Die Bedeutung der Ephrine und Eph-Rezeptoren für die Entwicklung des somatosensorischen Systems in der Maus und die Auswirkungen des funktionellen Knockouts von Ephrin A5 auf die Genexpression

Die Eph-Rezeptoren und ihre membranständigen Liganden, die Ephrine, vermitteln durch Zell-Zell-Adhäsion bzw. –Repulsion die Lenkung von auswachsenden Axonen und migrierenden Zellen. Am Beispiel des thalamokortikalen Systems der Rodentia wurde beschrieben, dass einige Ephrine und Eph-Rezeptoren ein interareales Mapping der Axone auf dem Niveau des ventralen Telencephalons aber auch die Topografie der thalamischen Projektionen innerhalb eines kortikalen Areals ermöglichen, wo sie wiederum an der Ausbildung schichtspezifischer Projektion thalamischer Eingänge und kortikaler Schaltkreise beteiligt sind. Diese Arbeit liefert am Modell des somatosensorischen Systems erstmals ein umfassendes und vergleichendes Expressionsscreening aller Ephrine und Eph-Rezeptoren an den für die Entwicklung wichtigen embryonalen und postnatalen Entwicklungsstadien mit Sonden bekannter Markierungseffizienz und getesteter Kreuzhybridisierungen. Hierdurch konnte das bestehende Wissen über die für die neuronale Entwicklung wichtigen Gene aus der Familie der Ephrine und Eph-Rezeptoren und mögliche Interaktionspartner, auch hinsichtlich des Reverse Signaling, erweitert werden. Insgesamt waren im Verlauf der Entwicklung im somatosensorischen System 7 Ephrin-Liganden und 11 Eph-Rezeptoren exprimiert; darunter 4 A-Ephrine und 6 EphA-Rezeptoren sowie alle B-Ephrine und EphB-Rezeptoren. Auffällig war, dass sowohl im Thalamus als auch im somatosensorischen Kortex die mRNA einiger Liganden und Rezeptoren entweder transient oder erst zu späteren Entwicklungsstadien nachweisbar war

Multiple roles of ephrins during the formation of thalamocortical projections: maps and more

ABSTRACT: The functional architecture of the cerebral cortex is based on intrinsic connections that precisely link neurons from distinct cortical laminae as well as layer-specific afferent and efferent projections. Experimental strategies using in vitro assays originally developed by Friedrich Bonhoeffer have suggested that positional cues confined to individual layers regulate the assembly of local cortical circuits and the formation of thalamocortical projections. One of these wiring molecules is ephrinA5, a ligand for Eph receptor tyrosine kinases. EphrinA5 and Eph receptors exhibit highly dynamic expression patterns in distinct regions of the cortex and thalamus during early and late stages of thalamocortical and cortical circuit formation. In vitro assays suggest that ephrinA5 is a multifunctional wiring molecule for different populations of cortica

Essential role of mitochondrial Stat3 in p38MAPK mediated apoptosis under oxidative stress

Stat3 is an oncogene, frequently associated with malignant transformation. A body of evidence implicates that phospho-Stat3(Y705) contributes to its nucleic translocation, while phospho-Stat3(S727) leads to the accumulation in mitochondria. Both are of importance for tumor cell proliferation. In comparison to well-characterized signaling pathways interplaying with Stat3(Y705), little is known about Stat3(S727). In this work, we studied the influence of Stat3 deficiency on the viability of cells exposed to H2O2 or hypoxia using siRNA and CRISPR/Cas9 genome-editing. We found dysregulation of mitochondrial activity, which was associated with excessive ROS formation and reduced mitochondrial membrane potential, and observed a synergistic effect for oxidative stress-mediated apoptosis in Stat3-KD cells or cells carrying Stat3(Y705F), but not Stat3(S727D), suggesting the importance of functional mitochondrial Stat3 in this context. We also found that ROS-mediated activation of ASK1/p38(MAPK) was involved and adding antioxidants, p38(MAPK) inhibitor, or genetic repression of ASK1 could easily rescue the cellular damage. Our finding reveals a new role of mitochondrial Stat3 in preventing ASK1/p38(MAPK)-mediated apoptosis, wich further support the notion that selective inhibition mitochondrial Stat3 could provide a primsing target for chemotherapy

Gene Expression of Quaking in Sporadic Alzheimer’s Disease Patients is Both Upregulated and Related to Expression Levels of Genes Involved in Amyloid Plaque and Neurofibrillary Tangle Formation

Quaking (QKI) is a gene exclusively expressed within glial cells. QKI has previously been implicated in various neurological disorders and diseases, including Alzheimer’s disease (AD), a condition for which increasing evidence suggests a central role of glia cells. The objective of the present study was to investigate the expression levels of QKI and three QKI isoforms (QKI5, QKI6, and QKI7) in AD. Genes that have previously been related to the ontogeny and progression of AD, specifically APP, PSEN1, PSEN2, and MAPT, were also investigated. A real-time PCR assay of 123 samples from human postmortem sporadic AD patients and control brains was performed. The expression values were analyzed with an analysis of covariance model and subsequent multiple regressions to explore the possibility of related expression values between QKI, QKI isoforms, and AD-related genes. Further, the sequences of AD-related genes were analyzed for the presence of QKI binding domains. QKI and all measured QKI isoforms were found to be significantly upregulated in AD samples, relative to control samples. However, APP, PSEN1, PSEN2, and MAPT were not found to be significantly different. QKI and QKI isoforms were found to be predictive for the variance of APP, PSEN1, PSEN2, and MAPT, and putative QKI binding sites suggests an interaction with QKI. Overall, these results implicate a possible role of QKI in AD, although the exact mechanism by which this occurs remains to be uncovered

SLC10A4 regulates IgE-mediated mast cell degranulation in vitro and mast cell-mediated reactions in vivo

Mast cells act as sensors in innate immunity and as effector cells in adaptive immune reactions. Here we demonstrate that SLC10A4, also referred to as the vesicular aminergic-associated transporter, VAAT, modifies mast cell degranulation. Strikingly, Slc10a4(-/-) bone marrow-derived mast cells (BMMCs) had a significant reduction in the release of granule-associated mediators in response to IgE/antigen-mediated activation, whereas the in vitro development of mast cells, the storage of the granule-associated enzyme mouse mast cell protease 6 (mMCP-6), and the release of prostaglandin D2 and IL-6 were normal. Slc10a4-deficient mice had a strongly reduced passive cutaneous anaphylaxis reaction and a less intense itching behaviour in response to the mast cell degranulator 48/80. Live imaging of the IgE/antigen-mediated activation showed decreased degranulation and that ATP was retained to a higher degree in mast cell granules lacking SLC10A4. Furthermore, ATP was reduced by two thirds in Slc10a4(-/-) BMMCs supernatants in response to IgE/antigen. We speculate that SLC10A4 affects the amount of granule-associated ATP upon IgE/antigen-induced mast cell activation, which affect the release of granule-associated mast cell mediators. In summary, SLC10A4 acts as a regulator of degranulation in vitro and of mast cell-related reactions in vivo

Characterization and Expression of the Zebrafish qki Paralogs

Quaking (QKI) is an RNA-binding protein involved in post-transcriptional mRNA processing. This gene is found to be associated with several human neurological disorders. Early expression of QKI proteins in the developing mouse neuroepithelium, together with neural tube defects in Qk mouse mutants, suggest the functional requirement of Qk for the establishment of the nervous system. As a knockout of Qk is embryonic lethal in mice, other model systems like the zebrafish could serve as a tool to study the developmental functions of qki. In the present study we sought to characterize the evolutionary relationship and spatiotemporal expression of qkia, qki2, and qkib; zebrafish homologs of human QKI. We found that qkia is an ancestral paralog of the single tetrapod Qk gene that was likely lost during the fin-to-limb transition. Conversely, qkib and qki2 are orthologs, emerging at the root of the vertebrate and teleost lineage, respectively. Both qki2 and qkib, but not qkia, were expressed in the progenitor domains of the central nervous system, similar to expression of the single gene in mice. Despite having partially overlapping expression domains, each gene has a unique expression pattern, suggesting that these genes have undergone subfunctionalization following duplication. Therefore, we suggest the zebrafish could be used to study the separate functions of qki genes during embryonic development

Quantitative temporal expression of <i>qki</i> transcripts during development.

<p>Relative mRNA expression of <i>qkia</i>, <i>qki2</i>, and <i>qkib</i> is plotted across indicated developmental time points. Each point represents the average measurement of three biological replicates. Bars correspond to standard deviation of the mean. hpf: hours post-fertilization, dpf: days post-fertilization.</p