Adhesive interactions of cadherins induce crosstalk between adhesion complexes and the actin cytoskeleton, allowing strengthening of adhesions and cytoskeletal organization. The underlying mechanisms are not completely understood, and microtubules (MTs) might be involved, as for integrin-mediated cell-extracellular-matrix adhesions. Therefore, we investigated the relationship between N-cadherin and MTs by analyzing the influence of N-cadherin engagement on MT distribution and dynamics. MTs progressed less, with a lower elongation rate, towards cadherin adhesions than towards focal adhesions. Increased actin treadmilling and the presence of an actomyosin contractile belt, suggested that actin relays inhibitory signals from cadherin adhesions to MTs. The reduced rate of MT elongation, associated with reduced recruitment of end-binding (EB) proteins to plus ends, was alleviated by expression of truncated N-cadherin, but was only moderately affected when actomyosin was disrupted. By contrast, destabilizing actomyosin fibers allowed MTs to enter the adhesion area, suggesting that tangential actin bundles impede MT growth independently of MT dynamics. Blocking MT penetration into the adhesion area strengthened cadherin adhesions. Taken together, these results establish a crosstalk between N-cadherin, Factin and MTs. The opposing effects of cadherin and integrin engagement on actin organization and MT distribution might induce bias of the MT network during cell polarization.

E-cadherin is a major cell-cell adhesion molecule involved in mechanotransduction at cell-cell contacts in tissues. Because epithelial cells respond to rigidity and tension in tissue through E-cadherin, there must be active processes that test and respond to the mechanical properties of these adhesive contacts. Using submicrometer, E-cadherin–coated polydimethylsiloxane pillars, we find that cells generate local contractions between E-cadherin adhesions and pull to a constant distance for a constant duration, irrespective of pillar rigidity. These cadherin contractions require nonmuscle myosin IIB, tropomyosin 2.1, α-catenin, and binding of vinculin to α-catenin. Cells spread to different areas on soft and rigid surfaces with contractions, but spread equally on soft and rigid without. We further observe that cadherin contractions enable cells to test myosin IIA–mediated tension of neighboring cells and sort out myosin IIA–depleted cells. Thus, we suggest that epithelial cells test and respond to the mechanical characteristics of neighboring cells through cadherin contractions.

30 31 E-cadherin is a major cell-cell adhesion molecule involved in mechanotransduction at cell-32 cell contacts in tissues. Since epithelial cells respond to rigidity and tension in the tissue 33 through E-cadherin, there must be active processes that test and respond to the mechanical 34 properties of these adhesive contacts. Using sub-micrometer, E-cadherin-coated PDMS 35 pillars, we find that cells generate local contractions between E-cadherin adhesions and 36 pull to a constant distance for a constant duration, irrespective of pillar rigidity. These 37 cadherin contractions require non-muscle myosin IIB, tropomyosin 2.1, α-catenin and 38 binding of vinculin to α-catenin; plus, they are correlated with rigidity-dependent cell 39 spreading. Without contractions, cells fail to spread to different areas on soft and rigid 40 surfaces and to maintain monolayer integrity. We further observe that cadherin 41contractions enable cells to test myosin IIA-mediated tension of neighboring cells, and sort 42 out myosin IIA-depleted cells. Thus, we suggest that epithelial cells test and respond to the 43 mechanical characteristics of neighboring cells through cadherin contractions.For the proper organization of tissues, cells need to probe the mechanical properties of their 63 micro-environment including both extracellular matrix and neighboring cells through 64 adhesive contacts. These mechanical properties are then transduced into biochemical 65 information to regulate cell functions 1 , including single and collective cell motility 2, 3 , 66 proliferation 4 or differentiation 5 . Of the many mechanical properties that cells control, 67 stiffness appears to be an important parameter that is distinctive for a tissue and is reflected 68 in the cells that constitute the tissue 6 . It follows that cells should be able to measure the 69 stiffness of their neighbors to enable them to regulate their cell-cell contacts, cytoskeletal 70 rigidity and organize cell monolayers. Thus, it is important to understand how E-cadherin 71 rigidity might be sensed. Recent studies have indeed found that epithelial cells spread to 72 larger areas on rigid cadherin-coated surfaces than soft 7 . The testing of cadherin adhesion 73 rigidity 8 shares similarities with the testing of matrix rigidity described for fibroblasts 9 . In 74 the context of epithelial cell dynamics, this mechanism may allow cells to adapt to changes 75 in the local stiffness of their neighbors due to cytoskeleton remodeling and reinforcement 10-76 12 . 77 78 Cadherin rigidity is a complex mechanical parameter since it is defined as the force per 79 unit area needed to displace a cadherin adhesion by a given distance. In the case of matrix 80 rigidity sensing, cells pull matrix contacts to a constant deflection and measure the force 81 generated [13][14][15] . The local matrix rigidity sensor is a sarcomere-like contraction complex (2 82 micrometers in length) that contracts matrix adhesions by 120 nm and if the force exceeds 83 25 pN, then a rigid-matrix signal is activate...

Adhesive interactions of cadherins induce crosstalk between adhesion complexes and the actin cytoskeleton, allowing strengthening of adhesions and cytoskeletal organization. The underlying mechanisms are not completely understood, and microtubules (MTs) might be involved, as for integrin-mediated cell-extracellular-matrix adhesions. Therefore, we investigated the relationship between N-cadherin and MTs by analyzing the influence of N-cadherin engagement on MT distribution and dynamics. MTs progressed less, with a lower elongation rate, towards cadherin adhesions than towards focal adhesions. Increased actin treadmilling and the presence of an actomyosin contractile belt, suggested that actin relays inhibitory signals from cadherin adhesions to MTs. The reduced rate of MT elongation, associated with reduced recruitment of end-binding (EB) proteins to plus ends, was alleviated by expression of truncated N-cadherin, but was only moderately affected when actomyosin was disrupted. By contrast, destabilizing actomyosin fibers allowed MTs to enter the adhesion area, suggesting that tangential actin bundles impede MT growth independently of MT dynamics. Blocking MT penetration into the adhesion area strengthened cadherin adhesions. Taken together, these results establish a crosstalk between N-cadherin, Factin and MTs. The opposing effects of cadherin and integrin engagement on actin organization and MT distribution might induce bias of the MT network during cell polarization.

The sodium leak channel (NALCN) gene encodes a sodium leak channel that plays an important role in the regulation of the resting membrane potential and the control of neuronal excitability. Mutations in the NALCN gene have been reported in patients with infantile hypotonia with psychomotor retardation and characteristic facies (IHPRF) and congenital contractures of the limbs and face with hypotonia and developmental delay (CLIFAHDD syndrome). We describe the case of a father with drug-resistant left temporo-orbitofrontal epilepsy and his son with mildly-symptomatic temporal epilepsy (only recurrent déjà vu auras) whose genetic panels identified a likely pathogenic deletion of exon 27 on the NALCN gene. Our study helps broaden the clinical spectrum of diseases associated with mutations in the NALCN gene.

Background: Guidelines on epilepsy monitoring unit (EMU) standards have been recently published. We aimed to survey Canadian EMUs to describe the landscape of safety practices and compare these to the recommendations from the new guidelines. Methods: A 34-item survey was created by compiling questions on EMU structure, patient monitoring, equipment, personnel, standardized protocol use, and use of injury prevention tools. The questionnaire was distributed online to 24 Canadian hospital centers performing video-EEG monitoring (VEM) in EMUs. Responses were tabulated and descriptively summarized. Results: In total, 26 EMUs responded (100% response rate), 50% of which were adult EMUs. EMUs were on average active for 23.4 years and had on average 3.6 beds. About 81% of respondents reported having a dedicated area for VEM, and 65% reported having designated EMU beds. Although a video monitoring station was available in 96% of EMUs, only 48% of EMUs provided continuous observation of patients (video and/or physical). A total of 65% of EMUs employed continuous heart monitoring. The technologist-to-patient ratio was 1:1–2 in 52% of EMUs during the day. No technologist supervision was most often reported in the evening and at night. Nurse-to-EMU-patient ratio was mostly 1:1–4 independent of the time of day. Consent forms were required before admission in 27% of EMUs. Conclusion: Canadian EMUs performed decently in terms of there being dedicated space for VEM, continuous heart monitoring, and adequate nurse-to-patient ratios. Other practices were quite variable, and adjustments should be made on a case-by-case basis to adhere to the latest guidelines.

Lewy bodies (LBs), rich in α-synuclein, are a hallmark of Parkinson′s disease (PD). Understanding their biogenesis is likely to provide insight into the pathophysiology of PD, yet a cellular model for LB formation remains elusive. The realization that immune challenge is a trigger for neurodevelopmental disease has been a breakthrough in the understanding of PD. Here, iPSC-derived human dopaminergic (DA) neurons from multiple healthy donors were found to form LB-like inclusions following treatment with α-synuclein preformed fibrils, but only when coupled to an immune challenge (interferon-gamma) or when co-cultured with activated microglia. Human cortical neurons derived from the same iPSC lines did not form LB-like inclusions. Exposure to interferon-gamma impairs autophagy in a lysosomal-specific manner in vitro similar to the disruption of proteostasis pathways that contribute to PD. We find that lysosomal membrane proteins LAMP1 and LAMP2 and transcription factors regulating lysosomal biogenesis and function are downregulated in DA but not cortical neurons. Finally, due to the excellent sample preservation afforded by cells compared to post-mortem PD brain tissue, we conclude that the LB-like inclusions in DA neurons are membrane-bound, suggesting they are not limited to the cytoplasmic compartment.

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