A frizzled quest to dissect the molecular pharmacology of WNT signaling : from biology to signaling mechanism(s)

The wingless/int1 (WNT)/Frizzled (FZD) family of signal transduction pathways is highly conserved across species and controls essential physiological functions important for embryonic development, stem cell renewal, proliferation, differentiation, and cell polarity. Dysregulation of these signaling pathways leads to developmental abnormalities or other conditions such as inflammation, cancer, or neurological disorders. In mammals, 19 different WNTs can bind to and interact with ten isoforms of FZD in a plethora of combinations. These seven transmembrane-spanning receptors are categorized in the Class Frizzled within the superfamily of G protein-coupled receptors (GPCRs). Several important co-factors are known to aid in the activation of WNT/FZD signaling, such as Disheveled (DVL) or low density lipoprotein receptor related protein 5 and 6 (LRP5/6). In addition, interactions of FZDs with heterotrimeric G proteins have continuously been reported. Upon ligand binding, activation of β-catenin-dependent and/or β-catenin-independent downstream signaling pathways takes place. The overall aim of this thesis was to shed light on mechanistics of WNT/FZD signaling and pharmacology from different angles: In paper I, we investigated the presence and role of WNT-5A in human glioblastomas, a WNT important for neurological functions in the central nervous system (CNS) and found to be dysregulated in many cancers. In this study, we describe the correlative nature of high WNT-5A expression with upregulation of genes involved in immunological processes as well as increased microglia infiltration in the tumor microenvironment. In paper II and III, we focus on FZD4, a FZD isoform important for retinal vascularization. We provide functional evidence for the interaction of FZD4 with heterotrimeric Gα12/13, which is independent of DVL and LRP5/6, and show activation of downstream signaling events. We further describe a novel signaling route through NorrinFZD4-Gα12/13, which exerts an inhibitory effect on the classical Norrin-FZD4-β-catenin signaling pathway known to be important in angiogenesis, thus arguing for a concept of cross-talk and feedback inhibition from the same FZD isoform, a notion that is as of yet completely unappreciated. In addition, this thesis tries to point out the current limitations and struggles in the field of studying WNT/FZD signaling and the need for further studies identifying crucial links to signal specification, which would aid in future drug development targeting this pathway

Identifizierung von Haplotypen bei Pityogenes chalcographus (Col., Scolytidae) durch SSCP

Pityogenes chalcographus is a widely distributed spruce pest in Eurasia (KNIZEK et al. 2005). In 70ies, E. Führer studied the intraspecific variation of this spruce bark beetle and detected race differentiation among European populations based on crossing experiments (FÜHRER 1977), morphological characters FÜHRER 1978) and allozyme electrophoresis (RITZENGRUBER 1990). In order to verify the hypothesis differentiation, we analysed diverse European P. chalcographus populations using the Cytochrome Oxidase gene (COI) of the mitochondrial DNA. The complete COI gene of 96 individuals was sequenced. In facilitate the screening of the European populations, we applied a PCR-SSCP method. This polyacrylamide electrophoresis technique offers a sensitive but inexpensive, rapid and convenient method for detecting polymorphisms, reducing the amount of samples that require sequencing (SUNNUCKS et al. 2000).Der Kupferstecher Pityogenes chalcographus (Coleoptera, Scolytidae) gehört zu den am weitesten verbreiteten Borkenkäfern Europas. Käferpopulationen aus verschiedenen Gebieten Europas zeigten eine hohe Divergenz hinsichtlich der Nukleotidzusammensetzung des mitochondrialen Cytochrom Oxidase I Gens. Die Unterschiede betragen bis zu 2,26% zwischen einzelnen Herkünften. Die phylogenetische Auswertung der Sequenzen des kompletten Gens (1503bp) ergab einen 6-astigen Baum mit insgesamt 34 Haplotypen. Ausgehend von dieser Struktur wurden Primerpaare entworfen, um jeweils etwa 250 bp lange mutationsreiche Abschnitte des COI Gens zu amplifizieren. Die PCR Produkte wurden mittels Single Strand Conformation Polymorphism (SSCP) untersucht. Zwischen den einzelnen Haplotypen konnten zahlreiche Polymorphismen erkannt werden. Diese eignen sich als schnelles Werkzeug zum screening einzelner Individuen und verringern signifikant die Notwendigkeit klassischer Sequenzierreaktionen

Molekulare Ökologie in der Forstentomologie

Nach der Wiederentdeckung der Mendelschen Regeln Anfang des 20. Jahrhunderts waren es unter anderem Theodosius Dobzhansky und Ernst Mayr, die Evolution erstmals durch die Analyse von Populationen untersuchten. Bis 1980 wurden für diese populationsgenetischen Analysen morphologische, cytologische und enzymelektrophoretische Marker verwendet. Durch die Entdeckung der PCR wurde das Arbeiten mit DNA wesentlich erleichtert. Im Laufe der Zeit setzte sich der Begriff Molekulare Ökologie durch, mit dem man jenen Bereich beschreiben will, der molekulare Methoden der Populationsgenetik und der Genomanalyse mit ökologischen Fragestellungen verbindet. Genetische Marker können vergangene als auch zur Zeit ablaufende Prozesse aufzeigen. Mit Hilfe solcher Marker kann man einerseits Hinweise auf die Refugialgebiete von Organismen während der letzten Eiszeiten erhalten, anderseits Prozesse wie Genfluß, Selektion oder genetische Drift aufzeigen. Bei den meisten der von uns im Folgenden vorgestellten Arbeiten steht das Sequenzieren mitochondrialer Abschnitte im Vordergrund. Die mitochondriale DNA hat durch ihre im Vergleich zu nuklearer DNA erhöhte Mutationsrate und vereinfachte Genstruktur den Vorteil, bei intraspezifischen Fragestellungen gute Resultate zu erzielen.The term Molecular Ecology appeared after the discovery that DNA can be amplified in-vitro by PCR in the late 1980’s. Molecular Ecology can be defined as the scientific field that combines genetic techniques, population genetics and genomics with ecological relevant questions. Since then, many papers have been published in Molecular Ecology. Here we present some examples focusing on Palaearctic scolytid species

Multi-atlas segmentation using clustering, local non-linear manifold embeddings and target-specific templates

Multi-atlas segmentation (MAS) has become an established technique for the automated delineation of anatomical structures. The often manually annotated labels from each of multiple pre-segmented images (atlases) are typically transferred to a target through the spatial mapping of corresponding structures of interest. The mapping can be estimated by pairwise registration between each atlas and the target or by creating an intermediate population template for spatial normalisation of atlases and targets. The former is done at runtime which is computationally expensive but provides high accuracy. In the latter approach the template can be constructed from the atlases offline requiring only one registration to the target at runtime. Although this is computationally more efficient, the composition of deformation fields can lead to decreased accuracy. Our goal was to develop a MAS method which was both efficient and accurate. In our approach we create a target-specific template (TST) which has a high similarity to the target and serves as intermediate step to increase registration accuracy. The TST is constructed from the atlas images that are most similar to the target. These images are determined in low-dimensional manifold spaces on the basis of deformation fields in local regions of interest. We also introduce a clustering approach to divide atlas labels into meaningful sub-regions of interest and increase local specificity for TST construction and label fusion. Our approach was tested on a variety of MR brain datasets and applied to an in-house dataset. We achieve state-of-the-art accuracy while being computationally much more efficient than competing methods. This efficiency opens the door to the use of larger sets of atlases which could lead to further improvement in segmentation accuracy

Multi-atlas segmentation using clustering, local non-linear manifold embeddings and target-specific templates

Multi-atlas segmentation (MAS) has become an established technique for the automated delineation of anatomical structures. The often manually annotated labels from each of multiple pre-segmented images (atlases) are typically transferred to a target through the spatial mapping of corresponding structures of interest. The mapping can be estimated by pairwise registration between each atlas and the target or by creating an intermediate population template for spatial normalisation of atlases and targets. The former is done at runtime which is computationally expensive but provides high accuracy. In the latter approach the template can be constructed from the atlases offline requiring only one registration to the target at runtime. Although this is computationally more efficient, the composition of deformation fields can lead to decreased accuracy. Our goal was to develop a MAS method which was both efficient and accurate. In our approach we create a target-specific template (TST) which has a high similarity to the target and serves as intermediate step to increase registration accuracy. The TST is constructed from the atlas images that are most similar to the target. These images are determined in low-dimensional manifold spaces on the basis of deformation fields in local regions of interest. We also introduce a clustering approach to divide atlas labels into meaningful sub-regions of interest and increase local specificity for TST construction and label fusion. Our approach was tested on a variety of MR brain datasets and applied to an in-house dataset. We achieve state-of-the-art accuracy while being computationally much more efficient than competing methods. This efficiency opens the door to the use of larger sets of atlases which could lead to further improvement in segmentation accuracy

Pityogenes chalcographus (Coleoptera, Scolytinae) at the southernmost borderline of Norway spruce (Picea abies) in Greece

Το φλοιοφάγο έντομο Pityogenes chalcographus L. αποτελεί ένα από τα κύρια βλαπτικά έντομα της υποοικογένειας Scolytinae, που είναι ευρέως εξαπλωμένο στην Ευρώπη. Ο κύριος ξενιστής του εντόμου είναι η ερυθρελάτη (Picea abies) ενώ επίσης μπορεί να αναπτυχθεί επι- τυχώς σε αρκετά ακόμη είδη κωνοφόρων όπως το πεύκο (Pinus sp.), το έλατο (Abies alba), η λάρικα (Larix decidua) και η ψευδοτσούγκα (Pseudotsuga douglasii). Παρά το γεγονός ότι η φυσική εξάπλωση του εντόμου συμπίπτει με αυτή του κύριου ξενιστή του, το P. chalcographus δεν έχει καταγραφεί ούτε και παγιδευτεί στο δάσος ερυθρελάτης στην Ελατιά Δρά- μας, που αποτελεί το νοτιότερο άκρο της φυσικής, αυτόχθονης εξάπλωσης της ερυθρελάτης. Στα πλαίσια της έρευνας εγκαταστάθηκαν στο δάσος της Ελατιάς πέντε φερομονικές παγίδες, οι οποίες περιείχαν την προσελκυστική ουσία chalcogran. Ο συνολικός αριθμός των φλοιοφά- γων εντόμων που συγκεντρώθηκαν μετά το πέρας της περιόδου που οι παγίδες ήταν στο πεδίο, ανήλθε σε αρκετές χιλιάδες ατόμων. Η ερυθρελάτη που αναπτύσσεται στο φυσικό δάσος της Ελατιάς βρίσκεται σε οριακό περιβάλλον όσον αφορά τις συνθήκες ανάπτυξής της, γεγονός που επιτείνεται και από την κλιματική αλλαγή, η οποία γίνεται ακόμη πιο εμφανής σε τέτοια περιβάλλοντα. Η συνδυαστική δράση αυτών των δύο παραγόντων μπορεί να καταστήσει την ερυθρελάτη ιδιαίτερα ευάλωτη στην προσβολή του P. chalcographus, γεγονός που θα μπο- ρούσε εν δυνάμει να θέσει σε κίνδυνο και τα ενδημικά είδη πεύκου της Ελλάδας, καθώς το φλοιοφάγο αυτό έντομο έχει την δυνατότητα ανάπτυξης σε μια πλειάδα ξενιστών.The six toothed bark beetle, Pityogenes chalcographus L. (Coleoptera: Scolytinae) is a widely distributed pest in Europe, infesting mainly Norway spruce (Picea abies) as well as other conifer species such as Pinus sp., Abies alba, Larix deciduas, L. sibirica and Pseudotsuga douglasii. Even though the distribution of this bark beetle coincides that of its main host tree, P. abies, the occurrence of P. chalcographus has never been recorded in the spruce forest of Elatia-Drama, Northern Greece, which is the southernmost area of the natural, autochthonous distribution of P. abies. In this study we installed five pheromone traps baited with chalcogran dispensers in the forest of Elatia. The total number of bark beetles attracted to these traps exceeded several thousands of individuals. Norway spruce trees growing in the natural forest of Elatia demonstrate low vigor, something that can be attributed to the marginal environmental conditions in concert with the effects of climate change. The combination of these factors inhibits the regular growth of spruce, rendering trees more susceptible to the attack of P. chalcographus

Pityogenes chalcographus (Coleoptera, Scolytinae) at the southernmost borderline of Norway spruce (Picea abies) in Greece

Το φλοιοφάγο έντομο Pityogenes chalcographus L. αποτελεί ένα από τα κύρια βλαπτικά έντομα της υποοικογένειας Scolytinae, που είναι ευρέως εξαπλωμένο στην Ευρώπη. Ο κύριος ξενιστής του εντόμου είναι η ερυθρελάτη (Picea abies) ενώ επίσης μπορεί να αναπτυχθεί επι- τυχώς σε αρκετά ακόμη είδη κωνοφόρων όπως το πεύκο (Pinus sp.), το έλατο (Abies alba), η λάρικα (Larix decidua) και η ψευδοτσούγκα (Pseudotsuga douglasii). Παρά το γεγονός ότι η φυσική εξάπλωση του εντόμου συμπίπτει με αυτή του κύριου ξενιστή του, το P. chalcographus δεν έχει καταγραφεί ούτε και παγιδευτεί στο δάσος ερυθρελάτης στην Ελατιά Δρά- μας, που αποτελεί το νοτιότερο άκρο της φυσικής, αυτόχθονης εξάπλωσης της ερυθρελάτης. Στα πλαίσια της έρευνας εγκαταστάθηκαν στο δάσος της Ελατιάς πέντε φερομονικές παγίδες, οι οποίες περιείχαν την προσελκυστική ουσία chalcogran. Ο συνολικός αριθμός των φλοιοφά- γων εντόμων που συγκεντρώθηκαν μετά το πέρας της περιόδου που οι παγίδες ήταν στο πεδίο, ανήλθε σε αρκετές χιλιάδες ατόμων. Η ερυθρελάτη που αναπτύσσεται στο φυσικό δάσος της Ελατιάς βρίσκεται σε οριακό περιβάλλον όσον αφορά τις συνθήκες ανάπτυξής της, γεγονός που επιτείνεται και από την κλιματική αλλαγή, η οποία γίνεται ακόμη πιο εμφανής σε τέτοια περιβάλλοντα. Η συνδυαστική δράση αυτών των δύο παραγόντων μπορεί να καταστήσει την ερυθρελάτη ιδιαίτερα ευάλωτη στην προσβολή του P. chalcographus, γεγονός που θα μπο- ρούσε εν δυνάμει να θέσει σε κίνδυνο και τα ενδημικά είδη πεύκου της Ελλάδας, καθώς το φλοιοφάγο αυτό έντομο έχει την δυνατότητα ανάπτυξης σε μια πλειάδα ξενιστών.The six toothed bark beetle, Pityogenes chalcographus L. (Coleoptera: Scolytinae) is a widely distributed pest in Europe, infesting mainly Norway spruce (Picea abies) as well as other conifer species such as Pinus sp., Abies alba, Larix deciduas, L. sibirica and Pseudotsuga douglasii. Even though the distribution of this bark beetle coincides that of its main host tree, P. abies, the occurrence of P. chalcographus has never been recorded in the spruce forest of Elatia-Drama, Northern Greece, which is the southernmost area of the natural, autochthonous distribution of P. abies. In this study we installed five pheromone traps baited with chalcogran dispensers in the forest of Elatia. The total number of bark beetles attracted to these traps exceeded several thousands of individuals. Norway spruce trees growing in the natural forest of Elatia demonstrate low vigor, something that can be attributed to the marginal environmental conditions in concert with the effects of climate change. The combination of these factors inhibits the regular growth of spruce, rendering trees more susceptible to the attack of P. chalcographus

A Worker-Like Female of Myrmica sabuleti (Meinert, 1861) (Hymenoptera: Formicidae: Myrmicinae) in a Pitfall Trap with Five Mermithids (Nematoda: Mermithidae) Protruding from the Gaster

A worker-like female of Myrmica sabuleti (Meinert, 1861), pitfall-trapped near Jena, Germany, in late summer 2016, was infested by five postparasitic juvenile mermithids. They poked out of the ant´s gaster as a trail of seven filaments of various lengths. Apart from its swollen gaster, the ant differed from conspecifics in several morphometric parameters. Using both morphological and molecular techniques, the parasite family Mermithidae was confirmed. Our stray find raises multiple questions concerning the genus and species identity of the parasite, its biology, and the infestation rate of the host ant population. More mermithid awareness by the various researchers working with Myrmica will help, but directed fieldwork, experimental life-history research, and molecular studies are needed to emancipate progress in ant-mermithid research from serendipity