Push or pull: how cytoskeletal crosstalk facilitates nuclear movement through 3D environments

As cells move from two-dimensional (2D) surfaces into complex 3D environments, the nucleus becomes a barrier to movement due to its size and rigidity. Therefore, moving the nucleus is a key step in 3D cell migration. In this review, we discuss how coordination between cytoskeletal and nucleoskeletal networks is required to pull the nucleus forward through complex 3D spaces. We summarize recent migration models which utilize unique molecular crosstalk to drive nuclear migration through different 3D environments. In addition, we speculate about the role of proteins that indirectly crosslink cytoskeletal networks and the role of 3D focal adhesions and how these protein complexes may drive 3D nuclear migration.

From a hard nuclear state towards a soft nuclear repository state – participation, co-designing, learning and reversibility in the site selection process for a nuclear waste repository

Since 2013 the site search for a repository for highly radioactive waste has been taking place in Germany within the framework of a new governance architecture and under new political guidelines. Based on experiences with nuclear politics in the past, Jungk (1977) coined the term hard nuclear state, characterized by decisions made in a top-down manner. The Decide-Announce-Defend (DAD) strategy, which branded the nuclear state at that time, led to conflicts, mistrust of authorities and blockages. In particular, massive resistance developed against the planned final repository site at Gorleben. Nowadays, after more than 60 years deploying nuclear energy, the (energy) political balance of power has fundamentally changed. Parts of the anti-nuclear movement have been integrated into the political party system and have contributed significantly to the nuclear phase-out. In the course of this, the unfinished task of final disposal has been readdressed: with the Repository Site Selection Act (StandAG, 2017), which was passed in 2013 and amended in 2017, an ongoing process of public participation is stated. The site selection process is required to be learning, self-questioning, science-based, reversible, and participatory. The StandAG § 5 not only provides a basis for a fundamental dialogue between the regulator, the operator, and the public, but also for „co-design“ by common citizens. The StandAG considers various elements from different participation-friendly theories of democracy as well as specific governance concepts, which we refer to collectively as the soft nuclear repository state (cf. Brunnengräber, 2021). Its characteristics need to be worked out, as the StandAG only provides some indications, but no criteria, for what good and sufficient participation in the site selection process means and what its conditions for success should be. Based on preliminary considerations on democratic theory and governance aspects (part 1), we present what good participation could mean in the current procedure and what the framework conditions for good participation could be (part 2). Additionally, we present main findings from participatory observations from the ongoing site search process and identify conditions and indications of a successful future participation process based on the ongoing process (part 3). In the résumé, we turn to the question of which of the democracy-theoretical elements of the soft repository state are already recognizable in the present procedure, but also whether the current procedure provides additional indications towards the soft nuclear repository state (part 4).

Ensconsin-dependent changes in microtubule organization and LINC complex-dependent changes in nucleus-nucleus interactions result in quantitatively distinct myonuclear positioning defects

Nuclear movement is a fundamental process of eukaryotic cell biology. Skeletal muscle presents an intriguing model to study nuclear movement because its development requires the precise positioning of multiple nuclei within a single cytoplasm. Furthermore, there is a high correlation between aberrant nuclear positioning and poor muscle function. Although many genes that regulate nuclear movement have been identified, the mechanisms by which these genes act is not known. Using Drosophila melanogaster muscle development as a model system, and a combination of live-embryo microscopy and laser ablation of nuclei, we have found that clustered nuclei encompass at least two phenotypes that are caused by distinct mechanisms. Specifically, Ensconsin is necessary for productive force production to drive any movement of nuclei whereas Bocksbeutel and Klarsicht are necessary to form distinct populations of nuclei that move to different cellular locations. Mechanisitcally, Ensconsin regulates the number of growing microtubules that are used to move nuclei whereas Bocksbeutel and Klarsicht regulate interactions between nuclei. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text]

QSL: Subliminal Messaging by the Nuclear Industry in Germany during the 1980s

During the late 1970s and early 1980s, the German nuclear power industry came under considerable socio-political pressure from the growing environmental and anti-nuclear movement. As part of a diversified public relations strategy, the Kraftwerk Union (KWU, later Siemens) as the main manufacturer of nuclear power plants distributed pre-printed QSL cards to amateur radio enthusiasts. These cards carried images of the latest nuclear power plants built by KWU. This paper examines the history, iconography and distribution of these QSL cards in the context of the heritage of the German nuclear power industry. It is the first study of its kind to examine the heritage significance of QSL cards.

Nature, Knowledge, and Protest

Melanie Arndt: Tschernobylkinder. Die transnationale Geschichte einer nuklearen Ka- tastrophe, Göttingen: Vandenhoeck & Ruprecht, 2020, 499 pp., ISBN: 978-3-525- 35208-3. Nils Güttler: Alles über das Fliegen. Eine politische Wissensgeschichte des Frankfurter Flughafens, Vienna: Turia & Kant, 2020, 123 pp., ISBN: 978-3-85132-981-0. Katrin Jordan: Ausgestrahlt. Die mediale Debatte um „Tschernobyl“ in der Bundesrepu- blik und in Frankreich 1986/87, Göttingen: Wallstein, 2018, 424 pp., ISBN: 978-3- 8353-3304-8. Stephen Milder: Greening Democracy. The Anti-Nuclear Movement and Political Envi- ronmentalism in West Germany and Beyond, 1968–1983, Cambridge: Cambridge Uni- versity Press, 2017, 280 pp., ISBN: 978-1-107-13510-9. Christian Möller: Umwelt und Herrschaft in der DDR. Politik, Protest und die Gren- zen der Partizipation in der Diktatur, Göttingen: Vandenhoeck & Ruprecht, 2020, 396 pp., ISBN: 978-3-525-31096-0. Martin Spenger: Green Beat. Gary Snyder und die moderne amerikanische Umweltbe- wegung, Göttingen: Vandenhoeck & Ruprecht, 2020, 239 pp., ISBN: 978-3-525- 31098-4.

Understanding Strategies of Anti-Nuclear Movement: A Study of ICAN [Memahami Strategi Gerakan Anti-Nuklir:Sebuah Studi Tentang ICAN

This article argues that the most unique characteristic of the ICAN’s activism is its transnational scope, which was made possible by the use of eight strategies by the organization including geostrategic headquarters, internet and technology, government relations, NGOs connection, celebrity spotlight, perfect timing, creativity, and responsiveness. In evaluating the argument, this article provides evidence by employing process-tracing methods and conducting archival analysis to closely examine the historical timeline of important events or moments surrounding the ICAN’s activism since its inception in 2007 to the adoption of the Treaty on the Prohibition of Nuclear Weapons in 2017. This article first provides a literature review on social movements against nuclear weapons to provide some background. It then describes how the eight strategies are employed by the ICAN as they are reflected in its transnationalactivism. It finally notes the five key milestones that are achieved by the organization.AbstrakArtikel ini berargumen bahwa karakteristik paling unik dari aktivisme ICAN adalah jangkauannya yang bersifat transnasional, yang dicapai berkat penggunaan delapan strategi mencakup letak kantor pusat yang strategis, internet dan teknologi, hubungan dengan pemerintah, jejaring LSM, sorotan selebriti, pemilihan waktu yang tepat, kreativitas, dan kemampuan merespon. Dalam mengevaluasi argumen tersebut, artikel ini memaparkan data dengan menggunakan metode process tracing dan melakukan analisis arsip untuk memeriksa secara detail peristiwa-peristiwa penting seputar aktivisme ICAN sejak didirikan pada 2007 hingga diadopsinya Perjanjian Pelarangan Senjata Nuklir pada 2017. Artikel ini menyediakan tinjauan pustaka tentang gerakan sosial melawan senjata nuklir untuk menjelaskan latar belakang isu ini. Kemudian artikel ini menjelaskan bagaimana delapan strategi tersebut digunakan oleh ICAN, sebagaimana tercermin dalam aktivisme transnasionalnya. Di akhir, artikel ini mengidentifikasi lima pencapaian utama yang diraih oleh ICAN.

3D matrix adhesion composition facilitates nuclear force coupling to drive invasive cell migration

Cell invasion and metastasis is a multi-step process, initialised through the acquisition of a migratory phenotype and the ability to move through differing and complex 3D extracellular environments. In this study we set out to identify the parameters required for invasive cell migration in 3D environments. Cells interact with the extracellular matrix via transmembranespanning integrin adhesion complexes, which are well characterised in cells plated on 2D surfaces, yet much less is known about them in cells embedded in 3D matrices. We establish a technique to determine the composition of cell matrix adhesion complexes of invasive breast cancer cells in 3D matrices and on 2D surfaces and we identify an interaction complex enriched in 3D adhesive sites required for 3D invasive migration. Depletion of β-PIX-Myosin18A (Myo18A) abolishes cancer cell invasion, without negatively affecting matrix degradation, Rho GTPase signalling, or protrusion formation in collagen matrices. Instead, in a mechanism only seen in cells moving through 3D matrix, β-PIX and Myo18A drive the polarised recruitment of non-muscle Myosin 2A (NM2A) to the tips of protrusions. This recruitment of NM2A is required for the creation of an NM2A-NM2B isoform gradient, which ranges from the protrusion to the nucleus. We observe a requirement for active force transmission to the nucleus during invasive migration that is needed to pull the nucleus forward. We postulate that the establishment of the NM2A-NM2B actomyosin gradient facilitates the coupling of cell-matrix interactions at the protrusive cell front with nuclear movement, enabling effective invasive migration and front-rear cell polarity.

Local density determines nuclear movements during syncytial blastoderm formation in a cricket

Animal embryos pass through an early stage called the blastoderm, in which cells are arranged in a continuous layer at the periphery of the embryo. Despite the broad evolutionary conservation of this embryonic stage, the cellular behaviours that lead to blastoderm formation vary across animals, and the mechanisms that regulate these behaviours are poorly understood. In most insects, pre-blastoderm development begins as a syncytium: that is, many nuclei divide and move throughout the single shared cytoplasm of the embryo. Then these syncytial nuclei must move from their scattered positions within the cytoplasm to form a single layer at the cortex. Recent work showed that in the fruit fly Drosophila melanogaster, some of these early nuclear movements are caused by pulses of cytoplasmic flows that are coupled to synchronous divisions. Here, we show that the cricket Gryllus bimaculatus has an altogether different solution to the problem. We quantified nuclear dynamics during the period of syncytial cleavages and movements that lead to blastoderm formation in G. bimaculatus embryos with transgenically labeled nuclei. We found that: (1) cytoplasmic flows were unimportant for nuclear movement, and (2) division cycles, nuclear speeds, and the directions of nuclear movement were not synchronized across the embryo as in D. melanogaster, but instead were heterogeneous in space and time. Moreover, several aspects of nuclear divisions and movements were correlated with local nuclear density. We show that previously proposed models for the movement of D. melanogaster syncytial nuclei cannot explain the behaviours of G. bimaculatus syncytial nuclei. We introduce a novel geometric model based on asymmetric local pulling forces on nuclei, which recapitulates the density-dependent nuclear speeds and orientations of unperturbed G. bimaculatus embryos, without invoking the common paradigms of localized polarity cues or cell lineage as determinants of nuclear activity. Our model also accurately predicts nuclear behavior in embryos physically manipulated to contain regions of atypical nuclear densities. We show that this model can be used to generate falsifiable predictions about the dynamics of blastoderm formation in other insect species.