Molekulare Untersuchungen der mex-3/pal-1 Interaktion und genomweiter phylogenetischer Vergleich des MEX-3 Protein Netzwerks in Nematoden

Die korrekte Lokalisation bestimmter maternaler Genprodukte ist essentiell für die Embryonalentwicklung des Modellorganismus C. elegans. Durch den Eintritt des Spermiums am posterioren Pol kommt es schon vor der ersten Teilung zum Bruch der Symmetrie und zur Etablierung der anterior posterioren Körperachse. Der anterior posterioren Verteilung der PAR Protein Komplexe folgt eine asymmetrische Teilung der Zygote in eine Soma- (AB) und eine Keimbahnzelle (P1). Letztere teilt sich im Folgenden asymmetrisch in die Keimbahnzelle P2 und die endo mesodermale Gründerzelle EMS, während sich AB symmetrisch in ABa und ABp teilt. Für die Musterbildung entlang der anterior posterioren Achse im 4 Zellstadium von C. elegans ist die Lokalisation des MEX-3 Proteins in den anterioren Blastomeren ABa und ABp, sowie die der pal-1 mRNA in den posterioren Zellen EMS und P2 notwendig. Hierbei wirkt das mRNA bindende KH Domänen Protein MEX-3 als negativer Regulator der pal-1 mRNA, indem es an das MEX-3 Recognition Element (MRE), eine konservierte Sequenz in der 3‘UTR bindet (Pagano et al., 2009)und so deren Abbau initiiert. Da prominente Unterschiede auf zellulärer Ebene gefunden worden waren, die für eine korrekte Frühentwicklung von C. elegans essentiell sind, habe ich in meiner Arbeit 9 Nematodenspezies auf zelluläre und molekulare Unterschiede zu C. elegans in untersucht. In keinem von diesen konnte ein zu C. elegans vergleichbares mex-3/pal-1 mRNA Expressionsmuster gefunden werden. Alle von mir untersuchten Nematoden besitzen im Gegensatz zu C. elegans sowohl für mex-3, als auch für pal-1 eine späte mRNA Expressionsdomäne. Für diese Arbeit von besonderer Bedeutung ist aber die frühe Lokalisation von mex-3 und pal-1 mRNA, die bei C. elegans anterior bzw. posterior zu finden ist. Diese konnte ebenfalls bei keinem untersuchten Nematoden gefunden werden. Es treten vielmehr gravierende Unterschiede im Expressionsmuster im Vergleich zu C. elegans auf. Sogar in einem nahen Verwandten von C. elegans sind sowohl die mex-3, als auch die pal-1 mRNA in den posterioren Blastomeren (EMS und P2) lokalisiert. In dieser Arbeit durchgeführte Genomsequenzanalysen zeigen, dass der, von C. elegans bekannte Mechanismus der Lokalisation von mex-3 und pal-1 mRNA innerhalb der Nematoden nicht konserviert sein kann. Das für die Bindung des MEX-3 Proteins an die pal-1 mRNA entscheidende MRE (Pagano et al., 2009) konnte von mir nur innerhalb der Gattung Caenorhabditis und in keiner der übrigen untersuchten pal-1 3’UTR Sequenzen gefunden werden. Dies lässt darauf schließen, dass bei den übrigen Nematoden keine negative Regulation der pal-1 mRNA durch das MEX-3 Protein stattfindet. Auch die für C. elegans essentielle Lokalisation des MEX-3 Proteins muss in den untersuchten Nematoden anders erfolgen. Homologe der MEX-5 und MEX-6 Proteine, die positive Regulatoren des MEX-3 Proteins sind und für dessen korrekte Lokalisierung in den anterioren Blastomeren ABa und ABp notwendig sind, konnten in keinem der untersuchten Nematoden gefunden werden. Das in der C. elegans Gonade zur Lokalisation der mex-3 und pal-1 mRNA essentielle GLD-1 Protein fehlt ebenfalls bei allen analysierten Spezies. Sein Homolog ASD-2, das bei C. elegans eine ganz andere Funktion erfüllt, konnte jedoch identifiziert werden. Möglicherweise übernimmt ASD-2 eine entscheidende Rolle in der Lokalisation der mex-3 und pal-1 mRNA nicht nur in der Gonade sondern auch während der frühen Embryonalentwicklung Um die Notwendigkeit des MRE für die mex-3/pal-1 Interaktion zu untersuchen, wurden transgene C. elegans hergestellt, die ein GFP::pal-1 3’UTR Fusionskonstrukt trugen

Influence of Myocardial Infarction on QRS Properties: A Simulation Study

The interplay between structural and electrical changes in the heart after myocardial infarction (MI) plays a key role in the initiation and maintenance of arrhythmia. The anatomical and electrophysiological properties of scar, border zone, and normal myocardium modify the electrocardiographic morphology, which is routinely analysed in clinical settings. However, the influence of various MI properties on the QRS is not intuitively predictable.In this work, we have systematically investigated the effects of 17 post-MI scenarios, varying the location, size, transmural extent, and conductive level of scarring and border zone area, on the forward-calculated QRS. Additionally, we have compared the contributions of different QRS score criteria for quantifying post-MI pathophysiology.The propagation of electrical activity in the ventricles is simulated via a Eikonal model on a unified coordinate system.The analysis has been performed on 49 subjects, and the results imply that the QRS is capable of identifying MI, suggesting the feasibility of inversely reconstructing infarct regions from QRS.There exist sensitivity variations of different QRS criteria for identifying 17 MI scenarios, which is informative for solving the inverse problem.Comment: 10 pages, accpeted by FIMH 202

Electrocardiogram Analysis Reveals Ionic Current Dysregulation Relevant for Atrial Fibrillation

Antiarrhythmic drug choice for atrial fibrillation (AF) neglects the individual ionic current profile of the patient, even though it determines drug safety and efficacy. We hypothesize that the electrocardiogram (ECG) might contain information critical for pharmacological treatment personalization. Thus, this study aims to identify the extent of atrial ionic information embedded in the ECG, using multi-scale modeling and simulation. A dataset of 1,000 simulated ECGs was computed using a population of human-based whole-atria models with 200 individual ionic profiles and 5 different torso-atria orientations. A regression neural network was built to predict key atrial ionic conductances based on P- and T$_a$ -wave biomarkers. The neural network predicted, with >80% precision, the density of seven ionic currents relevant for AF, namely, ultra-rapid (I$_{Kur}$ ), rapid (I$_{Kr}$ ), outward transient (I$_{to}$ ), inward rectifier K$^+$ (I$_{K1}$ ), L-type Ca$^{2+}$ (I$_{CaL}$ ), Na$^+$ /K$^+$ pump (I$_{NaK}$ ) and fast Na$^+$ (I$_{Na}$) currents. These ionic densities were identified through the P- (i.e., I$_{Na}$), Ta - (i.e., I$_{K1}$ , I$_{NaK}$) or both waves (i.e., I$_{Kur}$ , I$_{Kr}$ , I$_{to}$ , I$_{CaL}$), providing a non- invasive characterization of the atrial electrophysiology. This could improve patient stratification and cardiac safety and the efficacy of AF pharmacological treatment

Inference of ventricular activation properties from non-invasive electrocardiography

The realisation of precision cardiology requires novel techniques for the non-invasive characterisation of individual patients' cardiac function to inform therapeutic and diagnostic decision-making. The electrocardiogram (ECG) is the most widely used clinical tool for cardiac diagnosis. Its interpretation is, however, confounded by functional and anatomical variability in heart and torso. In this study, we develop new computational techniques to estimate key ventricular activation properties for individual subjects by exploiting the synergy between non-invasive electrocardiography and image-based torso-biventricular modelling and simulation. More precisely, we present an efficient sequential Monte Carlo approximate Bayesian computation-based inference method, integrated with Eikonal simulations and torso-biventricular models constructed based on clinical cardiac magnetic resonance (CMR) imaging. The method also includes a novel strategy to treat combined continuous (conduction speeds) and discrete (earliest activation sites) parameter spaces, and an efficient dynamic time warping-based ECG comparison algorithm. We demonstrate results from our inference method on a cohort of twenty virtual subjects with cardiac volumes ranging from 74 cm3 to 171 cm3 and considering low versus high resolution for the endocardial discretisation (which determines possible locations of the earliest activation sites). Results show that our method can successfully infer the ventricular activation properties from non-invasive data, with higher accuracy for earliest activation sites, endocardial speed, and sheet (transmural) speed in sinus rhythm, rather than the fibre or sheet-normal speeds.Comment: Submitted to Medical Image Analysi

The genome of Romanomermis culicivorax:revealing fundamental changes in the core developmental genetic toolkit in Nematoda

Background: The genetics of development in the nematode Caenorhabditis elegans has been described in exquisite detail. The phylum Nematoda has two classes: Chromadorea (which includes C. elegans) and the Enoplea. While the development of many chromadorean species resembles closely that of C. elegans, enoplean nematodes show markedly different patterns of early cell division and cell fate assignment. Embryogenesis of the enoplean Romanomermis culicivorax has been studied in detail, but the genetic circuitry underpinning development in this species has not been explored. Results: We generated a draft genome for R. culicivorax and compared its gene content with that of C. elegans, a second enoplean, the vertebrate parasite Trichinella spiralis, and a representative arthropod, Tribolium castaneum. This comparison revealed that R. culicivorax has retained components of the conserved ecdysozoan developmental gene toolkit lost in C. elegans. T. spiralis has independently lost even more of this toolkit than has C. elegans. However, the C. elegans toolkit is not simply depauperate, as many novel genes essential for embryogenesis in C. elegans are not found in, or have only extremely divergent homologues in R. culicivorax and T. spiralis. Our data imply fundamental differences in the genetic programmes not only for early cell specification but also others such as vulva formation and sex determination. Conclusions: Despite the apparent morphological conservatism, major differences in the molecular logic of development have evolved within the phylum Nematoda. R. culicivorax serves as a tractable system to contrast C. elegans and understand how divergent genomic and thus regulatory backgrounds nevertheless generate a conserved phenotype. The R. culicivorax draft genome will promote use of this species as a research model

Neuroprotective effects of the multitarget agent AVCRI104P3 in brain of middle-aged mice

Molecular factors involved in neuroprotection are key in the design of novelmultitarget drugs in aging and neurodegeneration. AVCRI104P3 is a huprine derivative that exhibits potent inhibitory effects on human AChE, BuChE, and BACE-1 activities, as well as on AChE-induced and self-induced Abeta aggregation. More recently, cognitive protection and anxiolytic-like effects have also been reported in mice treated with this compound. Now, we have assessed the ability of AVCRI104P3 (0.43 mg/kg, 21 days) to modulate the levels of some proteins involved in the anti-apoptotic/apoptotic processes (pAkt1, Bcl2, pGSK3beta, p25/p35), inflammation (GFAP and Iba1) and neurogenesis in C57BL/6 mice. The effects of AVCRI104P3 on AChE-R/AChE-S isoforms have been also determined. We have observed that chronic treatment of C57BL/6 male mice with AVCRI104P3 results in neuroprotective effects, increasing significantly the levels of pAkt1 and pGSK3beta in the hippocampus and Bcl2 in both hippocampus and cortex, but slightly decreasing synaptophysin levels. Astrogliosis and neurogenic markers GFAP and DCX remained unchanged after AVCRI104P3 treatment, whereas microgliosis was found to be significantly decreased pointing out the involvement of this compound in inflammatory processes. These results suggest that the neuroprotective mechanisms that are behind the cognitive and anxiolytic effects of AVCRI104P3 could be partly related to the potentiation of some anti-apoptotic and anti-inflammatory proteins and support the potential of AVCRI104P3 for the treatment of brain dysfunction associated with aging and/or dementi

Biological activity of extracts from some Mediterranean Macrophytes

5 páginas, 1 tablaSeventy one species of marine macrophytes from the Central Mediterranean have been screened for the production of antibacterial, antifungal, antiviral, cytotoxic and antimitotic compounds. Sixty five of the species displayed some kind of activity and most of them were active on more than one organism or cell tested. Antifungal activity was the most widespread (70% of the plants), whilst the incidence of antibacterial activity was extraordinarily low (6% of the plants). Of the plants tested 21% showed antiviral activity, 35% were cytotoxic and nearly 50% had antimitotic properties. The maximum level of activity was found among the Chlorophyfa; some members of the Bryopsidales (Flabellia petiolata, Caulerpa prolifera, Halimeda tuna) were the most active species. Most of the dominant species in Mediterranean phytobenthic communities (Corallina elongata, Lithophyllurn lichenoides, Phyllophora crispa, Cystoseira spp., Halopteris spp., Codium spp., Halimeda tuna, Valonia utricularis, Posidonia oceanica, Zostera noltii and Cyrnodocea nodosa) exhibited strong antifungal properties.This study was supported by the projects ECOFARM and CICYT MAR91-0528.Peer reviewe

Black hole uniqueness theorems and new thermodynamic identities in eleven dimensional supergravity

We consider stationary, non-extremal black holes in 11-dimensional supergravity having isometry group $\mathbb{R} \times U(1)^8$. We prove that such a black hole is uniquely specified by its angular momenta, its electric charges associated with the various 7-cycles in the manifold, together with certain moduli and vector valued winding numbers characterizing the topological nature of the spacetime and group action. We furthermore establish interesting, non-trivial, relations between the thermodynamic quantities associated with the black hole. These relations are shown to be a consequence of the hidden $E_{8(+8)}$ symmetry in this sector of the solution space, and are distinct from the usual "Smarr-type" formulas that can be derived from the first law of black hole mechanics. We also derive the "physical process" version of this first law applicable to a general stationary black hole spacetime without any symmetry assumptions other than stationarity, allowing in particular arbitrary horizon topologies. The work terms in the first law exhibit the topology of the horizon via the intersection numbers between cycles of various dimensions.Comment: 50pp, 3 figures, v2: references added, correction in appendix B, conclusions added, v3: reference section edited, typos removed, minor changes in appendix