Skolevægring

Resume Skolevægring er generelt set blevet et stigende problem blandt danske skoleelever (Knudsen & Møller 2017, Lund 2021) og især børn med diagnoser er overrepræsenterede i statistikker over børn der har svært ved at komme i skole. Samtidig er skolevægring som fænomen, noget vi ikke ved så meget om i en dansk kontekst. Artiklens ærinde er, ud fra et litteraturstudie, at afsøge forståelser af og grunde til skolevægring, samt diskutere skolens rolle og opgave ift. børn der vælger skolen fra. Artiklen tager udgangspunkt i et state-of- the-art litteraturstudie om skolevægring i et international perspektiv, men med et primært fokus på Danmark. Studiet er styret af følgende forskningsspørgsmål: Hvilke forståelser peges der på i litteraturen ift. børn der vælger skolen fra, samt hvilken betydning kan disse forståelser få for det forebyggende og indgribende arbejde i praksis? Abstract School refusal – Children with diagnoses and their difficulties in getting to school School refusal has become an increasing problem among Danish school students (Knudsen & Møller 2017, Lund 2021) and especially children with diagnoses are represented in statistics on children who have difficulty participating in school. At the same time, school refusal as a phenomenon is something we know very little about in a Danish context. Based on a literature study the purpose of this article is to make school refusal visible as a growing problem in a Danish school context, as well as to discuss the role and tasks of the school in relation to children who don’t want to go to school. The article is based on a state-of-the-art literature study on school refusal in an international perspective, but with a primary focus on school refusal in Denmark. The study is guided by the following research question: What is known from the literature regarding child-motivated refusal to attend school (School Refusal) and how can this information be used to prevent and intervene in practice

Skolevægring: – børn med udfordringer og deres vanskeligheder med at komme i skole

ResumeSkolevægring er generelt set blevet et stigende problem blandt danske skoleelever (Knudsen & Møller 2017, Lund 2021) og især børn med diagnoser er overrepræsenterede i statistikker over børn der har svært ved at komme i skole. Samtidig er skolevægring som fænomen, noget vi ikke ved så meget om i en dansk kontekst. Artiklens ærinde er, ud fra et litteraturstudie, at afsøge forståelser af og grunde til skolevægring, samt diskutere skolens rolle og opgave ift. børn der vælger skolen fra. Artiklen tager udgangspunkt i et state-of- the-art litteraturstudie om skolevægring i et international perspektiv, men med et primært fokus på Danmark. Studiet er styret af følgende forskningsspørgsmål: Hvilke forståelser peges der på i litteraturen ift. børn der vælger skolen fra, samt hvilken betydning kan disse forståelser få for det forebyggende og indgribende arbejde i praksis?AbstractSchool refusal – Children with diagnoses and their difficulties in getting to schoolSchool refusal has become an increasing problem among Danish school students (Knudsen & Møller 2017, Lund 2021) and especially children with diagnoses are represented in statistics on children who have difficulty participating in school. At the same time, school refusal as a phenomenon is something we know very little about in a Danish context. Based on a literature study the purpose of this article is to make school refusal visible as a growing problem in a Danish school context, as well as to discuss the role and tasks of the school in relation to children who don’t want to go to school. The article is based on a state-of-the-art literature study on school refusal in an international perspective, but with a primary focus on school refusal in Denmark. The study is guided by the following research question: What is known from the literature regarding child-motivated refusal to attend school (School Refusal) and how can this information be used to prevent and intervene in practice

Migration of Zebrafish Primordial Germ Cells: A Role for Myosin Contraction and Cytoplasmic Flow

SummaryThe molecular and cellular mechanisms governing cell motility and directed migration in response to the chemokine SDF-1 are largely unknown. Here, we demonstrate that zebrafish primordial germ cells whose migration is guided by SDF-1 generate bleb-like protrusions that are powered by cytoplasmic flow. Protrusions are formed at sites of higher levels of free calcium where activation of myosin contraction occurs. Separation of the acto-myosin cortex from the plasma membrane at these sites is followed by a flow of cytoplasm into the forming bleb. We propose that polarized activation of the receptor CXCR4 leads to a rise in free calcium that in turn activates myosin contraction in the part of the cell responding to higher levels of the ligand SDF-1. The biased formation of new protrusions in a particular region of the cell in response to SDF-1 defines the leading edge and the direction of cell migration

Systemic and local cues drive neural stem cell niche remodelling during neurogenesis in Drosophila.

Successful neurogenesis requires adequate proliferation of neural stem cells (NSCs) and their progeny, followed by neuronal differentiation, maturation and survival. NSCs inhabit a complex cellular microenvironment, the niche, which influences their behaviour. To ensure sustained neurogenesis, niche cells must respond to extrinsic, environmental changes whilst fulfilling the intrinsic requirements of the neurogenic program and adapting their roles accordingly. However, very little is known about how different niche cells adjust their properties to such inputs. Here, we show that nutritional and NSC-derived signals induce the remodelling of Drosophila cortex glia, adapting this glial niche to the evolving needs of NSCs. First, nutrition-induced activation of PI3K/Akt drives the cortex glia to expand their membrane processes. Second, when NSCs emerge from quiescence to resume proliferation, they signal to glia to promote membrane remodelling and the formation of a bespoke structure around each NSC lineage. The remodelled glial niche is essential for newborn neuron survival

The Drosophila neural lineages: a model system to study brain development and circuitry

In Drosophila, neurons of the central nervous system are grouped into units called lineages. Each lineage contains cells derived from a single neuroblast. Due to its clonal nature, the Drosophila brain is a valuable model system to study neuron development and circuit formation. To better understand the mechanisms underlying brain development, genetic manipulation tools can be utilized within lineages to visualize, knock down, or over-express proteins. Here, we will introduce the formation and development of lineages, discuss how one can utilize this model system, offer a comprehensive list of known lineages and their respective markers, and then briefly review studies that have utilized Drosophila neural lineages with a look at how this model system can benefit future endeavors

Cxcl12 evolution – subfunctionalization of a ligand through altered interaction with the chemokine receptor

The active migration of primordial germ cells (PGCs) from their site of specification towards their target is a valuable model for investigating directed cell migration within the complex environment of the developing embryo. In several vertebrates, PGC migration is guided by Cxcl12, a member of the chemokine superfamily. Interestingly, two distinct Cxcl12 paralogs are expressed in zebrafish embryos and contribute to the chemotattractive landscape. Although this offers versatility in the use of chemokine signals, it also requires a mechanism through which migrating cells prioritize the relevant cues that they encounter. Here, we show that PGCs respond preferentially to one of the paralogs and define the molecular basis for this biased behavior. We find that a single amino acid exchange switches the relative affinity of the Cxcl12 ligands for one of the duplicated Cxcr4 receptors, thereby determining the functional specialization of each chemokine that elicits a distinct function in a distinct process. This scenario represents an example of protein subfunctionalization – the specialization of two gene copies to perform complementary functions following gene duplication – which in this case is based on receptor-ligand interaction. Such specialization increases the complexity and flexibility of chemokine signaling in controlling concurrent developmental processes

Redundant Mechanisms for Regulation of Midline Crossing in Drosophila

During development, all neurons have to decide on whether to cross the longitudinal midline to project on the contralateral side of the body. In vertebrates and invertebrates regulation of crossing is achieved by interfering with Robo signalling either through sorting and degradation of the receptor, in flies, or through silencing of its repulsive activity, in vertebrates. Here I show that in Drosophila a second mechanism of regulation exists that is independent from sorting. Using in vitro and in vivo assays I mapped the region of Robo that is sufficient and required for its interaction with Comm, its sorting receptor. By modifying that region, I generated new forms of Robo that are insensitive to Comm sorting in vitro and in vivo, yet still able to normally translate repulsive activity in vivo. Using gene targeting by homologous recombination I created new conditional alleles of robo that are sorting defective (roboSD). Surprisingly, expression of these modified proteins results in phenotypically normal flies, unveiling a sorting independent mechanism of regulation

A novel piggybac transposon inducible expression system identifies a role for akt signalling in primordial germ cell migration

In this work, we describe a single piggyBac transposon system containing both a tet-activator and a doxycycline-inducible expression cassette. We demonstrate that a gene product can be conditionally expressed from the integrated transposon and a second gene can be simultaneously targeted by a short hairpin RNA contained within the transposon, both in vivo and in mammalian and avian cell lines. We applied this system to stably modify chicken primordial germ cell (PGC) lines in vitro and induce a reporter gene at specific developmental stages after injection of the transposon-modified germ cells into chicken embryos. We used this vector to express a constitutively-active AKT molecule during PGC migration to the forming gonad. We found that PGC migration was retarded and cells could not colonise the forming gonad. Correct levels of AKT activation are thus essential for germ cell migration during early embryonic development

An Evolutionarily Conserved Arginine Is Essential for Tre1 G Protein-Coupled Receptor Function During Germ Cell Migration in Drosophila melanogaster

BACKGROUND: G protein-coupled receptors (GPCRs) play central roles in mediating cellular responses to environmental signals leading to changes in cell physiology and behaviors, including cell migration. Numerous clinical pathologies including metastasis, an invasive form of cell migration, have been linked to abnormal GPCR signaling. While the structures of some GPCRs have been defined, the in vivo roles of conserved amino acid residues and their relationships to receptor function are not fully understood. Trapped in endoderm 1 (Tre1) is an orphan receptor of the rhodopsin class that is necessary for primordial germ cell migration in Drosophila melanogaster embryos. In this study, we employ molecular genetic approaches to identify residues in Tre1 that are critical to its functions in germ cell migration. METHODOLOGY/PRINCIPAL FINDINGS: First, we show that the previously reported scattershot mutation is an allele of tre1. The scattershot allele results in an in-frame deletion of 8 amino acids at the junction of the third transmembrane domain and the second intracellular loop of Tre1 that dramatically impairs the function of this GPCR in germ cell migration. To further refine the molecular basis for this phenotype, we assayed the effects of single amino acid substitutions in transgenic animals and determined that the arginine within the evolutionarily conserved E/N/DRY motif is critical for receptor function in mediating germ cell migration within an intact developing embryo. CONCLUSIONS/SIGNIFICANCE: These structure-function studies of GPCR signaling in native contexts will inform future studies into the basic biology of this large and clinically important family of receptors