Bidirectional reprogramming of mouse embryonic stem cell/fibroblast hybrid cells is initiated at the heterokaryon stage

Immunofluorescent analysis of markers specific for parental genomes was used to study heterokaryons and hybrid cells soon after the fusion of diploid embryonic stem (ES) cells marked with green fluorescent protein and diploid fibroblasts labeled by blue fluorescent beads. Heterokaryons were identified by an analysis of parental mitochondrial DNAs. Within 20 h after fusion, most heterokaryons (up to 80%) had a fibroblast-like phenotype, being positive for typical fibroblast markers (collagen type I, fibronectin, lamin A/C) and for the modification me3H3K27 chromatin marking the inactive X chromosome but being negative for Oct4 and Nanog. Approximately 20% of heterokaryons had an alternative ES-like phenotype being positive for Oct4 and Nanog, with signs of reactivation of the previously inactive X-chromosome but negative for fibroblast markers. Hybrid cells having alternative phenotypes were easily identified from 24-48 h. The level of DNA methylation at the promoter of the fibroblast Oct4 allele in the ES-like hybrid cells at day 4 was similar to that of ES cells but at the same time, both parental Oct4 alleles were heavily methylated in fibroblast-like hybrid cells. Thus, bidirectional reprogramming initiated at the heterokaryon stage seems to lead to the formation of two types of hybrid cells with alternative dominance of the parental genomes. However, the further fates of two types of hybrid cells are different: ES-like hybrid cells form colonies at 4-6 days but no colonies are derived from the fibroblast-like hybrid cells. The latter grow as disconnected single cells and are unable to form colonies, like mouse embryonic fibroblasts.     

Synthesis of cycloalkane-annelated 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines and their evaluation as 5-HT6 receptor antagonists

Synthesis and biological evaluation of 1 (‘angular’) and 2 (‘linear’) сycloalkane-annelated 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines as novel ligands of the 5-HT₆ receptors are disclosed. The new compounds 1 and 2 are highly selective antagonists of the receptor with sub-nanomolar affinities (K_i <1 nM). In its structure, this new chemotype lacks a basic ionizable side chain, which is considered as the characteristic feature of the 5-HT₆ receptor antagonists pharmacophore model.     

Noncollagenous region of the streptococcal collagen‐like protein is a trimerization domain that supports refolding of adjacent homologous and heterologous collagenous domains

Proper folding of the (Gly‐Xaa‐Yaa)_n sequence of animal collagens requires adjacent N‐ or C‐terminal noncollagenous trimerization domains which often contain coiled‐coil or beta sheet structure. Collagen‐like proteins have been found recently in a number of bacteria, but little is known about their folding mechanism. The Scl2 collagen‐like protein from Streptococcus pyogenes has an N‐terminal globular domain, designated V_sp, adjacent to its triple‐helix domain. The V_sp domain is required for proper refolding of the Scl2 protein in vitro. Here, recombinant V_sp domain alone is shown to form trimers with a significant α‐helix content and to have a thermal stability of T_m = 45°C. Examination of a new construct shows that the V_sp domain facilitates efficient in vitro refolding only when it is located N‐terminal to the triple‐helix domain but not when C‐terminal to the triple‐helix domain. Fusion of the V_sp domain N‐terminal to a heterologous (Gly‐Xaa‐Yaa)_n sequence from Clostridium perfringens led to correct folding and refolding of this triple‐helix, which was unable to fold into a triple‐helical, soluble protein on its own. These results suggest that placement of a functional trimerization module adjacent to a heterologous Gly‐Xaa‐Yaa repeating sequence can lead to proper folding in some cases but also shows specificity in the relative location of the trimerization and triple‐helix domains. This information about their modular nature can be used in the production of novel types of bacterial collagen for biomaterial applications.     

Electromagnetic field effects on <Emphasis Type="Italic">Artemia</Emphasis> hatching and chromatin state

The influence of magnetic fields on hatching and chromatin state of brine shrimp, Artemia sp., was investigated. Dry Artemia cysts were exposed to a magnetic field of intensity 25 mT for 10 min. The magnetic field was applied in different variants: constant field, rotating field of different directions (right-handed and left-handed) and different magnet polarization. The effect of ultra wideband pulse radiation and microwave radiation was also investigated. The energy density on the surface of object exposed to ultra wideband pulse radiation was 10⁻², 10⁻³, 10⁻⁴, 10⁻⁵ and 10⁻⁶ W/cm², the power of microwave radiation was 10⁻⁴ and 10⁻⁵ W/cm², exposure time - 10 s. After incubation of the cysts for 48 hours in sea water the hatching percentage of Artemia from exposed cysts was higher than in controls. The number of heterochromatin granules was significantly higher in the nauplia (newborn larvae of Artemia) developed from cysts that had been exposed to magnetic and electromagnetic fields. The data obtained demonstrate an increase in percentage hatching of Artemia cysts after treatment with magnetic and electromagnetic fields and chromatin condensation in nauplia. We have also shown different effects of right-handed and left-handed rotating magnetic fields on these processes.     

Quantitative cortical synapse proteomics of a transgenic migraine mouse model with mutated CaV2.1 calcium channels

Familial hemiplegic migraine type 1 (FHM1) is caused by missense mutations in the CACNA1A gene that encodes the α1A pore‐forming subunit of Ca_V2.1 Ca²⁺ channels. Knock‐in (KI) transgenic mice expressing Ca_V2.1 Ca²⁺ channels with a human pathogenic FHM1 mutation reveal enhanced glutamatergic neurotransmission in the cortex. In this study, we employed an iTRAQ‐based LC‐LC MS/MS approach to identify differentially expressed proteins in cortical synapse proteomes of Cacna1a R192Q KI and wild‐type mice. All expression differences determined were subtle and in the range of 10–30%. Observed upregulated proteins in the mutant mice are involved in processes, such as neurite outgrowth and actin dynamics, vesicle turnover, and glutamate transporters. Our data support the view that in Cacna1a R192Q KI mice, several compensatory mechanisms counterbalancing a dysregulated glutamatergic signaling have come into effect. We propose that such adaptation mechanisms at the synapse level may play a role in the pathophysiology of FHM and possibly in the common forms of migraine.     

Genome-wide analysis of glucocorticoid receptor binding regions in adipocytes reveal gene network involved in triglyceride homeostasis

Glucocorticoids play important roles in the regulation of distinct aspects of adipocyte biology. Excess glucocorticoids in adipocytes are associated with metabolic disorders, including central obesity, insulin resistance and dyslipidemia. To understand the mechanisms underlying the glucocorticoid action in adipocytes, we used chromatin immunoprecipitation sequencing to isolate genome-wide glucocorticoid receptor (GR) binding regions (GBRs) in 3T3-L1 adipocytes. Furthermore, gene expression analyses were used to identify genes that were regulated by glucocorticoids. Overall, 274 glucocorticoid-regulated genes contain or locate nearby GBR. We found that many GBRs were located in or nearby genes involved in triglyceride (TG) synthesis (Scd-1, 2, 3, GPAT3, GPAT4, Agpat2, Lpin1), lipolysis (Lipe, Mgll), lipid transport (Cd36, Lrp-1, Vldlr, Slc27a2) and storage (S3-12). Gene expression analysis showed that except for Scd-3, the other 13 genes were induced in mouse inguinal fat upon 4-day glucocorticoid treatment. Reporter gene assays showed that except Agpat2, the other 12 glucocorticoid-regulated genes contain at least one GBR that can mediate hormone response. In agreement with the fact that glucocorticoids activated genes in both TG biosynthetic and lipolytic pathways, we confirmed that 4-day glucocorticoid treatment increased TG synthesis and lipolysis concomitantly in inguinal fat. Notably, we found that 9 of these 12 genes were induced in transgenic mice that have constant elevated plasma glucocorticoid levels. These results suggested that a similar mechanism was used to regulate TG homeostasis during chronic glucocorticoid treatment. In summary, our studies have identified molecular components in a glucocorticoid-controlled gene network involved in the regulation of TG homeostasis in adipocytes. Understanding the regulation of this gene network should provide important insight for future therapeutic developments for metabolic diseases.     

Coxiella burnetii in Humans and Ticks in Rural Senegal

Background

Q fever is a worldwide zoonotic disease caused by Coxiella burnetii. Epidemiologically, animals are considered reservoirs and humans incidental hosts.

Methodology/Principal Findings

We investigated Q fever in rural Senegal. Human samples (e.g., sera, saliva, breast milk, feces) were screened in the generally healthy population of two villages of the Sine-Saloum region. Ticks were collected in four regions. Seroprevalence was studied by immunofluorescence, and all other samples were tested by two qPCR systems for detection of C. burnetii. Positive samples were genotyped (multispacer typing) by amplification and sequencing of three spacers. Strains were isolated by cell culture. We found that the seroprevalence may be as high as 24.5% (59 of 238 studied) in Dielmo village. We identified spontaneous excretion of C. burnetii by humans through faeces and milk. Hard and soft ticks (8 species) were infected in 0–37.6%. We identified three genotypes of C. burnetii. The previously identified genotype 6 was the most common in ticks in all studied regions and the only one found in human samples. Three strains of genotype 6 of C. burnetii were also recovered from soft tick Ornithodoros sonrai. Two other genotypes found in ticks, 35 and 36, were identified for the first time.

Conclusions/Significance

Q fever should be considered a significant public health threat in Senegal. Humans, similar to other mammals, may continuously excrete C. burnetii.     

Voltage-dependent and -independent block of α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor channels

Polyamine-containing toxins and synthetic dicationic derivatives of adamantane and phenylcyclohexyl selectively antagonize Ca(2+)-permeable α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor channels. These compounds demonstrate voltage-dependent open-channel block and are trapped by closed channels. In this study, we describe an alternative mechanism of non-competitive AMPA receptor inhibition caused by 9-aminoacridine and some of its derivatives. These compounds exhibit similar potency against Ca(2+)-permeable and Ca(2+)-impermeable AMPA receptors. The inhibition is largely voltage-independent, binding and unbinding do not require presence of agonist. We conclude that 9-aminoacridine binds to a shallow site in the AMPA receptor, which is located above the activation gate. A comparison of three-dimensional structures of the antagonists suggests that the 'V-like' shape of the hydrophobic headgroup favors voltage-dependent binding to the deep site in the channel pore, whereas the compounds possessing flat aromatic headgroups preferably bind to the shallow site. The characterization of the novel mechanism of AMPA receptor channel antagonism opens a way to develop a new family of pharmacological agents, which can be of scientific and practical importance.     

Enhancement of TREK1 channel surface expression by protein-protein interaction with β-COP

TREK1 belongs to a family of two-pore-domain K⁺ (K_2P) channels and produce background currents that regulate cell excitability. In the present study, we identified a vesicle transport protein, β-COP, as an interacting partner by yeast two-hybrid screening of a human brain cDNA library with N-terminal region of TREK1 (TREK1-N) as bait. Several in vitro and in vivo binding assays confirmed the protein-protein interaction between TREK1 and β-COP. We also found that β-COP was associated with TREK1 in native condition at the PC3 cells. When RFP-β-COP was co-transfected with GFP-TREK1 into COS-7 cells, both proteins were found localized to the plasma membrane. In addition, the channel activity and surface expression of GFP-TREK1 increased dramatically by co-transfection with RFP-β-COP. Surface expression of the TREK1 channel was also clearly reduced with the addition of β-COP-specific shRNA. Collectively, these data suggest that β-COP plays a critical role in the forward transport of TREK1 channel to the plasma membrane.     

Femtosecond primary charge separation in Synechocystis sp. PCC 6803 photosystem I

The ultrafast (< 100 fs) conversion of delocalized exciton into charge-separated state between the primary donor P700 (bleaching at 705 nm) and the primary acceptor A₀ (bleaching at 690 nm) in photosystem I (PS I) complexes from Synechocystis sp. PCC 6803 was observed. The data were obtained by application of pump-probe technique with 20-fs low-energy pump pulses centered at 720 nm. The earliest absorbance changes (close to zero delay) with a bleaching at 690 nm are similar to the product of the absorption spectrum of PS I complex and the laser pulse spectrum, which represents the efficiency spectrum of the light absorption by PS I upon femtosecond excitation centered at 720 nm. During the first ∼ 60 fs the energy transfer from the chlorophyll (Chl) species bleaching at 690 nm to the Chl bleaching at 705 nm occurs, resulting in almost equal bleaching of the two forms with the formation of delocalized exciton between 690-nm and 705-nm Chls. Within the next ∼ 40 fs the formation of a new broad band centered at ∼ 660 nm (attributed to the appearance of Chl anion radical) is observed. This band decays with time constant simultaneously with an electron transfer to A₁ (phylloquinone). The subtraction of kinetic difference absorption spectra of the closed (state P700⁺A₀A₁) PS I reaction center (RC) from that of the open (state P700A₀A₁) RC reveals the pure spectrum of the P700⁺A₀⁻ ion-radical pair. The experimental data were analyzed using a simple kinetic scheme: An* [(PA₀)*A₁ P⁺A₀⁻A₁] P⁺A₀A₁⁻, and a global fitting procedure based on the singular value decomposition analysis. The calculated kinetics of transitions between intermediate states and their spectra were similar to the kinetics recorded at 694 and 705 nm and the experimental spectra obtained by subtraction of the spectra of closed RCs from the spectra of open RCs. As a result, we found that the main events in RCs of PS I under our experimental conditions include very fast (< 100 fs) charge separation with the formation of the P700⁺A₀⁻A₁ state in approximately one half of the RCs, the ∼ 5-ps energy transfer from antenna Chl* to P700A₀A₁ in the remaining RCs, and ∼ 25-ps formation of the secondary radical pair P700⁺A₀A₁⁻.