Dynamic 1D search and processive nucleosome translocations by RSC and ISW2 chromatin remodelers.

Eukaryotic gene expression is linked to chromatin structure and nucleosome positioning by ATP-dependent chromatin remodelers that establish and maintain nucleosome-depleted regions (NDRs) near transcription start sites. Conserved yeast RSC and ISW2 remodelers exert antagonistic effects on nucleosomes flanking NDRs, but the temporal dynamics of remodeler search, engagement, and directional nucleosome mobilization for promoter accessibility are unknown. Using optical tweezers and two-color single-particle imaging, we investigated the Brownian diffusion of RSC and ISW2 on free DNA and sparse nucleosome arrays. RSC and ISW2 rapidly scan DNA by one-dimensional hopping and sliding, respectively, with dynamic collisions between remodelers followed by recoil or apparent co-diffusion. Static nucleosomes block remodeler diffusion resulting in remodeler recoil or sequestration. Remarkably, both RSC and ISW2 use ATP hydrolysis to translocate mono-nucleosomes processively at ~30 bp/s on extended linear DNA under tension. Processivity and opposing push-pull directionalities of nucleosome translocation shown by RSC and ISW2 shape the distinctive landscape of promoter chromatin.

Determination of single-molecule loading rate during mechanotransduction in cell adhesion.

Cells connect with their environment through surface receptors and use physical tension in receptor-ligand bonds for various cellular processes. Single-molecule techniques have revealed bond strength by measuring "rupture force," but it has long been recognized that rupture force is dependent on loading rate-how quickly force is ramped up. Thus, the physiological loading rate needs to be measured to reveal the mechanical strength of individual bonds in their functional context. We have developed an overstretching tension sensor (OTS) to allow more accurate force measurement in physiological conditions with single-molecule detection sensitivity even in mechanically active regions. We used serially connected OTSs to show that the integrin loading rate ranged from 0.5 to 4 piconewtons per second and was about three times higher in leukocytes than in epithelial cells.

Frequency of diminished ovarian reserve in women with multiple sclerosis in Chile: An exploratory study.

INTRODUCTION: Multiple Sclerosis (MS) is a chronic disease affecting around 2.8 million people worldwide. Two-thirds are women, and the mean age at diagnosis is about 30 years old. Social trends are moving towards older age at first pregnancy, both in women with and without MS. OBJECTIVES: To determine the frequency of diminished ovarian reserve (DOR) through anti-Mullerian Hormone (AMH) measurement in women with MS at fertile age and Healthy Females (HF) in Chile. METHODS: Case-control, multicentric, cross-sectional study including relapsing-remitting people with MS (pwMS) between 18 and 40 years and sex and age-matched HF. We obtained a blood sample to determine AMH levels. We defined DOR as AMH <1.5 ng/mL and very-low AMH levels as <0.5 ng/mL. Also, we performed questions regarding reproductive decision-making. RESULTS: We included 79 sex and age-matched HF and 92 pwMS, median age 32(19-40) years, median disease duration 6 (1-17)years, median EDSS 1.0 (0-6), 95% were receiving disease-modifying therapy (DMT), 70% high-efficacy DMT and 37% with a treatment that contraindicates pregnancy. DOR was observed in 24% (n = 22) of the pwMS, compared to 14% (n = 11) of the HF (p = 0.09), while very-low AMH levels were observed in 7.6% (n = 7) of pwMS and none of the HF (p = 0.0166). We observed an inverse correlation between age and AMH levels. Age was the only significant risk factor for low AMH levels in pwMS (OR 1.14 95%CI(1.00-1-31), p = 0.04), including smoking, body mass index (BMI), hormonal contraception, autoimmune comorbidity, high/low-moderate efficacy DMT, and active disease as covariables. We did not find statistically significant differences in age at diagnosis, BMI, disease duration, EDSS, autoimmune comorbidity, use of hormonal contraception, or percentage of active disease between MS women with normal vs DOR. Over 70% of pwMS desired to become pregnant in the future, while 60% considered that the diagnosis of MS was a limitation for pregnancy planning. CONCLUSIONS: No differences in DOR, measured by levels of AMH, were observed between pwMS MS and HF in Chile. As expected, AMH levels were correlated only with ageing. This information may be evaluated early during the disease course to help patients and neurologists with fertility counselling and family planning considerations regarding DMT use.

ATP binding facilitates target search of SWR1 chromatin remodeler by promoting one-dimensional diffusion on DNA.

One-dimensional (1D) target search is a well-characterized phenomenon for many DNA-binding proteins but is poorly understood for chromatin remodelers. Herein, we characterize the 1D scanning properties of SWR1, a conserved yeast chromatin remodeler that performs histone exchange on +1 nucleosomes adjacent to a nucleosome-depleted region (NDR) at gene promoters. We demonstrate that SWR1 has a kinetic binding preference for DNA of NDR length as opposed to gene-body linker length DNA. Using single and dual color single-particle tracking on DNA stretched with optical tweezers, we directly observe SWR1 diffusion on DNA. We found that various factors impact SWR1 scanning, including ATP which promotes diffusion through nucleotide binding rather than ATP hydrolysis. A DNA-binding subunit, Swc2, plays an important role in the overall diffusive behavior of the complex, as the subunit in isolation retains similar, although faster, scanning properties as the whole remodeler. ATP-bound SWR1 slides until it encounters a protein roadblock, of which we tested dCas9 and nucleosomes. The median diffusion coefficient, 0.024 µm2/s, in the regime of helical sliding, would mediate rapid encounter of NDR-flanking nucleosomes at length scales found in cellular chromatin.

Safety and humoral response rate of inactivated and mRNA vaccines against SARS-CoV-2 in patients with Multiple Sclerosis.

BACKGROUND: Safety and effectiveness outcomes in Multiple Sclerosis (MS) patients receiving different disease-modifying therapies (DMT) and different types of vaccines against SARS-CoV-2 are limited. Growing evidence coming mainly from Israel, Europe and North America using mRNA and adenoviral vector vaccines has been published. OBJECTIVES: To assess the safety and humoral response of inactivated virus and mRNA vaccines against SARS-CoV-2 in patients with MS. METHODS: Ongoing, multicentric, prospective, observational study performed between February and September 2021. Humoral response (antibodies against spike-1 protein) was determined at least 4 weeks after the complete schedule of anti-SARS-CoV-2 vaccines. Categorical outcome (positive/negative) and total antibody titres were recorded. Adverse events supposedly attributable to vaccination (AESAV) were collected. RESULTS: 178 patients, 68% women, mean age 39.7 ± 11.2 years, 123 received inactivated (Coronavac-Sinovac), 51 mRNA (Pfizer-BioNtech), and 4 adenoviral vector vaccines (CanSino n = 2, Jonhson&Johnson-Jannsen n = 1, Oxford-AstraZeneca n = 1). Six patients had a history of COVID-19 before vaccination. Overall humoral response was observed in 66.9% (62.6% inactivated vs. 78.4% mRNA, p = 0.04). Positive anti-S1-antibodies were observed in 100% of patients with no DMT (n = 3), 100% with interferon/glatiramer-acetate (n = 11), 100% with teriflunomide/dimethyl-fumarate (n = 16), 100% with natalizumab (n = 10), 100% with alemtuzumab (n = 8), 90% with cladribine (n = 10), and 88% with fingolimod (n = 17), while 43% of patients receiving antiCD20 (n = 99) were positive (38% inactivated vaccine vs. 59% mRNA vaccine, p = 0.05). In the multivariate analysis including antiCD20 patients, the predictors for a positive humoral response were receiving the mRNA vaccine (OR 8.11 (1.79-36.8), p = 0.007) and a lower number of total infusions (OR 0.44 (0.27-0.74) p = 0.002. The most frequent AESAV was local pain (14%), with 4 (2.2%) patients experiencing mild-moderate relapses within 8 weeks of first vaccination compared to 11 relapses (6.2%) within the 8 weeks before vaccination (Chi-squared 3.41, p = 0.06). DISCUSSION: A higher humoral response rate was observed using the mRNA compared to the inactivated vaccine, while patients using antiCD20 had a significantly lower response rate, and patients using antiCD20 and fingolimod had lower antibody titres. In this MS patient cohort, inactivated and mRNA vaccines against SARS-CoV-2 appear to be safe, with no increase in relapse rate. This information may help guidelines including booster shots and types of vaccines in selected populations.

Regional brain atrophy is related to social cognition impairment in multiple sclerosis / La atrofia cerebral regional se relaciona con el deterioro de la cognición social en sclerosis múltiple

ABSTRACT Background: Multiple sclerosis exhibits specific neuropathological phenomena driving to both global and regional brain atrophy. At the clinical level, the disease is related to functional decline in cognitive domains as the working memory, processing speed, and verbal fluency. However, the compromise of social-cognitive abilities has concentrated some interest in recent years despite the available evidence suggesting the risk of disorganization in social life. Recent studies have used the MiniSEA test to assess the compromise of social cognition and have found relevant relationships with memory and executive functions, as well as with the level of global and regional brain atrophy. Objective: The present article aimed to identify structural changes related to socio-cognitive performance in a sample of patients with relapsing-remitting multiple sclerosis. Methods: 68 relapsing-remitting multiple sclerosis Chilean patients and 50 healthy control subjects underwent MRI scans and neuropsychological evaluation including social-cognition tasks. Total brain, white matter, and gray matter volumes were estimated. Also, voxel-based morphometry was applied to evaluate regional structural changes. Results: Patients exhibited lower scores in all neuropsychological tests. Social cognition exhibited a significant decrease in this group mostly related to the declining social perception. Normalized brain volume and white matter volume were significantly decreased when compared to healthy subjects. The regional brain atrophy analysis showed that changes in the insular cortex and medial frontal cortices are significantly related to the variability of social-cognitive performance among patients. Conclusions: In the present study, social cognition was only correlated with the deterioration of verbal fluency, despite the fact that previous studies have reported its link with memory and executive functions. The identification of specific structural correlates supports the comprehension of this phenomenon as an independent source of cognitive disability in these patients.

RESUMEN Antecedentes: La esclerosis múltiple presenta fenómenos neuropatológicos específicos que conducen a la atrofia cerebral global y regional. A nivel clínico, la enfermedad está relacionada con el deterioro funcional de los dominios cognitivos como la memoria de trabajo, la velocidad de procesamiento y la fluidez verbal. Sin embargo, el compromiso de las habilidades socio-cognitivas ha concentrado cierto interés en los últimos años debido a la evidencia disponible que sugiere el riesgo de desorganización en la vida social. Estudios recientes han utilizado la prueba MiniSEA para evaluar el compromiso de la cognición social y han encontrado relaciones relevantes con la memoria y funciones ejecutiva, así como con el nivel de atrofia cerebral global y regional. Objetivo: El presente artículo tiene como objetivo identificar cambios estructurales relacionados con el rendimiento sociocognitivo en una muestra de pacientes con esclerosis múltiple recurrente-remitente. Métodos: 68 pacientes Chilenos con esclerosis múltiple recurrente-remitente y 50 sujetos de control sanos se sometieron a resonancias magnéticas y evaluación neuropsicológica, incluidas las tareas de cognición social. Se estimaron los volúmenes cerebrales totales, de materia blanca y materia gris. Además, se aplicó la morfometría basada en vóxel para evaluar los cambios estructurales regionales. Resultados: Los pacientes muestran puntuaciones más bajas en todas las pruebas neuropsicológicas. La cognición social exhibe una disminución significativa en este grupo principalmente relacionada con la disminución de la percepción social. El volumen normalizado del cerebro y el volumen de la materia blanca disminuyeron significativamente en comparación con los sujetos sanos. El análisis regional de atrofia cerebral mostró que los cambios en la corteza insular y la corteza frontal medial están significativamente relacionados con la variabilidad del rendimiento sociocognitivo entre los pacientes. Conclusiones: En el presente estudio, la cognición social sólo se correlacionó con el deterioro de la fluencia verbal, a pesar de que estudios previos han reportado su vinculación con la memoria y funciones ejecutivas. La identificación de correlatos estructurales específicos apoya la comprensión de este fenómeno como una fuente independiente de discapacidad cognitiva en estos pacientes.

Prevalence of comorbidities in Multiple Sclerosis and impact on physical disability according to disease phenotypes.

BACKGROUND: Comorbidities are prevalent among Multiple Sclerosis (MS) patients. Few studies have characterized their prevalence and impact in Latin American populations. OBJECTIVE: We aim to assess the prevalence of comorbidities and their impact on the risk of physical disability across different MS phenotypes. METHODS: Cross-sectional multicenter study of patients under regular clinical care at the Programa de Esclerosis Múltiple UC and Hospital Dr. Sótero del Río in Chile. Prevalence of comorbidities was estimated from the retrospective assessment of electronic medical charts. Disease phenotypes were categorized into two groups: clinically isolated syndrome/relapsing-remitting (inflammatory group) and primary/secondary progressive MS patients (progressive group). A multivariable analysis using binary logistic regression for assessing the risk of EDSS ≥ 6.0 in each group was performed. RESULTS: A total of 453 patients was included, 71% female, mean age at onset 31 years, mean disease duration 10 years, and median EDSS 2.0 (range 0-10). In the whole sample, most prevalent comorbidities were ever-smoking (42.2%), depression/anxiety (34.9%), thyroid disease (15.7%), hypertension (11.3%) and insulin resistance/type 2 diabetes mellitus (11.0%). When assessing the risk of EDSS ≥ 6, in the inflammatory group (N = 366), age at onset (OR 1.06, 95%CI(1.02-1.11), p = 0.008), disease duration (OR 1.06, 95%CI(1.00-1.12), p = 0.039) and epilepsy comorbidity (OR 5.36, 95%CI(1.33-21.5), p = 0.018) were associated with a higher risk of disability. In the progressive group (N = 87), disease duration was a risk factor (OR 1.08 95%CI(1.02-1.16), p = 0.014), while shorter diagnostic delay (OR 0.91 95%CI(0.85-0.99), p = 0.025) and insulin resistance/type 2 diabetes mellitus comorbidity were protective factors (OR 0.18 95%CI(0.04-0.83), p = 0.028), 72% of these patients were receiving metformin. CONCLUSIONS: Comorbidities are common across different MS disease phenotypes. Epilepsy seems particularly related with a higher risk of physical disability in relapsing-remitting patients, while the role of insulin resistance/type 2 diabetes mellitus or the impact of metformin use as a protective factor should be further studied. Prospective and larger studies are still needed in order to assess the real impact of comorbidities and their management in MS outcomes.

Homologs of the Tumor Suppressor Protein p53: A Bioinformatics Study for Drug Design.

Sequence and structure of proteins related to the tumor suppressor protein p53 were studied from the perspective of gaining insight for the development of therapeutic drugs. Our study addresses two major issues encumber bringing novel drugs to market: side effects and artifacts from animal models. In the first phase of our study, we performed a genome-wide search to identify potentially similar proteins to p53 that may be susceptible to off target effects. In the second phase, we chose a selection of common model organisms that could potentially be available to undergraduate researchers in the university setting to assess which ones utilize p53 most similar to humans on the basis of sequence homology and structural similarity from predicted structures. Our results confirm the proteins in the humans significantly similar to p53 are known paralogs within the p53 family. In considering model organisms, murine p53 bore great similarity to human p53 in terms of both sequence and structure, but others performed similarly well. We discuss the findings against the background of other structural benchmarks and point out potential benefits and drawbacks of various alternatives for use in future drug design pilot studies.

Corpus callosum atrophy and post-surgical seizures in temporal lobe epilepsy associated with hippocampal sclerosis.

OBJECTIVE: Our aim in this retrospective study was to explore whether corpus callosum atrophy could predict the post-surgical seizure control in patients with temporal lobe epilepsy associated with Hippocampal Sclerosis (HS). METHODS: We used the Corpus Callosum Index (CCI) obtained from best mid-sagittal T2/FLAIR or T1-weighted MRI at two time-points, more than one year apart. CCI has been mainly used in Multiple Sclerosis (MS), but not in epilepsy, so we tested the validity of our results performing a proof of concept cohort, incorporating MS patients with and without epilepsy. Then, we explored this measurement in a well-characterized and long-term cohort of patients with temporal lobe epilepsy associated with HS. RESULTS: In the proof of concept cohort (MS without epilepsy n:40, and MS with epilepsy, n:15), we found a larger CCI atrophy rate in MS patients with poor epilepsy control vs. MS without epilepsy (p:0.01). Then, in HS patients (n:74), annualized CCI atrophy rate was correlated with the long-term Engel scale (Rho:0.31, p:0.007). In patients with post-surgical seizure recurrence, a larger CCI atrophy rate was found one year before any seizure relapse. Univariate analysis showed an increased risk of seizure recurrence in males, higher pre-surgical seizure frequency, necessity of invasive EEG monitoring, and higher CCI atrophy rate. Two of these variables were independent predictors in the multivariate analysis, male gender (HR:4.87, p:0.002) and CCI atrophy rate (HR:1.21, p:0.001). CONCLUSION: We demonstrated that atrophy of the corpus callosum, using the CCI, is related with poor seizure control in two different neurological disorders presenting with epilepsy, which might suggest that corpus callosum atrophy obtained in early post-surgical follow-up, could be a biomarker for predicting recurrences and guiding treatment plans.

[Antibodies against galectin-8 in patients with systemic lupus erythematosus]. / Autoanticuerpos anti-galectina-8 en pacientes con lupus eritematoso sistémico.

BACKGROUND: The family of lectins known as galectins (galectins 1-14) are involved in the regulation of the immune system and in oncogenesis. During a search for antigens recognized by antibodies produced by a patient with systemic lupus erythematosus (SLE) we found reactivity against galectin-8, for which autoantibodies have not been previously described. AIM: To determine the frequency of autoantibodies against galectin-8 in lupus patients compared with healthy controls. PATIENTS AND METHODS: Galectin-8 was purified from a bacterial expression system and used in immunoblot assays as antigen to screen the sera of 55 SLE patients and matched controls. Disease activity was evaluated using the Mexican Modification of the Systemic Lupus Erythematosus Disease Activity Index (MEX-SLEDAI). RESULTS: Reactivity against galectin-8 was detected in 30% of SLE patients, compared to 7% of controls (p=0.003). We could not detect any particular SLE manifestation associated to the presence of these autoantibodies. CONCLUSIONS: This is the first description of autoantibodies against galectin-8. Its higher frequency in patients with SLE suggests a pathogenic role. Further studies are needed to determine their clinical relevance.

Autoanticuerpos anti-galectina-8 en pacientes con lupus eritematoso sistémico / Antibodies against galectin-8 in patients with systemic lupus erythematosus

Background: The family of lectins known as galectins (galectins 1-14) are involved in the regulation of the immune system and in oncogenesis. During a search for antigens recognized by antibodies produced by a patient with systemic lupus erythematosus (SLE) we found reactivity against galectin-8, for which autoantibodies have not been previously described. Aim: To determine the frequency of autoantibodies against galectin-8 in lupus patients compared with healthy controls. Patients and Methods: Galectin-8 was purified from a bacterial expression system and used in immunoblot assays as antigen to screen the sera of 55 SLE patients and matched controls. Disease activity was evaluated using the Mexican Modification of the Systemic Lupus Erythematosus Disease Activity Index (MEX-SLEDAI). Results: Reactivity against galectin-8 was detected in 30% of SLE patients, compared to 7% of controls (p=0.003). We could not detect any particular SLE manifestation associated to the presence of these autoantibodies. Conclusions: This is the first description of autoantibodies against galectin-8. Its higher frequency in patients with SLE suggests a pathogenic role. Further studies are needed to determine their clinical relevance.

Galectin-8 binds specific beta1 integrins and induces polarized spreading highlighted by asymmetric lamellipodia in Jurkat T cells.

Integrin-mediated encounters of T cells with extracellular cues lead these cells to adhere to a variety of substrates and acquire a spread phenotype needed for their tissue incursions. We studied the effects of galectin-8 (Gal-8), a beta-galactoside binding lectin, on Jurkat T cells. Immobilized Gal-8 bound alpha1beta1, alpha3beta1 and alpha5beta1 but not alpha2beta1 and alpha4beta1 and adhered these cells with similar kinetics to immobilized fibronectin (FN). Function-blocking experiments with monoclonal anti-integrin antibodies suggested that alpha5beta1 is the main mediator of cell adhesion to this lectin. Gal-8, but not FN, induced extensive cell spreading frequently leading to a polarized phenotype characterized by an asymmetric lamellipodial protrusion. These morphological changes involved actin cytoskeletal rearrangements controlled by PI3K, Rac-1 and ERK1/2 activity. Gal-8-induced Rac-1 activation and binding to alpha1 and alpha5 integrins have not been described in any other cellular system. Strikingly, Gal-8 was also a strong stimulus on Jurkat cells in suspension, triggering ERK1/2 activation that in most adherent cells is instead dependent on cell attachment. In addition, we found that patients with systemic lupus erythematosus (SLE), a prototypic autoimmune disorder, produce Gal-8 autoantibodies that impede both its binding to integrins and cell adhesion. These are the first function-blocking autoantibodies reported for a member of the galectin family. These results indicate that Gal-8 constitutes a novel extracellular stimulus for T cells, able to bind specific beta1 integrins and to trigger signaling pathways conducive to cell spreading. Gal-8 could modulate a wide range of T cell-driven immune processes that eventually become altered in autoimmune disorders.