Myelinosome formation represents an early stage of oligodendrocyte damage in multiple sclerosis and its animal model

Oligodendrocyte damage is a central event in the pathogenesis of the common neuro-inflammatory condition, multiple sclerosis (MS). Where and how oligodendrocyte damage is initiated in MS is not completely understood. Here, we use a combination of light and electron microscopy techniques to provide a dynamic and highly resolved view of oligodendrocyte damage in neuroinflammatory lesions. We show that both in MS and in its animal model structural damage is initiated at the myelin sheaths and only later spreads to the oligodendrocyte cell body. Early myelin damage itself is characterized by the formation of local myelin out-foldings-'myelinosomes'-, which are surrounded by phagocyte processes and promoted in their formation by anti-myelin antibodies and complement. The presence of myelinosomes in actively demyelinating MS lesions suggests that oligodendrocyte damage follows a similar pattern in the human disease, where targeting demyelination by therapeutic interventions remains a major open challenge

An Evidence-Based Digital Prevention Program to Improve Oral Health Literacy of People With a Migration Background: Intervention Mapping Approach

BackgroundStudies in Germany have shown that susceptible groups, such as people with a migration background, have poorer oral health than the majority of the population. Limited oral health literacy (OHL) appears to be an important factor that affects the oral health of these groups. To increase OHL and to promote prevention-oriented oral health behavior, we developed an evidence-based prevention program in the form of an app for smartphones or tablets, the Förderung der Mundgesundheitskompetenz und Mundgesundheit von Menschen mit Migrationshintergrund (MuMi) app. ObjectiveThis study aims to describe the development process of the MuMi app. MethodsFor the description and analysis of the systematic development process of the MuMi app, we used the intervention mapping approach. The approach was implemented in 6 steps: needs assessment, formulation of intervention goals, selection of evidence-based methods and practical strategies for behavior change, planning and designing the intervention, planning the implementation and delivery of the intervention, and planning the evaluation. ResultsOn the basis of our literature search, expert interviews, and a focus group with the target population, we identified limited knowledge of behavioral risk factors or proper oral hygiene procedures, limited proficiency of the German language, and differing health care socialization as the main barriers to good oral health. Afterward, we selected modifiable determinants of oral health behavior that were in line with behavior change theories. On this basis, performance objectives and change objectives for the relevant population at risk were formalized. Appropriate behavior change techniques to achieve the program objectives, such as the provision of health information, encouragement of self-control and self-monitoring, and sending reminders, were identified. Subsequently, these were translated into practical strategies, such as multiple-choice quizzes or videos. The resulting program, the MuMi app, is available in the Apple app store and Android app store. The effectiveness of the app was evaluated in the MuMi intervention study. The analyses showed that users of the MuMi app had a substantial increase in their OHL and improved oral hygiene (as measured by clinical parameters) after 6 months compared with the control group. ConclusionsThe intervention mapping approach provided a transparent, structured, and evidence-based process for the development of our prevention program. It allowed us to identify the most appropriate and effective techniques to initiate behavior change in the target population. The MuMi app takes into account the cultural and specific determinants of people with a migration background in Germany. To our knowledge, it is the first evidence-based app that addresses OHL among people with a migration background

Mundgesundheitskompetenz von Menschen mit Migrationshintergrund – Erste Auswertungen der MuMi-Studie

Hintergrund: Erste Studien heben den Migrationshintergrund von Menschen in Deutschland als eigenständigen Risikofaktor für eine mangelhafte Mundgesundheit hervor. Ein wichtiger Einflussfaktor könnte hierbei eine niedrigere Mundgesundheitskompetenz von Menschen mit Migrationshintergrund sein. In diesem Artikel werden Ergebnisse zur Mundgesundheitskompetenz und Mundgesundheit aus der MuMi-Studie (Förderung der Mundgesundheit und Mundgesundheitskompetenz von Menschen mit Migrationshintergrund) vorgestellt. Material und Methoden: In 40 Hamburger Zahnarztpraxen wurden von Patient*innen mit und ohne Migrationshintergrund Daten zu Soziodemografie, Mundgesundheit und Mundgesundheitskompetenz erhoben. Der Zusammenhang zwischen Mundgesundheitskompetenz und Mundgesundheit wurde mittels logistischer Regressionen berechnet. Potenzielle Einflussfaktoren wurden schrittweise in die Berechnungsmodelle eingefügt. Ergebnisse: Die Gruppen mit und ohne Migrationshintergrund unterschieden sich signifikant hinsichtlich ihrer Mundgesundheitskompetenz und ausgewählter klinischer Parameter ihrer Mundgesundheit (Approximalraum-Plaqueindex und Kariessanierungsgrad). Die logistischen Regressionsanalysen zeigen einen deutlichen Zusammenhang zwischen Migrationshintergrund, Mundgesundheitskompetenz und Mundhygiene auch unter Berücksichtigung von Bildung und sozioökonomischem Status. Diskussion: Der Migrationshintergrund stellt einen eigenständigen Indikator für eine niedrige Mundgesundheitskompetenz und schlechtere Mundgesundheit dar. Dieser Umstand sollte stärker in den Fokus von Forschung und politischen Entscheidungen rücken, um die mundgesundheitliche Chancengleichheit in Deutschland zu erhöhen

Loss of Myelin Basic Protein Function Triggers Myelin Breakdown in Models of Demyelinating Diseases

Breakdown of myelin sheaths is a pathological hallmark of several autoimmune diseases of the nervous system. We employed autoantibody-mediated animal models of demyelinating diseases, including a rat model of neuromyelitis optica (NMO), to target myelin and found that myelin lamellae are broken down into vesicular structures at the innermost region of the myelin sheath. We demonstrated that myelin basic proteins (MBP), which form a polymer in between the myelin membrane layers, are targeted in these models. Elevation of intracellular Ca2+ levels resulted in MBP network disassembly and myelin vesiculation. We propose that the aberrant phase transition of MBP molecules from their cohesive to soluble and non-adhesive state is a mechanism triggering myelin breakdown in NMO and possibly in other demyelinating diseases

Myelin Membrane Assembly Is Driven by a Phase Transition of Myelin Basic Proteins Into a Cohesive Protein Meshwork

<div><p>Rapid conduction of nerve impulses requires coating of axons by myelin. To function as an electrical insulator, myelin is generated as a tightly packed, lipid-rich multilayered membrane sheath. Knowledge about the mechanisms that govern myelin membrane biogenesis is required to understand myelin disassembly as it occurs in diseases such as multiple sclerosis. Here, we show that myelin basic protein drives myelin biogenesis using weak forces arising from its inherent capacity to phase separate. The association of myelin basic protein molecules to the inner leaflet of the membrane bilayer induces a phase transition into a cohesive mesh-like protein network. The formation of this protein network shares features with amyloid fibril formation. The process is driven by phenylalanine-mediated hydrophobic and amyloid-like interactions that provide the molecular basis for protein extrusion and myelin membrane zippering. These findings uncover a physicochemical mechanism of how a cytosolic protein regulates the morphology of a complex membrane architecture. These results provide a key mechanism in myelin membrane biogenesis with implications for disabling demyelinating diseases of the central nervous system.</p> </div

Low mobility of MBP domains.

<p>(A) Schematic representation of the reporter construct used to measure mobility of MBP in primary oligodendrocytes. (B) Dendra2 was fused to the N-terminus of either TM (Dendra2-TM) or TM-MBP (Dendra2-TM-MBP) and expressed in primary oligodendrocytes. A squared region of interest was photoconverted from green-to-red via excitation with 405 nm laser. The decay of signal in the photoconveted region of interest was measured over time. Decay of photoconverted signal with time is shown in the representative, zoomed-in images for primary oligodendrocyte cultures expressing either Dendra2-TM or Dendra2-TM-MBP. Scale bar, 10 µm. (C) Curves depict the decay of signal over time for the indicated constructs. (D) Average decay after photoconversion. Bars represent mean ± SEM (<i>n</i> = 3, **<i>p</i><0.01, <i>t</i> test). (E) Fluorescence recovery was monitored in primary cells expressing GFP-TM or GFP-TM-MBP after bleaching a squared region of interest. Recovery curves are presented in the form of graphs. (F) Average recovery after photobleaching. Bars represent mean ± SEM (<i>n</i> = 3, ***<i>p</i><0.001, <i>t</i> test). (G) Dendra2 was fused to the N-terminus of either TM (Dendra2-TM) or TM-MBP (Dendra2-TM-MBP) and expressed in PtK2 cells. A squared region of interest was photoconverted from green-to-red via excitation with 405 nm laser. The decay of signal in the photoconveted region of interest was measured over time. Decay of photoconverted signal with time is shown in the representative, zoomed-in images for PtK2 cells expressing either Dendra2-TM or Dendra2-TM-MBP. Scale bar, 10 µm. (H) The decay of signal is presented in the form of curves. (I) Average decay after photoconversion. Bars represent mean ± SEM (<i>n</i> = 3, **<i>p</i><0.01, <i>t</i> test). (J) Fluorescence recovery was monitored in PtK2 cells expressing GFP-TM or GFP-TM-MBP after bleaching a squared region of interest. Recovery curves are presented in the form of graphs. (K) Average recovery after photobleaching. Bars represent mean ± SEM (<i>n</i> = 3, ***<i>p</i><0.001, <i>t</i> test).</p

Phase transition of wild-type, but not the F→S mutant of MBP.

<p>(A) In basic solution MBP (5 mg/mL) forms droplets as visualized by phase contrast microscopy. (B) Droplets contain Atto-488-labeled MBP (5 mg/mL) as visualized by wide field (right panel) microscopy. (C) Time-lapse images of two merging droplets. Scale bar, 5 µm.</p

Self-association of MBP molecules via hydrophobic interactions is required for its function.

<p>(A) Quantification of FRET efficiency in PtK2 cells expressing GFP-Tm10 (Donor) and mCherry-GyPTM (Acceptor) both harboring at the C-terminal end either wild-type MBP or MBP F→S. While Tm10 represents the transmembrane domain of Tmem10, GyPTM represents the mutated monomeric transmembrane domain of the glycophorin protein. Bars indicate mean ± SD (<i>n</i> = 20 cells, *<i>p</i><0.05, ANOVA). (B) Comparison of interaction forces between wild-type MBP or F→S mutant molecules pre-adsorbed, both to the mica surface and AFM tip. Inset shows the schematic depiction of shape of the curve as cantilever tip approaches the sample surface (1), as tip touches the surface (2), and as tip is retracted from the sample surface (3). Histogram of peak force measured for MBP (black), MBP F→S (red), and buffer (green). (C) Representative images of a biomimetic assay in which MBP or MBP F→S is sandwiched between SLBs (inner myelin leaflet lipid composition) and GUVs (PC∶PS in 3∶1 mole%). Scale bar, 10 µm. (D) Quantification of percentage GUV bursting. Bars show mean ± SEM (<i>n</i> = 3 experiments, ***<i>p</i><0.001, <i>t</i> test). (E) <i>Shiverer</i> cells at 0 DIV were infected with AAV2 viral particles expressing either wild-type MBP (MBP-HA) or F→S mutant (MBP F→S-HA) containing a C-terminal HA-tag. At 6 DIV, cells were immunostained for CNPase and the HA tags. Expression of MBP-HA induces the depletion of CNPase from regions within the sheets, whereas the F→S mutant fails in extruding CNPase despite entering the sheets of <i>shiverer</i> cells. Enlarged view of the selected regions in merged images is shown on the right side. Scale bar, 10 µm.</p

β-sheet structure mediates amyloid-like self-assembly of MBP.

<p>(A) Secondary structure determination from FTIR spectroscopy of wild-type MBP in the presence of 20 mM NaOH. Bars represent range from two independent experiments. (B) Secondary structure determination of wild-type and the F→S mutant after addition to the SLBs with the inner myelin leaflet lipid composition. (C) Aggregation-prone stretches within MBP sequence. (D) Transmission electron microscopy of peptide 1 and peptide 2 (left and middle panel) incubated in 25 mM HEPES (pH 7.5), 150 mM KCl, and 0.5 mM MgCl₂ for several days. The lower panel shows the fibrillar aggregates obtained in 20 mM HCl, 500 mM Na₂SO₄, and 5% ethanol for wild-type MBP, but not the MBP F→S mutant. (E) Thioflavin S staining of P18 MBP deficient <i>shiverer</i> and wild-type mice brain. Quantification of relative fluorescent intensity in corpus collosum. Bars show mean ± SEM (<i>n</i> = 3 animals, **<i>p</i><0.01, <i>t</i> test).</p