Maintenance of neuronal identity and function

Neurons in the CNS acquire specific characteristics throughout development and maintain them for the entire lifespan. Instructive regulation of the transcription machinery ensures the acquisition of identity by spatiotemporal patterns of transcription factor expression. Additionally, gene silencing of alternative lineages is important for specification of neuronal identity and function, however the mechanisms regulating transcriptional repression are poorly understood. In this study we focused on epigenetic regulation of gene expression and how perturbation of it can lead to loss of function and disease. In Paper I we characterized histone modifications on two clinically relevant neuronal populations, the dopaminergic and serotonergic neurons implicated in Parkinson’s disease and depression respectively. We studied the repressive modifications H3K27me3, H3K9me3 and active H3K4me3 and associated them with gene expression levels throughout cell maturation, from NPCs to adult postmitotic neurons. The generated comprehensive map also illustrates how drug induced stress in dopaminergic neurons alters the histone modifications pattern affecting gene expression. After acquisition of identity, Paper II focuses on how this can be maintained throughout life. Removal of H3K27me3 in dopaminergic and serotonergic neurons resulted to erroneous gene expression patterns and progressive loss of neuronal function. In dopaminergic neurons electrophysiological and molecular properties were perturbed in a region specific manner, with SNc being the most vulnerable, phenomenon similar to PD development. Mice showed phenotypic impairments with motor symptoms or anxiety-like behavior in cell-type dependent manner. In Paper III DNA methylation in neuroblastoma tumors was examined as a potential therapeutic approach. Hypermethylated loci keep potential tumor suppressors silenced leading to cancer formation. Here we showed that combined administration of the demethylating AZA with RA that promotes neuronal differentiation exhibited a favorable outcome in tumor growth. Further analysis of treated xenografted tumors revealed EPAS1 as a potential tumor suppressor, opposite to previously published data assigning the gene as an oncogene

Sequential Activation of Vulnerable Plaques Endorsing the Inflammatory Hypothesis of Atherosclerosis

A case of sequential activation of vulnerable plaques in two different coronary vessels over the course of 2 days is being presented probably related to inflammation inciting these acute coronary events. Rhythmos 2017;12(4): 69-70

Secondary Haemophagocytic Lymphohistiocytosis Syndrome (HLH) After Intravesical Instillation of Bacillus Calmette-Guérin (BCG): A Case Report and Review of the Literature

Intravesical bacillus Calmette-Guérin (BCG) instillation is widely used for the treatment of superficial bladder cancer. BCGitis is a serious immune-mediated complication with systematic manifestations and a high mortality rate. Here, we describe a case of a 64-year-old male patient who presented with haemophagocytic lymphohistiocytosis syndrome (HLH) after BCG instillation and was effectively treated with high-dose dexamethasone, intravenous immunoglobulins and anti-tuberculosis treatment

RASSF1A uncouples Wnt from Hippo signalling and promotes YAP mediated differentiation via p73

Transition from pluripotency to differentiation is a pivotal yet poorly understood developmental step. Here, we show that the tumour suppressor RASSF1A is a key player driving the early specification of cell fate. RASSF1A acts as a natural barrier to stem cell self-renewal and iPS cell generation, by switching YAP from an integral component in the β-catenin-TCF pluripotency network to a key factor that promotes differentiation. We demonstrate that epigenetic regulation of the Rassf1A promoter maintains stemness by allowing a quaternary association of YAP–TEAD and β-catenin–TCF3 complexes on the Oct4 distal enhancer. However, during differentiation, promoter demethylation allows GATA1-mediated RASSF1A expression which prevents YAP from contributing to the TEAD/β-catenin–TCF3 complex. Simultaneously, we find that RASSF1A promotes a YAP–p73 transcriptional programme that enables differentiation. Together, our findings demonstrate that RASSF1A mediates transcription factor selection of YAP in stem cells, thereby acting as a functional “switch” between pluripotency and initiation of differentiation

Regenerative Potential of Ependymal Cells for Spinal Cord Injuries Over Time

International audienc

A comprehensive map coupling histone modifications with gene regulation in adult dopaminergic and serotonergic neurons

The brain is composed of hundreds of different neuronal subtypes, which largely retain their identity throughout the lifespan of the organism. The mechanisms governing this stability are not fully understood, partly due to the diversity and limited size of clinically relevant neuronal populations, which constitute a technical challenge for analysis. Here, using a strategy that allows for ChIP-seq combined with RNA-seq in small neuronal populations in vivo, we present a comparative analysis of permissive and repressive histone modifications in adult midbrain dopaminergic neurons, raphe nuclei serotonergic neurons, and embryonic neural progenitors. Furthermore, we utilize the map generated by our analysis to show that the transcriptional response of midbrain dopaminergic neurons following 6-OHDA or methamphetamine injection is characterized by increased expression of genes with promoters dually marked by H3K4me3/H3K27me3. Our study provides an in vivo genome-wide analysis of permissive/repressive histone modifications coupled to gene expression in these rare neuronal subtypes.Correction in: NATURE COMMUNICATIONS, Volume: 9, Article Number: 4639, DOI: 10.1038/s41467-018-07154-5</p

Long-Term Outcomes of Aortic Stenosis Patients with Different Flow/Gradient Patterns Undergoing Transcatheter Aortic Valve Implantation

Background: Few data exist on the comparative long-term outcomes of severe aortic stenosis (AS) patients with different flow-gradient patterns undergoing transcatheter aortic valve implantation (TAVI). This study sought to evaluate the impact of the pre-TAVI flow-gradient pattern on long-term clinical outcomes after TAVI and assess changes in the left ventricular ejection fraction (LVEF) of different subtypes of AS patients following TAVI. Methods: Consecutive patients with severe AS undergoing TAVI in our institution were screened and prospectively enrolled. Patients were divided into four subgroups according to pre-TAVI flow/gradient pattern: (i) low flow—low gradient (LF-LG): stroke volume indexed (SVi) ≤ 35 mL/m2 and mean gradient (MG) 35 mL/m2 and MG 2 and MG ≥ 40 mmHg and (iv) normal flow—high gradient (NF-HG): SVi > 35 mL/m2 and MG ≥ 40 mmHg. Transthoracic echocardiography was repeated at 1-year follow-up. Clinical follow-up was obtained at 12 months, and yearly thereafter until 5-year follow-up was complete for all patients. Results: A total of 272 patients with complete echocardiographic and clinical follow-up were included in our analysis. Their mean age was 80 ± 7 years and the majority of patients (N = 138, 50.8%) were women. 62 patients (22.8% of the study population) were distributed in the LF-LG group, 98 patients (36%) were LF-HG patients, 95 patients (34.9%) were NF-HG, and 17 patients (6.3%) were NF-LG. There was a greater prevalence of comorbidities among LF-LG AS patients. One-year all-cause mortality differed significantly between the four subgroups of AS patients (log-rank p: 0.022) and was more prevalent among LF-LG patients (25.8%) compared to LF-HG (11.3%), NF-HG (6.3%) and NF-LG patients (18.8%). At 5-year follow-up, global mortality remained persistently higher among LF-LG patients (64.5%) compared to LF-HG (47.9%), NF-HG (42.9%), and NF-LG patients (58.8%) (log-rank p: 0.029). At multivariable Cox hazard regression analysis, baseline SVi (HR: 0.951, 95% C.I.; 0.918–0.984), the presence of at least moderate tricuspid regurgitation at baseline (HR: 3.091, 95% C.I: 1.645–5.809) and at least moderate paravalvular leak (PVL) post-TAVI (HR: 1.456, 95% C.I.: 1.106–1.792) were significant independent predictors of late global mortality. LF-LG patients and LF-HG patients exhibited a significant increase in LVEF at 1-year follow-up. A lower LVEF (p p Conclusions: Patients with LF-LG AS have acceptable 1-year outcomes with significant improvement in LVEF at 1-year follow-up, but exhibit exceedingly high 5-year mortality following TAVI. The presence of low transvalvular flow and at least moderate tricuspid regurgitation at baseline and significant paravalvular leak post-TAVI were associated with poorer long-term outcomes in the entire cohort of AS patients. The presence of a low LVEF or a low SVi predicts LVEF improvement at 1-year

RASSF1A disrupts the NOTCH signaling axis via SNURF/RNF4-mediated ubiquitination of HES1

RASSF1A promoter methylation has been correlated with tumor dedifferentiation and aggressive oncogenic behavior. Nevertheless, the underlying mechanism of RASSF1A-dependent tumor dedifferentiation remains elusive. Here, we show that RASSF1A directly uncouples the NOTCH-HES1 axis, a key suppressor of differentiation. Interestingly, the crosstalk of RASSF1A with HES1 occurs independently from the signaling route connecting RASSF1A with the Hippo pathway. At the molecular level, we demonstrate that RASSF1A acts as a scaffold essential for the SUMO-targeted E3 ligase SNURF/RNF4 to target HES1 for degradation. The reciprocal relationship between RASSF1A and HES1 is evident across a wide range of human tumors, highlighting the clinical significance of the identified pathway. We show that HES1 upregulation in a RASSF1A-depleted environment renders cells non-responsive to the downstream effects of gamma-secretase inhibitors (GSIs) which restrict signaling at the level of the NOTCH receptor. Taken together, we report a mechanism through which RASSF1A exerts autonomous regulation of the critical Notch effector HES1, thus classifying RASSF1A expression as an integral determinant of the clinical effectiveness of Notch inhibitors