Biology subjects

Cheung, K.

Publications and source records attributed to Cheung, K..

At least 19 recordsLinked to original sources

bioRxiv2026

A synthetic xeno-free extracellular matrix surrogate supports robust human induced pluripotent stem cell maintenance and multilineage differentiation

Animal-derived surface coatings present the gold standard in stem cell culture. However, they come with major drawbacks such as lot-to-lot inconsistency and an ethically problematic production. Approaches to develop synthetic coating alternatives have largely failed to recapitulate biological functions essential to PSC-self renewal and differentiation. In this study, we have investigated the suitability of a fully synthetic, chemically defined extracellular matrix-mimicking coating named BIOINSTRUCT for hiPSC culture. BIOINSTRUCT was employed during maintenance culture of IMR90-4 cells, as well as directed differentiation of HIHCNi008-A, ACTN2-GFP, and UKKI-011-A cells. BIOINSTRUCT preserved hiPSC characteristics over the experimental period of 10 passages similar to Matrigel. Spontaneous differentiation resulted in the formation of ectodermal, mesodermal and endodermal derivatives, confirming the retention of pluripotency. Directed differentiation on BIOINSTRUCT enabled the generation of neuronal, cardiac and pancreatic endocrine cells. Altogether, our data underscore BIOINSTRUCT as a promising alternative to animal-derived extracellular matrix coatings.

cell biology↗

bioRxiv2026

Proteostasis sustains T cell differentiation potential and tumor-infiltrating lymphocyte function

Tumor-infiltrating lymphocytes (TIL) often fail to restrain tumor growth due to progressive differentiation to an exhausted state. In healthy tissues, tissue-resident memory T cells (TRM) maintain protection for years, and patient tumors that contain TIL with TRM features are associated with better prognosis. Proteomic and transcriptomic profiling of T cell populations identified proteostasis as a significant factor distinguishing TRM and progenitor-exhausted TIL from terminally-exhausted TIL, including loss of E3 ubiquitin ligases NEURL3, RNF149, and WSB1, with accumulation of unfolded proteins in spite of functional proteasome activity. Enforced expression of these ligases by TIL preserved stem-like TCF1+ populations and improved anti-tumor function, whereas their knockout impaired TIL and altered T cell differentiation in acute infection. Sustained ligase expression rescued accumulation of unfolded proteins in TIL and improved immunotherapy outcome in preclinical models, highlighting the critical role of proteostasis in TIL function and identifying new avenues for advancing cancer immunotherapy.

immunology↗

bioRxiv2025

Optical Properties of Gelatin Methacrylate and Implications for In Situ Cross-Linking in Spinal Cord Lesions and EngineeredHydrogel Systems

Understanding how light interacts with biomaterials is critical not only for therapeutic delivery in vivo but also for enabling emerging light-based fabrication methods such as volumetric bioprinting. In particular, optical characterization of photosensitive hydrogels like Gelatin Methacrylate (GelMA) provides foundational data for additive manufacturing of complex, tissue-engineered constructs with spatially controlled architecture. GelMA is a promising candidate for use as an injectable hydrogel for spinal cord injury (SCI) repair. This is primarily due to its highly tunable properties, allowing it to mimic tissue. Additionally, GelMA can be optically crosslinked. Optical simulations of this material within the spinal cord can inform whether the cross-linking of this material is feasible and uniform within a particular injury with a chosen exposure paradigm. These simulations require the optical properties of the tissues and materials of interest. However, the optical properties of GelMA have not been studied. The optical properties of GelMA were measured using a double integrating sphere setup and modelled with inverse adding doubling. We measured the absorption coefficient ({micro}a [mm-1]), reduced scattering coefficient ({micro}s[mm-1]), and scattering anisotropy (g [unitless]) for GelMA hydrogels, and examined the effect on these properties when magnetically alignable microstructures were suspended in the hydrogel. We conducted Monte Carlo simulations using these optical properties to determine whether the GelMA hydrogels would be cross-linked under different illumination conditions within a representative spinal cord injury geometry. The depth of hydrogel cross-linking for this representative spinal cord injury geometry was experimentally validated. Overall, it was found that GelMA without rods has an {micro}a = 0.516 {+/-} 0.025 mm-1, with insignificant scattering at 450 nm, GelMA with rods has an {micro}a = 0.588 {+/-} 0.018 mm-1, {micro}s = 0.196 {+/-} 0.024 mm-1, and g = 0.906 {+/-} 0.014 at 450 nm. Additionally, it was observed that in fluid-filled lesions, external illumination is often sufficient to achieve uniform gel curing. In contrast, fibrotic lesions require an intraspinal approach to adequately deliver light throughout the lesion, although the dose distribution will be nonuniform. Finally, experimental results confirmed the simulation findings, showing that when exposing GelMA to 63.29 mW/cm2 of 450 nm light, curing is uniform within the first 4 mm of gel and worsens with depth. These findings support the conclusion that larger volumes of photosensitive GelMA can be feasibly cured within the porcine spinal cord, but an intraspinal exposure will likely be required within human spinal tissue. These findings not only support the feasibility of in situ photopolymerization for SCI repair, but also provide critical optical parameters and validation approaches relevant to bioprinting systems.

bioengineering↗

bioRxiv2025

iPSC-derived hepatocytes accurately recapitulate population diversity in alpha-1-antitrypsin deficiency and offer a novel in vitro model for large-scale drug efficacy screening studies.

BackgroundAlpha-1 antitrypsin deficiency (A1ATD) is a hereditary recessive disorder caused by mutations in the SERPINA1 gene. It is a clinically under-recognised disease characterised by low circulating A1AT levels and intracellular accumulation of misfolded A1AT in hepatocytes. Deposition of excessive abnormal A1AT in the liver leads to liver failure, yet no specific treatments are available due to the lack of physiologically relevant disease modelling platforms. MethodsWe have hypothesised that human induced pluripotent stem cell (iPSC)-derived hepatocytes can provide an efficient platform to study A1ATD. Using CRISPR/Cas9, we have generated wild-type and A1ATD iPSC-derived hepatocytes (Opti-HEP) from healthy and A1ATD donors and developed a bioassay that mimics the accumulation of misfolded A1AT in the liver. Responses to the reference drug carbamazepine (CBZ), known to reduce intracellular misfolded A1AT levels, and RNA-based therapeutics were subsequently investigated. ResultsAll lines successfully differentiated into hepatocytes as measured by comparable key hepatic and disease markers to those seen in primary human hepatocytes. The diseased lines displayed increased intracellular accumulation of misfolded A1AT compared to isogenic controls. Diseased cell lines showed significant decreases in intracellular accumulation of polymeric A1AT following transfection with RNA-based therapeutics, but a differential response upon treatment with CBZ. ConclusionWe have developed a specific and robust in vitro model of A1ATD that recapitulates disease pathophysiology and responds to small molecule-based treatments and advanced therapeutic strategies. These data demonstrate the suitability of this model for large-scale efficacy screening studies for the treatment of A1ATD and help pave the way towards the development of novel therapies.

cell biology↗

bioRxiv2024

Repeat-rich regions cause false positive detection of NUMTs - a case study in amphibians using an improved cane toad reference genome

Mitochondrial DNA (mtDNA) has been widely used in genetics research for decades. Contamination from nuclear DNA of mitochondrial origin (NUMT) can confound studies of phylogenetic relationships and mtDNA heteroplasmy. Homology searches with mtDNA are widely used to detect NUMTs in the nuclear genome. Nevertheless, false positive detection of NUMTs is common when handling repeat-rich sequences, whilst fragmented genomes might result in missing true NUMTs. In this study, we investigated different NUMT detection methods and how the quality of the genome assembly affects them. We presented an improved nuclear genome assembly (aRhiMar1.3) of the invasive cane toad (Rhinella marina) with additional long-read Nanopore and 10x linked-read sequencing. The final assembly was 3.47 Gb in length with 91.3% of tetrapod universal single-copy orthologs (n=5,310), indicating the gene-containing regions were well assembled. We used three complementary methods (NUMTFinder, dinumt and PALMER) to study the NUMT landscape of the cane toad genome. All three methods yielded consistent results, showing very few NUMTs in the cane toad genome. Furthermore, we expanded NUMT detection analyses to other amphibians and confirmed a weak relationship between genome size and the number of NUMTs present in the nuclear genome. Amphibians are repeat-rich, and we show that the number of NUMTs found in highly repetitive genomes is prone to inflation when using homology-based detection without filters. Together, this study provides an exemplar of how to robustly identify NUMTs in complex genomes when confounding effects on mtDNA analyses are a concern. SignificanceThis study uses an updated cane toad nuclear genome assembly and multiple NUMT detection methods to confirm a lack of NUMTs that might confound the use of mtDNA as a population genetic marker in the cane toad. We provide an exemplar study for NUMT detection accounting for genome assembly quality and composition, and highlight the risks of using BLASTN-based approaches in highly repetitive nuclear genomes.

genomics↗

bioRxiv2024

Functional Diversity of Memory CD8 T Cells is Spatiotemporally Imprinted

Tissue-resident memory CD8 T cells (TRM) kill infected cells and recruit additional immune cells to limit pathogen invasion at barrier sites. Small intestinal (SI) TRM cells consist of distinct subpopulations with higher expression of effector molecules or greater memory potential. We hypothesized that occupancy of diverse anatomical niches imprints these distinct TRM transcriptional programs. We leveraged human samples and a murine model of acute systemic viral infection to profile the location and transcriptome of pathogen-specific TRM cell differentiation at single-transcript resolution. We developed computational approaches to capture cellular locations along three anatomical axes of the small intestine and to visualize the spatiotemporal distribution of cell types and gene expression. TRM populations were spatially segregated: with more effector- and memory-like TRM preferentially localized at the villus tip or crypt, respectively. Modeling ligand-receptor activity revealed patterns of key cellular interactions and cytokine signaling pathways that initiate and maintain TRM differentiation and functional diversity, including different TGF{beta} sources. Alterations in the cellular networks induced by loss of TGF{beta}RII expression revealed a model consistent with TGF{beta} promoting progressive TRM maturation towards the villus tip. Ultimately, we have developed a framework for the study of immune cell interactions with the spectrum of tissue cell types, revealing that T cell location and functional state are fundamentally intertwined.

immunology↗

bioRxiv2023

An injectable in situ crosslinkable platform for ultra-long-acting delivery of hydrophilic therapeutics

Achieving ultra-long-term release of hydrophilic drugs over several months remains a significant challenge for existing long-acting injectables (LAIs). Existing platforms, such as in situ forming implants (ISFI), exhibit high burst release due to solvent efflux and microsphere-based approaches lead to rapid drug diffusion due to significant water exchange and large pores. Addressing these challenges, we have developed an injectable platform that, for the first time, achieves ultra-long-term release of hydrophilic drugs for over six months. This system employs a methacrylated ultra-low molecular weight pre-polymer (polycaprolactone) to create in situ cross-linked depots (ISCD). The ISCDs solvent-free design and dense mesh network, both attributed to the ultra-low molecular weight of the pre-polymer, effectively minimizes burst release and water influx/efflux. In vivo studies in rats demonstrate that ISCD outperforms ISFI by achieving lower burst release and prolonged drug release. We demonstrated the versatility of ISCD by showcasing ultra-long-term delivery of several hydrophilic drugs, including antiretrovirals (tenofovir alafenamide, emtricitabine, abacavir, and lamivudine), antibiotics (vancomycin and amoxicillin) and an opioid antagonist naltrexone. Additionally, ISCD achieved ultra-long-term release of the hydrophobic drug tacrolimus and enabled co-delivery of hydrophilic drug combinations encapsulated in a single depot. We also identified design parameters to tailor the polymer network, tuning drug release kinetics and ISCD degradation. Pharmacokinetic modeling predicted over six months of drug release in humans, significantly surpassing the one-month standard achievable for hydrophilic drugs with existing LAIs. The platforms biodegradability, retrievability, and biocompatibility further underscore its potential for improving treatment adherence in chronic conditions.

bioengineering↗

bioRxiv2023

Mitochondrial genome analyses uncover intriguing population structure across the invasive trajectory of an iconic invader

Invasive species offer insights into rapid adaptations in novel environments. The iconic cane toad (Rhinella marina) is an excellent model for studying rapid adaptation during invasion. Previous research using the mitochondrial NADH dehydrogenase 3 (ND3) gene in the Hawaiian and Australian invasive populations found a single haplotype, indicating an extreme genetic bottleneck following introduction. Nuclear genetic diversity also exhibited reductions across the genome in these two populations. Here, we investigated the mitochondrial genome diversity of cane toads across this invasion trajectory. We created the first reference mitochondrial genome of the cane toad with long-read sequencing and constructed a phylogeny of Anura full mitochondrial genomes. We used transcriptomic data of 125 individuals from the native (French Guiana) and introduced (Hawaii and Australia) ranges to construct nearly-complete mitochondrial genomes for population genomics analyses. As expected, the cane toad belongs to family Bufonidae, distinct from genus Bufo. In agreement with previous investigations of these populations, we identified genetic bottlenecks in both Hawaiian and Australian introduced populations, alongside evidence of population expansion in the invasive ranges. Although mitochondrial genetic diversity in introduced populations was reduced, our results revealed that it had been underestimated: we identified 45 mitochondrial haplotypes in Hawaiian and Australian samples, none of which were found in the native range. Additionally, we identified two distinct groups of haplotypes from the native range, separated by a minimum of 110 base pairs (0.6%). These findings enhance our understanding of Anura phylogenetics and how invasion has shaped the genetic landscape of this species.

genomics↗

bioRxiv2023

An anciently diverged family of RNA binding proteins maintain correct splicing of ultra-long exons through cryptic splice site repression.

We previously showed that the germ cell specific nuclear protein RBMXL2 represses cryptic splicing patterns during meiosis and is required for male fertility. RBMXL2 evolved from the X-linked RBMX gene, which is silenced during meiosis due to sex chromosome inactivation. It has been unknown whether RBMXL2 provides a direct replacement for RBMX in meiosis, or whether RBMXL2 evolved to deal with the transcriptionally permissive environment of meiosis. Here we find that RBMX primarily operates as a splicing repressor in somatic cells, and specifically regulates a distinct class of exons that exceed the median human exon size. RBMX protein-RNA interactions are enriched within ultra-long exons, particularly within genes involved in genome stability, and repress the selection of cryptic splice sites that would compromise gene function. These similarities in overall function suggested that RBMXL2 might replace the function of RBMX during meiosis. To test this prediction we carried out inducible expression of RBMXL2 and the more distantly related RBMY protein in somatic cells, finding each could rescue aberrant patterns of RNA processing caused by RBMX depletion. The C-terminal disordered domain of RBMXL2 is sufficient to rescue proper splicing control after RBMX depletion. Our data indicate that RBMX and RBMXL2 have parallel roles in somatic tissues and the germline that must have been conserved for at least 200 million years of mammalian evolution. We propose RBMX family proteins are particularly important for the splicing inclusion of some ultra-long exons with increased intrinsic susceptibility to cryptic splice site selection.

molecular biology↗

bioRxiv2023

Accurate and interpretable gene expression imputation on scRNA-seq data using IGSimpute

Single-cell RNA-sequencing (scRNA-seq) enables the quantification of gene expression at the transcriptomic level with single-cell resolution, enhancing our understanding of cellular heterogeneity. However, the excessive missing values present in scRNA-seq data (termed dropout events) hinder downstream analysis. While numerous imputation methods have been proposed to recover scRNA-seq data, high imputation performance often comes with low or no interpretability. Here, we present IGSimpute, an accurate and interpretable imputation method for recovering missing values in scRNA-seq data with an interpretable instance-wise gene selection layer. IGSimpute outperforms ten other state-of-the-art imputation methods on nine tissues of the Tabula Muris atlas with the lowest mean squared error as the chosen benchmark metric. We demonstrate that IGSimpute can give unbiased estimates of the missing values compared to other methods, regardless of whether the average gene expression values are small or large. Clustering results of imputed profiles show that IGSimpute offers statistically significant improvement over other imputation methods. By taking the heart-and-aorta and the limb muscle tissues as examples, we show that IGSimpute can also denoise gene expression profiles by removing outlier entries with unexpected high expression values via the instance-wise gene selection layer. We also show that genes selected by the instance-wise gene selection layer could indicate the age of B cells from bladder fat tissue of the Tabula Muris Senis atlas. IGSimpute has linear time-complexity with respect to cell number, and thus applicable to large datasets.

bioinformatics↗

bioRxiv2022

The giant diploid faba genome unlocks variation in a global protein crop

Increasing the proportion of locally produced plant protein in currently meat-rich diets could substantially reduce greenhouse gas emission and loss of biodiversity. However, plant protein production is hampered by the lack of a cool-season legume equivalent to soybean in agronomic value. Faba bean (Vicia faba L.) has a high yield potential and is well-suited for cultivation in temperate regions, but genomic resources are scarce. Here, we report a high-quality chromosome-scale assembly of the faba bean genome and show that it has grown to a massive 13 Gb in size through an imbalance between the rates of amplification and elimination of retrotransposons and satellite repeats. Genes and recombination events are evenly dispersed across chromosomes and the gene space is remarkably compact considering the genome size, though with significant copy number variation driven by tandem duplication. Demonstrating practical application of the genome sequence, we develop a targeted genotyping assay and use high-resolution genome-wide association (GWA) analysis to dissect the genetic basis of hilum colour. The resources presented constitute a genomics-based breeding platform for faba bean, enabling breeders and geneticists to accelerate improvement of sustainable protein production across Mediterranean, subtropical, and northern temperate agro-ecological zones.

plant biology↗

bioRxiv2021

Multiscale interactome analysis coupled with off-target drug predictions reveals drug repurposing candidates for human coronavirus disease

The COVID-19 pandemic has led to an urgent need for the identification of new antiviral drug therapies that can be rapidly deployed to treat patients with this disease. COVID-19 is caused by infection with the human coronavirus SARS-CoV-2. We developed a computational approach to identify new antiviral drug targets and repurpose clinically-relevant drug compounds for the treatment of COVID-19. Our approach is based on graph convolutional networks (GCN) and involves multiscale host-virus interactome analysis coupled to off-target drug predictions. Cellbased experimental assessment reveals several clinically-relevant repurposing drug candidates predicted by the in silico analyses to have antiviral activity against human coronavirus infection. In particular, we identify the MET inhibitor capmatinib as having potent and broad antiviral activity against several coronaviruses in a MET-independent manner, as well as novel roles for host cell proteins such as IRAK1/4 in supporting human coronavirus infection, which can inform further drug discovery studies.

cell biology↗

bioRxiv2020

RBMX enables productive RNA processing of ultra-long exons important for genome stability

Previously we showed that the germline-specific RNA binding protein RBMXL2 is essential for male meiosis where it represses cryptic splicing patterns (1). Here we find that its ubiquitously expressed paralog RBMX helps underpin human genome stability by preventing non-productive splicing. In particular, RBMX blocks selection of aberrant splice and polyadenylation sites within some ultra-long exons that would interfere with genes needed for normal replication fork activity. Target exons include within the ETAA1 (Ewings Tumour Associated 1) gene, where RBMX collaborates with its interaction partner Tra2{beta} to enable full-length exon inclusion by blocking selection of an aberrant 3 splice site. Our data reveal a novel group of RNA processing targets potently repressed by RBMX, and help explain why RBMX is associated with gene expression networks in cancer, replication and sensitivity to genotoxic drugs.

molecular biology↗

bioRxiv2020

New insights on the modelling of the molecular mechanisms underlying neural maps alignment in the midbrain

We previously identified and modelled a principle of visual maps alignment in the midbrain involving the mapping of the retinal projections and concurrent transposition of retinal guidance cues into the superior colliculus providing positional information for the organization of cortical V1 projections onto the retinal map (Savier et al., 2017). This principle relies on mechanisms involving Epha/Efna signaling, correlated neuronal activity and axon competition. Here, using the 3-step map alignment computational model, we predict and validate in vivo the visual mapping defects in a well-characterized mouse model. Our results challenge previous hypotheses and provide an alternative, although complementary, explanation for the phenotype observed. In addition, we propose a new quantification method to assess the degree of alignment and organization between maps, allowing inter-model comparisons. This work generalizes the validity and robustness of the 3-step map alignment algorithm as a predictive tool and confirms the basic mechanisms of visual maps organization.

bioinformatics↗

bioRxiv2020

Dissection of the Spindle Assembly Checkpoint by Proximity Proteomics

The spindle assembly checkpoint (SAC) is critical for sensing defective microtubule-kinetochore attachments and tension across the kinetochore and functions to arrest cells in prometaphase to allow time to repair any errors prior to proceeding into anaphase. The SAC has a central role in ensuring the fidelity of chromosome segregation and its dysregulation has been linked to the development of human diseases like cancer. The establishment and maintenance of the SAC relies on multiple protein complexes that are intricately regulated in a spatial and temporal manner through posttranslational modifications like phosphorylation. Over the past few decades the SAC has been highly investigated and much has been learned about its protein constituents and the pathways and factors that regulate its activity. However, the spatio-temporal proximity associations of the core SAC components have not been explored in a systematic manner. Here, we have taken a BioID2 proximity-labeling proteomic approach to define the proximity protein environment for each of the five core SAC proteins BUB1, BUB3, BUBR1, MAD1L1, and MAD2L1 under conditions where the SAC is active in prometaphase. These five protein association maps were integrated to generate the SAC proximity protein network that contains multiple layers of information related to core SAC protein complexes, protein-protein interactions, and proximity associations. Our analysis validated many of the known SAC complexes and protein-protein interactions. Additionally, it uncovered new protein associations that lend insight into the functioning of the SAC and highlighted future areas that should be investigated to generate a comprehensive understanding of the SAC.

biochemistry↗

bioRxiv2020

Dynamic chromatin accessibility landscape changes following interleukin-1 stimulation

Genome-wide methods for examining chromatin modification provide detailed information on regulatory regions of the genome. Dynamic modifications of chromatin allow rapid access of the gene regulatory machinery to condensed genomic regions facilitating subsequent gene expression. Inflammatory cytokine stimulation of cells can cause rapid gene expression changes through direct signalling pathway-mediated transcription factor activation and regulatory element binding. Here we used the Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq) to assess regions of the genome that are differentially accessible following treatment of cells with interleukin-1 (IL-1). We identified 126,483 open chromatin regions, with 241 regions significantly differentially accessible following stimulation, with 64 and 177 more or less accessible, respectively. These differentially accessible regions predominantly correspond to regions of the genome marked as enhancers. Motif searching identified an overrepresentation of a number of transcription factors, most notably RelA in the regions becoming more accessible, with analysis of ChIP-seq data confirmed RelA binding to these regions. A significant correlation in differential chromatin accessibility and gene expression was also observed. Functionality in regulating gene expression was confirmed using CRISPR/Cas9 genome-editing to delete regions for that became more accessible following stimulation in the genes MMP13, IKBKE and C1QTNF1. These same regions were also accessible for activation using a dCas9-transcriptional activator and showed enhancer activity in a cellular model. Together, these data describe and functionally validate a number of dynamically accessible chromatin regions involved in inflammatory signalling.

genomics↗

bioRxiv2020

microRNA-seq of cartilage reveals an over-abundance of miR-140-3p which contains functional isomiRs

MiR-140 is selectively expressed in cartilage. Deletion of the entire miR-140 locus in mice results in growth retardation and early-onset osteoarthritis-like pathology, however the relative contribution of miR-140-5p or miR-140-3p to the phenotype remains to be determined. An unbiased small RNA sequencing approach identified miR-140-3p as significantly more abundant (>10-fold) than miR-140-5p in human cartilage. Analysis of these data identified multiple miR-140-3p isomiRs differing from the miRBase annotation at both the 5 and 3 end, with >99% having one of two seed sequences (5 bases 2-8). Canonical (miR-140-3p.2) and shifted (miR-140-3p.1) seed isomiRs were overexpressed in chondrocytes and transcriptomics performed to identify targets. miR-140-3p.1 and miR-140-3p.2 significantly down-regulated 694 and 238 genes respectively, of which only 162 genes were commonly down-regulated. IsomiR targets were validated using 3 UTR luciferase assays. miR-140-3p.1 targets were enriched within up-regulated genes in rib chondrocytes of Mir140-null mice and within down-regulated genes during human chondrogenesis. Finally, through imputing the expression of miR-140 from the expression of the host gene WWP2 in 124 previously published datasets, an inverse correlation with miR-140-3p.1 predicted targets was identified. Together these data suggest the novel seed containing isomiR miR-140-3p.1 is more functional than original consensus miR-140-3p seed containing isomiR.

molecular biology↗

bioRxiv2020

Multi-tissue epigenetic analysis of the osteoarthritis susceptibility locus mapping to the plectin gene PLEC

ObjectiveOsteoarthritis (OA) associated single nucleotide polymorphism (SNP) rs11780978 correlates with differential expression of PLEC, and methylation quantitative trait loci (mQTLs) at PLEC CpGs in cartilage. This implies that methylation links chondrocyte genotype and phenotype, thus driving the functional effect. PLEC encodes plectin, a cytoskeletal protein that enables tissues to respond to mechanical forces. We sought to assess whether PLEC functional effects were cartilage specific. MethodCartilage, fat pad, synovium and peripheral blood were collected from patients undergoing arthroplasty. PLEC CpGs were analysed for mQTLs and allelic expression imbalance (AEI) was performed. We focussed on previously reported mQTL clusters neighbouring cg19405177 and cg14598846. Plectin was knocked down in a mesenchymal stem cell (MSC) line using CRISPR/Cas9 and cells phenotyped by RNA-sequencing. ResultsNovel mQTLs were discovered in fat pad, synovium and peripheral blood at both clusters. The genotype-methylation effect of rs11780978 was stronger in cg14598846 than in cg19405177 and stronger in joint tissues than in peripheral blood. We observed AEI in synovium in the same direction as for cartilage. Knocking-down plectin impacted on pathways reported to have a role in OA, including Wnt signalling, glycosaminoglycan biosynthesis and immune regulation. ConclusionsSynovium is also a target of the rs11780978 OA association functionally operating on PLEC. In fat pad, mQTLs were identified but these did not correlate with PLEC expression, suggesting the functional effect is not joint-wide. Our study highlights interplay between genetic risk, DNA methylation and gene expression in OA, and reveals clear differences between tissues from the same diseased joint.

genetics↗