The developmentally regulated neural crest-associated glycotope HNK-1 predicts metastasis in cutaneous malignant melanoma

Aberrant glycosylation is a common feature of metastatic sub-clones of malignant tumours and in uveal melanoma in particular, the HNK-1 glycotope has been positively correlated with poor prognosis. So far, no such correlation has been investigated in cutaneous melanoma. In order to do so, HNK-1 expression was evaluated immunohistochemically in 100 primary cutaneous melanomas and correlated with metastasis after up to 10-years' follow-up. Furthermore, HNK-1 expression was analysed in metastatic deposits (19 distant cutaneous metastases and six sentinel lymph node metastases), as well as in benign nevi. Kaplan-Meier analysis revealed a positive association between HNK-1 expression and metastasis (p < 0.005) and multivariate Cox regression analysis adjusted for the standard prognostic markers ulceration and vertical tumour thickness confirmed HNK-1 expression as an independent prognostic marker. HNK-1 expression was preserved in 42% of the distant cutaneous metastases, but metastatic cells in lymph nodes were devoid of HNK-1 immunoreactivity. None of the benign pigmented lesions exhibited HNK-1 immunoreactivity. Expression of the HNK-1 glycotope in cutaneous malignant melanoma is an independent prognostic marker of metastasis. Differential HNK-1 expression at the metastatic sites implies that its expression is modulated by the surrounding environment. As HNK-1 is also transiently expressed during migration of melanocyte precursor cells derived from the neural crest, recapitulation of this transient expression might occur during metastatic spread of cutaneous malignant melanoma.     

Lateral Mobility of the Cell Adhesion Molecule L1 Within the Surface Membrane of Morphologically Undifferentiated and Differentiated Neuroblastoma Cells

Lateral mobility and localization in the surface membrane of the adhesion molecule L1 was studied in morphologically undifferentiated and differentiated neuroblastoma cells to gain insight into its possible association with the different molecular forms of N-CAM. In undifferentiated cells, the fraction of mobile L1 molecules is high and similar to that of N-CAM 140. Upon long-term morphological differentiation, the fraction of mobile L1 molecules is reduced by a factor of three and is similar to that of N-CAM 180, the predominant molecular form of N-CAM in differentiated neuroblastoma cells. Comparable to N-CAM 180, L1 is also preferentially accumulated at contact sites between these cells as seen by indirect immunofluorescence. These observations raise the question of whether at least part of the L1 molecules may be directly or indirectly (e.g. via N-CAM 180) linked to the cytoskeleton, thus stabilizing cell contacts between differentiated cells.     

Cell Type-specific Effects of the Neural Adhesion Molecules L1 and N-CAM on Diverse Second Messenger Systems

We have previously shown that the neural adhesion molecules L1 and N-CAM influence second messenger systems when triggered with specific antibodies at the surface of the phaeochromocytoma PC12 cell line (Schuch et al., Neuron, 3, 13 - 20, 1989). To determine whether the two molecules are linked to the same intracellular signalling cascades, independent of the cell type expressing them, or whether different neural cell types respond with different signal transduction mechanisms, we have investigated the effects of antibodies to L1 and N-CAM, and the isolated molecules themselves, on second messenger systems in different neural cell types. We have investigated cultures of cerebellar and dorsal root ganglion neurons and transformed Schwann cells and related these results to those obtained with the PC12 cell line. Here we show that addition of L1 and N-CAM antibodies and the isolated molecules themselves elicit cell type-specific responses that can be modulated by the substrate on which the cells are maintained. Depending on the cell type, cells respond to the triggering of L1 and N-CAM with antibodies, or addition of the purified molecules, by either up-regulation or down-regulation of inositol phosphate turnover, by a rise in intracellular Ca2+ levels dependent on or independent of the opening of voltage-gated Ca2+ channels, or by an increase or decrease in intracellular pH. Moreover, cerebellar neurons expressing N-CAM respond to addition N-CAM, but not to N-CAM antibodies, in contrast to the other neural cell types studied, which respond to both triggers. Furthermore, cerebellar neurons were the only cells to show a rise in cAMP levels in response to any of the ligands tested. This stimulation of cAMP production by L1 antibodies depended on the cross-linking of L1 molecules at the cell surface, whereas the other responses did not depend on clustering of L1. Simultaneous addition of L1 and N-CAM antibodies either elicited an additive or more than additive effect on the intracellular responses which, for cerebellar neurons, depends on the substrate on which the cells are maintained. These observations indicate that L1 and N-CAM or their antibodies activate cell type-specific intracellular signalling systems and that the two molecules can act interdependently or independently of each other.     

Divalent Cations Modulate the Inhibitory Substrate Properties of Murine Glia-derived J1-160 and J1-180 Extracellular Matrix Glycoproteins for Neuronal Adhesion

J1-160 and J1-180 are developmentally late appearing J1 extracellular matrix glycoproteins derived from oligodendrocytes. They prevent adhesion of neurons (but not of astrocytes or fibroblasts) when offered as a substrate in mixture with laminin (Pesheva et al., J. Cell Biol., 109, 1765 - 1778, 1989). In the present study we have examined the influence of divalent cations on the inhibitory substrate properties of J1-160/180 glycoproteins towards adhesion of neurons. By metal chelate affinity chromatography, we show that J1-180, but not J1-160, binds Ca2+, while both J1 components are capable of binding Zn2+ and other divalent metal ions. Divalent cation binding was observed by gel filtration, aggregation assays with coated latex beads and electron microscopic examination to elicit aggregation of the molecules. Divalent cation binding also affects their non-permissive substrate properties towards neurons from early postnatal mouse cerebellum. Without divalent cations, J1-160 and J1-180 are inhibitory for substrate adhesion of neurons independently of the adhesive substrate present (laminin or poly-l-lysine). This effect is neutralized when J1-180 is preincubated with Ca2+ or Zn2+ prior to coating as substrate. In contrast, preincubation with Ca2+ ions does not affect the inhibitory substrate properties of J1-160 under these conditions. These observations show that J1-160/180 molecules may undergo self-aggregation in a divalent cation-dependent mechanism, which correlates with the neutralization of their inhibitory effect on neuronal adhesion. The aggregation state of the molecules may thus influence the process of myelination by a homophilic binding mechanism and determine the effectiveness of neurite extension during central nervous system development and under traumatic conditions in the adult.     

Physical activity,mental health and well-being of adults during initial COVID-19 containment strategies: A multi-country cross-sectional analysis

ObjectivesTo assess physical activity (PA), mental health and well-being of adults in the United Kingdom (UK), Ireland, New Zealand and Australia during the initial stages of National governments’ Coronavirus disease (COVID-19) containment responses.DesignObservational, cross-sectional.MethodsAn online survey was disseminated to adults (n = 8,425; 44.5 ± 14.8y) residing in the UK, Ireland, New Zealand and Australia within the first 2-6 weeks of government-mandated COVID-19 restrictions. Main outcome measures included: Stages of Change scale for exercise behaviour change; International Physical Activity Questionnaire (short-form); World Health Organisation-5 Well-being Index; and the Depression Anxiety and Stress Scale-9.ResultsParticipants who reported a negative change in exercise behaviour from before initial COVID-19 restrictions to during the initial COVID-19 restrictions demonstrated poorer mental health and well-being compared to those demonstrating either a positive-or no change in their exercise behaviour (p < 0.001). Whilst women reported more positive changes in exercise behaviour, young people (18-29y) reported more negative changes (both p < 0.001). Individuals who had more positive exercise behaviours reported better mental health and well-being (p < 0.001). Although there were no differences in PA between countries, individuals in New Zealand reported better mental health and well-being (p < 0.001).ConclusionThe initial COVID-19 restrictions have differentially impacted upon PA habits of individuals based upon their age and sex, and therefore have important implications for international policy and guideline recommendations. Public health interventions that encourage PA should target specific groups (e.g., men, young adults) who are most vulnerable to the negative effects of physical distancing and/or self-isolation.     

Syntenin‐a promotes spinal cord regeneration following injury in adult zebrafish

In contrast to mammals, adult zebrafish recover locomotor function after spinal cord injury, in part due to the capacity of the central nervous system to repair severed connections. To identify molecular cues that underlie regeneration, we conducted mRNA expression profiling and found that syntenin‐a expression is upregulated in the adult zebrafish spinal cord caudal to the lesion site after injury. Syntenin is a scaffolding protein involved in mammalian cell adhesion and movement, axonal outgrowth, establishment of cell polarity, and protein trafficking. It could thus be expected to be involved in supporting regeneration in fish. Syntenin‐a mRNA and protein are expressed in neurons, glia and newly generated neural cells, and upregulated caudal to the lesion site on days 6 and 11 following spinal cord injury. Treatment of spinal cord‐injured fish with two different antisense morpholinos to knock down syntenin‐a expression resulted in significant inhibition of locomotor recovery at 5 and 6 weeks after injury, when compared to control morpholino‐treated fish. Knock‐down of syntenin‐a reduced regrowth of descending axons from brainstem neurons into the spinal cord caudal to the lesion site. These observations indicate that syntenin‐a is involved in regeneration after traumatic insult to the central nervous system of adult zebrafish, potentially leading to novel insights into the cellular and molecular mechanisms that require activation in the regeneration‐deficient mammalian central nervous system.