Reelin Together with ApoER2 Regulates Interneuron Migration in the Olfactory Bulb

One pathway regulating the migration of neurons during development of the mammalian cortex involves the extracellular matrix protein Reelin. Reelin and components of its signaling cascade, the lipoprotein receptors ApoER2 and Vldlr and the intracellular adapter protein Dab1 are pivotal for a correct layer formation during corticogenesis. The olfactory bulb (OB) as a phylogenetically old cortical region is known to be a prominent site of Reelin expression. Although some aspects of Reelin function in the OB have been described, the influence of Reelin on OB layer formation has so far been poorly analyzed. Here we studied animals deficient for either Reelin, Vldlr, ApoER2 or Dab1 as well as double-null mutants. We performed organotypic migration assays, immunohistochemical marker analysis and BrdU incorporation studies to elucidate roles for the different components of the Reelin signaling cascade in OB neuroblast migration and layer formation. We identified ApoER2 as being the main receptor responsible for Reelin mediated detachment of neuroblasts and correct migration of early generated interneurons within the OB, a prerequisite for correct OB laminatio

Morphology, input–output relations and synaptic connectivity of Cajal–Retzius cells in layer 1 of the developing neocortex of CXCR4-EGFP mice

Layer 1 (L1) neurons, in particular Cajal–Retzius (CR) cells are among the earliest generated neurons in the neocortex. However, their role and that of L1 GABAergic interneurons in the establishment of an early cortical microcircuit are still poorly understood. Thus, the morphology of whole-cell recorded and biocytin-filled CR cells was investigated in postnatal day (P) 7–11 old CXCR4-EGFP mice where CR cells can be easily identified by their fluorescent appearance. Confocal-, light- and subsequent electron microscopy was performed to investigate their developmental regulation, morphology, synaptic input–output relationships and electrophysiological properties. CR cells reached their peak in occurrence between P4 to P7 and from thereon declined to almost complete disappearance at P14 by undergoing selective cell death through apoptosis. CR cells formed a dense and long-range horizontal network in layer 1 with a remarkable high density of synaptic boutons along their axons. They received dense GABAergic and non-GABAergic synaptic input and in turn provided synaptic output preferentially with spines or shafts of terminal tuft dendrites of pyramidal neurons. Interestingly, no dye-coupling between CR cells with other cortical neurons was observed as reported for other species, however, biocytin-labeling of individual CR cells leads to co-staining of L1 end foot astrocytes. Electrophysiologically, CR cells are characterized by a high input resistance and a characteristic firing pattern. Increasing depolarizing currents lead to action potential of decreasing amplitude and increasing half width, often terminated by a depolarization block. The presence of membrane excitability, the high density of CR cells in layer 1, their long-range horizontal axonal projection together with a high density of synaptic boutons and their synaptic input–output relationship suggest that they are an integral part of an early cortical network important not only in layer 1 but also for the establishment and formation of the cortical column

Who’s more vulnerable? A generational investigation of COVID-19 perceptions’ effect on organisational citizenship behaviours in the MENA region:job insecurity, burnout and job satisfaction as mediators

BACKGROUND: This paper is an empirical investigation that examines a path model linking COVID-19 perceptions to organisational citizenship behaviour (OCBs) via three mediators: job insecurity, burnout, and job satisfaction. The research examines the path model invariance spanning Generations X, Y, and Z. Three countries in the Middle East and North Africa (MENA) were the focus of the study. METHODS: The data was collected from a sample of employees in service companies (n = 578). We used a Partial Least Square Structural Equation Modelling (PLS-SEM) to analyse the data. RESULTS: Our findings reveal that COVID-19 perceptions positively predict job insecurity, which positively impacts burnout levels. Burnout negatively predicts job satisfaction. The findings established that job satisfaction positively predicts OCBs. The mediation analysis determined that job insecurity, burnout and job satisfaction convey the indirect effects of COVID-19 perceptions onto OCBs. Finally, our hypothesised model is non-equivalent across Generations X, Y and Z. In that regard, our multi-group analysis revealed that the indirect effects of COVID-19 perceptions on OCBs were only valid amongst younger generations, i.e., Generation Y and Generation Z. Specifically, younger generations are substantially more vulnerable to the indirect effects of COVID-19 perceptions on their engagement in OCBs than Generation X whose job satisfaction blocks the effects of COVID-19 perceptions on OCBs. CONCLUSIONS: The present study extends our knowledge of workplace generational differences in responding to the perceptions of crises or pandemics. It offers evidence that suggests that burnout, job attitudes and organisational outcomes change differently across generations in pandemic times. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-021-11976-2

Functional integrity of the rostral migratory stream (RMS) and detachment process in vivo.

<p>Immunohistochemistry for PSA-NCAM (red), GFAP (green) and DAPI on sagittal sections through the forebrain of adult wild-type mice, <i>Vldlr</i>^−/−, <i>ApoER2</i>^−/−, <i>Dab1</i>^−/−, <i>reeler</i> and ApoER2^−/−:<i>Vldlr^−/−</i> mutant animals show the presence of neuroblasts proximal to the SVZ (arrows) (column A) and approaching the OB (open arrowheads) (column B) in all animals analyzed. Higher magnification on frontal sections and PSA-NCAM staining revealed a proper detachment of neuroblasts with the typical switch from chain migration to radial ascension into layers in wild-type mice, <i>Vldlr</i>^−/− and <i>ApoER2^−/−</i> mutants (column C). Single cells extend their leading process towards outer layers (open arrowheads, dashed arrow indicates migration direction from the RMS towards distal/upper layers). In contrast, <i>reeler</i> mutants as well as double receptor knockout mice exhibit a severe impairment of the detachment process (column C). Dab1^−/− animals appear to have only a minor phenotype (arrowheads). In (<b>D</b>) the number of BrdU labeled nuclei 16 days after BrdU injection in different areas of the OB (core (proximal to the RMS), GCL (granule cell layer), MCL (mitral cell layer) and EPL (external plexiform layer) area and GL (glomerular cell layer) are shown. Numbers are given as BrdU⁺/total cells [%]. Student′s test compared number of BrdU⁺ in mutants to corresponding region of wild-type animals. *p<0.05; **p<0.01. V = ventricle; Scale bars: column A 100 µm, column B 200 µm and column C 50 µm.</p

Expression of Reelin and components of its signaling pathway in the forebrain.

<p>(A) RT-PCR analysis at P0, P7, P14 and adult age revealed <i>Reelin</i>, <i>ApoER2</i>, <i>Vldlr</i> and <i>Dab1</i> mRNA expression in the OB. Samples were normalized to <i>β-actin</i> expression. (B) RT-PCR primers sequences (C) Western immunoblot analysis of adult OB tissue and transfected control fibroblasts confirming protein in the OB. (D-F) At P0 strong Reelin expression is found in the mitral cell layer of the OB (open arrowheads, D). Adult mice express Reelin in the MCL (open arrowhead) and in a periglomerular position (arrowhead, F). Reelin positive cells (arrows) are also seen in close vicinity to the rostral migratory stream (RMS, E). Migrating precursors in the RMS are negative at both analyzed timepoints. (G-I) Early postnatal <i>Vldlr</i> expression is restricted to the MCL (open arrowhead, G). At adult age <i>Vldlr</i> mRNA is found in the RMS (arrows, H and insert, arrowhead), in the MCL (open arrowheads, I) and in the innermost part of the glomerular cell layer (GL), (arrowheads, I). Similar expression patterns were obtained by in situ hybridization for <i>ApoER2</i> (K-L) and <i>Dab1</i> (N, O) on sagittal sections of adult wt forebrains. Of note, both are expressed in the RMS at P0 (J, M) and migrating precursors. Scale bars: D, G, H, J, K, M, N: 200 µm; E, F, I, L, O: 100 µm.</p

Labeling of early generated interneurons.

<p>Immunohistochemistry for Calbindin on frontal sections through the OB of adult wild-type mice showed strong expression in the glomerular cell layer (GL, column A, wt). A similar staining pattern was observed in <i>Vldlr^−/−</i> mice (column A, <i>Vldlr^−/−</i>) although few positive cells hosted in the external plexiform layer. <i>ApoER2^−/−</i>, <i>Dab1^−/−</i>, <i>reeler</i> and <i>ApoER2</i>^−/−:<i>Vldlr^−/−</i> mutants show clearly two separate cell populations using Calbindin as marker (column A). A superficial one in the typical periglomerular position and a deep one in the EPL (arrowheads, column A). (Column B) Immunohistochemistry for Parvalbumin on frontal sections through the OB of adult mice labeled interneurons in the external plexiform layer (EPL). No differences were observed for the analyzed mutants compared to wild-type mice. Staining for Tbr1 (column C) and Reelin (column D) as markers of the MCL showed no alterations in the analyzed animals except the loss of Reelin immunoreactivity in <i>reeler</i> mutants. Quantification of the relative number of Calbindin positive (E) cells per area in the EPL after normalization to the wt situation (n = 3−5 animals per genotype). Wilcoxon-Mann-Whitney test; Data expressed as mean ± SEM. Scale bar 100 µm. MCL, mitral cell layer; GCL, granule cell layer.</p

Pandemic pains to Instagram gains! COVID-19 perceptions effects on behaviours towards fashion brands on Instagram in Sub-Saharan Africa: Tech-native vs non-native generations

This study represents a novel attempt to investigate the cascading effects of COVID-19 perceptions onto behavioural patterns towards fashion brands on Instagram and across two generations tech-native vs tech non-native) in a Sub-Saharan African context. We drew our study on a sample of 338 Instagram users that experienced fashion brands on Instagram in two Sub-Saharan African countries: Uganda and Nigeria. We used partial least square structural equation modelling (PLS-SEM) to test the hypothetical model. We found that COVID-19 perception positively predicted enjoyment and usefulness, leading to more satisfaction with fashion brand accounts on Instagram and hence greater intention to follow and recommend those accounts. Finally, running a multigroup analysis (MGA), we found the effects of COVID-19 perceptions pronounced into both intentions to follow and intention to recommend via the sequence of mediators: enjoyment and satisfaction were only valid amongst the tech-native generational cohort. Our research suggested a new generational categorisation based on technology nativity – offering a new direction of generational studies in digital marketing communications

Cellular/Molecular Role for Reelin in Neurotransmitter Release

The extracellular matrix molecule Reelin is known to control neuronal migration during development. Recent evidence suggests that it also plays a role in the maturation of postsynaptic dendrites and spines as well as in synaptic plasticity. Here, we aimed to address the question whether Reelin plays a role in presynaptic structural organization and function. Quantitative electron microscopic analysis of the number of presynaptic boutons in the stratum radiatum of hippocampal region CA1 did not reveal differences between wild-type animals and Reelin-deficient reeler mutant mice. However, additional detailed analysis showed that the number of presynaptic vesicles was significantly increased in CA1 synapses of reeler mutants. To test the hypothesis that vesicle fusion is altered in reeler, we studied proteins known to control transmitter release. SNAP25, a protein of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, was found to be significantly reduced in reeler mutants, whereas other SNARE complex proteins remained unaltered. Addition of recombinant Reelin to organotypic slice cultures of reeler hippocampi substantially rescued not only SNAP25 protein expression levels but also the number of vesicles per bouton area indicating a role for Reelin in presynaptic functions. Next, we analyzed paired-pulse facilitation, a presynaptic mechanism associated with transmitter release, and observed a significant decrease at CA1 synapses of reeler mutants when compared with wild-type animals. Together, these novel findings suggest a role for Reelin in modulating presynaptic release mechanisms

MALIS-Praxisprojekte 2011 : Projektberichte aus dem berufsbegleitenden Masterstudiengang Bibliotheks- und Informationswissenschaft der Fachhochschule Köln.

This book provides selected project reports by participants of the Master program "Library and Information Science" (MALIS) at Cologne University of Applied Sciences. MALIS is a four-semester Master’s program which qualifies graduates of any academic discipline as well as librarians holding at least a Bachelor’s degree for highly-specialized responsibilities and leadership positions in libraries and other information centers. Projects with practical relevance for LIS institutions are a fundamental part of the qualification concept of the MALIS program