MiRNAs and piRNAs from bone marrow mesenchymal stem cell extracellular vesicles induce cell survival and inhibit cell differentiation of cord blood hematopoietic stem cells: a new insight in transplantation

Hematopoietic stem cells (HSC), including umbilical cord blood CD34+ stem cells (UCB-CD34+), are used for the treatment of several diseases. Although different studies suggest that bone marrow mesenchymal stem cells (BM-MSC) support hematopoiesis, the exact mechanism remains unclear. Recently, extracellular vesicles (EVs) have been described as a novel avenue of cell communication, which may mediate BM-MSC effect on HSC. In this work, we studied the interaction between UCB-CD34+ cells and BM-MSC derived EVs. First, by sequencing EV derived miRNAs and piRNAs we found that EVs contain RNAs able to influence UCB-CD34+ cell fate. Accordingly, a gene expression profile of UCB-CD34+ cells treated with EVs, identified about 100 down-regulated genes among those targeted by EV-derived miRNAs and piRNAs (e.g. miR-27b/MPL, miR-21/ANXA1, miR-181/EGR2), indicating that EV content was able to modify gene expression profile of receiving cells. Moreover, we demonstrated that UCB-CD34+ cells, exposed to EVs, significantly changed different biological functions, becoming more viable and less differentiated. UCB-CD34+ gene expression profile also identified 103 up-regulated genes, most of them codifying for chemokines, cytokines and their receptors, involved in chemotaxis of different BM cells, an essential function of hematopoietic reconstitution. Finally, the exposure of UCB-CD34+ cells to EVs caused an increased expression CXCR4, paralleled by an in vivo augmented migration from peripheral blood to BM niche in NSG mice. This study demonstrates the existence of a powerful cross talk between BM-MSC and UCB-CD34+ cells, mediated by EVs, providing new insight in the biology of cord blood transplantation.

Reactive Oxygen Species Derived from NOX3 and NOX5 Drive Differentiation of Human Oligodendrocytes

Reactive oxygen species (ROS) are signaling molecules that mediate stress response, apoptosis, DNA damage, gene expression and differentiation. We report here that differentiation of oligodendrocytes (OLs), the myelin forming cells in the CNS, is driven by ROS. To dissect the OL differentiation pathway, we used the cell line MO3-13, which display the molecular and cellular features of OL precursors. These cells exposed 1-4 days to low levels of H2O2 or to the protein kinase C (PKC) activator, phorbol-12-Myristate-13-Acetate (PMA) increased the expression of specific OL differentiation markers: the specific nuclear factor Olig-2, and Myelin Basic Protein (MBP), which was processed and accumulated selectively in membranes. The induction of differentiation genes was associated with the activation of ERK1-2 and phosphorylation of the nuclear cAMP responsive element binding protein 1 (CREB). PKC mediates ROS-induced differentiation because PKC depletion or bis-indolyl-maleimide (BIM), a PKC inhibitor, reversed the induction of differentiation markers by H2O2. H2O2 and PMA increased the expression of membrane-bound NADPH oxidases, NOX3 and NOX5. Selective depletion of these proteins inhibited differentiation induced by PMA. Furthermore, NOX5 silencing down regulated NOX3 mRNA levels, suggesting that ROS produced by NOX5 up-regulate NOX3 expression. These data unravel an elaborate network of ROS-generating enzymes (NOX5 to NOX3) activated by PKC and necessary for differentiation of OLs. Furthermore, NOX3 and NOX5, as inducers of OL differentiation, represent novel targets for therapies of demyelinating diseases, including multiple sclerosis, associated with impairment of OL differentiation.

Targeted DNA methylation by homology-directed repair in mammalian cells. Transcription reshapes methylation on the repaired gene

We report that homology-directed repair of a DNA double-strand break within a single copy Green Fluorescent Protein (GFP) gene in HeLa cells alters the methylation pattern at the site of recombination. DNA methyl transferase (DNMT)1, DNMT3a and two proteins that regulate methylation, Np95 and GADD45A, are recruited to the site of repair and are responsible for selective methylation of the promoter-distal segment of the repaired DNA. The initial methylation pattern of the locus is modified in a transcription-dependent fashion during the 15–20 days following repair, at which time no further changes in the methylation pattern occur. The variation in DNA modification generates stable clones with wide ranges of GFP expression. Collectively, our data indicate that somatic DNA methylation follows homologous repair and is subjected to remodeling by local transcription in a discrete time window during and after the damage. We propose that DNA methylation of repaired genes represents a DNA damage code and is source of variation of gene expression.

Epilepsy, unawareness of seizures and driving license: the potential role of 24-hour ambulatory EEG in defining seizure freedom

INTRODUCTION

Seizures represent a potential source of accidents/death. Permission to drive may, therefore, be granted in a seizure-free period. Laws and regulations regarding this issue vary widely, and the onus of reporting seizures ultimately rests on the individual. Unfortunately, as some patients are unaware of their seizures, their reports may be unreliable.

METHODS

In this retrospective study, we selected, from a group of 1100 consecutive patients, 57 cases (26 males/31 females; mean age: 42.5 years) in whom the AEEG documented ictal events (UIEs) not reported in a self-kept diary. By means of a simple questionnaire, we interviewed all these patients to collect information on driving licenses. We, thus, assessed how many of these patients (both drug resistant and seizure free) drove regularly.

RESULTS

Our study shows a relatively large number of patients with epilepsy and UIEs. Fifteen patients suffered from idiopathic generalized epilepsy (IGE) while 42 had partial epilepsy (PE). The patients were seizure free in 21 cases and 36 had drug-resistant seizures. Many patients in both these subgroups had a driving license and drove normally (active driving in 12/36 drug-resistant patients and in 18/21 seizure-free patients). Worthy of note is the finding that an "apparently" seizure-free group of patients drove regularly.

CONCLUSIONS

This study revealed a large number of patients (both drug resistant and seizure free) with AEEG-documented UIEs. This finding highlights the usefulness of AEEG in clinical practice as a means of more accurately ascertaining seizure freedom and supporting decisions involving the renewal or granting of a driving license.

GADD45α inhibition of DNMT1 dependent DNA methylation during homology directed DNA repair

In this work, we examine regulation of DNA methyltransferase 1 (DNMT1) by the DNA damage inducible protein, GADD45α. We used a system to induce homologous recombination (HR) at a unique double-strand DNA break in a GFP reporter in mammalian cells. After HR, the repaired DNA is hypermethylated in recombinant clones showing low GFP expression (HR-L expressor class), while in high expressor recombinants (HR-H clones) previous methylation patterns are erased. GADD45α, which is transiently induced by double-strand breaks, binds to chromatin undergoing HR repair. Ectopic overexpression of GADD45α during repair increases the HR-H fraction of cells (hypomethylated repaired DNA), without altering the recombination frequency. Conversely, silencing of GADD45α increases methylation of the recombined segment and amplifies the HR-L expressor (hypermethylated) population. GADD45α specifically interacts with the catalytic site of DNMT1 and inhibits methylation activity in vitro. We propose that double-strand DNA damage and the resulting HR process involves precise, strand selected DNA methylation by DNMT1 that is regulated by GADD45α. Since GADD45α binds with high avidity to hemimethylated DNA intermediates, it may also provide a barrier to spreading of methylation during or after HR repair.

DNA damage, homology-directed repair, and DNA methylation

To explore the link between DNA damage and gene silencing, we induced a DNA double-strand break in the genome of Hela or mouse embryonic stem (ES) cells using I-SceI restriction endonuclease. The I-SceI site lies within one copy of two inactivated tandem repeated green fluorescent protein (GFP) genes (DR-GFP). A total of 2%–4% of the cells generated a functional GFP by homology-directed repair (HR) and gene conversion. However, ~50% of these recombinants expressed GFP poorly. Silencing was rapid and associated with HR and DNA methylation of the recombinant gene, since it was prevented in Hela cells by 5-aza-2′-deoxycytidine. ES cells deficient in DNA methyl transferase 1 yielded as many recombinants as wild-type cells, but most of these recombinants expressed GFP robustly. Half of the HR DNA molecules were de novo methylated, principally downstream to the double-strand break, and half were undermethylated relative to the uncut DNA. Methylation of the repaired gene was independent of the methylation status of the converting template. The methylation pattern of recombinant molecules derived from pools of cells carrying DR-GFP at different loci, or from an individual clone carrying DR-GFP at a single locus, was comparable. ClustalW analysis of the sequenced GFP molecules in Hela and ES cells distinguished recombinant and nonrecombinant DNA solely on the basis of their methylation profile and indicated that HR superimposed novel methylation profiles on top of the old patterns. Chromatin immunoprecipitation and RNA analysis revealed that DNA methyl transferase 1 was bound specifically to HR GFP DNA and that methylation of the repaired segment contributed to the silencing of GFP expression. Taken together, our data support a mechanistic link between HR and DNA methylation and suggest that DNA methylation in eukaryotes marks homologous recombined segments.

Genomic DNA can be modified by cytosine methylation. This epigenetic modification is layered on the primary genetic information and can silence the affected gene. Epigenetic modification has been implicated in cancer and aging. To date, the primary cause and the mechanism leading to DNA methylation are not known. By using a sophisticated genetic system, we have induced a single break in the double helix of the genomes of mouse or human cells. This rupture was repaired by a very precise mechanism: the damaged chromosome pairs and retrieves genetic information from an undamaged and homologous DNA partner. This homology-directed repair was marked in half of the repaired molecules by de novo methylation of cytosines flanking the cut. As a direct consequence, the gene in these repaired molecules was silenced. In the remaining molecules, the recombinant DNA was undermethylated and expressed the reconstituted gene. Since homology-directed repair may duplicate or delete genetic information, epigenetic modification of repaired DNA represents a powerful evolutionary force. If the expression of the repaired gene is harmful, only cells inheriting the silenced copy will survive. Conversely, if the function of the repaired gene is beneficial, cells inheriting the under-methylated copy will have a selective advantage.

Lithium prevents colchicine-induced apoptosis in rat cerebellar granule neurons

OBJECTIVES

Here we evaluated the neuroprotective effects of two well-known mood stabilizers, lithium and valproic acid (VPA), against colchicine neurotoxicity in cerebellar granule cells (CGNs).

METHODS

The CGNs were differentiated for 7 days, pretreated with lithium or VPA for 24 h and after colchicine 1 microM was added. Cellular damage was assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) method and apoptosis in CGNs was characterized by chromatin condensation and DNA fragmentation.

RESULTS

Incubation with lithium (1-5 mM) attenuated this apoptosis markedly, in a dose-dependent way however, the addition of VPA (0.5-2 mM) did not protect CGNs. Colchicine-induced apoptosis is mediated through the activation of caspase-3. An increase in caspase-3 activity was detected within 18 h and was blocked in presence of lithium 5 mM.

CONCLUSIONS

Our data indicate that lithium treatment is selectively neuroprotective; however, in our experimental conditions VPA did not protect CGNs from apoptosis induced by colchicine. Our results support the hypothesis that distinct pathways mediate the neuroprotective effects of lithium and VPA.

Differential Phosphorylation of c-Jun and JunD in Response to the Epidermal Growth Factor Is Determined by the Structure of MAPK Targeting Sequences

MAPK phosphorylation of various substrates is mediated by the presence of docking sites, including the D domain and the DEF motif. Depending on the number and sequences of these domains, substrates are phosphorylated by specific subsets of MAPKs. For example, a D domain targets JNK to c-Jun, whereas a DEF motif is required for ERK phosphorylation of c-Fos. JunD, in contrast, contains both D and DEF domains. Here we show that these motifs mediate JunD phosphorylation in response to either ERK or JNK activation. An intact D domain is required for phosphorylation and activation of JunD by both subtypes of MAPK. The DEF motif acts together with the D domain to elicit efficient phosphorylation of JunD in response to the epidermal growth factor (EGF) but has no function on JunD phosphorylation and activation by JNK signaling. Furthermore, we show that conversion of a c-Jun sequence to a canonical DEF domain, as it is present in JunD, elicits c-Jun activation in response to EGF. Our results suggest that evolution of a particular modular system of MAPK targeting sequences has determined a differential response of JunD and c-Jun to ERK activation.

Risk-factors for Parkinson's disease: case-control study in the province of Cáceres, Spain

This case-control study, performed in a mixed rural and urban province, of 74 patients with Parkinson's disease (PD) and 148 unselected age and sex-matched controls, attempted to look possible risk factors for PD. Rural living, well-water drinking, positive family history for PD and postural tremor, were associated to an increased risk for PD, with results regarding exposure to pesticides near to statistical significance. Alcohol-drinking habit in males were associated to a decreased risk for PD, with results regarding cigarette-smoking habit in males near to statistical significance. We did not find association between the risk for PD and the following variables: 1) exposure to industrial toxins; 2) agricultural work; 3) cranial trauma; 4) previous common illnesses including some infections, arterial hypertension, diabetes mellitus, coronary heart disease and thyroid disease; 5) coffee and tea drinking habits.