Topoisomerase VI participates in an insulator-like function that prevents H3K9me2 spreading.

The organization of the genome into transcriptionally active and inactive chromatin domains requires well-delineated chromatin boundaries and insulator functions in order to maintain the identity of adjacent genomic loci with antagonistic chromatin marks and functionality. In plants that lack known chromatin insulators, the mechanisms that prevent heterochromatin spreading into euchromatin remain to be identified. Here, we show that DNA Topoisomerase VI participates in a chromatin boundary function that safeguards the expression of genes in euchromatin islands within silenced heterochromatin regions. While some transposable elements are reactivated in mutants of the Topoisomerase VI complex, genes insulated in euchromatin islands within heterochromatic regions of the Arabidopsis thaliana genome are specifically down-regulated. H3K9me2 levels consistently increase at euchromatin island loci and decrease at some transposable element loci. We further show that Topoisomerase VI physically interacts with S-adenosylmethionine synthase methionine adenosyl transferase 3 (MAT3), which is required for H3K9me2. A Topoisomerase VI defect affects MAT3 occupancy on heterochromatic elements and its exclusion from euchromatic islands, thereby providing a possible mechanistic explanation to the essential role of Topoisomerase VI in the delimitation of chromatin domains.

GTL1 and DF1 regulate root hair growth through transcriptional repression of ROOT HAIR DEFECTIVE 6-LIKE 4 in Arabidopsis.

How plants determine the final size of growing cells is an important, yet unresolved, issue. Root hairs provide an excellent model system with which to study this as their final cell size is remarkably constant under constant environmental conditions. Previous studies have demonstrated that a basic helix-loop helix transcription factor ROOT HAIR DEFECTIVE 6-LIKE 4 (RSL4) promotes root hair growth, but how hair growth is terminated is not known. In this study, we demonstrate that a trihelix transcription factor GT-2-LIKE1 (GTL1) and its homolog DF1 repress root hair growth in Arabidopsis Our transcriptional data, combined with genome-wide chromatin-binding data, show that GTL1 and DF1 directly bind the RSL4 promoter and regulate its expression to repress root hair growth. Our data further show that GTL1 and RSL4 regulate each other, as well as a set of common downstream genes, many of which have previously been implicated in root hair growth. This study therefore uncovers a core regulatory module that fine-tunes the extent of root hair growth by the orchestrated actions of opposing transcription factors.

Clostridium difficile infection after pediatric solid organ transplantation: a practical single-center experience.

BACKGROUND: During the last two decades, there has been a worldwide increase in frequency and severity of infections with Clostridium difficile (CDI). Solid organ transplant (SOT) recipients receiving immunosuppressing medications are especially at risk. METHODS: We collected data from immunocompromised pediatric patients, including kidney and liver transplant recipients, at our tertiary pediatric care center in Germany. For this, we performed a retrospective review of institutional databases and analyzed data from all children who underwent diagnostic tests for CDI in a 3-year study period. RESULTS: A total of 797 diagnostic tests in 343 patients were performed. We found 104 infection episodes in 69 patients (42% female, ages 12 days-20 years). Children after SOT accounted for 20% of all detected CDI patients in our series. Median time of CDI onset after transplantation was 588 days. Overall antibiotic exposure was identified as the major risk factor, particularly in immunocompromised children after SOT (exposure in > 95% of all cases). CONCLUSIONS: The occurrence of CDI in the pediatric SOT population contributes to a greater length of stay and higher hospital charges. However, only very few severe complications from CDI were observed in our cohort. A potentially fulminant course of CDI can be prevented in most cases if timely diagnosis and treatment are carried out.

ABA Suppresses Root Hair Growth via the OBP4 Transcriptional Regulator.

Plants modify organ growth and tune morphogenesis in response to various endogenous and environmental cues. At the cellular level, organ growth is often adjusted by alterations in cell growth, but the molecular mechanisms underlying this control remain poorly understood. In this study, we identify the DNA BINDING WITH ONE FINGER (DOF)-type transcription regulator OBF BINDING PROTEIN4 (OBP4) as a repressor of cell growth. Ectopic expression of OBP4 in Arabidopsis (Arabidopsis thaliana) inhibits cell growth, resulting in severe dwarfism and the repression of genes involved in the regulation of water transport, root hair development, and stress responses. Among the basic helix-loop-helix transcription factors known to control root hair growth, OBP4 binds the ROOT HAIR DEFECTIVE6-LIKE2 (RSL2) promoter to repress its expression. The accumulation of OBP4 proteins is detected in expanding root epidermal cells, and its expression level is increased by the application of abscisic acid (ABA) at concentrations sufficient to inhibit root hair growth. ABA-dependent induction of OBP4 is associated with the reduced expression of RSL2 Furthermore, ectopic expression of OBP4 or loss of RSL2 function results in ABA-insensitive root hair growth. Taken together, our results suggest that OBP4-mediated transcriptional repression of RSL2 contributes to the ABA-dependent inhibition of root hair growth in Arabidopsis.

Synthesis and kinetic evaluation of ethyl acrylate and vinyl sulfone derived inhibitors for human cysteine cathepsins.

A series of inhibitors targeting human cathepsins have been designed and synthesized following a combinatorial approach. The compounds bear an α,ß-unsaturated phenyl vinyl sulfone or ethyl acrylate warhead and a peptidomimetic portion aligned to the non-primed binding region. Biochemical evaluation toward four human cathepsins was carried out and the kinetic characterization confirmed an irreversible mode of inhibition. Compound 6c combining the most advantageous building blocks for cathepsin S inhibition was identified as a potent cathepsin S inactivator exhibiting a second-order rate constant of 30600 M-1 s-1.

Transcriptional repression of the APC/C activator CCS52A1 promotes active termination of cell growth.

Spatial and temporal control of cell growth is central for the morphogenesis of multicellular organisms. For some cell types that undergo extensive post-mitotic cell growth, such as neurons and hair cells, orchestrating the extent of post-mitotic cell growth with development is vital for their physiology and function. Previous studies suggested that the extent of cell growth is linked with an increase in ploidy by endoreduplication but how developmental signals control endocycling and cell growth is not understood in both animals and plants. In this study we show that a trihelix transcription factor, GT2-LIKE 1 (GTL1), actively terminates ploidy-dependent cell growth and its developmentally regulated expression is one of the key determinants of cell size in Arabidopsis leaf hair cells (trichomes). Through genome-wide chromatin-binding studies (ChIP-chip) coupled with transcriptional profiling, we further demonstrate that GTL1 directly represses the transcription of CDH1/FZR/CCS52, an activator of the anaphase-promoting complex/cyclosome (APC/C), to stop the endocycle progression and ploidy-dependent cell growth. Thus, our findings uncover a previously uncharacterised key molecular link between developmental programming and cell-size control, highlighting the central role of APC/C in post-mitotic cell growth.

Unemployment and Suicide Mortality: Evidence from Regional Panel Data in Europe.

This paper addresses the influence of economic activity on suicide mortality in Europe. To this end, it employs a new panel data set of 275 regions in 29 countries over the period 1999-2010. The results suggest that unemployment does have a significantly positive influence on suicides. In line with economic theory, this influence varies among gender and age groups. Men of working age are particularly sensitive, while old-age suicide mortality (older than 65 years old) hardly responds to unemployment. Moreover, real economic growth negatively affects the suicide rates of working-age men. The results withstand several robustness checks, such as sample variations, and after controlling for serial and spatial autocorrelation.

My body is a cage: mechanisms and modulation of plant cell growth.

388 I. 388 II. 389 III. 389 IV. 390 V. 391 VI. 393 VII. 394 VIII. 398 399 References 399 SUMMARY: The wall surrounding plant cells provides protection from abiotic and biotic stresses, and support through the action of turgor pressure. However, the presence of this strong elastic wall also prevents cell movement and resists cell growth. This growth can be likened to extending a house from the inside, using extremely high pressures to push out the walls. Plants must increase cell volume in order to explore their environment, acquire nutrients and reproduce. Cell wall material must stretch and flow in a controlled manner and, concomitantly, new cell wall material must be deposited at the correct rate and site to prevent wall and cell rupture. In this review, we examine biomechanics, cell wall structure and growth regulatory networks to provide a 'big picture' of plant cell growth.

Co-incident BK and Epstein-Barr virus replication in a 3-year-old immunocompetent boy.

We present a unique case of infectious mononucleosis attended with transient asymptomatic BK virus (BKV) manifestation in the urine of an immunocompetent caucasian boy without kidney dysfunction. The urine sediment showed abundant decoy cells initially misdiagnosed as malignant cancer cells. This case demonstrates that the occurrence of polyoma-BKV bearing decoy cells is self-limiting and not necessarily associated with overt kidney disease in an immunocompetent child. The shedding of decoy cells into the urine might be promoted by viral co-infections modulating the host's immune response such as infectious mononucleosis.

MYB3R-SCL28-SMR module with a role in cell size control negatively regulates G2 progression in Arabidopsis.

Cell size control is one of the prerequisites for plant growth and development. Recently, a GRAS family transcription factor, SCARECROW-LIKE28 (SCL28), was identified as a critical regulator for both mitotic and postmitotic cell-size control. Here, we show that SCL28 is specifically expressed in proliferating cells and exerts its function to delay G2 progression during mitotic cell cycle in Arabidopsis thaliana. Overexpression of SCL28 provokes a significant enlargement of cells in various organs and tissues, such as leaves, flowers and seeds, to different extents depending on the type of cells. The increased cell size is most likely due to a delayed G2 progression and accelerated onset of endoreplication, an atypical cell cycle repeating DNA replication without cytokinesis or mitosis. Unlike DWARF AND LOW-TILLERING, a rice ortholog of SCL28, SCL28 may not have a role in brassinosteroid (BR) signaling because sensitivity against brassinazole, a BR biosynthesis inhibitor, was not dramatically altered in scl28 mutant and SCL28-overexpressing plants. Collectively, our findings strengthen a recently proposed model of cell size control by SCL28 and suggest the presence of diversified evolutionary mechanisms for the regulation and action of SCL28.

A hierarchical transcriptional network activates specific CDK inhibitors that regulate G2 to control cell size and number in Arabidopsis.

How cell size and number are determined during organ development remains a fundamental question in cell biology. Here, we identified a GRAS family transcription factor, called SCARECROW-LIKE28 (SCL28), with a critical role in determining cell size in Arabidopsis. SCL28 is part of a transcriptional regulatory network downstream of the central MYB3Rs that regulate G2 to M phase cell cycle transition. We show that SCL28 forms a dimer with the AP2-type transcription factor, AtSMOS1, which defines the specificity for promoter binding and directly activates transcription of a specific set of SIAMESE-RELATED (SMR) family genes, encoding plant-specific inhibitors of cyclin-dependent kinases and thus inhibiting cell cycle progression at G2 and promoting the onset of endoreplication. Through this dose-dependent regulation of SMR transcription, SCL28 quantitatively sets the balance between cell size and number without dramatically changing final organ size. We propose that this hierarchical transcriptional network constitutes a cell cycle regulatory mechanism that allows to adjust cell size and number to attain robust organ growth.

An Activity-Based Probe for Cathepsin K Imaging with Excellent Potency and Selectivity.

The cysteine protease cathepsin K is a target for the treatment of diseases associated with high bone turnover. Cathepsin K is mainly expressed in osteoclasts and responsible for the destruction of the proteinaceous components of the bone matrix. We designed various fluorescent activity-based probes (ABPs) and their precursors that bind to and inactivate cathepsin K. ABP 25 exhibited extraordinary potency (kinac/Ki = 35,300 M-1s-1) and selectivity for human cathepsin K. Crystal structures of cathepsin K in complex with ABP 25 and its nonfluorescent precursor 21 were determined to characterize the binding mode of this new type of acrylamide-based Michael acceptor with the particular orientation of the dibenzylamine moiety to the primed subsite region. The cyanine-5 containing probe 25 allowed for sensitive detection of cathepsin K, selective visualization in complex proteomes, and live cell imaging of a human osteosarcoma cell line, underlining its applicability in a pathophysiological environment.

Mandibular aneurysmal bone cyst in a child misdiagnosed as acute osteomyelitis: a case report and a review of the literature.

The aneurysmal bone cyst is a very infrequent, benign bone lesion in children which rarely can be found at the craniofacial skeleton. Here, we describe a case presenting in the mandible as an acute swelling of the cheek, which was initially misdiagnosed as osteomyelitis resulting in a delay to definitive surgical treatment. The cause of misleading diagnosis is often owing to the rapid growth of the lesion, sometimes associated with painful soft tissue swelling indicating an infectious origin or a malignant tumor. Magnetic resonance imaging revealed the classic characteristics of aneurysmal bone cyst with severe destruction of the mandible. Therefore, curative tumor embolization and complete surgical excision was successfully performed. The aneurysmal bone cyst is a curable condition by radical excision, although relapse may occur when only incomplete excision is obtained. Therefore, aneurysmal bone cyst should be considered early when children present with unusual, rapid-growing neoformations of the extremities or the facial region.

Splenic infarction in a patient hereditary spherocytosis, protein C deficiency and acute infectious mononucleosis.

Splenic infarction is a common cause of left upper quadrant pain and must be suspected in patients with hematologic or thromboembolic conditions and signs of localized or systemic inflammation. Although several mechanisms have been proposed for splenic infarction in patients with various hematologic disorders, hereditary spherocytosis (HS) is usually not associated with an increased risk for thromboembolic events. We report a 13-year-old male with HS who was referred to our hospital with a 4-day history of fever and left upper quadrant pain. Ultrasound scans and magnetic resonance imaging showed lesions suggestive of splenic infarction. Initially, antibiotic treatment was started because secondary infection was suspected. However, 1 week after admission the patient developed typical clinical signs of acute infectious mononucleosis. Further laboratory work up confirmed the diagnosis of acute Epstein-Barr virus infection and additionally revealed protein C deficiency. This association has not been reported previously and may have contributed to the development of splenic infarction. Since infectious mononucleosis is a common cause for clinical consultations in adolescence, physicians caring for children with hematologic disorders should be particularly aware of those possible complications.

Diagnostic Yield of Next-generation Sequencing in Very Early-onset Inflammatory Bowel Diseases: A Multicentre Study.

BACKGROUND AND AIMS: An expanding number of monogenic defects have been identified as causative of severe forms of very early-onset inflammatory bowel diseases [VEO-IBD]. The present study aimed at defining how next-generation sequencing [NGS] methods can be used to improve identification of known molecular diagnosis and to adapt treatment. METHODS: A total of 207 children were recruited in 45 paediatric centres through an international collaborative network [ESPGHAN GENIUS working group] with a clinical presentation of severe VEO-IBD [n = 185] or an anamnesis suggestive of a monogenic disorder [n = 22]. Patients were divided at inclusion into three phenotypic subsets: predominantly small bowel inflammation, colitis with perianal lesions, and colitis only. Methods to obtain molecular diagnosis included functional tests followed by specific Sanger sequencing, custom-made targeted NGS, and in selected cases whole exome sequencing [WES] of parents-child trios. Genetic findings were validated clinically and/or functionally. RESULTS: Molecular diagnosis was achieved in 66/207 children [32%]: 61% with small bowel inflammation, 39% with colitis and perianal lesions, and 18% with colitis only. Targeted NGS pinpointed gene mutations causative of atypical presentations, and identified large exonic copy number variations previously missed by WES. CONCLUSIONS: Our results lead us to propose an optimised diagnostic strategy to identify known monogenic causes of severe IBD.