Biology subjects

Mok, K. Y.

Publications and source records attributed to Mok, K. Y..

8 recordsLinked to original sources

bioRxiv2026

Antiviral Sulfonated Polymersomes Inhibit Corona-, Influenza-, and Alphavirus

A broad-spectrum antiviral is required to enable rapid intervention against current, newly emerging and mutating viruses. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus (IAV), Sindbis virus (SINV) and chikungunya virus (CHIKV) all engage negatively charged moieties on host cells, such as heparan sulfate (HS) and sialic acid, to facilitate attachment for entry and infection. We designed HS-mimetic nanoparticles in the form of polymer vesicles (polymersomes) by blending membrane-forming and sulfonated copolymers. These biocompatible polymersomes successfully inhibited host cell infection of HS-dependent SARS-CoV-2 and HS-independent IAV in vitro with sub-nanomolar potency. Multivalent interaction of several virus ligands with a single polymersome as quantified by fluorescence correlation spectroscopy likely contributes to their potency. The sulfonated polymersomes also functioned in vivo as demonstrated by a reduction in the spread of SINV, an alphavirus model for CHIKV, in zebrafish embryos, which led to a significantly increased survival. Hence, our polymersomes could form the basis for an urgently required multifunctional broad-spectrum antiviral nanomedicine.

bioengineering↗

bioRxiv2023

Genetic, transcriptomic, histological, and biochemical analysis of progressive supranuclear palsy implicates glial activation and novel risk genes

Progressive supranuclear palsy (PSP) is a rare Parkinsonian disorder characterized by problems with movement, balance, cognition, and other symptoms. PSP differs from Alzheimers disease (AD) and other neurodegenerative diseases displaying abnormal forms of the microtubule-associated protein tau ("tauopathies") by the presence of pathology not only in neurons, but also in astrocytes and oligodendrocytes. Genetic contributors may mediate these differences, however much of PSP genetics remains unexplained. Here we conducted the largest genome-wide association study (GWAS) of PSP to date including 2,779 cases (2,595 neuropathologically-confirmed) and 5,584 controls and identified six independent PSP susceptibility loci with genome-wide significant (p < 5x10-8) associations including five known (MAPT, MOBP, STX6, RUNX2, SLCO1A2) and one novel locus (C4A). Integration with cell type-specific epigenomic annotations revealed a unique oligodendrocytic signature that distinguishes PSP from AD and Parkinsons disease. Candidate PSP risk gene prioritization using expression quantitative trait loci (eQTLs) identified oligodendrocyte-specific effects on gene expression in half of the genome-wide significant loci, as well as an association with elevated C4A expression in bulk brain tissue which may be driven by increased C4A copy number in PSP cases. Finally, histological studies demonstrated abnormal tau aggregates in oligodendrocytes that colocalize with C4 (complement) deposition. Integrating GWAS with functional studies including epigenomic and eQTL analyses, we identified potential causal roles for variation in MOBP, STX6, RUNX2, SLCO1A2, and C4A in the pathogenesis of PSP.

neuroscience↗

bioRxiv2023

Tricontinental detection of Streptococcus pyogenes M1UK: A call for wider research and active surveillance.

The Streptococcus pyogenes M1UK lineage, characterised by an intrinsic ability to express SpeA toxin and defined by 27 single nucleotide polymorphisms in the core genome, dominates the population of emm1 S. pyogenes isolates throughout Europe, Canada, South America, Japan and Oceania. While not the sole deterministic factor, enhanced SpeA expression is likely to have contributed to M1UK lineage expansion, but was not sufficient to support expansion of intermediate lineage M123SNP, that expresses SpeA at a similar level to M1UK. A single nucleotide polymorphism (SNP) in the ssrA leader sequence upstream of speA is one of a limited number of SNPs that distinguish intermediate sublineages that differ in SpeA production. It was recently shown that this SNP leads to increased ssrA terminator read-through, and consequent increased transcription of speA, which lies downstream of ssrA. In this work, introduction of the ssrA SNP into representative isolates of the widely disseminated M1global clone and the intermediate M113SNP lineage, that cannot otherwise produce readily-detectable SpeA in culture, resulted in SpeA expression, confirming the importance of the ssrA SNP to SpeA phenotype. Consistent with this, correction of the ssrA SNP in M1UK abrogated SpeA expression. However, RNAseq analysis of 8 emm1 clinical pharyngitis strains showed that presence of the SNP was not invariably linked to read-through from the ssrA leader sequence or SpeA expression. Read-through was observed in isolates that did not possess the ssrA SNP. Critical review of existing data suggests that speA mRNA transcript length may be impacted by the two-component regulator CovRS, pointing to a complex regulatory network interaction between the bacterial chromosome and phage-encoded superantigens.

microbiology↗

bioRxiv2020

Common variation at the LRRK2 locus is associated with survival in the primary tauopathy progressive supranuclear palsy

The genetic basis of variation in the rate of disease progression of primary tauopathies has not been determined. In two independent progressive supranuclear palsy cohorts, we show that common variation at the LRRK2 locus determines survival from motor symptom onset to death, possibly through regulation of gene expression. This links together genetic risk in alpha-synuclein and tau disorders, and suggests that modulation of proteostasis and neuro-inflammation by LRRK2 inhibitors may have a therapeutic role across disorders.

genetics↗

bioRxiv2020

Patient-specific Alzheimer-like pathology in trisomy 21 cerebral organoids reveals BACE2 as a gene-dose-sensitive AD-suppressor in human brain

A population of >6 million people worldwide at high risk of Alzheimers disease (AD) are those with Down Syndrome (DS, caused by trisomy 21 (T21)), 70% of whom develop dementia during lifetime, caused by an extra copy of {beta}-amyloid-(A{beta})-precursor-protein gene. We report AD-like pathology in cerebral organoids grown in vitro from non-invasively sampled strands of hair from 71% of DS donors. The pathology consisted of extracellular diffuse and fibrillar A{beta} deposits, hyperphosphorylated/pathologically conformed Tau, and premature neuronal loss. Presence/absence of AD-like pathology was donor-specific (reproducible between individual organoids/iPSC lines/experiments). Pathology could be triggered in pathology-negative T21 organoids by CRISPR/Cas9-mediated elimination of the third copy of chromosome-21-gene BACE2, but prevented by combined chemical {beta} and {gamma}-secretase inhibition. We found that T21-organoids secrete increased proportions of A{beta}-preventing (A{beta}1-19) and A{beta}-degradation products (A{beta}1-20 and A{beta}1-34). We show these profiles mirror in cerebrospinal fluid of people with DS. We demonstrate that this protective mechanism is mediated by BACE2-trisomy and cross-inhibited by clinically trialled BACE1-inhibitors. Combined, our data prove the physiological role of BACE2 as a dose-sensitive AD-suppressor gene, potentially explaining the dementia delay in [~]30% of people with DS. We also show that DS cerebral organoids could be explored as pre-morbid AD-risk population detector and a system for hypothesis-free drug screens as well as identification of natural suppressor genes for neurodegenerative diseases.

neuroscience↗

bioRxiv2018

Variation at the TRIM11 locus modifies Progressive Supranuclear Palsy phenotype

ObjectiveThe basis for clinical variation related to underlying Progressive Supranuclear Palsy (PSP) pathology is unknown. We performed a genome wide association study (GWAS) to identify genetic determinants of PSP phenotype.\n\nMethodsTwo independent pathological and clinically diagnosed PSP cohorts were genotyped and phenotyped to create Richardsons syndrome (RS) and non-RS groups. We carried out separate logistic regression GWAS to compare RS and non-RS groups and then combined datasets to carry out a whole cohort analysis (RS=367, non-RS=130). We validated our findings in a third cohort by referring to data from 100 deeply phenotyped cases from a recent GWAS. We assessed the expression/co-expression patterns of our identified genes and used our data to carry out gene-based association testing.\n\nResultsOur lead single nucleotide polymorphism (SNP), rs564309, showed an association signal in both cohorts, reaching genome wide significance in our whole cohort analysis - OR 5.5 (3.2-10.0), p-value 1.7x10-9. rs564309 is an intronic variant of the tripartite motif-containing protein 11 (TRIM11) gene, a component of the ubiquitin proteasome system (UPS). In our third cohort, minor allele frequencies of surrogate SNPs in high linkage disequilibrium with rs564309 replicated our findings. Gene based association testing confirmed an association signal at TRIM11. We found that TRIM11 is predominantly expressed neuronally, in the cerebellum and basal ganglia.\n\nInterpretationOur study suggests that the TRIM11 locus is a genetic modifier of PSP phenotype and potentially adds further evidence for the UPS having a key role in tau pathology, therefore representing a target for disease modifying therapies.

neuroscience↗

bioRxiv2018

Neurofilament light as a blood biomarker for neurodegeneration in Down syndrome

INTRODUCTIONDown syndrome (DS) may be considered a genetic form of Alzheimers disease (AD) due to universal development of AD neuropathology, but diagnosis and treatment trials are hampered by a lack of reliable blood biomarkers. A potential biomarker is neurofilament light (NF-L), due to its association with axonal damage in neurodegenerative conditions.\n\nMETHODSWe measured blood NF-L concentration in 100 adults with DS using Simoa NF-light(R) assays, and examined relationships with age, and cross-sectional and longitudinal dementia diagnosis.\n\nRESULTSNF-L levels increased with age (Spearmans rho = 0.789, p<0.001), with a steep increase after age 40, and were predictive of dementia status (p=0.022 adjusting for age, sex, and APOE4) but showed no relationship with longstanding epilepsy or premorbid ability. Baseline NF-L levels were associated with longitudinal dementia status.\n\nDISCUSSIONNF-L is a biomarker for neurodegeneration in DS, with potential for use in future clinical trials to prevent or delay dementia.\n\nResearch in contextO_ST_ABSSystematic reviewC_ST_ABSThe authors reviewed the literature using PubMed searches supplemented with our knowledge of pending papers in this research area. While blood NF-L has been associated with clinical features of progression in a number of neurodegenerative conditions, we have not identified any reports of NF-L associated with cognitive decline in DS, a genetic form of AD.\n\nInterpretationOur findings demonstrate the potential utility of NF-L as a blood biomarker of neurodegeneration in DS, a population that may not be able to tolerate more invasive procedures such as neuroimaging and lumbar punctures to track progression.\n\nFuture directionsThe association between NF-L and other markers of longitudinal AD progression should be explored further in future work.

molecular biology↗

bioRxiv2018

Sequence of cognitive changes associated with development of Alzheimer’s disease in Down syndrome – data driven analysis

ObjectiveIndividuals with Down syndrome (DS) have an extremely high genetic risk for Alzheimers disease (AD) however the course of cognitive decline associated with progression to dementia is ill-defined. Data-driven methods can estimate long-term trends from cross-sectional data while adjusting for variability in baseline ability, which complicates dementia assessment in those with DS.\n\nMethodsWe applied an event-based model to cognitive test data and informant-rated questionnaire data from 283 adults with DS (the largest study of cognitive functioning in DS to date) to estimate the sequence of cognitive decline and individuals disease stage.\n\nResultsDecline in tests of memory, sustained attention / motor coordination, and verbal fluency occurred early, demonstrating that AD in DS follows a similar pattern of change to other forms of AD. Later decline was found for informant measures. Using the resulting staging model, we showed that adults with a clinical diagnosis of dementia and those with APOE 3:4 or 4:4 genotype were significantly more likely to be staged later, suggesting the model is valid.\n\nInterpretationOur results identify tests of memory and sustained attention may be particularly useful measures to track decline in the preclinical/prodromal stages of AD in DS whereas informant-measures may be useful in later stages (i.e. during conversion to dementia, or post-diagnosis). These results have implications for the selection of outcome measures of treatment trials to delay or prevent cognitive decline due to AD in DS. As clinical diagnoses are generally made late into AD progression, early assessment is essential.

neuroscience↗