Nucleoporin Condensates Drive Nuclear Pore Complex Assembly in Oocytes

Oocytes stockpile nuclear pore complexes (NPCs) in cytoplasmic membrane sheets called annulate lamellae (AL) in preparation for rapid cell cycles during embryogenesis. Recently, Hampoelz et al. reported that AL–NPC assembly depends on the coordinated formation, transport, and interaction of biomolecular condensates containing distinct sets of nucleoporins

Effectiveness of battlefield-ethics training during combat deployment: a programme assessment

Background Breakdowns in the ethical conduct of soldiers towards non-combatants on the battlefi eld are of grave concern in war. Evidence-based training approaches to prevent unethical conduct are scarce. We assessed the eff ectiveness of battlefi eld-ethics training and factors associated with unethical battlefi eld conduct. Methods The training package, based on movie vignettes and leader-led discussions, was administered 7 to 8 months into a 15-month high-intensity combat deployment in Iraq, between Dec 11, 2007, and Jan 30, 2008. Soldiers from an infantry brigade combat team (total population about 3500) were randomly selected, on the basis of company and the last four digits of each soldier’s social security number, and invited to complete an anonymous survey 3 months after completion of the training. Reports of unethical behaviour and attitudes in this sample were compared with a randomly selected pre-training sample from the same brigade. The response patterns for ethical behaviour and reporting of ethical violations were analysed with chi-square analyses. We developed two logistic regression models using self-reported unethical behaviours as dependent variables. Factors associated with unethical conduct, including combat experiences and post-traumatic stress disorder (PTSD), were assessed with validated scales. Findings Of 500 randomly selected soldiers 421 agreed to participate in the anonymous post-training survey. A total of 397 soldiers of the same brigade completed the pre-training survey. Training was associated with significantly lower rates of unethical conduct of soldiers and greater willingness to report and address misconduct than in those before training. For example, reports of unnecessary damage or destruction of private property decreased from 13·6% (54 of 397; 95% CI 10·2–17·0) before training to 5·0% (21 of 421; 2·9–7·1) after training (percent difference –63·2%; p\u3c0·0001), and willingness to report a unit member for mistreatment of a non-combatant increased from 36·0% (143 of 397; 31·3–40·7) to 58·9% (248 of 421; 54·2–63·6; percent difference 63·6; p\u3c0·0001). Nearly all participants (410 [97%]) reported that training made it clear how to respond towards non-combatants. Combat frequency and intensity was the strongest predictor of unethical behaviour; PTSD was not a significant predictor of unethical behaviour after controlling for combat experiences. Interpretation Leader-led battlefield ethics training positively influenced soldiers’ understanding of how to interact with and treat non-combatants, and reduced reports of ethical misconduct. Unethical battlefield conduct was associated with high-intensity combat but not with PTSD

Architecture of the symmetric core of the nuclear pore

INTRODUCTION: The nuclear pore complex (NPC) is the primary gateway for the transport of macromolecules between the nucleus and cytoplasm, serving as both a critical mediator and regulator of gene expression. NPCs are very large (~120 MDa) macromolecular machines embedded in the nuclear envelope, each containing ~1000 protein subunits, termed nucleoporins. Despite substantial progress in visualizing the overall shape of the NPC by means of cryoelectron tomography (cryo-ET) and in determining atomic-resolution crystal structures of nucleoporins, the molecular architecture of the assembled NPC has thus far remained poorly understood, hindering the design of mechanistic studies that could investigate its many roles in cell biology. RATIONALE: Existing cryo-ET reconstructions of the NPC are too low in resolution to allow for de novo structure determination of the NPC or unbiased docking of nucleoporin fragment crystal structures. We sought to bridge this resolution gap by first defining the interaction network of the NPC, focusing on the evolutionarily conserved symmetric core. We developed protocols to reconstitute NPC protomers from purified recombinant proteins, which enabled the generation of a high-resolution biochemical interaction map of the NPC symmetric core. We next determined high-resolution crystal structures of key nucleoporin interactions, providing spatial restraints for their relative orientation. By superposing crystal structures that overlapped in sequence, we generated accurate full-length structures of the large scaffold nucleoporins. Lastly, we used sequential unbiased searches, supported by the biochemical data, to place the nucleoporin crystal structures into a previously determined cryo-ET reconstruction of the intact human NPC, thus generating a composite structure of the entire NPC symmetric core. RESULTS: Our analysis revealed that the inner and outer rings of the NPC use disparate mechanisms of interaction. Whereas the structured coat nucleoporins of the outer ring form extensive surface contacts, the scaffold proteins of the inner ring are bridged by flexible sequences in linker nucleoporins. Our composite structure revealed a defined spoke architecture in which each of the eight spokes spans the nuclear envelope, with limited cross-spoke interactions. Most nucleoporins are present in 32 copies, with the exceptions of Nup170 and Nup188, which are present in 48 and 16 copies, respectively. Lastly, we observed the arrangement of the channel nucleoporins, which orient their N termini into two 16-membered rings, thus ensuring that their N-terminal FG repeats project evenly into the central transport channel. CONCLUSION: Our composite structure of the NPC symmetric core can be used as a platform for the rational design of experiments to investigate NPC structure and function. Each nucleoporin occupies multiple distinct biochemical environments, explaining how such a large macromolecular complex can be assembled from a relatively small number of genes. Our integrated, bottom-up approach provides a paradigm for the biochemical and structural characterization of similarly large biological mega-assemblies

Identification of responsive cells in the developing somite supports a role for Β-catenin-dependent Wnt signaling in maintaining the DML myogenic progenitor pool

Somitic Β-catenin is involved in both maintaining a stem cell population and controlling myogenic differentiation. It is unclear how Β-catenin-dependent Wnt signaling accomplishes these disparate roles. The present study shows that only dorsal cells in the early somite respond to Β-catenin-dependent Wnt signaling and as the somites compartmentalize to form the dermomyotome and myotome, responding cells are detected primarily in the dorsomedial lip (DML). Forced activation of Wnt target genes in DML cells prevents their progeny from entering the myotome, while blocking activation allows myotomal entry. This suggests a role for Β-catenin-dependent/Wnt signaling in maintaining progenitor cells in the DML and that if Β-catenin-dependent/Wnt signaling is required to induce myogenesis, the response is transitory and rapidly down-regulated. Developmental Dynamics 239:222–236, 2010. © 2009 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64520/1/22098_ftp.pd

Order in Spontaneous Behavior

Brains are usually described as input/output systems: they transform sensory input into motor output. However, the motor output of brains (behavior) is notoriously variable, even under identical sensory conditions. The question of whether this behavioral variability merely reflects residual deviations due to extrinsic random noise in such otherwise deterministic systems or an intrinsic, adaptive indeterminacy trait is central for the basic understanding of brain function. Instead of random noise, we find a fractal order (resembling Lévy flights) in the temporal structure of spontaneous flight maneuvers in tethered Drosophila fruit flies. Lévy-like probabilistic behavior patterns are evolutionarily conserved, suggesting a general neural mechanism underlying spontaneous behavior. Drosophila can produce these patterns endogenously, without any external cues. The fly's behavior is controlled by brain circuits which operate as a nonlinear system with unstable dynamics far from equilibrium. These findings suggest that both general models of brain function and autonomous agents ought to include biologically relevant nonlinear, endogenous behavior-initiating mechanisms if they strive to realistically simulate biological brains or out-compete other agents

Architecture of the linker-scaffold in the nuclear pore

Quantitative docking of crystal and single particle cryo-EM structures into low resolution human and S. cerevisiae cryo-ET and X. laevis cryo-EM maps of the nuclear pore complex.Related Publication: Architecture of the linker-scaffold in the nuclear pore Petrovic, Stefan Caltech Samanta, Dipanjan Caltech Perriches, Thibaud Caltech Bley, Christopher Caltech Thierbach, Karsten Caltech Brown, Bonnie Caltech Nie, Si Caltech Mobbs, George Caltech Stevens, Taylor Caltech Liu, Xiaoyu Caltech Tomaleri, Giovani Pinton Caltech Schaus, Lucas Caltech Hoelz, Andre Caltech Science 2022-06-10 https://doi.org/10.1126/science.abm9798 en