PRC2 complexes with JARID2, MTF2, and esPRC2p48 in ES cells to modulate ES cell pluripotency and somatic cell reprogramming

Polycomb repressive complex two (PRC2) has been implicated in embryonic stem (ES) cell pluripotency; however, the mechanistic roles of this complex are unclear. It was assumed that ES cells contain PRC2 with the same subunit composition as that identified in HeLa cells and Drosophila embryos. Here, we report that PRC2 in mouse ES cells contains at least three additional subunits: JARID2, MTF2, and a novel protein denoted esPRC2p48. JARID2, MTF2, and esPRC2p48 are highly expressed in mouse ES cells compared to differentiated cells. Importantly, knockdowns of JARID2, MTF2, or esPRC2p48 alter the level of PRC2-mediated H3K27 methylation and result in the expression of differentiation-associated genes in ES cells. Interestingly, expression of JARID2, MTF2, and esPRC2p48 together, but not individually, enhances Oct4/Sox2/Klf4-mediated reprogramming of mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells, whereas knockdown or knockout of JARID2, MTF2, or esPRC2p48 significantly inhibits reprogramming. JARID2, MTF2, and esPRC2p48 modulate H3K27 methylation and facilitate repression of lineage-associated gene expression when transduced into MEFs, and synergistically stimulate the histone methyltransferase activity of PRC2 in vitro. Therefore, these studies identify JARID2, MTF2, and esPRC2p48 as important regulatory subunits of PRC2 in ES cells and reveal critical functions of these subunits in modulating PRC2's activity and gene expression both in ES cells and during somatic cell reprogramming.

Smart sensor systems for human health breath monitoring applications

Breath analysis techniques offer a potential revolution in health care diagnostics, especially if these techniques can be brought into standard use in the clinic and at home. The advent of microsensors combined with smart sensor system technology enables a new generation of sensor systems with significantly enhanced capabilities and minimal size, weight and power consumption. This paper discusses the microsensor/smart sensor system approach and provides a summary of efforts to migrate this technology into human health breath monitoring applications. First, the basic capability of this approach to measure exhaled breath associated with exercise physiology is demonstrated. Building from this foundation, the development of a system for a portable asthma home health care system is described. A solid-state nitric oxide (NO) sensor for asthma monitoring has been identified, and efforts are underway to miniaturize this NO sensor technology and integrate it into a smart sensor system. It is concluded that base platform microsensor technology combined with smart sensor systems can address the needs of a range of breath monitoring applications and enable new capabilities for healthcare.

Spatiotemporally distinct protein kinase D activation in adult cardiomyocytes in response to phenylephrine and endothelin

Protein kinase D (PKD) is a nodal point in cardiac hypertrophic signaling. It triggers nuclear export of class II histone deacetylase (HDAC) and regulates transcription. Although this pathway is thought to be critical in cardiac hypertrophy and heart failure, little is known about spatiotemporal aspects of PKD activation at the myocyte level. Here, we demonstrate that in adult cardiomyocytes two important neurohumoral stimuli that induce hypertrophy, endothelin-1 (ET1) and phenylephrine (PE), trigger comparable global PKD activation and HDAC5 nuclear export, but via divergent spatiotemporal PKD signals. PE-induced HDAC5 export is entirely PKD-dependent, involving fleeting sarcolemmal PKD translocation (for activation) and very rapid subsequent nuclear import. In contrast, ET1 recruits and activates PKD that remains predominantly sarcolemmal. This explains why PE-induced nuclear HDAC5 export in myocytes is totally PKD-dependent, whereas ET1-induced HDAC5 export depends more prominently on InsP(3) and CaMKII signaling. Thus α-adrenergic and ET-1 receptor signaling via PKD in adult myocytes feature dramatic differences in cellular localization and translocation in mediating hypertrophic signaling. This raises new opportunities for targeted therapeutic intervention into distinct limbs of this hypertrophic signaling pathway.

Focused ion beam-fabricated Au micro/nanostructures used as a surface enhanced Raman scattering-active substrate for trace detection of molecules and influenza virus

The focused ion beam (FIB) technique was used to precisely fabricate patterned Au micro/nanostructures (fibAu). The effects of surface enhanced Raman scattering (SERS) on the fibAu samples were investigated by adjusting the geometrical, dimensional, and spacing factors. The SERS mechanism was evaluated using low-concentration rhodamine 6G (R6G) molecules, physically adsorbed or suspended on/within the micro/nanostructures. The results indicated that for detecting R6G molecules, hexagon-like micro/nanostructures induced a higher electromagnetic mechanism (EM) due to the availability of multiple edges and small curvature. By decreasing the dimensions from 300 to 150 nm, the laser-focused area contained an increasing number of micro/nanostructures and therefore intensified the excitation of SERS signals. Moreover, with an optimized geometry and dimensions of the micro/nanostructures, the relative intensity/surface area value reached a maximum as the spacing was 22 nm. An exponential decrease was found as the spacing was increased, which most probably resulted from the loss of EM. The spacing between the micro/nanostructures upon the fibAu was consequently regarded as the dominant factor for the detection of R6G molecules. By taking an optimized fibAu to detect low-concentration influenza virus, the amino acids from the outermost surface of the virus can be well distinguished through the SERS mechanism.

Effect of dopants on the soft magnetic properties and high frequency characteristics of FeCoBM (M = Ti, Nb, Hf, and Ta) thin films

Effect of dopants on the soft magnetic properties and high frequency characteristics of FeCoBM thin films (M = Ti, Nb, Hf, and Ta) have been studied. For (Fe0.55Co0.45)(100-x)B(x) (x = 5-15) thin films, with the increase of B content, the resistivity was increased because B could decrease the crystallinity of the films. The (Fe0.55Co0.45)90B10 thin film showed the optimum properties, where 4piM(s) = 16.1 kG, H(ce) = 64.2 Oe, H(ch) = 13.5 Oe, H(k) = 310 Oe and p = 338 microomega-cm. To reduce the coercivity of the film, the elements M, including Ti, Nb, Hf, and Ta, were selected to substitute for B in the FeCoB films. It was found that (Fe0.55Co0.45)90B6Ti2Nb2 thin film after annealing at a temperature of 200 degrees C for 30 min showed the optimal properties, where 4piM(s) = 15.8 kG, H(ce) = 4.8 Oe, H(ch) = 3.6 Oe, H(k) = 224 Oe and p = 290 microomega-cm. The theoretically calculated ferromagnetic resonance frequency of the developed films can be higher than 5 GHz.

Green fabrication of agar-conjugated Fe3O4 magnetic nanoparticles

Magnetic nanoparticles are of great interest both for fundamental research and emerging applications. In the biomedical field, magnetite (Fe(3)O(4)) has shown promise as a hyperthermia-based tumor therapeutic. However, preparing suitable solubilized magnetite nanoparticles is challenging, primarily due to aggregation and poor biocompatibility. Thus methods for coating Fe(3)O(4) NPs with biocompatible stabilizers are required. We report a new method for preparing Fe(3)O(4) nanoparticles by co-precipitation within the pores of agar gel samples. Permeated agar gels were then dried and ground into a powder, yielding agar-conjugated Fe(3)O(4) nanoparticles. Samples were characterized using XRD, FTIR, TGA, TEM and SQUID. This method for preparing agar-coated Fe(3)O(4) nanoparticles is environmentally friendly, inexpensive and scalable.

Continuous depth-sensing nano-mechanical characterization of living, fixed and dehydrated cells attached on a glass substrate

Continuous depth-sensing nano-indentation on living, fixed and dehydrated fibroblast cells was performed using a dynamic contact module and vertically measured from a pre-contact state to the glass substrate. The nano-indentation tip-on-cell approaches took advantage of finding a contact surface, followed by obtaining a continuous nano-mechanical profile along the nano-indentation depths. In the experiment, serial indentations from the leading edge, i.e., the lamellipodium to nucleus regions of living, fixed and dehydrated fibroblast cells were examined. Nano-indentations on a living cell anchored upon glass substrate were competent in finding the tip-on-cell contact surfaces and cell heights. For the result on the fixed and the dehydrated cells, cellular nano-mechanical properties were clearly characterized by continuous harmonic contact stiffness (HCS) measurements. The relations of HCS versus measured displacement, varied from the initial tip-on-cell contact to the glass substrate, were presumably divided into three stages, respectively induced by cellular intrinsic behavior, the substrate-dominant property, and the substrate property. This manifestation is beneficial to elucidate how the underlying substrate influences the interpretation of the nano-mechanical property of thin soft matter on a hard substrate. These findings, based upon continuous depth-sensing nano-indentations, are presumably valuable as a reference to related work, e.g., accomplished by atomic force microscopy.

Increased ATP generation in the host cell is required for efficient vaccinia virus production

To search for cellular genes up-regulated by vaccinia virus (VV) infection, differential display-reverse transcription-polymerase chain reaction (ddRT-PCR) assays were used to examine the expression of mRNAs from mock-infected and VV-infected HeLa cells. Two mitochondrial genes for proteins that are part of the electron transport chain that generates ATP, ND4 and CO II, were up-regulated after VV infection. Up-regulation of ND4 level by VV infection was confirmed by Western blotting analysis. Up-regulation of ND4 was reduced by the MAPK inhibitor, apigenin, which has been demonstrated elsewhere to inhibit VV replication. The induction of ND4 expression occurred after viral DNA replication since ara C, an inhibitor of poxviral DNA replication, could block this induction. ATP production was increased in the host cells after VV infection. Moreover, 4.5 μM oligomycin, an inhibitor of ATP production, reduced the ATP level 13 hr after virus infection to that of mock-infected cells and inhibited viral protein expression and virus production, suggesting that increased ATP production is required for efficient VV production. Our results further suggest that induction of ND4 expression is through a Bcl-2 independent pathway.

In vitro photothermal destruction of neuroblastoma cells using carbon nanotubes conjugated with GD2 monoclonal antibody

Despite aggressive multimodality therapy, most neuroblastoma-bearing patients relapse and survival rate remains poor. Exploration of alternative therapeutic modalities is needed. Carbon nanotubes (CNTs), revealing optical absorbance in the near-infrared region, warrant their merits in photothermal therapy. In order to specifically target disialoganglioside (GD2) overexpressed on the surface of neuroblastoma stNB-V1 cells, GD2 monoclonal antibody (anti-GD2) was conjugated to acidified CNTs. To examine the fate of anti-GD2 bound CNTs after incubation with stNB-V1 cells, rhodamine B was labeled on carboxylated CNTs functionalized with and without anti-GD2. Our results illustrated that anti-GD2-linked CNTs were extensively internalized by neuroblastoma cells via GD2-mediated endocytosis. In addition, we showed that anti-GD2 bound CNTs were not ingested by PC12 cells without GD2 expression. After anti-GD2 conjugated CNTs were incubated with neuroblastoma cells for 6 h and endocytosed by the cells, CNT-laden neuroblastoma cells were further irradiated with an 808 nm near-infrared (NIR) laser with intensity ramping from 0.6 to 6 W cm(-2) for 10 min which was then maintained at 6 W cm(-2) for an additional 5 min. Post-NIR laser exposure, and after being examined by calcein-AM dye, stNB-V1 cells were all found to undergo necrosis, while non-GD2 expressing PC12 cells all remained viable. Based on the in vitro study, CNTs bound with anti-GD2 have the potential to be utilized as a therapeutic thermal coupling agent that generates heat sufficient to selectively kill neuroblastoma cells under NIR laser light exposure.

Polycistronic lentiviral vector for "hit and run" reprogramming of adult skin fibroblasts to induced pluripotent stem cells

We report the derivation of induced pluripotent stem (iPS) cells from adult skin fibroblasts using a single, polycistronic lentiviral vector encoding the reprogramming factors Oct4, Sox2, and Klf4. Porcine teschovirus-1 2A sequences that trigger ribosome skipping were inserted between human cDNAs for these factors, and the polycistron was subcloned downstream of the elongation factor 1 alpha promoter in a self-inactivating (SIN) lentiviral vector containing a loxP site in the truncated 3' long terminal repeat (LTR). Adult skin fibroblasts from a humanized mouse model of sickle cell disease were transduced with this single lentiviral vector, and iPS cell colonies were picked within 30 days. These cells expressed endogenous Oct4, Sox2, Nanog, alkaline phosphatase, stage-specific embryonic antigen-1, and other markers of pluripotency. The iPS cells produced teratomas containing tissue derived from all three germ layers after injection into immunocompromised mice and formed high-level chimeras after injection into murine blastocysts. iPS cell lines with as few as three lentiviral insertions were obtained. Expression of Cre recombinase in these iPS cells resulted in deletion of the lentiviral vector, and sequencing of insertion sites demonstrated that remnant 291-bp SIN LTRs containing a single loxP site did not interrupt coding sequences, promoters, or known regulatory elements. These results suggest that a single, polycistronic "hit and run" vector can safely and effectively reprogram adult dermal fibroblasts into iPS cells.

Ultra-thin phospholipid layers physically adsorbed upon glass characterized by nano-indentation at the surface contact level

Dipalmitoylphosphatic acid was chosen as a model to interpret how molecules physically adsorbed upon glass responded to an infinitesimal oscillation force at the surface contact level. Oscillation of a nano-indentation tip toward the phospholipid layers was driven by a dynamic contact module at a constant harmonic frequency; the phase angle of the oscillation frequency was exponentially relaxed along the nano-scale displacement. The tip-on-molecule contact was thereafter identified and influenced by the characteristic of the physically adsorbed phospholipids. By applying the harmonic displacement of the nano-indentation tip and making a distinction between full contact displacements, the thickness of the phospholipid layers was thereafter estimated. Moreover, the additional force required to penetrate through the physically adsorbed molecules was minor compared to the analogous process for the chemically adsorbed ones. The importance of recognizing the physically adsorbed molecules is relevant to applications of contact mechanics for the distinction of various phospholipids. Furthermore it is very promising to interpret the mechanism by which cells convert mechanical stimuli into biochemical responses on the channels of phospholipids.

The robotic radiosynthesis of 5-[(18)F]fluoro-2'-deoxyuridine and its biological characterization

5-[(18)F]fluoro-2'-deoxyuridine ([(18)F]FUdR) was synthesized using a robotic system as a proliferation probe for PET. [(18)F]FUdR was prepared via radiofluorodestannylation reaction from its organotin precursor. Biodistribution study and microPET imaging of [(18)F]FUdR in NG4TL4 sarcoma-bearing FVB/n mice were performed. The tumor-to-blood and tumor-to-muscle ratio increased steadily from 15 (1.81 and 3.42) to 120min (9.10 and 11.9) post injection. The dynamic microPET imaging demonstrates remarkable radioactivity retention in the tumor, which is consistent with the results of biodistribution study.

Global reorganization of replication domains during embryonic stem cell differentiation

DNA replication in mammals is regulated via the coordinate firing of clusters of replicons that duplicate megabase-sized chromosome segments at specific times during S-phase. Cytogenetic studies show that these “replicon clusters” coalesce as subchromosomal units that persist through multiple cell generations, but the molecular boundaries of such units have remained elusive. Moreover, the extent to which changes in replication timing occur during differentiation and their relationship to transcription changes has not been rigorously investigated. We have constructed high-resolution replication-timing profiles in mouse embryonic stem cells (mESCs) before and after differentiation to neural precursor cells. We demonstrate that chromosomes can be segmented into multimegabase domains of coordinate replication, which we call “replication domains,” separated by transition regions whose replication kinetics are consistent with large originless segments. The molecular boundaries of replication domains are remarkably well conserved between distantly related ESC lines and induced pluripotent stem cells. Unexpectedly, ESC differentiation was accompanied by the consolidation of smaller differentially replicating domains into larger coordinately replicated units whose replication time was more aligned to isochore GC content and the density of LINE-1 transposable elements, but not gene density. Replication-timing changes were coordinated with transcription changes for weak promoters more than strong promoters, and were accompanied by rearrangements in subnuclear position. We conclude that replication profiles are cell-type specific, and changes in these profiles reveal chromosome segments that undergo large changes in organization during differentiation. Moreover, smaller replication domains and a higher density of timing transition regions that interrupt isochore replication timing define a novel characteristic of the pluripotent state.

Microscopy studies have suggested that chromosomal DNA is composed of multiple, megabase-sized segments, each replicated at different times during S-phase of the cell cycle. However, a molecular definition of these coordinately replicated sequences and the stability of the boundaries between them has not been established. We constructed genome-wide replication-timing maps in mouse embryonic stem cells, identifying multimegabase coordinately replicated chromosome segments—“replication domains”—separated by remarkably distinct temporal boundaries. These domain boundaries were shared between several unrelated embryonic stem cell lines, including somatic cells reprogrammed to pluripotency (so-called induced pluripotent stem cells). However, upon differentiation to neural precursor cells, domains encompassing approximately 20% of the genome changed their replication timing, temporally consolidating into fewer, larger replication domains that were conserved between different neural precursor cell lines. Domains that changed replication timing showed a unique sequence composition, a strongly biased directionality for changes in resident gene expression, and altered radial positioning within the three-dimensional space in the cell nucleus, suggesting that changes in replication timing are related to the reorganization of higher-order chromosome structure and function during differentiation. Moreover, the property of smaller discordantly replicating domains may define a novel characteristic of pluripotency.

Analyzing the temporal order of DNA replication across the genome during embryonic stem cell differentiation reveals stable boundaries between coordinately replicated regions that consolidate into fewer, larger domains during differentiation.

Breakdown of Fourier's law in nanotube thermal conductors

We present experimental evidence that the room temperature thermal conductivity (kappa) of individual multiwalled carbon and boron-nitride nanotubes does not obey Fourier's empirical law of thermal conduction. Because of isotopic disorder, kappa's of carbon nanotubes and boron-nitride nanotubes show different length dependence behavior. Moreover, for these systems we find that Fourier's law is violated even when the phonon mean free path is much shorter than the sample length.