Augmin complex activity finetunes dendrite morphology through non-centrosomal microtubule nucleation in vivo.

During development, neurons achieve a stereotyped neuron type-specific morphology, which relies on dynamic support by microtubules (MTs). An important player is the augmin complex (hereafter augmin), which binds to existing MT filaments and recruits the γ-tubulin ring complex (γ-TuRC), to form branched MTs. In cultured neurons, augmin is important for neurite formation. However, little is known about the role of augmin during neurite formation in vivo. Here, we have revisited the role of mammalian augmin in culture and then turned towards the class four Drosophila dendritic arborization (c4da) neurons. We show that MT density is maintained through augmin in cooperation with the γ-TuRC in vivo. Mutant c4da neurons show a reduction of newly emerging higher-order dendritic branches and in turn also a reduced number of their characteristic space-filling higher-order branchlets. Taken together, our data reveal a cooperative function for augmin with the γ-TuRC in forming enough MTs needed for the appropriate differentiation of morphologically complex dendrites in vivo.

Transplantation of dorsal root ganglia overexpressing the NaChBac sodium channel improves locomotion after complete SCI.

Spinal cord injury (SCI) is a debilitating condition currently lacking treatment. Severe SCI causes the loss of most supraspinal inputs and neuronal activity caudal to the injury, which, coupled with the limited endogenous capacity for spontaneous regeneration, can lead to complete functional loss even in anatomically incomplete lesions. We hypothesized that transplantation of mature dorsal root ganglia (DRGs) genetically modified to express the NaChBac sodium channel could serve as a therapeutic option for functionally complete SCI. We found that NaChBac expression increased the intrinsic excitability of DRG neurons and promoted cell survival and neurotrophic factor secretion in vitro. Transplantation of NaChBac-expressing dissociated DRGs improved voluntary locomotion 7 weeks after injury compared to control groups. Animals transplanted with NaChBac-expressing DRGs also possessed higher tubulin-positive neuronal fiber and myelin preservation, although serotonergic descending fibers remained unaffected. We observed early preservation of the corticospinal tract 14 days after injury and transplantation, which was lost 7 weeks after injury. Nevertheless, transplantation of NaChBac-expressing DRGs increased the neuronal excitatory input by an increased number of VGLUT2 contacts immediately caudal to the injury. Our work suggests that the transplantation of NaChBac-expressing dissociated DRGs can rescue significant motor function, retaining an excitatory neuronal relay activity immediately caudal to injury.

Extracellular vesicles from mesenchymal stem cells reduce neuroinflammation in hippocampus and restore cognitive function in hyperammonemic rats.

Chronic hyperammonemia, a main contributor to hepatic encephalopathy (HE), leads to neuroinflammation which alters neurotransmission leading to cognitive impairment. There are no specific treatments for the neurological alterations in HE. Extracellular vesicles (EVs) from mesenchymal stem cells (MSCs) reduce neuroinflammation in some pathological conditions. The aims were to assess if treatment of hyperammonemic rats with EVs from MSCs restores cognitive function and analyze the underlying mechanisms. EVs injected in vivo reach the hippocampus and restore performance of hyperammonemic rats in object location, object recognition, short-term memory in the Y-maze and reference memory in the radial maze. Hyperammonemic rats show reduced TGFß levels and membrane expression of TGFß receptors in hippocampus. This leads to microglia activation and reduced Smad7-IkB pathway, which induces NF-κB nuclear translocation in neurons, increasing IL-1ß which alters AMPA and NMDA receptors membrane expression, leading to cognitive impairment. These effects are reversed by TGFß in the EVs from MSCs, which activates TGFß receptors, reducing microglia activation and NF-κB nuclear translocation in neurons by normalizing the Smad7-IkB pathway. This normalizes IL-1ß, AMPA and NMDA receptors membrane expression and, therefore, cognitive function. EVs from MSCs may be useful to improve cognitive function in patients with hyperammonemia and minimal HE.

Management of small subepithelial tumors by endoscopic banding without resection and single-incision needle-knife-assisted biopsy sampling: a prospective multicenter study.

BACKGROUND AND AIMS: Endoscopic band ligation (EBL) without resection combined with single-incision needle-knife (SINK) biopsy sampling may have a positive impact on small GI subepithelial tumor (SET) management, but the method needs to be tested. The aim was to evaluate the feasibility of this strategy in small-sized SETs. METHODS: This prospective multicenter observational cohort study in 7 centers included patients with SETs ≤15 mm (confirmed by EUS) between March 2017 and March 2020. The primary outcome was clinical success at 4 weeks, defined as complete SET disappearance on EUS. Secondary outcomes were long-term (1-year) clinical success, technical difficulty level, clinical impact, yield pathology, and safety. RESULTS: Of 273 patients screened, 122 (62.3% women; mean age, 60.9 ± 13.2 years) were included with SETs (mean size, 9 ± 2.8 mm; gastric location, 77%; superficial layer dependence, 63%). The primary endpoint was achieved in 73.6% of patients (95% confidence interval [CI], 64.8-81.2). At the 1-year follow-up, the success rate was 68.4% (95% CI, 59.1-76.8). A favorable clinical impact was observed in 97 cases (79.5%; 95% CI, 71.3-86.3). Pathology diagnosis was known in 70%. Potentially malignant lesions were present in 24.7%. The related adverse events rate was 4.1% (95% CI, 1.3-9.3; all mild: 2 bleeding, 2 abdominal pain). On multivariable analysis, the ≤10-mm SET group was associated with a greater success rate (1 year, 87%; relative risk, 5.07; 95% CI, 2.63-9.8) and clinical impact rate (92.7%; relative risk, 6.15; 95% CI, 2.72-13.93). CONCLUSIONS: EBL plus SINK biopsy sampling seems to be feasible and safe, and it may offer a favorable clinical impact in small-sized SETs. In particular, SETs ≤10 mm are the best candidates. (Clinical trial registration number: NCT03247231.).

Endoscopic removal of lumen-apposing metal stents - risk factors for stent embedment, complex removals, and adverse events: analysis from a multicenter prospective case series.

BACKGROUND: Removing lumen-apposing metal stents (LAMSs) may be difficult and even harmful, but these features have seldom been analyzed. We aimed to generate a comprehensive assessment of the feasibility and safety of LAMS retrieval procedures. METHODS: A prospective multicenter case series including all technically successfully deployed LAMSs between January 2019 and January 2020 that underwent endoscopic stent removal. All retrieval-related data were prospectively recorded using standardized telephone questionnaires as part of centralized follow-up that ended after stent removal had been performed. Multivariable logistic regression models assessed the potential risk factors for complex removal. RESULTS: For the 407 LAMSs included, removal was attempted in 158 (38.8 %) after an indwell time of 46.5 days (interquartile range [IQR] 31-70). The median (IQR) removal time was 2 (1-4) minutes. Removal was labelled as complex in 13 procedures (8.2 %), although advanced endoscopic maneuvers were required in only two (1.3 %). Complex removal risk factors were stent embedment (relative risk [RR] 5.84, 95 %CI 2.14-15.89; P = 0.001), over-the-wire deployment (RR 4.66, 95 %CI 1.60-13.56; P = 0.01), and longer indwell times (RR 1.14, 95 %CI 1.03-1.27; P = 0.01). Partial and complete embedment were observed in 14 (8.9 %) and five cases (3.2 %), respectively. The embedment rate during the first 6 weeks was 3.1 % (2/65), reaching 15.9 % (10/63) during the following 6 weeks (P = 0.02). The adverse event rate was 5.1 %, including seven gastrointestinal bleeds (5 mild, 2 moderate). CONCLUSIONS: LAMS removal is a safe procedure, mostly requiring basic endoscopic techniques attainable in conventional endoscopy rooms. Referral to advanced endoscopy units should be considered for stents with known embedment or long indwell times, which may require more technically demanding procedures.

International and multicenter real-world study of sorafenib-treated patients with hepatocellular carcinoma under dialysis.

BACKGROUND & AIMS: Information on safety and efficacy of systemic treatment in patients with hepatocellular carcinoma (HCC) under dialysis are limited due to patient exclusion from clinical trials. Thus, we aimed to evaluate the rate, prevalence, tolerability, and outcome of sorafenib in this population. METHODS: We report a multicenter study comprising patients from Latin America and Europe. Patients treated with sorafenib were enrolled; demographics, dose modifications, adverse events (AEs), treatment duration, and outcome of patients undergoing dialysis were recorded. RESULTS: As of March 2018, 6156 HCC patients were treated in 44 centres and 22 patients were concomitantly under dialysis (0.36%). The median age was 65.5 years, 40.9% had hepatitis C, 75% had Child-Pugh A, and 85% were Barcelona Clinic Liver Cancer-C. The median time to first dose modification, treatment duration and overall survival rate were 2.4 months (interquartile ranges [IQR], 0.8-3.8), 10.8 months (IQR, 4.5-16.9), and 17.5 months (95% CI, 7.2-24.5), respectively. Seventeen patients required at least 1 dose modification. The main causes of first dose modification were asthenia/worsening of Eastern Cooperative Oncology Group-Performance Status and diarrhoea. At the time of death or last follow-up, four patients were still on treatment and 18 had discontinued sorafenib: 14 were due to tumour progression, 2 were sorafenib-related, and 2 were non-sorafenib-related AE. CONCLUSIONS: The outcomes observed in this cohort seem comparable to those in the non-dialysis population. Thus, to the best of our knowledge, this is the largest and most informative dataset regarding systemic treatment outcomes in HCC patients undergoing dialysis.

Complete response under sorafenib in patients with hepatocellular carcinoma: Relationship with dermatologic adverse events.

The clinical benefit of sorafenib in patients with hepatocellular carcinoma (HCC) has been undervalued due to the absence of complete responses, even though patients who develop early dermatologic reactions have shown to have a positive outcome. In addition, sorafenib is described as an antiangiogenic drug, but it also acts on immunological cells. Thus, the goal of this study was to assess the complete response rate in a retrospective cohort of HCC patients treated with sorafenib and to describe the profile of the patients who achieve complete response for identifying factors related to this event and their connection with the immunological profile of sorafenib. Ten Spanish centers submitted cases of complete response under sorafenib. The baseline characteristics, development of early dermatologic reactions, and cause of treatment discontinuation were annotated. Radiological images taken before starting sorafenib, at first control, after starting sorafenib, at the time of complete response, and at least 1 month after treatment were centrally reviewed. Of the 1119 patients studied, 20 had been classified as complete responders by the centers, but eight of these patients were excluded after central review. Ten patients had complete disappearance of all tumor sites, and two had just a small residual fibrotic scar. Thus, 12 patients were classified as complete responders (58% HCV, median age 59.7 years, 83.4% Child-Pugh class A, Eastern Cooperative Oncology Group performance status 0 91.7%, and Barcelona Clinic Liver Cancer stage C 83.3%). The median overall survival and treatment duration were 85.8 and 40.1 months, respectively. All but one patient developed early dermatologic reactions, and seven patients discontinued sorafenib after achieving complete response due to adverse events, patient decision, or liver decompensation. Conclusion: Complete response affects 1% of patients with HCC who are treated with sorafenib. The association of complete response with early dermatologic reactions supports the role of a specific immune/inflammatory patient profile in the improved response to sorafenib. (Hepatology 2018;67:612-622).

Lichen planus of the esophagus: a case report.

Esophageal lichen planus (ELP) is an inflammatory disorder that affects the skin, cutaneous appendages and mucous membranes. The esophageal involvement is rare. We present the case of a 70-year-old woman with years of dysphagia and a history of erosive lichen planus involving the vulva, vagina, gingiva, and skin, who was eventually diagnosed with esophageal lichen planus. The patient's condition was refractory and progressed to the development of intraepithelial squamous neoplasia. We reviewed the literature on this condition.

CREB-Dependent Regulation of GAD65 Transcription by BDNF/TrkB in Cortical Interneurons.

In the cerebral cortex, the functional output of projection neurons is fine-tuned by inhibitory neurons present in the network, which use γ-aminobutyric acid (GABA) as their main neurotransmitter. Previous studies have suggested that the expression levels of the rate-limiting GABA synthetic enzyme, GAD65, depend on brain derived neurotrophic factor (BDNF)/TrkB activation. However, the molecular mechanisms by which this neurotrophic factor and its receptor controls GABA synthesis are still unknown. Here, we show a direct regulation of the GAD65 gene by BDNF-TrkB signaling via CREB in cortical interneurons. Conditional ablation of TrkB in cortical interneurons causes a cell-autonomous decrease in the synaptically enriched GAD65 protein and its transcripts levels, suggesting that transcriptional regulation of the GAD65 gene is altered. Dissection of the intracellular pathway that underlies this process revealed that BDNF/TrkB signaling controls the transcription of GAD65 in a Ras-ERK-CREB-dependent manner. Our study reveals a novel molecular mechanism through which BDNF/TrkB signaling may modulate the maturation and function of cortical inhibitory circuits.

With the Permission of Microtubules: An Updated Overview on Microtubule Function During Axon Pathfinding.

During the establishment of neural circuitry axons often need to cover long distances to reach remote targets. The stereotyped navigation of these axons defines the connectivity between brain regions and cellular subtypes. This chemotrophic guidance process mostly relies on the spatio-temporal expression patterns of extracellular proteins and the selective expression of their receptors in projection neurons. Axon guidance is stimulated by guidance proteins and implemented by neuronal traction forces at the growth cones, which engage local cytoskeleton regulators and cell adhesion proteins. Different layers of guidance signaling regulation, such as the cleavage and processing of receptors, the expression of co-receptors and a wide variety of intracellular cascades downstream of receptors activation, have been progressively unveiled. Also, in the last decades, the regulation of microtubule (MT) assembly, stability and interactions with the submembranous actin network in the growth cone have emerged as crucial effector mechanisms in axon pathfinding. In this review, we will delve into the intracellular signaling cascades downstream of guidance receptors that converge on the MT cytoskeleton of the growing axon. In particular, we will focus on the microtubule-associated proteins (MAPs) network responsible of MT dynamics in the axon and growth cone. Complementarily, we will discuss new evidences that connect defects in MT scaffold proteins, MAPs or MT-based motors and axon misrouting during brain development.

The +TIP Navigator-1 is an actin-microtubule crosslinker that regulates axonal growth cone motility.

Microtubule (MT) plus-end tracking proteins (+TIPs) are central players in the coordination between the MT and actin cytoskeletons in growth cones (GCs) during axon guidance. The +TIP Navigator-1 (NAV1) is expressed in the developing nervous system, yet its neuronal functions remain poorly elucidated. Here, we report that NAV1 controls the dynamics and motility of the axonal GCs of cortical neurons in an EB1-dependent manner and is required for axon turning toward a gradient of netrin-1. NAV1 accumulates in F-actin-rich domains of GCs and binds actin filaments in vitro. NAV1 can also bind MTs independently of EB1 in vitro and crosslinks nonpolymerizing MT plus ends to actin filaments in axonal GCs, preventing MT depolymerization in F-actin-rich areas. Together, our findings pinpoint NAV1 as a key player in the actin-MT crosstalk that promotes MT persistence at the GC periphery and regulates GC steering. Additionally, we present data assigning to NAV1 an important role in the radial migration of cortical projection neurons in vivo.

NEK7 regulates dendrite morphogenesis in neurons via Eg5-dependent microtubule stabilization.

Organization of microtubules into ordered arrays is best understood in mitotic systems, but remains poorly characterized in postmitotic cells such as neurons. By analyzing the cycling cell microtubule cytoskeleton proteome through expression profiling and targeted RNAi screening for candidates with roles in neurons, we have identified the mitotic kinase NEK7. We show that NEK7 regulates dendrite morphogenesis in vitro and in vivo. NEK7 kinase activity is required for dendrite growth and branching, as well as spine formation and morphology. NEK7 regulates these processes in part through phosphorylation of the kinesin Eg5/KIF11, promoting its accumulation on microtubules in distal dendrites. Here, Eg5 limits retrograde microtubule polymerization, which is inhibitory to dendrite growth and branching. Eg5 exerts this effect through microtubule stabilization, independent of its motor activity. This work establishes NEK7 as a general regulator of the microtubule cytoskeleton, controlling essential processes in both mitotic cells and postmitotic neurons.

Non-centrosomal nucleation mediated by augmin organizes microtubules in post-mitotic neurons and controls axonal microtubule polarity.

Neurons display a highly polarized microtubule network that mediates trafficking throughout the extensive cytoplasm and is crucial for neuronal differentiation and function. In newborn migrating neurons, the microtubule network is organized by the centrosome. During neuron maturation, however, the centrosome gradually loses this activity, and how microtubules are organized in more mature neurons remains poorly understood. Here, we demonstrate that microtubule organization in post-mitotic neurons strongly depends on non-centrosomal nucleation mediated by augmin and by the nucleator γTuRC. Disruption of either complex not only reduces microtubule density but also microtubule bundling. These microtubule defects impair neurite formation, interfere with axon specification and growth, and disrupt axonal trafficking. In axons augmin does not merely mediate nucleation of microtubules but ensures their uniform plus end-out orientation. Thus, the augmin-γTuRC module, initially identified in mitotic cells, may be commonly used to generate and maintain microtubule configurations with specific polarity.