Dysregulated Cholinergic Signaling Inhibits Oligodendrocyte Maturation Following Demyelination.

Dysregulation of oligodendrocyte progenitor cell (OPC) recruitment and oligodendrocyte differentiation contribute to failure of remyelination in human demyelinating diseases such as multiple sclerosis (MS). Deletion of muscarinic receptor enhances OPC differentiation and remyelination. However, the role of ligand-dependent signaling versus constitutive receptor activation is unknown. We hypothesized that dysregulated acetylcholine (ACh) release upon demyelination contributes to ligand-mediated activation hindering myelin repair. Following chronic cuprizone (CPZ)-induced demyelination (male and female mice), we observed a 2.5-fold increase in ACh concentration. This increase in ACh concentration could be attributed to increased ACh synthesis or decreased acetylcholinesterase-/butyrylcholinesterase (BChE)-mediated degradation. Using choline acetyltransferase (ChAT) reporter mice, we identified increased ChAT-GFP expression following both lysolecithin and CPZ demyelination. ChAT-GFP expression was upregulated in a subset of injured and uninjured axons following intraspinal lysolecithin-induced demyelination. In CPZ-demyelinated corpus callosum, ChAT-GFP was observed in Gfap+ astrocytes and axons indicating the potential for neuronal and astrocytic ACh release. BChE expression was significantly decreased in the corpus callosum following CPZ demyelination. This decrease was due to the loss of myelinating oligodendrocytes which were the primary source of BChE. To determine the role of ligand-mediated muscarinic signaling following lysolecithin injection, we administered neostigmine, a cholinesterase inhibitor, to artificially raise ACh. We identified a dose-dependent decrease in mature oligodendrocyte density with no effect on OPC recruitment. Together, these results support a functional role of ligand-mediated activation of muscarinic receptors following demyelination and suggest that dysregulation of ACh homeostasis directly contributes to failure of remyelination in MS.

Pd-Catalyzed Picolinamide-Directed C(sp2)-H Sulfonylation of Amino Acids/Peptides with Sodium Sulfinates.

This report describes a Pd-catalyzed picolinamide-directed site-selective C(sp2)-H sulfonylation of amino acids and peptides with sodium sulfinates in moderate to good yields. Sulfonylation of levodopa and dopamine drug molecules and late-stage directed peptide sulfonylation are studied for the first time. Broad substrate scope having various functionalities, late-stage drug modifications, and various post synthetic utilities such as chalcogenation, bromination, olefination, and arylation are potential advantages.

Ru(II)-Catalyzed C(sp2)-H Activation Annulation: Synthesis of Fluorescent Benzoisoquinolonyl Acetate/Peptides from N-Arylamides and Ethyne at Room Temperature.

Benzoisoquinolones are aryl ring extended isoquinolinone derivatives, which are constituents of alkaloid natural products. This report describes the synthesis of novel benzoisoquinolone amino acid/peptide derivatives from the respective N-aryl amino esters/peptides through Ru-catalyzed C(sp2)-H annulation at room temperature. The N-terminal amide acts as an intrinsic directing group and coordinates with the active Ru(II) catalyst for the C-H bond activation and annulation of the aryl ring to produce benzoisoqunolone derivatives. Importantly, these benzoisoquinolinones exhibit fluorescence (QY ∼35%) in protic polar solvents, possibly due to charge transfer, and exhibit cell internalization to the cell nucleus without any significant cytotoxicity to human cell lines (HEK293T). Hence, our results are exceptional to transform standard amino acids/peptides into fluorescent peptides at room temperature in the late stage, which could be applicable for tracking specific target peptides by fluorescence microscopy.

Tropolone-Conjugated DNA: A Fluorescent Thymidine Analogue Exhibits Solvatochromism, Enzymatic Incorporation into DNA and HeLa Cell Internalization.

Tropolone is a non-benzenoid aromatic scaffold with unique photophysical and metal-chelating properties. Recently, it has been conjugated with DNA, and the photophysical properties of this conjugate have been explored. Tropolonyl-deoxyuridine (tr-dU) is a synthetic fluorescent DNA nucleoside analogue that exhibits pH-dependent emissions. However, its solvent-dependent fluorescence properties are unexplored owing to its poor solubility in most organic solvents. It would be interesting to incorporate it into DNA primer enzymatically. This report describes the solvent-dependent fluorescence properties of the silyl-derivative, and enzymatic incorporation of its triphosphate analogue. For practical use, its cell-internalization and cytotoxicity are also explored. tr-dU nucleoside was found to be a potential analogue to design DNA probes and can be explored for various therapeutic applications in the future.

Pd-Catalyzed Picolinamide-Directed Late-Stage Chalcogenation of Tryptophan-Containing Peptides.

This report describes the Pd-catalyzed late-stage chalcogenation of tryptophan-containing peptides with disulfides/diselenides in moderate to good yields. It comprises broad substrate scope, functional group diversity, late-stage modification of drug molecules, and various valuable synthetic transformations, including room temperature easy removal of the picolinamide auxiliary, which could be applicable to tune the structure and function of peptides.

A new transient directing group diethoxyethyl-L-proline facilitates ortho-arylation of aryl-amines/-amino acids via Pd-catalyzed C(sp2)-H activation.

Mono-ortho-arylated arylamines are constituents of various natural products but their syntheses are challenging. This report describes a new synthetic methodology for the ortho-arylation of arylamines and α-aromatic amino acids (phenylglycine and phenylalanine) through a Pd-catalyzed C(sp2)-H activation using the synthetic transient directing group diethoxyethyl-L-proline (DEP). A catalytic amount of diethoxyethyl-L-proline is sufficient to form mono-arylated arylamines as the major products using aryliodides. This method could be useful for the synthesis of various biphenyl amines and novel peptidomimetics.

Synthesis of N-isoindolinonyl peptides via Pd-catalyzed C(sp2)-H olefination-activation and their conformational studies.

Isoindolinone is a constituent of several natural products that show a wide range of bioactivity, such as anticancer, antimicrobial, antiviral and anti-inflammatory properties. It would be interesting to explore the carbonyl group (H-bond acceptor) of isoindolinone and its structural and conformational changes. However, the synthesis of isoindolinone-comprising peptides in short steps is challenging. Herein, we have developed a synthetic methodology for introducing the isoindolinone residue to peptides via Pd-catalyzed C(sp2)-H activation/olefination, and demonstrated the conformational changes owing to the isoindolinone scaffold. Hence, isoindolinonyl peptides provide an avenue for the synthesis of novel foldamers and therapeutic agents.

A new amino acid, hybrid peptides and BODIPY analogs: synthesis and evaluation of 2-aminotroponyl-L-alanine (ATA) derivatives.

Natural aromatic α-amino acid residues play critical roles in the structural and functional organization of proteins owing to π-interactions. Their aromatic residues are derived from benzenoid scaffolds. Non-benzenoid aromatic scaffolds such as tropone and tropolone are also constituents of troponoid natural products. Tropolone has also the ability to exhibit π-interactions along with additional hydrogen bonding. Thus, amino acids comprising troponyl could be potential building blocks of novel peptidomimetics. This report describes the synthesis of the L-aminotroponylalanine amino acid (ATA) and its unusual activity with the peptide coupling agent EDC. Importantly, its di-peptides form ß-sheet/-turn type secondary structures in organic solvents owing to the troponyl residue. This amino acid is an excellent scaffold for the synthesis of fluorescent amino acids such as BODIPY amino acid analogs. Nevertheless, this amino acid and its BODIPY derivatives can enter HeLa cells without exhibiting significant cytotoxicity at low concentrations (∼50 µM). Hence, ATA and its BODIPY derivatives are promising aromatic amino acids for the construction of potential peptidomimetics and fluorescent labelling of target peptides.

Structural and functional analysis of CCT family genes in pigeonpea.

BACKGROUND: Pigeonpea (Cajanus cajan L.) is a photoperiod-sensitive short-day plant. Understanding the flowering-related genes is critical to developing photoperiod insensitive cultivars. METHODS: The CCT family genes were identified using 'CCT DOMAIN PROTEIN' as a keyword and localized on the chromosomes using the BLAST search option available at the LIS database. The centromeric positions were identified through BLAST search using the centromeric repeat sequence of C. cajan as a query against the chromosome-wise FASTA files downloaded from the NCBI database. The CCT family genes were classified based on additional domains and/or CCT domains. The orthologous and phylogenetic relationships were inferred using the OrthoFinder and MEGA 10.1 software, respectively. The CCT family genes' expression level in photoperiod-sensitive and insensitive genotypes was compared using RNA-seq data and qRT-PCR analysis. RESULTS: We identified 33 CCT family genes in C. cajan distributed on ten chromosomes and nine genomic scaffolds. They were classified into CMF-type, COL-type, PRR-type, and GTCC- type. The CCT family genes of legumes exhibited an extensive orthologous relationship. Glycine max showed the maximum similarity of CCT family genes with C. cajan. The expression analysis of CCT family genes using photoperiod insensitive (ICP20338) and photoperiod sensitive (MAL3) genotypes of C. cajan demonstrated that CcCCT4 and CcCCT23 are the active CONSTANS in ICP20338. In contrast, only CcCCT23 is active in MAL3. CONCLUSION: The CCT family genes in C. cajan vary considerably in structure and domain types. They are maximally similar to soybean's CCT family genes. The differential photoperiod response of pigeonpea genotypes, ICP20338 and MAL3, is possibly due to the difference in the number and types of active CONSTANS in them.

CRISPR-Cas9 directed genome engineering for enhancing salt stress tolerance in rice.

Crop productivity in rice is harshly limited due to high concentration of salt in the soil. To understand the intricacies of the mechanism it is important to unravel the key pathways operating inside the plant cell. Emerging state-of-the art technologies have provided the tools to discover the key components inside the plant cell for salt tolerance. Among the molecular entities, transcription factors and/or other important components of sensing and signaling cascades have been the attractive targets and the role of NHX and SOS1 transporters amply described. Not only marker assisted programs but also transgenic approaches by using reverse genetic strategies (knockout or knockdown) or overexpression have been extensively used to engineer rice crop. CRISPR/Cas is an attractive paradigm and provides the feasibility for manipulating several genes simultaneously. Here, in this review we highlight some of the molecular entities that could be potentially targeted for generating rice amenable to sustain growth under high salinity conditions by employing CRISPR/Cas. We also try to address key questions for rice salt stress tolerance other than what is already known.

Synergistic efficacy of inhibiting MYCN and mTOR signaling against neuroblastoma.

BACKGROUND: Neuroblastoma (NB) patients with MYCN amplification or overexpression respond poorly to current therapies and exhibit extremely poor clinical outcomes. PI3K-mTOR signaling-driven deregulation of protein synthesis is very common in NB and various other cancers that promote MYCN stabilization. In addition, both the MYCN and mTOR signaling axes can directly regulate a common translation pathway that leads to increased protein synthesis and cell proliferation. However, a strategy of concurrently targeting MYCN and mTOR signaling in NB remains unexplored. This study aimed to investigate the therapeutic potential of targeting dysregulated protein synthesis pathways by inhibiting the MYCN and mTOR pathways together in NB. METHODS: Using small molecule/pharmacologic approaches, we evaluated the effects of combined inhibition of MYCN transcription and mTOR signaling on NB cell growth/survival and associated molecular mechanism(s) in NB cell lines. We used two well-established BET (bromodomain extra-terminal) protein inhibitors (JQ1, OTX-015), and a clinically relevant mTOR inhibitor, temsirolimus, to target MYCN transcription and mTOR signaling, respectively. The single agent and combined efficacies of these inhibitors on NB cell growth, apoptosis, cell cycle and neurospheres were assessed using MTT, Annexin-V, propidium-iodide staining and sphere assays, respectively. Effects of inhibitors on global protein synthesis were quantified using a fluorescence-based (FamAzide)-based protein synthesis assay. Further, we investigated the specificities of these inhibitors in targeting the associated pathways/molecules using western blot analyses. RESULTS: Co-treatment of JQ1 or OTX-015 with temsirolimus synergistically suppressed NB cell growth/survival by inducing G1 cell cycle arrest and apoptosis with greatest efficacy in MYCN-amplified NB cells. Mechanistically, the co-treatment of JQ1 or OTX-015 with temsirolimus significantly downregulated the expression levels of phosphorylated 4EBP1/p70-S6K/eIF4E (mTOR components) and BRD4 (BET protein)/MYCN proteins. Further, this combination significantly inhibited global protein synthesis, compared to single agents. Our findings also demonstrated that both JQ1 and temsirolimus chemosensitized NB cells when tested in combination with cisplatin chemotherapy. CONCLUSIONS: Together, our findings demonstrate synergistic efficacy of JQ1 or OTX-015 and temsirolimus against MYCN-driven NB, by dual-inhibition of MYCN (targeting transcription) and mTOR (targeting translation). Additional preclinical evaluation is warranted to determine the clinical utility of targeted therapy for high-risk NB patients.

Unusual Pseudopeptides: Syntheses and Structural Analyses of Ethylenediprolyl Peptides and Their Metal Complexes with Cu(II) Ion.

The synthetic unnatural amino acids and their peptides as peptidomimetics have shown remarkable structural and functional properties. In the repertoire of synthetic peptides, pseudopeptides have emerged as attractive small peptidomimetics that are capable of forming the characteristic secondary structures in the solid/solution phase, as in natural peptides. This report describes the synthesis and structural analyses of novel pseudopeptides as ethylenediprolyl (etpro) tetra/hexapeptides, comprising a chiral diaminedicarboxylate scaffold. Their NMR and CD spectral analyses strongly support the formation of the ß-turn-type structures in organic solvents (ACN/MeOH). Further, the single-crystal X-ray studies of tetrapseudopeptide confirm the formation of a unique self-assembly structure as ß-strand type in the solid state through hydrogen bonding. Importantly, their diamine moiety influences the formation of Cu-complexes with Cu(II) ions. A tetrapseudopeptide monocarboxylate-Cu(II) complex forms the single crystal that is studied by the single-crystal X-ray diffractometer. The crystal structure of the tetrapseudopeptide-Cu(II) complex confirms the formation of the distorted square planar geometry structure, almost like the amyloid ß(Aß)-peptide-Cu(II) complex structural geometry. Hence, these etpro-pseudopeptides are emerging peptidomimatics that form ß-turn types of structures and metal complexes mainly with Cu(II) ions. These molecules could be considered for the development of peptide-based catalysts and peptide-based therapeutic drug candidates.

Pd-Catalyzed C(sp2)-H olefination: synthesis of N-alkylated isoindolinone scaffolds from aryl amides of amino acid esters.

Isoindolinone is a constituent of various natural products and synthetic biologically active compounds. The classical multi-step synthetic methods used to prepare various indolinone derivatives are tedious and challenging. One-pot synthetic methods are attractive and economical. Transition-metal-catalyzed C-H activation is an emerging tool for synthesizing natural products and small organic molecules via reducing the number of synthetic steps necessary. This paper describes the synthesis of N-alkyl-3-methenyl chiral isoindolinone derivatives from aryl amides of L-amino acids and non-activated alkene via Pd-catalyzed C(sp2)-H olefination. Herein, the amino acid residue acts as a directing group for olefination at the aryl ring, and then cyclization occurs at the amide NH. Hence, this methodology could be helpful to transform standard amino acids into respective chiral isoindolinone derivatives.

The 2'-caged-tethered-siRNA shows light-dependent temporal controlled RNAi activity for GFP gene into HEK293T cells.

Small interfering RNA (siRNA) exhibits gene-specific RNAi activity by the formation of RISC complex with mRNA of gene. The structural modification of siRNA at appropriate positions affects the structure of RISC complex and then RNAi activity. The modified siRNA are mostly prepared from the incorporation of sugar ring modified, and nucleobase modified RNA nucleotides. It is learned that the introduction of the sterically hindered nucleoside at the specific position of siRNA, severely affects siRNA-RISC complex formation. This report describes the syntheses of bulkier siRNA from 2'-caged-tethered-siRNAs, containing bulkier photolabile protecting group (o-nitrobenzyl) at 2'-position of ribose nucleoside. Importantly, these 2'-caged-siRNAs exhibit the light-dependent RNA interference (RNAi) activity into HEK293T cells for the GFP gene expression. The 2'-caged-siRNAs are synthesized by caging the sense and antisense strand of siRNA. The biochemical evaluations of these caged-siRNAs show that antisense-strand caged-siRNAs decrease RNAi activity temporarily in dark while enhancing RNAi activity, almost like control, after exposure withUV- light. However, 2'-caged sense strand siRNA increase RNAi activity temporarily while decreasing RNAi activity after exposure with light. These caged-siRNAs are also stable in the serum (fetal bovine serum) as like native siRNA. Hence these results strongly support that 2'-caged-tethered-siRNAs are promising analogues to control RNAi activity by UV-light.

Allele mining for a drought responsive gene DRO1 determining root growth angle in donors of drought tolerance in rice (Oryza sativa L.).

Deeper Rooting 1 (DRO1) gene identified from a major QTL on chromosome 9 increases the root growth angle (RGA) and thus facilitates survival under drought and hence is an excellent candidate for rice improvement. Twenty-four major Indian upland and lowland genotypes including the 'yield under drought' (DTY) QTL donors were subjected to allele mining of DRO1 (3058 bp) using four pairs of overlapping primers. A total of 216 and 52 SNPs were identified across all genotypes in the gene and coding region (756 bp) respectively with transversions 3.6 fold more common than transitions in the gene and 2.5 times in the CDS. In 251 amino acid long protein, substitutions were found in 19 positions, wherein change in position 92 was the most frequent. Based on allele mining, the 24 genotypes can be classified into 16 primary structure variants ranging from complete functional allele (Satti, IR36 and DTY 3.1 donor, IR81896-B-B-195) to truncated non-functional alleles in PMK2, IR64, IR20 and Swarna. All the DTY donors, other than IR81896-B-B-195, and most of the upland drought tolerant cultivars (Nagina 22, Vandana and Dhagaddeshi) had accumulated 6-19 SNPs and 4-8 amino acid substitutions resulting in substantial differences in their protein structure. The expression analysis revealed that all the genotypes showed upregulation under drought stress though the degree of upregulation varied among genotypes. The information on structural variations in DRO1 gene will be very useful for the breeders, especially in the light of recent breeding programmes on improving drought tolerance using several DTY donors and upland accessions. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s12298-021-00950-2).

Biomarkers of Delirium Duration and Delirium Severity in the ICU.

OBJECTIVES: Both delirium duration and delirium severity are associated with adverse patient outcomes. Serum biomarkers associated with delirium duration and delirium severity in ICU patients have not been reliably identified. We conducted our study to identify peripheral biomarkers representing systemic inflammation, impaired neuroprotection, and astrocyte activation associated with delirium duration, delirium severity, and in-hospital mortality. DESIGN: Observational study. SETTING: Three Indianapolis hospitals. PATIENTS: Three-hundred twenty-one critically ill delirious patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We analyzed the associations between biomarkers collected at delirium onset and delirium-/coma-free days assessed through Richmond Agitation-Sedation Scale/Confusion Assessment Method for the ICU, delirium severity assessed through Confusion Assessment Method for the ICU-7, and in-hospital mortality. After adjusting for age, gender, Acute Physiology and Chronic Health Evaluation II score, Charlson comorbidity score, sepsis diagnosis and study intervention group, interleukin-6, -8, and -10, tumor necrosis factor-α, C-reactive protein, and S-100ß levels in quartile 4 were negatively associated with delirium-/coma-free days by 1 week and 30 days post enrollment. Insulin-like growth factor-1 levels in quartile 4 were not associated with delirium-/coma-free days at both time points. Interleukin-6, -8, and -10, tumor necrosis factor-α, C-reactive protein, and S-100ß levels in quartile 4 were also associated with delirium severity by 1 week. At hospital discharge, interleukin-6, -8, and -10 retained the association but tumor necrosis factor-α, C-reactive protein, and S-100ß lost their associations with delirium severity. Insulin-like growth factor-1 levels in quartile 4 were not associated with delirium severity at both time points. Interleukin-8 and S-100ß levels in quartile 4 were also associated with higher in-hospital mortality. Interleukin-6 and -10, tumor necrosis factor-α, and insulin-like growth factor-1 were not found to be associated with in-hospital mortality. CONCLUSIONS: Biomarkers of systemic inflammation and those for astrocyte and glial activation were associated with longer delirium duration, higher delirium severity, and in-hospital mortality. Utility of these biomarkers early in delirium onset to identify patients at a higher risk of severe and prolonged delirium, and delirium related complications during hospitalization needs to be explored in future studies.

Amino Acid Profile and Lactate Pyruvate Ratio: Potential Adjunct Markers for Differentiating Inborn Errors of Metabolism.

Inborn errors of metabolism (IEM) lead to the physical and mental disability and death of infants, which can be prevented if treated early. Hence it is imperative in diagnosing these disorders at the earliest. The study is planned to differentiate suspected IEM by quantifying the lactate-pyruvate ratio (L/P ratio), Amino acid profiling by HPLC in addition to blood ammonia using the basic methodology in comparison to globally accepted mass spectroscopy technique and specific enzyme activity assays. The objective of this study is not to compete with the existing gold standard methodology rather makes the best of basic diagnostic modalities available. Five cases out of 100 referred cases of IEM suspicion showed the altered pattern of Aminogram correlating with high L/P ratio and Hyperammonemia, which were positive cases, as confirmed by the clinician who referred. Hence study parameters could be used as preliminary protocol to investigate and screen the IEM.

Targeting cyclin-dependent kinase 9 sensitizes medulloblastoma cells to chemotherapy.

Medulloblastoma (MB) is a highly aggressive, malignant brain tumor in children with poor prognosis. Cyclin-dependent kinase 9 (CDK9), a serine-threonine kinase, is widely implicated in the control of basal gene expression by phosphorylating Serine 2 (Ser2) of the heptad repeat in the RNA Polymerase II (RNA Pol II) C-terminal domain (CTD). Although CDK9 plays a pathogenic role in various cancers, its function in MB remains unknown. Here, we show that CDK9 is highly expressed in MB tumors and increased CDK9 expression is correlated with high risk MB patients. CDK9 expression along with phospho-Ser2 RNA Pol II (pRNA Pol II ser2) and bromodomain-binding protein 4 (BRD4), which recruits CDK9, were elevated in multiple MB cell lines and in MB tumors originated spontaneously from Ptch1+/-p53-/- mice. Inhibition of CDK9 with LDC067 suppressed MB cell growth, reduced pRNA Pol II ser2 level and expression of oncogenic markers, including MYC. Moreover, LDC067 treatment synergistically sensitizes MB cells to chemotherapeutic agent cisplatin. Further, LDC067 in combination with BRD4 inhibitor decreased MB cells growth, delayed cell migration and attenuated pRNA Pol II ser2 occupancy to CCND1 and BCL2 gene promoters as revealed by chromatin immunoprecipitation assay (ChIP). Together, these findings highlight the importance of CDK9 in MB pathogenesis and suggest that it may serve as a promising therapeutic target for the treatment of MB.

Tropolone-Conjugated DNA: Fluorescence Enhancement in the Duplex.

Tropolone (2-hydroxycyclohepta-2,4,6-triene-1-one and tautomer) is a non-benzenoid bioactive natural chromophore with pH-dependent fluorescence character and extraordinary metal binding affinities, especially with transition-metal ions Cu2+ /Zn2+ /Ni2+ . This report describes the syntheses and biophysical studies of a new tropolonyl thymidine [(4(5)-hydroxy-5(4)-oxo-5(4)H-cyclohepta-1,3,6-trienyl)thymidine] (tr-T) nucleoside and of corresponding tropolone-conjugated DNA oligonucleotides that form B-form DNA duplex structures with a complementary DNA strand, although their duplex structures are less stable than that of the control. Furthermore, the stabilities of those DNA duplex structures are lowered by the presence of increasing numbers of tr-T residue or by decreasing pH of their environments. Most importantly, these duplex structures are made fluorescent because of the presence of the tropolone moieties conjugated to the thymidine residues. The fluorescence behavior of those duplex structures exhibits pH dependence, with stronger fluorescence at lower pH and weaker fluorescence at high pH. Importantly, the fluorescence characters of tr-DNA oligonucleotides are significantly enhanced by nearly threefold after duplex structure formation with their complementary control DNA oligonucleotide. Further, the fluorescence behavior of these tr-DNA duplex structures is also dependent on the pH conditions. Hence, tropolonyl-conjugated DNA represents a class of new fluorescent analogues that might be be employed for sensing DNA duplex formation and provide opportunities to improve fluorescence properties further.

Role of protein arginine methyltransferase 5 in group 3 (MYC-driven) Medulloblastoma.

BACKGROUND: MYC amplification or overexpression is common in Group 3 medulloblastoma and is associated with the worst prognosis. Recently, protein arginine methyl transferase (PRMT) 5 expression has been closely associated with aberrant MYC function in various cancers, including brain tumors such as glioblastoma. However, the role of PRMT5 and its association with MYC in medulloblastoma have not been explored. Here, we report the role of PRMT5 as a novel regulator of MYC and implicate PRMT5 as a potential therapeutic target in MYC-driven medulloblastoma. METHODS: Expression and association between PRMT5 and MYC in primary medulloblastoma tumors were investigated using publicly available databases. Expression levels of PRMT5 protein were also examined using medulloblastoma cell lines and primary tumors by western blotting and immunohistochemistry, respectively. Using MYC-driven medulloblastoma cells, we examined the physical interaction between PRMT5 and MYC by co-immunoprecipitation and co-localization experiments. To determine the functional role of PRMT5 in MYC-driven medulloblastoma, PRMT5 was knocked-down in MYC-amplified cells using siRNA and the consequences of knockdown on cell growth and MYC expression/stability were investigated. In vitro therapeutic potential of PRMT5 in medulloblastoma was also evaluated using a small molecule inhibitor, EPZ015666. RESULTS: We observed overexpression of PRMT5 in MYC-driven primary medulloblastoma tumors and cell lines compared to non-MYC medulloblastoma tumors and adjacent normal tissues. We also found that high expression of PRMT5 is inversely correlated with patient survival. Knockdown of PRMT5 using siRNA in MYC-driven medulloblastoma cells significantly decreased cell growth and MYC expression. Mechanistically, we found that PRMT5 physically associated with MYC by direct protein-protein interaction. In addition, a cycloheximide chase experiment showed that PRMT5 post-translationally regulated MYC stability. In the context of therapeutics, we observed dose-dependent efficacy of PRMT5 inhibitor EPZ015666 in suppressing cell growth and inducing apoptosis in MYC-driven medulloblastoma cells. Further, the expression levels of PRMT5 and MYC protein were downregulated upon EPZ015666 treatment. We also observed a superior efficacy of this inhibitor against MYC-amplified medulloblastoma cells compared to non-MYC-amplified medulloblastoma cells, indicating specificity. CONCLUSION: Our results reveal the regulation of MYC oncoprotein by PRMT5 and suggest that targeting PRMT5 could be a potential therapeutic strategy for MYC-driven medulloblastoma.