Failure of human rhombic lip differentiation underlies medulloblastoma formation

Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hindbrain with strong links to early development of the hindbrain^1-4. Mutations that activate Sonic hedgehog signalling lead to Sonic hedgehog MB in the upper rhombic lip (RL) granule cell lineage^5-8. By contrast, mutations that activate WNT signalling lead to WNT MB in the lower RL^9,10. However, little is known about the more commonly occurring group 4 (G4) MB, which is thought to arise in the unipolar brush cell lineage^3,4. Here we demonstrate that somatic mutations that cause G4 MB converge on the core binding factor alpha (CBFA) complex and mutually exclusive alterations that affect CBFA2T2, CBFA2T3, PRDM6, UTX and OTX2. CBFA2T2 is expressed early in the progenitor cells of the cerebellar RL subventricular zone in Homo sapiens, and G4 MB transcriptionally resembles these progenitors but are stalled in developmental time. Knockdown of OTX2 in model systems relieves this differentiation blockade, which allows MB cells to spontaneously proceed along normal developmental differentiation trajectories. The specific nature of the split human RL, which is destined to generate most of the neurons in the human brain, and its high level of susceptible EOMES⁺KI67⁺ unipolar brush cell progenitor cells probably predisposes our species to the development of G4 MB.

The considerations, experiences and support needs of family members making treatment decisions for patients admitted with major stroke: a qualitative study

Background

Treatment decision-making by family members on behalf of patients with major stroke can be challenging because of the shock of the diagnosis and lack of knowledge of the patient’s treatment preferences. We aimed to understand how, and why, family members made certain treatment decisions, and explored their information and support needs.

Method

Semi-structured interviews with family members (n = 24) of patients with major stroke, within 2 weeks of hospital admission. Data were analysed thematically.

Results

Families’ approach to treatment decision-making lay on a spectrum according to the patient’s state of health pre-stroke (i.e. patient’s prior experience of illness and functional status) and any views expressed about treatment preferences in the event of life-threatening illness. Support and information needs varied according to where they were on this spectrum. At one extreme, family members described deciding not to initiate life-extending treatments from the outset because of the patients’ deteriorating health and preferences expressed pre-stroke. Information from doctors about poor prognosis was merely used to confirm this decision. In the middle of the spectrum were family members of patients who had been moderately independent pre-stroke. They described the initial shock of the diagnosis and how they had initially wanted all treatments to continue. However, once they overcame their shock, and had gathered relevant information, including information about poor prognosis from doctors, they decided that life-extending treatments were no longer appropriate. Many reported this process to be upsetting and expressed a need for psychological support. At the other end of the spectrum were family members of previously independent patients whose preferences pre-stroke had not been known. Family members described feeling extremely distressed at such an unexpected situation and wanting all treatments to continue. They described needing psychological support and hope that the patient would survive.

Conclusion

The knowledge that family members’ treatment decision-making approaches lay on a spectrum depending on the patient’s state of health and stated preferences pre-stroke may allow doctors to better prepare for discussions regarding the patient’s prognosis. This may enable doctors to provide information and support that is tailored towards family members’ needs.

N⁶-Methyladenosine Landscape of Glioma Stem-Like Cells: METTL3 Is Essential for the Expression of Actively Transcribed Genes and Sustenance of the Oncogenic Signaling

Despite recent advances in N⁶-methyladenosine (m⁶A) biology, the regulation of crucial RNA processing steps by the RNA methyltransferase-like 3 (METTL3) in glioma stem-like cells (GSCs) remains obscure. An integrated analysis of m⁶A-RIP (RNA immunoprecipitation) and total RNA-Seq of METTL3-silenced GSCs identified that m⁶A modification in GSCs is principally carried out by METTL3. The m⁶A-modified transcripts showed higher abundance compared to non-modified transcripts. Further, we showed that the METTL3 is essential for the expression of GSC-specific actively transcribed genes. Silencing METTL3 resulted in the elevation of several aberrant alternative splicing events. We also found that putative m⁶A reader proteins play a key role in the RNA stabilization function of METTL3. METTL3 altered A-to-I and C-to-U RNA editing events by differentially regulating RNA editing enzymes ADAR and APOBEC3A. Similar to protein-coding genes, lincRNAs (long intergenic non-coding RNAs) with m⁶A marks showed METTL3-dependent high expression. m⁶A modification of 3'UTRs appeared to result in a conformation-dependent hindrance to miRNA binding to their targets. The integrated analysis of the m⁶A regulome in METTL3-silenced GSCs showed global disruption in tumorigenic pathways that are indispensable for GSC maintenance and glioma progression. We conclude that METTL3 plays a vital role in many steps of RNA processing and orchestrates successful execution of oncogenic pathways in GSCs.

Assessment of Radiation Resistance and Therapeutic Targeting of Cancer Stem Cells: A Raman Spectroscopic Study of Glioblastoma

Radiation is the standard therapy used for treating Glioblastoma (GBM), a grade IV brain cancer. Glioma Stem-like Cells (GSCs), an integral part of GBM, enforces resistance to radiation therapy of GBM. Studying the differential biomolecular composition of GSCs with varying levels of radiation sensitivity can aid in identifying the molecules and their associated pathways which impose resistance to cells thereby unraveling new targets which would serve as potential adjuvant therapy. Raman spectroscopy being a noninvasive, label free technique can determine the biomolecular constituent of cells under live conditions. In this study, we have deduced Raman spectral signatures to predict the radiosensitivity of any GSC accurately using the inherent and radiation induced biomolecular composition. Our study identified the differential regulation of several biomolecules which can be potential targets for adjuvant therapy. We radiosensitized the resistant GSCs using small molecule inhibitors specific to the metabolic pathways of these biomolecules. Efficient antitumor therapy can be attained with lower dosage of radiation along with these inhibitors and thus improving the survival rate of GBM patients with reduced side-effects from radiation.

IGF2 mRNA binding protein 3 (IMP3) promotes glioma cell migration by enhancing the translation of RELA/p65

The diffusely infiltrative nature of glioblastoma (GBM) makes them highly recurrent. IGF2 mRNA-binding protein 3 (IMP3), a GBM upregulated RNA binding protein, promotes glioma cell migration. An integrative bioinformatics analysis identified p65 (RELA), a subunit of NF-κB heterodimer as a target and an important mediator of IMP3 promoted glioma cell migration. IMP3 increased p65 protein levels without any change in p65 transcript levels, but promoted its polysome association. RIP-PCR demonstrated the binding of IMP3 to p65 transcript. UV crosslinking experiments with in vitro transcribed RNA confirmed the specific and direct binding of IMP3 to sites on p65 3′UTR. Further, IMP3 induced luciferase activity from p65 3′UTR reporter carrying wild type sites but not mutated sites. Exogenous overexpression of p65 from a 3′UTR-less construct rescued the reduced migration of glioma cells in IMP3 silenced condition. In addition, IMP3 silencing inhibited glioma stem-like cell maintenance and migration. The exogenous overexpression of 3′UTR-less p65 significantly alleviated the inhibition of neurosphere formation observed in IMP3 silenced glioma stem-like cells. Further, we show that IMP3 is transcriptionally activated by NF-κB pathway indicating the presence of a positive feedback loop between IMP3 and p65. This study establishes p65 as a novel target of IMP3 in increasing glioma cell migration and underscores the significance of IMP3-p65 feedback loop for therapeutic targeting in GBM.

mRNA Traffic Control Reviewed: N6-Methyladenosine (m6 A) Takes the Driver's Seat

Messenger RNA is a flexible tool box that plays a key role in the dynamic regulation of gene expression. RNA modifications variegate the message conveyed by the mRNA. Similar to DNA and histone modifications, mRNA modifications are reversible and play a key role in the regulation of molecular events. Our understanding about the landscape of RNA modifications is still rudimentary in contrast to DNA and histone modifications. The major obstacle has been the lack of sensitive detection methods since they are non-editing events. However, with the advent of next-generation sequencing techniques, RNA modifications are being identified precisely at single nucleotide resolution. In recent years, methylation at the N6 position of adenine (m⁶ A) has gained the attention of RNA biologists. The m⁶ A modification has a set of writers (methylases), erasers (demethylases), and readers. Here, we provide a summary of interesting facts, conflicting findings, and recent advances in the technical and functional aspects of the m⁶ A epitranscriptome.

Smartphone apps in microbiology--is better regulation required?

Increasing diversity of available medical applications (apps) has led to their widespread use in healthcare delivery. However, app involvement in diagnosis and patient management has raised concerns, specifically regarding accuracy and reliability of content. Here, we report on the contemporary range of microbiology-themed apps and prevalence of medical professional involvement in app development. Of 94 microbiology-themed apps identified, only 34% had stated medical professional involvement. The lack of such involvement in app design is concerning and undermines consumers' ability to be informed regarding quality of content. We propose that increased regulatory measures are introduced to safeguard patient welfare.

Effect of the small molecule plasminogen activator inhibitor-1 (PAI-1) inhibitor, PAI-749, in clinical models of fibrinolysis

BACKGROUND

The principal inhibitor of fibrinolysis in vivo is plasminogen activator inhibitor-1 (PAI-1). PAI-749 is a small molecule inhibitor of PAI-1 with proven antithrombotic efficacy in several preclinical models.

OBJECTIVE

To assess the effect of PAI-749, by using an established ex vivo clinical model of thrombosis and a range of complementary in vitro human plasma-based and whole blood-based models of fibrinolysis.

METHODS

In a double-blind, randomized, crossover study, ex vivo thrombus formation was assessed using the Badimon chamber in 12 healthy volunteers during extracorporeal administration of tissue-type plasminogen activator (t-PA) in the presence of PAI-749 or control. t-PA-mediated lysis of plasma clots and of whole blood model thrombi were assessed in vitro. The role of vitronectin was examined by assessing lysis of fibrin clots generated from purified plasma proteins.

RESULTS

There was a dose-dependent reduction in ex vivo thrombus formation by t-PA (P < 0.0001). PAI-749 had no effect on in vitro or ex vivo thrombus formation or fibrinolysis in the presence or absence of t-PA. Inhibition of PAI-1 with a blocking antibody enhanced fibrinolysis in vitro (P < 0.05).

CONCLUSIONS

Despite its efficacy in a purified human system and in preclinical models of thrombosis, the current study suggests that PAI-749 does not affect thrombus formation or fibrinolysis in a range of established human plasma and whole blood-based systems.

Substrate specificity and kinetic mechanism of human placental insulin receptor/kinase

The insulin receptor has been shown to be a protein kinase which phosphorylates its substrates on tyrosine residues. To examine the acceptor specificity of affinity-purified insulin receptor/kinase, hydroxyamino acid containing analogues of the synthetic peptide substrate Arg-Arg-Leu-Ile-Glu-Asp-Ala-Glu-Tyr-Ala-Ala-Arg-Gly were prepared. Substitution of serine, threonine, or D-tyrosine for L-tyrosine completely ablated the acceptor activity of the synthetic peptides. These peptides, along with a phenylalanine-containing analogue, did serve as competitive inhibitors of the insulin receptor/kinase with apparent Ki values in the range of 2-4 mM. These data suggest that the insulin receptor/kinase is specific for tyrosine residues in its acceptor substrate and imply that serine phosphate or threonine phosphate present in receptor is due to phosphorylation by other protein kinases. The kinetics of the phosphorylation of the L-tyrosine-containing peptide were examined by using prephosphorylated insulin receptor/kinase. Prephosphorylation of the receptor was necessary to maximally activate the kinase and to linearize the initial velocity of the peptide phosphorylation reaction. The data obtained rule out a ping-pong mechanism and are consistent with a random-order rapid-equilibrium mechanism for the phosphorylation of this peptide substrate. Additional experiments demonstrated that the autophosphorylated insulin receptor was not able to transfer the preincorporated phosphate to the synthetic peptide substrate. Thus, the insulin receptor/kinase catalyzes the reaction via a mechanism that does not involve transfer of phosphate from a phosphotyrosine-containing enzyme intermediate.

Effect of high-fat diet on cholesterol distribution in plasma lipoproteins, cholesterol esterifying activity in leucocytes, and erythrocyte membrane components studied: importance of body weight

Effects of isocaloric changes in dietary fat on plasma lipoproteins and lipids and enzymes of erythrocytes and leucocytes were assessed. Subjects with a higher Brocca index showed increase in total and LDL cholesterol, significant reduction in HDL cholesterol, and increased total cholesterol:HDL cholesterol ratio after high-fat diet consumption. Due to high-fat diet feeding, erythrocyte membrane and leucocyte cholesterol and phospholipid contents were increased, cholesterol:phospholipid molar ratio was elevated, and erythrocyte enzymes (G6PD and 6PGD) and leucocyte enzymes (CEH and CES) were elevated. Erythrocyte membrane glycoprotein components showed marked increase, indicating possible alterations of membrane surfaces. The metabolic alterations were reversed slowly after resumption of the normal (low-fat) diet. Body weight plays an important role in the alterations in major lipoprotein cholesterol contents in response to changes in dietary fat composition. Cellular changes indicate alterations in structure and function of blood cells due to high-fat diet feeding.

Ferric acetate-uranium acetate reagent in cholesterol estimations in plasma and high density lipoprotein fractions: comparison with existing methods

The use of ferric acetate-uranium acetate colour reaction for the estimation of cholesterol in the supernatants of plasma samples after precipitation of low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterol by heparin-MnCl2 was assessed and compared with the conventional method using the FeCl3 colour reaction and also with the method using o-phthalaldehyde as the colouring reagent. All three methods gave comparable values when total cholesterol in plasma samples was determined and also when high density lipoprotein (HDL) fractions were separated by ultracentrifugation and the cholesterol contents determined. But when heparin-MnCl2 precipitation was used for HDL separation, and the cholesterol content determined, the FeCl3 method gave significantly lower values. This could be due to interference of the cholesterol colour reaction with FeCl3, due to Mn2+ ions present in the supernatant. Addition of Mn2+ to cholesterol standards and subsequent colour development with ferric acetate-uranium acetate and FeCl3 reagents showed that Mn2+ decreased the absorbancy of the coloured complex at 560 nm only when FeCl3 was used. Percentage recovery of added cholesterol was also lower when the heparin-MnCl2 supernatant was treated with FeCl3 reagent for colour development. Use of ferric acetate-uranium acetate reagent provides a simpler and quicker method. It does not suffer from interference due to the presence of Mn2+ ions and gives results comparable to the o-phthalaldehyde method and those using ultracentrifugation as the separation procedure.

Effect of iodobenzene therapy on mitochondrial activity in 2-thiouracil-induced hypothyroidism in weanling rats

Hypothyroidism was produced in weanling albino rats by the oral administration of 2-thiouracil (TU) for 110 days. These animals recorded nearly 50 per cent reduction in mitochondrial oxidation of succinate, protein content and the activity of inner mitochondrial membrane-bound beta-hydroxybutyrate dehydrogenase. Administration of iodobenzene (IB; 0.1 microgram/rat/day) and L-thyroxine (T4; 0.6 microgram/rat/day) to two sets of hypothyroid rats restored the reduced oxidation rate, enzyme activity and protein content to near normal values. IB was comparable to T4 and may act as a thyroid stimulant.