Telomeres cluster de novo before the initiation of synapsis: a three-dimensional spatial analysis of telomere positions before and during meiotic prophase.

We have analyzed the progressive changes in the spatial distribution of telomeres during meiosis using three-dimensional, high resolution fluorescence microscopy. Fixed meiotic cells of maize (Zea mays L.) were subjected to in situ hybridization under conditions that preserved chromosome structure, allowing identification of stage-dependent changes in telomere arrangements. We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres. Quantitative measurements on the spatial arrangements of telomeres revealed that, as cells passed through premeiotic interphase and into leptotene, there was an increase in the frequency of large telomere-to-telomere distances and a decrease in the bias toward peripheral localization of telomeres. By leptotene, there was no obvious evidence of telomere grouping, and the large, singular nucleolus was internally located, nearly concentric with the nucleus. At the end of leptotene, telomeres clustered de novo at the nuclear periphery, coincident with a displacement of the nucleolus to one side. The telomere cluster persisted throughout zygotene and into early pachytene. The nucleolus was adjacent to the cluster at zygotene. At the pachytene stage, telomeres rearranged again by dispersing throughout the nuclear periphery. The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions. Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over

Human rights and ethical reasoning : capabilities, conventions and spheres of public action

This interdisciplinary article argues that human rights must be understood in terms of opportunities for social participation and that social and economic rights are integral to any discussion of the subject. We offer both a social constructionist and a normative framework for a sociology of human rights which reaches beyond liberal individualism, combining insights from the work of Amartya Sen and from French convention theory. Following Sen, we argue that human rights are founded on the promotion of human capabilities as ethical demands shaped by public reasoning. Using French convention theory, we show how the terms of such deliberation are shaped by different constructions of collectively held values and the compromises reached between them. We conclude by demonstrating how our approach offers a new perspective on spheres of public action and the role these should play in promoting social cohesion, individual capabilities and human rights

Reorganization of complex ciliary flows around regenerating Stentor coeruleus

This is the final version. Available on open acccess from the Royal Society via the DOI in this record.For sample videos and detailed methodology, please refer to the electronic supplementary material uploaded as part of this article. Code used for the analysis can be found at https:// github.com/shurlimann/stentor-cilia-autocorrelation). Additional datasets are available at https://doi.org/10.5281/zenodo.3590430.The phenomenon of ciliary coordination has garnered increasing attention in recent decades and multiple theories have been proposed to explain its occurrence in different biological systems. While hydrodynamic interactions are thought to dictate the large-scale coordinated activity of epithelial cilia for fluid transport, it is rather basal coupling that accounts for synchronous swimming gaits in model microeukaryotes such as Chlamydomonas. Unicellular ciliates present a fascinating yet understudied context in which coordination is found to persist in ciliary arrays positioned across millimetre scales on the same cell. Here, we focus on the ciliate Stentor coeruleus, chosen for its large size, complex ciliary organization, and capacity for cellular regeneration. These large protists exhibit ciliary differentiation between cortical rows of short body cilia used for swimming, and an anterior ring of longer, fused cilia called the membranellar band (MB). The oral cilia in the MB beat metachronously to produce strong feeding currents. Remarkably, upon injury, the MB can be shed and regenerated de novo. Here, we follow and track this developmental sequence in its entirety to elucidate the emergence of coordinated ciliary beating: from band formation, elongation, curling and final migration towards the cell anterior. We reveal a complex interplay between hydrodynamics and ciliary restructuring in Stentor, and highlight for the first time the importance of a ring-like topology for achieving long-range metachronism in ciliated structures. This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’

Control of daughter centriole formation by the pericentriolar material

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Cell Biology 10 (2008): 322-328, doi:10.1038/ncb1694.Controlling the number of its centrioles is vital for the cell as supernumerary centrioles result in multipolar mitosis and genomic instability. Normally, just one daughter centriole forms on each mature (mother) centriole; however, a mother centriole can produce multiple daughters within a single cell cycle. The mechanisms that prevent centriole ‘overduplication’ are poorly understood. Here we use laser microsurgery to test the hypothesis that attachment of the daughter centriole to the wall of the mother inhibits formation of additional daughters. We show that physical removal of the daughter induces reduplication of the mother in Sarrested cells. Under conditions when multiple daughters simultaneously form on a single mother, all of these daughters must be removed to induce reduplication. Intriguingly, the number of daughter centrioles that form during reduplication does not always match the number of ablated daughter centrioles. We also find that exaggeration of the pericentriolar material (PCM) via overexpression of the PCM protein pericentrin in S-arrested CHO cells induces formation of numerous daughter centrioles. We propose that that the size of the PCM cloud associated with the mother centriole restricts the number of daughters that can form simultaneously.This work was supported by grants from the National Institutes of Health (GM GM59363) and the Human Frontiers Science Program (RGP0064). Construction of our laser microsurgery workstation was supported in part by a fellowship from Nikon/Marine Biological Laboratory (A.K.)

Use of clinical chromosomal microarray in Chinese patients with autism spectrum disorder—implications of a copy number variation involving DPP10

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A practical conservation tool to combine diverse types of evidence for transparent evidence-based decision-making

Funder: Arcadia Fund; Id: http://dx.doi.org/10.13039/100012088Funder: MAVA Foundation; Id: http://dx.doi.org/10.13039/100013324Funder: The David and Claudia Harding FoundationFunder: University of Cambridge, Department of Zoology; Id: http://dx.doi.org/10.13039/501100000735Making the reasoning and evidence behind conservation management decisions clear and transparent is a key challenge for the conservation community. Similarly, combining evidence from diverse sources (e.g., scientific and local knowledge) into decision-making is also difficult. Our group of conservation researchers and practitioners has co-produced an intuitive tool and template (Evidence-to-Decision [E2D] tool: www.evidence2decisiontool.com) to guide practitioners through a structured process to transparently document and report the evidence and reasoning behind decisions. The tool has three major steps: (1). Define the Decision Context; (2). Gather Evidence; and (3). Make an Evidence-Based Decision. In each step, practitioners enter information (e.g., from the scientific literature, practitioner knowledge and experience, and costs) to inform their decision-making and document their reasoning. The tool packages this information into a customized downloadable report (or is documented if using the offline template), which we hope can stimulate the exchange of information on decisions within and between organizations. By enabling practitioners to revisit how and why past decisions were made, and integrate diverse forms of evidence, we believe our open-access tool's template can help increase the transparency and quality of decision-making in conservation.William J. Sutherland and Harriet Downey were supported by Arcadia, The David and Claudia Harding Foundation, and MAVA. Alec P. Christie was supported by the Natural Environment Research Council as part of the Cambridge Earth System Science NERC DTP (NE/L002507/1) and The David and Claudia Harding Foundation. Thomas B. White was supported by the Balfour Studentship awarded by the Department of Zoology, Cambridge University

Intraflagellar Transport (IFT) Protein IFT25 Is a Phosphoprotein Component of IFT Complex B and Physically Interacts with IFT27 in Chlamydomonas

BACKGROUND: Intraflagellar transport (IFT) is the bidirectional movement of IFT particles between the cell body and the distal tip of a flagellum. Organized into complexes A and B, IFT particles are composed of at least 18 proteins. The function of IFT proteins in flagellar assembly has been extensively investigated. However, much less is known about the molecular mechanism of how IFT is regulated. METHODOLOGY/PRINCIPAL FINDINGS: We herein report the identification of a novel IFT particle protein, IFT25, in Chlamydomonas. Dephosphorylation assay revealed that IFT25 is a phosphoprotein. Biochemical analysis of temperature sensitive IFT mutants indicated that IFT25 is an IFT complex B subunit. In vitro binding assay confirmed that IFT25 binds to IFT27, a Rab-like small GTPase component of the IFT complex B. Immunofluorescence staining showed that IFT25 has a punctuate flagellar distribution as expected for an IFT protein, but displays a unique distribution pattern at the flagellar base. IFT25 co-localizes with IFT27 at the distal-most portion of basal bodies, probably the transition zones, and concentrates in the basal body region by partially overlapping with other IFT complex B subunits, such as IFT46. Sucrose density gradient centrifugation analysis demonstrated that, in flagella, the majority of IFT27 and IFT25 including both phosphorylated and non-phosphorylated forms are cosedimented with other complex B subunits in the 16S fractions. In contrast, in cell body, only a fraction of IFT25 and IFT27 is integrated into the preassembled complex B, and IFT25 detected in complex B is preferentially phosphorylated. CONCLUSION/SIGNIFICANCE: IFT25 is a phosphoprotein component of IFT particle complex B. IFT25 directly interacts with IFT27, and these two proteins likely form a subcomplex in vivo. We postulate that the association and disassociation between the subcomplex of IFT25 and IFT27 and complex B might be involved in the regulation of IFT

Re-reading in Stylistics

Cognitive stylistics is primarily concerned with the cognitive processes – mental simulations – experienced by readers. Most cognitive stylisticians agree that experiences of reading texts are dynamic and flexible. Changes in the context of reading, our attentional focus on a given day, our extra background knowledge about the text, and so on, are all factors that contribute to our experience of a fictional world. A second reading of a text is a different experience to a first reading. As researchers begin to systematically distinguish between the ‘solitary’ and ‘social’ readings that constitute reading as a phenomenon (Peplow et al., 2016), the relationship between multiple readings and the nature of their processing become increasingly pertinent. In order to explore this relationship, firstly we examine the different ways in which re-reading has previously been discussed in stylistics, grounding our claims in an empirical analysis of articles published in key stylistics journals over the past two decades. Next, we draw on reader response data from an online questionnaire in order to assess the role of re-reading and the motivations that underpin it. Finally, we describe an exercise for the teaching of cognitive stylistics, specifically applying schema theory in literary linguistic analysis (Cook, 1994), which illustrates the need to distinguish between readings as part of an analysis. Through these three sections we argue that our experiences of texts should be considered diachronically, and propose that the different readings that make up an analysis of a text should be given greater attention in stylistic research and teaching

Knocking at the brain’s door: intravital two-photon imaging of autoreactive T cell interactions with CNS structures

Since the first applications of two-photon microscopy in immunology 10 years ago, the number of studies using this advanced technology has increased dramatically. The two-photon microscope allows long-term visualization of cell motility in the living tissue with minimal phototoxicity. Using this technique, we examined brain autoantigen-specific T cell behavior in experimental autoimmune encephalitomyelitis, the animal model of human multiple sclerosis. Even before disease symptoms appear, the autoreactive T cells arrive at their target organ. There they crawl along the intraluminal surface of central nervous system (CNS) blood vessels before they extravasate. In the perivascular environment, the T cells meet phagocytes that present autoantigens. This contact activates the T cells to penetrate deep into the CNS parenchyma, where the infiltrated T cells again can find antigen, be further activated, and produce cytokines, resulting in massive immune cell recruitment and clinical disease