Biology subjects

Lai, K.

Publications and source records attributed to Lai, K..

14 recordsLinked to original sources

bioRxiv2025

AAV-based gene replacement reverses Neurexin-2 downregulation in the cerebellum of a mouse model of phosphomannomutase 2 deficiency (PMM2-CDG)

Phosphomannomutase 2 (PMM2) deficiency is the most common congenital disorders of glycosylation (CDG) with an estimated incidence ranging from 1:20,000 to 1:80,000. Patients manifest a broad spectrum of clinical manifestations, with neurological deficits often emerging as the earliest sign, and may progress to severe multi-organ dysfunction. Mortality reaches 20% by the age of six, primarily due to severe infections, liver insufficiency, or cardiomyopathy. The pathophysiology of the tissue-specific complications remains unclear and there is currently no cure for the disease. In this study, we performed omics analyses of cerebella isolated from a mouse model of PMM2-CDG. RNA-Seq analysis revealed altered gene expression in pathways involved in immune responses and coagulation, while proteomic analysis of proteins enriched by lectin-affinity chromatography identified proteins required for neurodevelopment and neurotransmission. We validated our results by demonstrating significant downregulation of Neurexin-2 in the Pmm2 knockout (KO) mouse cerebella and showed that its reduced abundance can be reversed by AAV9-PMM2 gene treatment of the Pmm2 KO mice.

genetics↗

bioRxiv2025

PGM1 deficiency disrupts sarcomere and mitochondrial function in a stem-cell cardiomyocyte model

BackgroundPhosphoglucomutase-1 (PGM1) plays a pivotal role in glycolysis, glycogen metabolism, and glycosylation. Pathogenic variants in PGM1 cause PGM1-congenital disorder of glycosylation (PGM1-CDG), a multisystem disorder with cardiac involvement. While glycosylation abnormalities in PGM1-CDG are treatable with galactose, cardiomyopathy does not improve suggesting a glycosylation-independent pathomechanism. Recently, mitochondrial abnormalities have been shown in a heart of a PGM1-deficicient patient and PGM1-mouse model. In addition, PGM1 has been associated with LDB3 (ZASP/Cypher), a sarcomeric Z-disk protein also associated with cardiomyopathy. However, the cardiac-specific role of PGM1 remains poorly understood, and targeted therapies for PGM1-related cardiomyopathy are currently lacking. MethodsInduced pluripotent stem cell-derived cardiomyocytes (iCMs) were generated from PGM1-deficient patient fibroblasts. Multielectrode array (MEA) recordings, untargeted (glyco)proteomics, and pathway analysis were performed to assess functional and molecular changes. Key findings were validated using tracer metabolomics and mitochondrial respiration assays. ResultsPGM1-deficient iCMs exhibited reduced beating frequency, impaired contractility, and prolonged contraction kinetics. Proteomic analyses revealed depletion of Z-disk components, including LDB3. AlphaFold3 structural modeling predicted a direct interaction between PGM1 and LDB3, implicating PGM1 in Z-disk integrity, which was confirmed in vitro. In addition, mitochondrial proteins were severely depleted, prompting us to investigate mitochondrial function. Functional validation confirmed extensive metabolic rewiring, energy depletion, and severely impaired mitochondrial respiration. Finally, the in silico drug repurposing identified possible therapeutic options that could target PGM1-deficient cardiomyopathy. ConclusionPGM1 is a key regulator of cardiomyocyte function, linking sarcomeric Z-disk integrity with mitochondrial metabolism. These mechanistic insights offer a foundation for developing targeted therapies for PGM1-CDG and potentially other cardiomyopathies involving Z-disk dysfunction. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=175 HEIGHT=200 SRC="FIGDIR/small/662580v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@17da449org.highwire.dtl.DTLVardef@1acb669org.highwire.dtl.DTLVardef@1fbbeecorg.highwire.dtl.DTLVardef@b38b6f_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Experimental galactose-1 phosphate uridylyltransferase (GALT) mRNA therapy improves motor-related phenotypes in a mouse model of Classic Galactosemia

Despite life-saving newborn screening programs and a life-long galactose-restricted diet, many patients with Classic Galactosemia continue to develop long-term debilitating neurological deficits, speech dyspraxia, and primary ovarian insufficiency (POI). Earlier, we showed that administration of an experimental human GALT mRNA predominantly expressed in the liver of the GalT gene-trapped mouse model augmented the expression of hepatic GALT activity, which reduced build-up of galactose and its toxic metabolites not only in the liver, but also in the peripheral tissues. Moreover, we showed that administration of GALT mRNA in the mutant mice restored whole-body galactose oxidation (WBGO), a functional biomarker. In this study, we extended our proof-of-concept (POC) efficacy studies to a disease-relevant phenotype, motor impairment. We found that a biweekly dosing regimen at 2mg/kg for 2 months could improve the motor performance of the animals in Rotarod and Composite Phenotype Scoring tests.

genetics↗

bioRxiv2024

Glutamate as a co-agonist for acid-sensing ion channels to aggravate ischemic brain damage

Glutamate is traditionally viewed as the first messenger to activate N-methyl-D-aspartate receptors (NMDARs) and downstream cell death pathways in stroke1,2, but unsuccessful clinical trials with NMDAR antagonists implicate the engagement of other NMDAR-independent mechanisms3-7. Here we show that glutamate and its structural analogs, including NMDAR antagonist L-AP5 (or APV), robustly potentiated currents mediated by acid-sensing ion channels (ASICs) which are known for driving acidosis-induced neurotoxicity in stroke4. Glutamate increased the proton affinity and open probability of ASICs, aggravating ischemic neurotoxicity in both in vitro and in vivo models. Site-directed mutagenesis and structure-based in silico molecular docking and simulations uncovered a novel glutamate binding cavity in the extracellular domain of ASIC1a. Computational drug screening of NMDAR competitive antagonist analogs identified a small molecule, LK-2, that binds to this cavity and abolishes glutamate-dependent potentiation of ASIC currents but spares NMDARs, providing strong neuroprotection efficacy comparable to that in ASIC1a or other cation ion channel knockout mouse models4-7. We conclude that glutamate serves as the first messenger for ASICs to exacerbate neurotoxicity, and that selective blockage of glutamate binding sites on ASICs without affecting NMDARs may be of strategic importance for developing effective stroke therapeutics devoid of the psychotic side effects of NMDAR antagonists.

neuroscience↗

bioRxiv2023

Viruses that 'infect' viruses: Cas12f1 and Cas9 gene drive in HSV1

Synthetic CRISPR-Cas9 gene drive has been developed as a potential tool to control harmful species. However, Cas9 gene drive faces high resistance rate and mitigation strategies developed so far are difficult to implement. Furthermore, studying the resistance to gene drive is time consuming and challenging in higher organisms. We here tackled these two challenges simultaneously by generating Cas9 and Un1Cas12f1 gene drive in a fast-replicating DNA virus, HSV1. We assessed the transmission dynamics and resistance formation through phenotypical staining and next-generation sequencing, and demonstrated that HSV1 supported fast and effective transmission of gene drives, and the Un1Cas12f1 gene drives yielded greater conversion and lower resistance than did the Cas9 gene drives. This positions the Un1Cas12f1 gene drive as a promising alternative, and HSV1 emerges as a dependable and swift platform for gene drive assessment. The gene drive viruses function like pathogens that specifically infect viruses, offering potential applications in attenuating viral infections.

microbiology↗

bioRxiv2023

Cellular protein painting for structural and binding sites analysis via lysine reactivity profiling with o-phthalaldehyde

The three-dimensional structure and the molecular interaction of proteins determine their roles in many cellular processes. Chemical protein painting with protein mass spectrometry can identify changes in structural conformations and molecular interactions of proteins including their binding sites. Nevertheless, most current protein painting techniques identified protein targets and binding sites of drugs in vitro using cell lysate or purified protein. Here, we screened 11 membrane-permeable lysine-reactive chemical probes for intracellular covalent labeling of endogenous proteins, which reveals ortho-phthalaldehyde (OPA) as the most reactive probe in intracellular environment. An MS workflow was developed and coupled with a new data analysis strategy termed RAPID (Reactive Amino acid Profiling by Inverse Detection) to enhance detection sensitivity. RAPID-OPA successfully identified structural change induced by allosteric drug TEPP-46 on its target protein PKM2, and was applied to profile conformation change of the proteome occurring in cells during thermal denaturation. Application of RAPID-OPA on cells treated with geldanamycin, selumetinib, and staurosporine successfully revealed their binding sites on target proteins. Thus, RAPID-OPA for cellular protein painting permits the identification of ligand-binding sites and detection of protein structural changes occurring in cells. Significance StatementProtein painting can be used to identify changes in the three-dimensional structure and molecular interaction of proteins that govern many cellular processes but are mostly applied to cell lysate or purified protein. We identified lysine reactive probes for the intracellular labeling of endogenous proteins, and developed an MS procedure with new data analysis strategy termed RAPID-OPA to characterize the intracellular conformation change of the proteome during thermal denaturation, and identified structural change mediated by allosteric regulator TEPP-46 on target protein PKM2. Furthermore, the approach could identify ligand binding sites exemplified by labeling of target proteins in cells treated with geldanamycin, selumetinib and staurosporine. Overall, RAPID-OPA for cellular protein painting enables the detection of protein structural changes happening in cells as well as the identification of ligand-binding sites.

cell biology↗

bioRxiv2023

Disease-associated gut microbiome and metabolome changes in chronic low back pain patients with bone marrow lesions

Chronic low back pain (LBP) is the leading cause of global disability. Vertebral bone marrow lesions (BMLs), one etiological factor for chronic LBP, are MRI signal changes in the vertebral bone marrow that extend from the disc endplate. The adipogenesis of bone marrow mesenchymal stem cells (BM-MSCs) could explain fatty replacement (FR) in normal bone marrow. FR is the most common type of BMLs. Here we show how the gut microbiome and serum metabolome change and how they interact in LBP patients with or without FR. The serum metabolome of chronic LBP patients with FR is characterized by decreased levels of branched-chain amino acids (BCAAs), which correlate with a gut microbiome that has important capability to regulate BCAA degradation pathway. Ruminococcus gnavus, Roseburia hominis and Lachnospiraceae bacterium 8 1 57FAA are identified as the main species driving the association between biosynthesis of BCAAs and BM-MSCs metabolism in LBP with FR individuals. In vitro work demonstrates that BCAAs can induce the adipogenesis of BM-MSCs by activating the SIRT4 pathway. Our findings provide a deep insight into understanding the role of the disturbed gut ecosystem in FR and LBP.

cell biology↗

bioRxiv2023

Discovery of microRNA-derived RNAs and proteins in human cells

MicroRNAs (miRNAs) are short noncoding RNAs that can regulate gene expression through the binding of their 5-ends to mRNAs. However, the biological effects of miRNA binding via their 3-ends remain unclear. Here, we discover that the exact reverse pairing of the 3-ends of miRNAs or miRNA-like RNAs, collectively termed microsized RNAs (msRNAs), with template RNAs can initiate the production of msRNA-derived RNAs (msdRs), which can subsequently be translated into polypeptides (msdPs). Using 2,632 human msRNAs from miRBase, 11,121 msdRs and 1,239 msdPs were predicted based on a 15-nucleotide pairing threshold, and the presence of representative msdRs and msdPs was confirmed in human cells. Of clinical relevance, msdP0188 is highly expressed in human lung and breast cancers, and its corresponding msRNAs and msdRs represent novel anti-cancer targets. Notably, inhibiting telomerase reverse transcriptase, a putative RNA-dependent RNA polymerase identified by bioinformatic screening, led to reduced levels of msdP0188 in human cancer cells. Our findings reveal a novel "msRNA [->] msdR [->] msdP" axis, expanding the classical central dogma and predicting many previously unrecognized RNAs and polypeptides with potential biological functions in human cells and other systems.

cell biology↗

bioRxiv2022

Novel gene-intergenic fusion involving ubiquitin E3 ligase UBE3C causes distal hereditary motor neuropathy: A new mechanism for motor neuron degeneration.

Distal hereditary motor neuropathies (dHMNs) are a group of inherited diseases involving the progressive, length-dependent axonal degeneration of the lower motor neurons. There are currently 29 reported causative genes and 4 disease loci implicated in dHMN. Despite the high genetic heterogeneity, mutations in the known genes account for less than 20% of dHMN cases with the mutations identified predominantly being point mutations or indels. We have expanded the spectrum of dHMN mutations with the identification of a 1.35 Mb complex structural variation (SV) causing a form of autosomal dominant dHMN (DHMN1 OMIM %182906). Given the complex nature of SV mutations and the importance of studying pathogenic mechanisms in a neuronal setting, we generated a patient-derived DHMN1 motor neuron model harbouring the 1.35 Mb complex insertion. The DHMN1 complex insertion creates a duplicated copy of the first 10 exons of the ubiquitin-protein E3 ligase gene (UBE3C) and forms a novel gene-intergenic fusion sense transcript by incorporating a terminal pseudo-exon from intergenic sequence within the DHMN1 locus. The UBE3C intergenic fusion (UBE3C-IF) transcript does not undergo nonsense-mediated decay and results in a significant reduction of wild type full length UBE3C (UBE3C-WT) protein levels in DHMN1 iPSC-derived motor neurons. An engineered transgenic C. elegans model expressing the UBE3C-IF transcript in GABA-ergic motor neurons shows neuronal synaptic transmission deficits. Furthermore, the transgenic animals are susceptible to heat stress which may implicate defective protein homeostasis underlying DHMN1 pathogenesis. Identification of the novel UBE3C-IF gene-intergenic fusion transcript in motor neurons highlights a potential new disease mechanism underlying axonal and motor neuron degeneration. These complementary models serve as a powerful paradigm for studying the DHMN1 complex SV and an invaluable tool for defining therapeutic targets for DHMN1.

neuroscience↗

bioRxiv2021

Single-cell transcriptome profiling reveals multicellular ecosystem of nucleus pulposus during degeneration progression

Degeneration of the nucleus pulposus (NP) is a major contributor to intervertebral disc degeneration (IVDD) and low back pain. However, the underlying molecular complexity and cellular heterogeneity remain poorly understood. Here, we first reported a comprehensive single-cell resolution transcriptional landscape of human NP. Six novel human nucleus pulposus cell (NPCs) populations were identified by distinct molecular signatures. The potential functional differences among NPC subpopulations were analyzed at the single-cell level. Predictive genes, transcriptional factors, and signal pathways with respect to degeneration grades were analyzed. We reported that fibroNPCs, one of our identified subpopulations, might be a population for NP regeneration. CD90+NPCs were observed to be progenitor cells in degenerative NP tissues. NP-infiltrating immune cells comprise a previously unrecognized diversity of cell types, including granulocytic myeloid-derived suppressor cells (G-MDSCs). We uncovered CD11b, OLR1, and CD24 as surface markers of NP-derived G-MDSCs. The G-MDSCs were also found to be enriched in mildly degenerated (grade I and II) NP tissues compared to severely degenerated (grade III and IV) NP tissues. Their immunosuppressive function and protective effects for NPCs were revealed. Collectively, this study revealed the NPC type complexity and phenotypic characteristics in NP, providing new insights and clues for IVDD treatment.

cell biology↗

bioRxiv2021

Modulation of SARS-CoV-2 Spike-induced Unfolded Protein Response (UPR) in HEK293T cells by selected small chemical molecules

Coronaviruses (CoV) exploits the endoplasmic reticulum (ER) of the host cells for replication and in doing so, increases ER stress. evokes Unfolded Protein Response (UPR) and possibly autophagy, which could all attribute to the pathophysiology of the viral infections. To date, little is known about the roles of ER stress, UPR, and autophagy in SARS-CoV-2 infection. Here we over-expressed the viral Spike (S) protein in cultured HEK293T cells, as it has been shown that such protein is largely responsible for UPR activation in other CoV-infected cells. We noticed, in the transfected cells, heightened ER stress, activation of the PERK-eIF2 arm of the UPR, induction of autophagy and cell death. When we treated the transfected cells with Tauroursodeoxycholic acid (TUDCA), 4-phenyl butyric acid (PBA), Salubrinal, Trazadone hydrochloride, and Dibenzoylmethane (DBM), we saw reduced the BiP/GRP78 levels, but only PBA and TUDCA could significantly diminish the levels of peIF2 and autophagy expression.

biochemistry↗

bioRxiv2020

Resistance to platinum chemotherapy in lung adenocarcinoma is driven by a non-genetic, cell-cycle dependent mechanism

We previously used a pulse-based in vitro assay to unveil targetable signalling pathways associated with innate cisplatin resistance in lung adenocarcinoma (Hastings et al., 2020). Here we advanced this model system and identified a non- genetic mechanism of resistance that drives recovery and regrowth in a subset of cells. Using RNAseq and a suite of biosensors to track single cell fates both in vitro and in vivo, we identified that early S phase cells have a greater ability to maintain proliferative capacity, which correlated with reduced DNA damage over multiple generations. In contrast, cells in G1, late S or those treated with PARP/RAD51 inhibitors, maintained higher levels of DNA damage and underwent prolonged S/G2 phase arrest and senescence. Combined with our previous work, these data indicate that there is a non-genetic mechanism of resistance in lung adenocarcinoma that is dependent on the cell cycle stage at the time of cisplatin exposure.

cell biology↗

bioRxiv2020

Organoid Polymer Functionality and Mode of Klebsiella Pneumoniae Membrane Antigen Presentation Regulates Ex Vivo Germinal Center Epigenetics in Young and Aged B Cells

Antibiotic-resistant bacteria are a major global health threat that continues to rise due to a lack of effective vaccines. Of concern are Klebsiella pneumoniae that fail to induce in vivo germinal center B cell responses, which facilitate antibody production to fight infection. Immunotherapies using antibodies targeting antibiotic-resistant bacteria are emerging as promising alternatives, however, cannot be efficiently derived ex vivo, necessitating the need for immune technologies to develop therapeutics. Here, four-arm PEG-organoids were developed to elucidate the effects of polymer end-point chemistry, integrin ligands, and mode of K. pneumoniae antigen presentation on germinal center-like B cell epigenetics, to better define the cell-microenvironment factors regulating ex vivo germinal center dynamics. Notably, PEG vinyl sulfone or acrylate failed to sustain primary immune cells, but functionalization with maleimide (PEG-4MAL) led to B cell expansion and germinal center-like induction. RNA sequencing analysis of lymph node stromal and germinal center B cells showed niche associated heterogeneity of integrin-related genes. Incorporation of niche-mimicking bioadhesive peptides revealed that collagen 1 mimicking peptides promoted germinal center-like dynamics and epigenetics. PEG-4MAL organoids elucidated the impact of K. pneumoniae membrane embedded protein antigen versus soluble antigen presentation on germinal center-like activation and preserved the response across young and aged mice.

immunology↗

bioRxiv2018

Estimation of Pharmacokinetic Parameters of Continuous Intravenous Flucloxacillin infusion in the Outpatient Settings (PKFLUCLOX)

Flucloxacillin, a beta-lactam antibiotic of the penicillin class, is considered first line therapy for methicillin sensitive Staphylococcus aureus (MSSA) in Australia. (1). At our tertiary referral hospital in the home (HITH) program, it has been prescribed in a standard dosage of 8 grams per day by continuous infusion for more than 20 years. The aim of this observational study was to characterize the pharmacokinetic profile of flucloxacillin in patients who receive continuous infusion in the HITH setting, and to undertake population pharmacokinetic analysis performed with NONMEM software by comparing various structural models. This study utilised flucloxacillin concentrations from 44 separate specimens obtained from 23 patients. Twenty-five of these were collected immediately after elastomeric device removal, representing steady-state concentrations, and the remaining 19 were each collected at least 45 minutes after device removal to determine clearance of the drug. Plasma concentrations ranged from 13 to 194 mg/L with median steady-state concentration of 51.5mg/L and inter-quartile range of 24.6 mg/L. The time-course of flucloxacillin was best described by a 1-compartment model. The best three covariates, CrCL ({Delta}OFV= -11.7), eGFR ({Delta}OFV= -5.9) and serum albumin ({Delta}OFV= -5.8) were found to be equivalent in terms of decreasing the OFV. CrCL was superior in explaining inter individual variability. The best model for flucloxacillin clearance was a one compartment model with CrCL as the sole covariate. The estimated population parameters were 9.5 L for volume of distribution and 8.1 L/h for flucloxacillin clearance.

pharmacology and toxicology↗