Displaying publications 41 - 55 of 55 in total

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  1. Fulltext Derivation of an endogenous small RNA from double-stranded Sox4 sense and natural antisense transcripts in the mouse brain
    Ling KH, Brautigan PJ, Moore S, Fraser R, Cheah PS, Raison JM, et al.
    Genomics, 2016 Mar;107(2-3):88-99.
    PMID: 26802803 DOI: 10.1016/j.ygeno.2016.01.006
    Natural antisense transcripts (NATs) are involved in cellular development and regulatory processes. Multiple NATs at the Sox4 gene locus are spatiotemporally regulated throughout murine cerebral corticogenesis. In the study, we evaluated the potential functional role of Sox4 NATs at Sox4 gene locus. We demonstrated Sox4 sense and NATs formed dsRNA aggregates in the cytoplasm of brain cells. Over expression of Sox4 NATs in NIH/3T3 cells generally did not alter the level of Sox4 mRNA expression or protein translation. Upregulation of a Sox4 NAT known as Sox4ot1 led to the production of a novel small RNA, Sox4_sir3. Its biogenesis is Dicer1-dependent and has characteristics resemble piRNA. Expression of Sox4_sir3 was observed in the marginal and germinative zones of the developing and postnatal brains suggesting a potential role in regulating neurogenesis. We proposed that Sox4 sense-NATs serve as Dicer1-dependent templates to produce a novel endo-siRNA- or piRNA-like Sox4_sir3.
  2. Fulltext DRD and GRIN2B polymorphisms and their association with the development of impulse control behaviour among Malaysian Parkinson's disease patients
    Zainal Abidin S, Tan EL, Chan SC, Jaafar A, Lee AX, Abd Hamid MH, et al.
    BMC Neurol, 2015;15:59.
    PMID: 25896831 DOI: 10.1186/s12883-015-0316-2
    Impulse control disorder (ICD) and behaviours (ICB) represent a group of behavioural disorders that have become increasingly recognised in Parkinson's disease (PD) patients who previously used dopaminergic medications, particularly dopamine agonists and levodopa. It has been suggested that these medications can lead to the development of ICB through the abnormal modulation of dopaminergic transmission and signalling in the mesocorticolimbic dopaminergic system. Several studies have reported an association between polymorphisms in the dopamine receptor (DRD) and N-methyl-D-aspartate 2B (GRIN2B) genes with the development of ICB in PD (PD-ICB) patients. Thus, this study aimed to investigate the association of selected polymorphisms within the DRD and GRIN2B genes with the development of ICB among PD patients using high resolution melt (HRM) analysis.
  3. Fulltext Glioblastoma-Associated Microglia Reprogramming Is Mediated by Functional Transfer of Extracellular miR-21
    Abels ER, Maas SLN, Nieland L, Wei Z, Cheah PS, Tai E, et al.
    Cell Rep, 2019 09 17;28(12):3105-3119.e7.
    PMID: 31533034 DOI: 10.1016/j.celrep.2019.08.036
    Gliomas are primary, diffusely infiltrating brain tumors. Microglia are innate immune cells in the CNS and make up a substantial portion of the tumor mass. Glioma cells shape their microenvironment, communicating with and reprogramming surrounding cells, resulting in enhanced angiogenesis, immune suppression, and remodeling of the extracellular matrix. Glioma cells communicate with microglia, in part by releasing extracellular vesicles (EVs). Mouse glioma cells stably expressing a palmitoylated GFP to label EVs were implanted intracranially into syngeneic miR-21-null mice. Here, we demonstrate functional delivery of miR-21, regulating specific downstream mRNA targets in microglia after uptake of tumor-derived EVs. These findings attest to EV-dependent microRNA delivery as studied in an in vivo-based model and provide insight into the reprograming of microglial cells by tumor cells to create a favorable microenvironment for cancer progression.
  4. Fulltext Screening of brain-derived neurotrophic factor (BDNF) single nucleotide polymorphisms and plasma BDNF levels among Malaysian major depressive disorder patients
    Aldoghachi AF, Tor YS, Redzun SZ, Lokman KAB, Razaq NAA, Shahbudin AF, et al.
    PLoS One, 2019;14(1):e0211241.
    PMID: 30677092 DOI: 10.1371/journal.pone.0211241
    BACKGROUND: Brain-derived neurotrophic factor (BDNF) is a neurotrophin found in abundance in brain regions such as the hippocampus, cortex, cerebellum and basal forebrain. It has been associated with the risk of susceptibility to major depressive disorder (MDD). This study aimed to determine the association of three BDNF variants (rs6265, rs1048218 and rs1048220) with Malaysian MDD patients.

    METHODS: The correlation of these variants to the plasma BDNF level among Malaysian MDD patients was assessed. A total of 300 cases and 300 matched controls recruited from four public hospitals within the Klang Valley of Selangor State, Malaysia and matched for age, sex and ethnicity were screened for BDNF rs6265, rs1048218 and rs1048220 using high resolution melting (HRM).

    FINDINGS: BDNF rs1048218 and BDNF rs1048220 were monomorphic and were excluded from further analysis. The distribution of the alleles and genotypes for BDNF rs6265 was in Hardy-Weinberg equilibrium for the controls (p = 0.13) but was in Hardy Weinberg disequilibrium for the cases (p = 0.011). Findings from this study indicated that having BDNF rs6265 in the Malaysian population increase the odds of developing MDD by 2.05 folds (95% CI = 1.48-3.65). Plasma from 206 cases and 206 controls were randomly selected to measure the BDNF level using enzyme-linked immunosorbent assay (ELISA). A significant decrease in the plasma BDNF level of the cases as compared to controls (p<0.0001) was observed. However, there was no evidence of the effect of the rs6265 genotypes on the BDNF level indicating a possible role of other factors in modulating the BDNF level that warrants further investigation.

    CONCLUSION: The study indicated that having the BDNF rs6265 allele (A) increase the risk of developing MDD in the Malaysian population suggesting a possible role of BDNF in the etiology of the disorder.

  5. Fulltext Stearoyl CoA Desaturase Is Essential for Regulation of Endoplasmic Reticulum Homeostasis and Tumor Growth in Glioblastoma Cancer Stem Cells
    Pinkham K, Park DJ, Hashemiaghdam A, Kirov AB, Adam I, Rosiak K, et al.
    Stem Cell Reports, 2019 04 09;12(4):712-727.
    PMID: 30930246 DOI: 10.1016/j.stemcr.2019.02.012
    Inherent plasticity and various survival cues allow glioblastoma stem-like cells (GSCs) to survive and proliferate under intrinsic and extrinsic stress conditions. Here, we report that GSCs depend on the adaptive activation of ER stress and subsequent activation of lipogenesis and particularly stearoyl CoA desaturase (SCD1), which promotes ER homeostasis, cytoprotection, and tumor initiation. Pharmacological targeting of SCD1 is particularly toxic due to the accumulation of saturated fatty acids, which exacerbates ER stress, triggers apoptosis, impairs RAD51-mediated DNA repair, and achieves a remarkable therapeutic outcome with 25%-100% cure rate in xenograft mouse models. Mechanistically, divergent cell fates under varying levels of ER stress are primarily controlled by the ER sensor IRE1, which either promotes SCD1 transcriptional activation or converts to apoptotic signaling when SCD1 activity is impaired. Taken together, the dependence of GSCs on fatty acid desaturation presents an exploitable vulnerability to target glioblastoma.
  6. Fulltext Virus vector-mediated genetic modification of brain tumor stromal cells after intravenous delivery
    Volak A, LeRoy SG, Natasan JS, Park DJ, Cheah PS, Maus A, et al.
    J Neurooncol, 2018 Sep;139(2):293-305.
    PMID: 29767307 DOI: 10.1007/s11060-018-2889-2
    The malignant primary brain tumor, glioblastoma (GBM) is generally incurable. New approaches are desperately needed. Adeno-associated virus (AAV) vector-mediated delivery of anti-tumor transgenes is a promising strategy, however direct injection leads to focal transgene spread in tumor and rapid tumor division dilutes out the extra-chromosomal AAV genome, limiting duration of transgene expression. Intravenous (IV) injection gives widespread distribution of AAV in normal brain, however poor transgene expression in tumor, and high expression in non-target cells which may lead to ineffective therapy and high toxicity, respectively. Delivery of transgenes encoding secreted, anti-tumor proteins to tumor stromal cells may provide a more stable and localized reservoir of therapy as they are more differentiated than fast-dividing tumor cells. Reactive astrocytes and tumor-associated macrophage/microglia (TAMs) are stromal cells that comprise a large portion of the tumor mass and are associated with tumorigenesis. In mouse models of GBM, we used IV delivery of exosome-associated AAV vectors driving green fluorescent protein expression by specific promoters (NF-κB-responsive promoter and a truncated glial fibrillary acidic protein promoter), to obtain targeted transduction of TAMs and reactive astrocytes, respectively, while avoiding transgene expression in the periphery. We used our approach to express the potent, yet toxic anti-tumor cytokine, interferon beta, in tumor stroma of a mouse model of GBM, and achieved a modest, yet significant enhancement in survival compared to controls. Noninvasive genetic modification of tumor microenvironment represents a promising approach for therapy against cancers. Additionally, the vectors described here may facilitate basic research in the study of tumor stromal cells in situ.
  7. Fulltext Transient prenatal ruxolitinib treatment suppresses astrogenesis during development and improves learning and memory in adult mice
    Lee HC, Hamzah H, Leong MP, Md Yusof H, Habib O, Zainal Abidin S, et al.
    Sci Rep, 2021 Feb 15;11(1):3847.
    PMID: 33589712 DOI: 10.1038/s41598-021-83222-z
    Ruxolitinib is the first janus kinase 1 (JAK1) and JAK2 inhibitor that was approved by the United States Food and Drug Administration (FDA) agency for the treatment of myeloproliferative neoplasms. The drug targets the JAK/STAT signalling pathway, which is critical in regulating the gliogenesis process during nervous system development. In the study, we assessed the effect of non-maternal toxic dosages of ruxolitinib (0-30 mg/kg/day between E7.5-E20.5) on the brain of the developing mouse embryos. While the pregnant mice did not show any apparent adverse effects, the Gfap protein marker for glial cells and S100β mRNA marker for astrocytes were reduced in the postnatal day (P) 1.5 pups' brains. Gfap expression and Gfap+ cells were also suppressed in the differentiating neurospheres culture treated with ruxolitinib. Compared to the control group, adult mice treated with ruxolitinib prenatally showed no changes in motor coordination, locomotor function, and recognition memory. However, increased explorative behaviour within an open field and improved spatial learning and long-term memory retention were observed in the treated group. We demonstrated transplacental effects of ruxolitinib on astrogenesis, suggesting the potential use of ruxolitinib to revert pathological conditions caused by gliogenic-shift in early brain development such as Down and Noonan syndromes.
  8. Fulltext Methods for Systematic Identification of Membrane Proteins for Specific Capture of Cancer-Derived Extracellular Vesicles
    Zaborowski MP, Lee K, Na YJ, Sammarco A, Zhang X, Iwanicki M, et al.
    Cell Rep, 2019 Apr 02;27(1):255-268.e6.
    PMID: 30943406 DOI: 10.1016/j.celrep.2019.03.003
    Analysis of cancer-derived extracellular vesicles (EVs) in biofluids potentially provides a source of disease biomarkers. At present there is no procedure to systematically identify which antigens should be targeted to differentiate cancer-derived from normal host cell-derived EVs. Here, we propose a computational framework that integrates information about membrane proteins in tumors and normal tissues from databases: UniProt, The Cancer Genome Atlas, the Genotype-Tissue Expression Project, and the Human Protein Atlas. We developed two methods to assess capture of EVs from specific cell types. (1) We used palmitoylated fluorescent protein (palmtdTomato) to label tumor-derived EVs. Beads displaying antibodies of interest were incubated with conditioned medium from palmtdTomato-expressing cells. Bound EVs were quantified using flow cytometry. (2) We also showed that membrane-bound Gaussia luciferase allows the detection of cancer-derived EVs in blood of tumor-bearing animals. Our analytical and validation platform should be applicable to identify antigens on EVs from any tumor type.
  9. Fulltext Gene replacement therapy in a schwannoma mouse model of neurofibromatosis type 2
    Prabhakar S, Beauchamp RL, Cheah PS, Yoshinaga A, Haidar EA, Lule S, et al.
    Mol Ther Methods Clin Dev, 2022 Sep 08;26:169-180.
    PMID: 35846573 DOI: 10.1016/j.omtm.2022.06.012
    Loss of function of the neurofibromatosis type 2 (NF2) tumor suppressor gene leads to the formation of schwannomas, meningiomas, and ependymomas, comprising ∼50% of all sporadic cases of primary nervous system tumors. NF2 syndrome is an autosomal dominant condition, with bi-allelic inactivation of germline and somatic alleles resulting in loss of function of the encoded protein merlin and activation of mammalian target of rapamycin (mTOR) pathway signaling in NF2-deficient cells. Here we describe a gene replacement approach through direct intratumoral injection of an adeno-associated virus vector expressing merlin in a novel human schwannoma model in nude mice. In culture, the introduction of an AAV1 vector encoding merlin into CRISPR-modified human NF2-null arachnoidal cells (ACs) or Schwann cells (SCs) was associated with decreased size and mTORC1 pathway activation consistent with restored merlin activity. In vivo, a single injection of AAV1-merlin directly into human NF2-null SC-derived tumors growing in the sciatic nerve of nude mice led to regression of tumors over a 10-week period, associated with a decrease in dividing cells and an increase in apoptosis, in comparison with vehicle. These studies establish that merlin re-expression via gene replacement in NF2-null schwannomas is sufficient to cause tumor regression, thereby potentially providing an effective treatment for NF2.
  10. Fulltext Mutant Allele-Specific CRISPR Disruption in DYT1 Dystonia Fibroblasts Restores Cell Function
    Cruz L, György B, Cheah PS, Kleinstiver BP, Eimer WA, Garcia SP, et al.
    Mol Ther Nucleic Acids, 2020 Sep 04;21:1-12.
    PMID: 32502938 DOI: 10.1016/j.omtn.2020.05.009
    Most individuals affected with DYT1 dystonia have a heterozygous 3-bp deletion in the TOR1A gene (c.907_909delGAG). The mutation appears to act through a dominant-negative mechanism compromising normal torsinA function, and it is proposed that reducing mutant torsinA may normalize torsinA activity. In this study, we used an engineered Cas9 variant from Streptococcus pyogenes (SpCas9-VRQR) to target the mutation in the TOR1A gene in order to disrupt mutant torsinA in DYT1 patient fibroblasts. Selective targeting of the DYT1 allele was highly efficient with most common non-homologous end joining (NHEJ) edits, leading to a predicted premature stop codon with loss of the torsinA C terminus (delta 302-332 aa). Structural analysis predicted a functionally inactive status of this truncated torsinA due to the loss of residues associated with ATPase activity and binding to LULL1. Immunoblotting showed a reduction of the torsinA protein level in Cas9-edited DYT1 fibroblasts, and a functional assay using HSV infection indicated a phenotypic recovery toward that observed in control fibroblasts. These findings suggest that the selective disruption of the mutant TOR1A allele using CRISPR-Cas9 inactivates mutant torsinA, allowing the remaining wild-type torsinA to exert normal function.
  11. Fulltext Membrane-bound Gaussia luciferase as a tool to track shedding of membrane proteins from the surface of extracellular vesicles
    Zaborowski MP, Cheah PS, Zhang X, Bushko I, Lee K, Sammarco A, et al.
    Sci Rep, 2019 Nov 22;9(1):17387.
    PMID: 31758005 DOI: 10.1038/s41598-019-53554-y
    Extracellular vesicles (EVs) released by cells play a role in intercellular communication. Reporter and targeting proteins can be modified and exposed on the surface of EVs to investigate their half-life and biodistribution. A characterization of membrane-bound Gaussia luciferase (mbGluc) revealed that its signal was detected also in a form smaller than common EVs (<70 nm). We demonstrated that mbGluc initially exposed on the surface of EVs, likely undergoes proteolytic cleavage and processed fragments of the protein are released into the extracellular space in active form. Based on this observation, we developed a new assay to quantitatively track shedding of membrane proteins from the surface of EVs. We used this assay to show that ectodomain shedding in EVs is continuous and is mediated by specific proteases, e.g. metalloproteinases. Here, we present a novel tool to study membrane protein cleavage and release using both in vitro and in vivo models.
  12. Fulltext Gene therapy for tuberous sclerosis complex type 2 in a mouse model by delivery of AAV9 encoding a condensed form of tuberin
    Cheah PS, Prabhakar S, Yellen D, Beauchamp RL, Zhang X, Kasamatsu S, et al.
    Sci Adv, 2021 Jan;7(2).
    PMID: 33523984 DOI: 10.1126/sciadv.abb1703
    Tuberous sclerosis complex (TSC) results from loss of a tumor suppressor gene - TSC1 or TSC2, encoding hamartin and tuberin, respectively. These proteins formed a complex to inhibit mTORC1-mediated cell growth and proliferation. Loss of either protein leads to overgrowth lesions in many vital organs. Gene therapy was evaluated in a mouse model of TSC2 using an adeno-associated virus (AAV) vector carrying the complementary for a "condensed" form of human tuberin (cTuberin). Functionality of cTuberin was verified in culture. A mouse model of TSC2 was generated by AAV-Cre recombinase disruption of Tsc2-floxed alleles at birth, leading to a shortened lifespan (mean 58 days) and brain pathology consistent with TSC. When these mice were injected intravenously on day 21 with AAV9-cTuberin, the mean survival was extended to 462 days with reduction in brain pathology. This demonstrates the potential of treating life-threatening TSC2 lesions with a single intravenous injection of AAV9-cTuberin.
  13. Fulltext Small RNA Sequencing across Diverse Biofluids Identifies Optimal Methods for exRNA Isolation
    Srinivasan S, Yeri A, Cheah PS, Chung A, Danielson K, De Hoff P, et al.
    Cell, 2019 04 04;177(2):446-462.e16.
    PMID: 30951671 DOI: 10.1016/j.cell.2019.03.024
    Poor reproducibility within and across studies arising from lack of knowledge regarding the performance of extracellular RNA (exRNA) isolation methods has hindered progress in the exRNA field. A systematic comparison of 10 exRNA isolation methods across 5 biofluids revealed marked differences in the complexity and reproducibility of the resulting small RNA-seq profiles. The relative efficiency with which each method accessed different exRNA carrier subclasses was determined by estimating the proportions of extracellular vesicle (EV)-, ribonucleoprotein (RNP)-, and high-density lipoprotein (HDL)-specific miRNA signatures in each profile. An interactive web-based application (miRDaR) was developed to help investigators select the optimal exRNA isolation method for their studies. miRDar provides comparative statistics for all expressed miRNAs or a selected subset of miRNAs in the desired biofluid for each exRNA isolation method and returns a ranked list of exRNA isolation methods prioritized by complexity, expression level, and reproducibility. These results will improve reproducibility and stimulate further progress in exRNA biomarker development.
  14. Fulltext TAF1 Transcripts and Neurofilament Light Chain as Biomarkers for X-linked Dystonia-Parkinsonism
    Al Ali J, Vaine CA, Shah S, Campion L, Hakoum A, Supnet ML, et al.
    Mov Disord, 2021 01;36(1):206-215.
    PMID: 32975318 DOI: 10.1002/mds.28305
    BACKGROUND: X-linked dystonia-parkinsonism is a rare neurological disease endemic to the Philippines. Dystonic symptoms appear in males at the mean age of 40 years and progress to parkinsonism with degenerative pathology in the striatum. A retrotransposon inserted in intron 32 of the TAF1 gene leads to alternative splicing in the region and a reduction of the full-length mRNA transcript.

    OBJECTIVES: The objective of this study was to discover cell-based and biofluid-based biomarkers for X-linked dystonia-parkinsonism.

    METHODS: RNA from patient-derived neural progenitor cells and their secreted extracellular vesicles were used to screen for dysregulation of TAF1 expression. Droplet-digital polymerase chain reaction was used to quantify the expression of TAF1 mRNA fragments 5' and 3' to the retrotransposon insertion and the disease-specific splice variant TAF1-32i in whole-blood RNA. Plasma levels of neurofilament light chain were measured using single-molecule array.

    RESULTS: In neural progenitor cells and their extracellular vesicles, we confirmed that the TAF1-3'/5' ratio was lower in patient samples, whereas TAF1-32i expression is higher relative to controls. In whole-blood RNA, both TAF1-3'/5' ratio and TAF1-32i expression can differentiate patient (n = 44) from control samples (n = 18) with high accuracy. Neurofilament light chain plasma levels were significantly elevated in patients (n = 43) compared with both carriers (n = 16) and controls (n = 21), with area under the curve of 0.79.

    CONCLUSIONS: TAF1 dysregulation in blood serves as a disease-specific biomarker that could be used as a readout for monitoring therapies targeting TAF1 splicing. Neurofilament light chain could be used in monitoring neurodegeneration and disease progression in patients. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

  15. Fulltext Discovery and Verification of Extracellular miRNA Biomarkers for Non-invasive Prediction of Pre-eclampsia in Asymptomatic Women
    Srinivasan S, Treacy R, Herrero T, Olsen R, Leonardo TR, Zhang X, et al.
    Cell Rep Med, 2020 05 19;1(2).
    PMID: 32864636 DOI: 10.1016/j.xcrm.2020.100013
    Development of effective prevention and treatment strategies for pre-eclampsia is limited by the lack of accurate methods for identification of at-risk pregnancies. We performed small RNA sequencing (RNA-seq) of maternal serum extracellular RNAs (exRNAs) to discover and verify microRNAs (miRNAs) differentially expressed in patients who later developed pre-eclampsia. Sera collected from 73 pre-eclampsia cases and 139 controls between 17 and 28 weeks gestational age (GA), divided into separate discovery and verification cohorts, are analyzed by small RNA-seq. Discovery and verification of univariate and bivariate miRNA biomarkers reveal that bivariate biomarkers verify at a markedly higher rate than univariate biomarkers. The majority of verified biomarkers contain miR-155-5p, which has been reported to mediate the pre-eclampsia-associated repression of endothelial nitric oxide synthase (eNOS) by tumor necrosis factor alpha (TNF-α). Deconvolution analysis reveals that several verified miRNA biomarkers come from the placenta and are likely carried by placenta-specific extracellular vesicles.
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