications and source records attributed to Lim, Y.-W..

12 recordsLinked to original sources

bioRxiv2026

A Cre-responsive reporter quail for flexible genetic lineage tracing

Genetic lineage tracing is a powerful approach for investigating cell fate and tissue development, but versatile Cre/loxP-based tools remain limited in avian models. Here, we generated and characterised a Cre-responsive transgenic quail line that enables permanent genetic labelling of embryonic cell populations. The reporter line ubiquitously expresses nuclear-localised mCherry, which is excised following Cre-mediated recombination, enabling expression of nuclear-localised EGFP. We demonstrate that this reporter can be coupled to multiple Cre delivery strategies, providing flexible spatial and temporal control of lineage labelling. Ubiquitous or cell-type-specific Cre expression induces recombination and stable EGFP labelling that is maintained during clonal expansion. Optogenetic activation of a split Cre system enables highly spatially and temporally restricted recombination. Furthermore, lipid nanoparticle-mediated delivery of Cre mRNA enables efficient recombination in distinct embryonic cell populations, including mesodermal, neuroepithelial, neural crest, endothelial and circulating cells. This transgenic reporter quail provides a flexible platform for permanent lineage labelling without the need to generate tissue-specific Cre transgenic lines and can be readily combined with diverse Cre delivery strategies to investigate cell fate, lineage and morphogenesis in vivo.

developmental biology↗

bioRxiv2025

A Standardized Protocol to Investigate Trans-Endothelial Trafficking in Zebrafish: Nano-bio Interactions of PEG-based Nanoparticles in Live Vasculature

Trans-endothelial transport of nanoparticles remains poorly characterized in live organisms. The zebrafish is a well-established model for direct in vivo imaging; however, standardized controls are not consistently applied across studies. Here, we developed a standardized protocol to assess nanoparticle trans-endothelial trafficking in live zebrafish. We tested a range of tracers and identified 2000 kDa dextran as an optimal control for standardizing microinjections and quantifying nanoparticle transport in a systematic unbiased manner. As validation, we identified the early physiological trans-endothelial transport pathways in zebrafish embryos using 40 kDa dextran as a nanoparticle surrogate. Using our workflow, we assessed the extravasation of 3, 7, 32 and 47 nm polyethylene glycol (PEG)-based nanoparticles. Using cAMP stimulation to restrict paracellular routes, and inhibitors to impede dynamin-dependent endocytosis, we demonstrated that PEG-based hyperbranched polymer (HBP) nanoparticles of 3 to 7 nm traverse the endothelial barrier via paracellular routes and 32 and 47 nm PEG micelles adopt dynamin- dependent endocytic trafficking over paracellular transport. We characterized the emergence of caveolae in the vasculature up to 17 days post-fertilization (dpf) using a cavin1b knock-in zebrafish line. Using cavin1a/cavin1b double knockout (DKO) zebrafish, and tumor-bearing Cavin-1 null mice, we showed that caveolae do not contribute to the transvascular transport of these PEG-based nanoparticles. This work highlights the rigour of the standardized protocol for assessing nanoparticle trans-endothelial transport in the live zebrafish, providing a systematic approach for quantification using a standardized control.

cell biology↗

bioRxiv2024

Vascular mural cells protect the adult brain from haemorrhage but do not control the blood-brain barrier in developing zebrafish

The blood-brain barrier (BBB) protects the brain from circulating metabolites and plays central roles in neurological diseases. Endothelial cells (ECs) of the BBB are enwrapped by mural cells including pericytes and vascular smooth muscle cells (vSMCs) that regulate angiogenesis, vessel stability and barrier function. To explore mural cell control of the BBB, we investigated neurovascular phenotypes in zebrafish pdgfrb mutants that lack brain pericytes and vSMCs. As expected, mutants showed an altered cerebrovascular network with mispatterned capillaries. Unexpectedly, mutants displayed no BBB leakage at larval stages of development. This demonstrates that pericytes and vSMCs do not control BBB function in developing zebrafish. Instead, we observed juvenile and adult BBB disruption occurring at "hotspot" focal hemorrhages at large vessel aneurysms. ECs at leakage hotspots showed induction of caveolae on abluminal surfaces and structural defects including basement membrane thickening and disruption. Our work suggests that capillary pericytes regulate cerebrovascular patterning in development and vSMCs of major arteries protect from hemorrhage and BBB breakdown in older zebrafish. The fact that young zebrafish have a functional BBB in the absence of mural cells calls for renewed interrogation of mural cell control of the BBB throughout vertebrate evolution.

developmental biology↗

bioRxiv2024

Unsaturated lipids as key control points for caveola formation and disassembly

Caveolae are specialized plasma membrane domains with a unique lipid composition. Recent work has implicated lipid peroxidation in triggering caveola disassembly, releasing caveolar proteins to regulate the cellular response to oxidative stress. Here we investigated the role of specific lipid species in caveola formation and response to oxidative stress. Systematic screening of lipid enzymes identified ACSL4, a critical enzyme in the synthesis of polyunsaturated fatty acid-containing lipids, and enzymes involved in the biosynthesis of pro-ferroptotic ether lipids, as key regulators of caveola formation. Omega-6 fatty acids promoted efficient caveola formation, while their oxidation or displacement by omega-3 or monounsaturated fatty acids disrupted this process. Moreover, we found that omega-6 fatty acid-containing membrane lipids were required for oxidative stress-induced caveola disassembly. These findings unveil a new model for caveola formation, highlighting specific unsaturated lipids as essential caveolar components and key control points for caveola disassembly in response to an oxidizing environment.

cell biology↗

bioRxiv2024

A modular encapsulation system for precision delivery of proteins, nucleic acids and therapeutics

Targeted nanoparticles have the potential to revolutionize therapeutics for medical applications. Here, we demonstrate the utility of a flexible precision nanovesicle delivery system for functional delivery of DNA, RNA, proteins and drugs into target cells. Nanovesicles generated by the membrane sculpting protein caveolin, termed caveospheres, can be loaded with RNA, DNA, proteins or drugs post-synthesis or incorporate genetically-encoded cargo proteins during production without the need for protein purification. Functionalized fluorescently-labeled caveospheres form a modular system that shows high stability in biological fluids, specific uptake by target-positive cells, and can deliver proteins, drugs, DNA, and mRNA directly to the cytoplasm and nuclei of only the target cells. The negligible level of off-target transduction and uniform levels of targeted expression demonstrates advantages of the system over lipid-mediated gene delivery. Caveospheres can also be engineered to mimic viral particles by displaying the SARS-CoV-2-RBD protein, enabling targeted delivery to human bronchial epithelial cells. We demonstrate their application as a targeted transfection system for cells in culture, and critically, their efficacy in precision tumor killing in vivo.

bioengineering↗

bioRxiv2023

Flexing fish: cell surface plasticity in response to shape change in the whole organism

Plasma membrane rupture can result in catastrophic cell death. The skeletal muscle fibre plasma membrane, the sarcolemma, provides an extreme example of a membrane subject to mechanical stress since these cells specifically evolved to generate contraction and movement. A quantitative model correlating ultrastructural remodelling of surface architecture with tissue changes in vivo is required to understand how membrane domains contribute to the shape changes associated with tissue deformation in whole animals. We and others have shown that loss of caveolae, small invaginations of the plasma membrane particularly prevalent in the muscle sarcolemma, renders the plasma membrane more susceptible to rupture during stretch1-3. While it is thought that caveolae are able to flatten and be absorbed into the bulk membrane to buffer local membrane expansion, a direct demonstration of this model in vivo has been unachievable since it would require measurement of caveolae at the nanoscale combined with detailed whole animal morphometrics under conditions of perturbation. Here, we describe the development and application of the "active trapping model" where embryonic zebrafish are immobilised in a curved state that mimics natural body axis curvature during an escape response. The model is amenable to multiscale, multimodal imaging including high-resolution whole animal three-dimensional quantitative electron microscopy. Using the active trapping model, we demonstrate the essential role of caveolae in maintaining sarcolemmal integrity and quantify the specific contribution of caveolar-derived membrane to surface expansion. We show that caveolae directly contribute to an increase in plasma membrane surface area under physiologically relevant membrane deformation conditions.

cell biology↗

bioRxiv2022

Haplotype resolved DNA methylome of African cassava genome

Cytosine DNA methylation is involved in biological processes such as transposable element (TE) silencing, imprinting, and X chromosome inactivation. Plant methylation is mediated by MET1 (mammalian DNMT1), DRM2 (mammalian DNMT3), and two plant-specific DNA methyltransferases, CMT2 and CMT3 (Law and Jacobsen, 2010). De novo DNA methylation in plants is established by DRM2 via the plant specific RNA-directed DNA methylation (RdDM) pathway that depends on two DNA-dependent RNA polymerases, Pol IV and Pol V (Gallego-Bartolome et al., 2019; Law and Jacobsen, 2010; Stroud et al., 2013). The DNA methylome of cassava has been previously documented based on its haploid collapsed genome (Wang et al., 2015). Since the cassava genome is highly heterozygous, DNA methylome analysis of the haplotype-collapsed genome misses many features of the methylome. With the development of long read sequencing and chromosomal conformation capture techniques, haplotype resolved genomes are available for highly heterozygous genomes (Mansfeld et al., 2021; Qi et al., 2022; Zhou et al., 2020), which provides high-quality reference genomes facilitating studies of haplotype resolved DNA methylomes.

plant biology↗

bioRxiv2022

Mutations in DNA polymerase δ subunit 1 mediate CMD2-type resistance to Cassava Mosaic Geminiviruses

Cassava mosaic disease suppresses cassava yields across the tropics. The dominant CMD2 locus confers resistance to the cassava mosaic geminiviruses. It has been reported that CMD2-type landraces lose resistance after regeneration through de novo morphogenesis. As full genome bisulfite sequencing failed to uncover an epigenetic mechanism for loss of resistance, we performed whole genome sequencing and genetic variant analysis and fine-mapped the CMD2 locus to a 190 kilobase interval. Data suggest that CMD2-type resistance is caused by a nonsynonymous, single nucleotide polymorphism in DNA polymerase {delta} subunit 1 (MePOLD1) located within this region. Virus-induced gene silencing of MePOLD1 in a Cassava mosaic disease-susceptible cassava variety produced a recovery phenotype typical of CMD2-type resistance. Analysis of other CMD2-type cassava varieties identified additional resistance alleles within MePOLD1. MePOLD1 resistance alleles represent important genetic resources for resistance breeding or genome editing, and elucidating mechanisms of resistance to geminiviruses.

plant biology↗

bioRxiv2021

The haplotype-resolved chromosome pairs and transcriptome of a heterozygous diploid African cassava cultivar

BackgroundCassava (Manihot esculenta) is an important clonally propagated food crop in tropical and sub-tropical regions worldwide. Genetic gain by molecular breeding is limited because cassava has a highly heterozygous, repetitive and difficult to assemble genome. FindingsHere we demonstrate that Pacific Biosciences high-fidelity (HiFi) sequencing reads, in combination with the assembler hifiasm, produced genome assemblies at near complete haplotype resolution with higher continuity and accuracy compared to conventional long sequencing reads. We present two chromosome scale haploid genomes phased with Hi-C technology for the diploid African cassava variety TME204. Genome comparisons revealed extensive chromosome re-arrangements and abundant intra-genomic and inter-genomic divergent sequences despite high gene synteny, with most large structural variations being LTR-retrotransposon related. Allele-specific expression analysis of different tissues based on the haplotype-resolved transcriptome identified both stable and inconsistent alleles with imbalanced expression patterns, while most alleles expressed coordinately. Among tissue-specific differentially expressed transcripts, coordinately and biasedly regulated transcripts were functionally enriched for different biological processes. We use the reference-quality assemblies to build a cassava pan-genome and demonstrate its importance in representing the genetic diversity of cassava for downstream reference-guided omics analysis and breeding. ConclusionsThe haplotype-resolved genome allows the first systematic view of the heterozygous diploid genome organization in cassava. The completely phased and annotated chromosome pairs will be a valuable resource for cassava breeding and research. Our study may also provide insights into developing cost-effective and efficient strategies for resolving complex genomes with high resolution, accuracy and continuity.

genomics↗

bioRxiv2021

Caveolae, CAVIN1, and lipid peroxidation mediate the oxidative stress response

Caveolae have been linked to many biological functions, but their precise roles are unclear. Using quantitative whole cell proteomics of genome-edited cells, we show that the oxidative stress response is the major pathway dysregulated in cells lacking the key caveola structural protein, CAVIN1. CAVIN1 deletion compromised sensitivity to oxidative stress in cultured cells and in animals. Wound-induced accumulation of reactive oxygen species and apoptosis were suppressed in Cavin1-null zebrafish, negatively affecting regeneration. Oxidative stress triggered lipid peroxidation and induced caveolar disassembly. The resulting release of CAVIN1 from caveolae allowed direct interaction between CAVIN1 and NRF2, a key regulator of the antioxidant response, facilitating NRF2 degradation. CAVIN1-null cells with impaired negative regulation of NRF2 showed resistance to lipid peroxidation-induced ferroptosis. Thus, caveolae, via lipid peroxidation and CAVIN1 release, maintain cellular susceptibility to oxidative stress-induced cell death demonstrating a crucial role for this enigmatic organelle in cellular homeostasis and wound response.

cell biology↗

bioRxiv2021

Muscle-specific Cavin4 interacts with Bin1 to promote T-tubule formation and stability in developing skeletal muscle

The cavin proteins are essential for caveola biogenesis and function. Here, we identify a role for the muscle-specific component, Cavin4, in skeletal muscle T-tubule development by analyzing two vertebrate systems: mouse and zebrafish. In both models Cavin4 localized to T-tubules and loss of Cavin4 resulted in aberrant T-tubule maturation. In zebrafish, which possess duplicated cavin4 paralogs, Cavin4b was shown to directly interact with the T-tubule-associated BAR domain protein, Bin1. Loss of both Cavin4a and Cavin4b caused aberrant accumulation of interconnected caveolae within the T-tubules, a fragmented T-tubule network enriched in Caveolin-3, and an impaired Ca2+ response upon mechanical stimulation. We propose a role for Cavin4 in remodeling the T-tubule membrane early in development by recycling caveolar components from the T-tubule to the sarcolemma. This generates a stable T-tubule domain lacking caveolae that is essential for T-tubule function.

cell biology↗

bioRxiv2020

An Endocytic Capture Model for Skeletal Muscle T-tubule Formation

The skeletal muscle T-tubule is a specialized membrane domain essential for coordinated muscle contraction that shows dysmorphology in a number of genetically inherited muscle diseases. However, in the absence of genetically tractable systems the mechanisms involved in T-tubule formation are unknown. Here, we have used the optically transparent and genetically tractable zebrafish system to probe T-tubule development in vivo. By combining live imaging with three-dimensional electron microscopy we derived a four-dimensional quantitative model for T-tubule formation. To elucidate the mechanisms involved in T-tubule formation in vivo we developed a quantitative screen for proteins that associate with and modulate early T-tubule formation including an overexpression screen of the entire zebrafish Rab protein family. We propose a new endocytic capture model involving i) formation of dynamic endocytic tubules at transient nucleation sites on the sarcolemma ii) stabilization by myofibrils/sarcoplasmic reticulum and iii) delivery of membrane from the recycling endosome and Golgi complex.

cell biology↗