Cytoskeletal transition at the paranodes: the Achilles' heel of myelinated axons

Myelination organizes axons into distinct domains that allow nerve impulses to propagate in a saltatory manner. The edges of the myelin sheath are sealed at the paranodes by axon–glial junctions that have a crucial role in organizing the axonal cytoskeleton. Here we propose a model in which the myelinated axons depend on the axon–glial junctions to stabilize the cytoskeletal transition at the paranodes. Thus paranodal regions are likely to be particularly susceptible to damage induced by demyelinating diseases such as multiple sclerosis

Myo10 in brain: developmental regulation, identification of a headless isoform and dynamics in neurons

Although Myo10 (myosin-X) is an unconventional myosin associated with filopodia, little is known about its isoforms and roles in the nervous system. We report here that, in addition to full-length Myo10, brain expresses a shorter form of Myo10 that lacks a myosin head domain. This ;headless' Myo10 is thus unable to function as a molecular motor, but is otherwise identical to full-length Myo10 and, like it, contains three pleckstrin homology (PH) domains, a myosin-tail homology 4 (MyTH4) domain, and a band-4.1/ezrin/radixin/moesin (FERM) domain. Immunoblotting demonstrates that both full-length and headless Myo10 exhibit dramatic developmental regulation in mouse brain. Immunofluorescence with an antibody that detects both isoforms demonstrates that Myo10 is expressed in neurons, such as Purkinje cells, as well as non-neuronal cells, such as astrocytes and ependymal cells. CAD cells, a neuronal cell line, express both full-length and headless Myo10, and this endogenous Myo10 is present in cell bodies, neurites, growth cones and the tips of filopodia. To investigate the dynamics of the two forms of Myo10 in neurons, CAD cells were transfected with GFP constructs corresponding to full-length or headless Myo10. Only full-length Myo10 localizes to filopodial tips and undergoes intrafilopodial motility, demonstrating that the motor domain is necessary for these activities. Live cell imaging also reveals that full-length Myo10 localizes to the tips of neuronal filopodia as they explore and interact with their surroundings, suggesting that this myosin has a role in neuronal actin dynamics

No effect of genetic deletion of contactin-associated protein (CASPR) on axonal orientation and synaptic plasticity

Myelinated axons are endowed with a specialized domain structure that is essential for saltatory action potential conduction. The paranodal domain contains the axoglial junctions and displays a unique ultrastructure that resembles the invertebrate septate junctions (SJs). Biochemical characterizations of the paranodal axoglial SJs have identified several molecular components that include Caspr and contactin (Cont) on the axonal side and neurofascin 155 kDa (NF155) isoform on the glial side. All these proteins are essential for the formation of the axoglial SJs. Based on the interactions between Caspr and Cont and their colocalization in the CA1 synaptic areas, it was proposed that the synaptic function of Cont requires Caspr. Here we have extended the phenotypic analysis of CASPR mutants to address further the role of Caspr at the axoglial SJs and also in axonal orientation and synaptic plasticity. We report that, in CASPR mutants, the smooth endoplasmic reticulum (SER) forms elongated membranous complexes that accumulate at the nodal/ paranodal region and stretch into the juxtaparanodal region, a defect that is consistent with the paranodal disorganization. We show that the cerebellar microorganization is unaffected in CASPR mutants. We also demonstrate that Caspr function is not essential for normal CA1 synaptic transmission and plasticity. Taken together with previous findings, our results highlight that the Caspr/ Cont complex is essential for the formation of axoglial SJs, whereas Cont may regulate axonal orientation and synaptic plasticity independent of its association with Caspr

Imaging Myosin-X at the Single-Molecule Level Reveals a Novel Form of Motility in Filopodia

Although many proteins, receptors, and viruses are transported rearward along filopodia by retrograde actin flow[1-3], it is less clear how molecules move forward in filopodia. Myosin-X (Myo10) is an actin-based motor hypothesized to use its motor activity to move forward along actin filaments to the tips of filopodia[4]. Here we use a sensitive total internal reflection fluorescence (TIRF) microscopy system to directly visualize the movements of GFP-Myo10. This reveals a novel form of motility at or near the single-molecule level in living cells wherein extremely faint particles of Myo10 move in a rapid and directed fashion towards the filopodial tip. These fast forward movements occur at ∼600 nm/s over distances of up to ∼10 μm and require Myo10 motor activity and actin filaments. As expected for imaging at the single-molecule level, the faint particles of GFP-Myo10 are diffraction-limited, have an intensity range similar to single GFP molecules, and exhibit stepwise bleaching. Faint particles of GFP-Myo5a can also move towards the filopodial tip, but at a slower characteristic velocity of ∼250 nm/s. Similar movements were not detected with GFP-Myo1a, indicating that not all myosins are capable of intrafilopodial motility. These data indicate the existence of a novel system of long-range transport based on the rapid movement of myosin molecules along filopodial actin filaments

Stereocilia-staircase spacing is influenced by myosin III motors and their cargos espin-1 and espin-like

Hair cells tightly control the dimensions of their stereocilia, which are actin-rich protrusions with graded heights that mediate mechanotransduction in the inner ear. Two members of the myosin-III family, MYO3A and MYO3B, are thought to regulate stereocilia length by transporting cargos that control actin polymerization at stereocilia tips. We show that eliminating espin-1 (ESPN-1), an isoform of ESPN and a myosin-III cargo, dramatically alters the slope of the stereocilia staircase in a subset of hair cells. Furthermore, we show that espin-like (ESPNL), primarily present in developing stereocilia, is also a myosin-III cargo and is essential for normal hearing. ESPN-1 and ESPNL each bind MYO3A and MYO3B, but differentially influence how the two motors function. Consequently, functional properties of different motor-cargo combinations differentially affect molecular transport and the length of actin protrusions. This mechanism is used by hair cells to establish the required range of stereocilia lengths within a single cell

Stereocilia-staircase spacing is influenced by myosin III motors and their cargos espin-1 and espin-like

Hair cells tightly control the dimensions of their stereocilia, which are actin-rich protrusions with graded heights that mediate mechanotransduction in the inner ear. Two members of the myosin-III family, MYO3A and MYO3B, are thought to regulate stereocilia length by transporting cargos that control actin polymerization at stereocilia tips. We show that eliminating espin-1 (ESPN-1), an isoform of ESPN and a myosin-III cargo, dramatically alters the slope of the stereocilia staircase in a subset of hair cells. Furthermore, we show that espin-like (ESPNL), primarily present in developing stereocilia, is also a myosin-III cargo and is essential for normal hearing. ESPN-1 and ESPNL each bind MYO3A and MYO3B, but differentially influence how the two motors function. Consequently, functional properties of different motor-cargo combinations differentially affect molecular transport and the length of actin protrusions. This mechanism is used by hair cells to establish the required range of stereocilia lengths within a single cell

Stereocilia-staircase spacing is influenced by myosin III motors and their cargos espin-1 and espin-like

Hair cells tightly control the dimensions of their stereocilia, which are actin-rich protrusions with graded heights that mediate mechanotransduction in the inner ear. Two members of the myosin-III family, MYO3A and MYO3B, are thought to regulate stereocilia length by transporting cargos that control actin polymerization at stereocilia tips. We show that eliminating espin-1 (ESPN-1), an isoform of ESPN and a myosin-III cargo, dramatically alters the slope of the stereocilia staircase in a subset of hair cells. Furthermore, we show that espin-like (ESPNL), primarily present in developing stereocilia, is also a myosin-III cargo and is essential for normal hearing. ESPN-1 and ESPNL each bind MYO3A and MYO3B, but differentially influence how the two motors function. Consequently, functional properties of different motor-cargo combinations differentially affect molecular transport and the length of actin protrusions. This mechanism is used by hair cells to establish the required range of stereocilia lengths within a single cell

Characterization of twenty-five ovarian tumour cell lines that phenocopy primary tumours

Currently available human tumour cell line panels consist of a small number of lines in each lineage that generally fail to retain the phenotype of the original patient tumour. Here we develop a cell culture medium that enables us to routinely establish cell lines from diverse subtypes of human ovarian cancers with >95% efficiency. Importantly, the 25 new ovarian tumour cell lines described here retain the genomic landscape, histopathology and molecular features of the original tumours. Furthermore, the molecular profile and drug response of these cell lines correlate with distinct groups of primary tumours with different outcomes. Thus, tumour cell lines derived using this methodology represent a significantly improved platform to study human tumour pathophysiology and response to therapy

The burden of injury in Central, Eastern, and Western European sub-region : a systematic analysis from the Global Burden of Disease 2019 Study

Background Injury remains a major concern to public health in the European region. Previous iterations of the Global Burden of Disease (GBD) study showed wide variation in injury death and disability adjusted life year (DALY) rates across Europe, indicating injury inequality gaps between sub-regions and countries. The objectives of this study were to: 1) compare GBD 2019 estimates on injury mortality and DALYs across European sub-regions and countries by cause-of-injury category and sex; 2) examine changes in injury DALY rates over a 20 year-period by cause-of-injury category, sub-region and country; and 3) assess inequalities in injury mortality and DALY rates across the countries. Methods We performed a secondary database descriptive study using the GBD 2019 results on injuries in 44 European countries from 2000 to 2019. Inequality in DALY rates between these countries was assessed by calculating the DALY rate ratio between the highest-ranking country and lowest-ranking country in each year. Results In 2019, in Eastern Europe 80 [95% uncertainty interval (UI): 71 to 89] people per 100,000 died from injuries; twice as high compared to Central Europe (38 injury deaths per 100,000; 95% UI 34 to 42) and three times as high compared to Western Europe (27 injury deaths per 100,000; 95%UI 25 to 28). The injury DALY rates showed less pronounced differences between Eastern (5129 DALYs per 100,000; 95% UI: 4547 to 5864), Central (2940 DALYs per 100,000; 95% UI: 2452 to 3546) and Western Europe (1782 DALYs per 100,000; 95% UI: 1523 to 2115). Injury DALY rate was lowest in Italy (1489 DALYs per 100,000) and highest in Ukraine (5553 DALYs per 100,000). The difference in injury DALY rates by country was larger for males compared to females. The DALY rate ratio was highest in 2005, with DALY rate in the lowest-ranking country (Russian Federation) 6.0 times higher compared to the highest-ranking country (Malta). After 2005, the DALY rate ratio between the lowest- and the highest-ranking country gradually decreased to 3.7 in 2019. Conclusions Injury mortality and DALY rates were highest in Eastern Europe and lowest in Western Europe, although differences in injury DALY rates declined rapidly, particularly in the past decade. The injury DALY rate ratio of highest- and lowest-ranking country declined from 2005 onwards, indicating declining inequalities in injuries between European countries.Peer reviewe