Dynamics of CTCF and cohesin mediated chromatin looping revealed by live-cell imaging

Animal genomes are folded into loops and topologically associating domains (TADs) by CTCF and cohesin, but whether these loops are stable or dynamic is unknown. Here, we directly visualize chromatin looping at the Fbn2 TAD in mouse embryonic stem cells using super-resolution live-cell imaging and quantify looping dynamics by Bayesian inference. Our results are consistent with cohesin-mediated loop extrusion in cells, and with CTCF both stopping and stabilizing cohesin. Surprisingly, the Fbn2 loop is both rare and dynamic, with a looped fraction of ~3-6.5% and a median loop lifetime of ~10-30 minutes. Instead of a stable loop, our results establish a highly dynamic view of TADs and loops where the Fbn2 TAD exists predominantly in a partially extruded conformation. This dynamic and quantitative view of TADs may facilitate a mechanistic understanding of their functions.

ADAPTATIONS TO SUBJECTIVE INSTRUMENTS FOR DYNAMIC VIEW ASSESSMENT EVALUATION

Although daylight changes seen through windows are likely to mediate positive responses in occupants, there are no specialized instruments capturing responses to dynamic attributes in views. This study mapped self-report instruments that could be readily adjusted to measure subjective responses to dynamic views. Through a revision of the literature, 55 papers in view assessment were clustered as a function of prevalent label types and constructs used to investigate responses to static outdoor views. Feature-type was the prevalent label distinction to investigate responses to window views, whilst preference and restoration were the predominant constructs in view out research. Four instruments were deemed appropriate to capture responses to dynamic attributes in views with respect to restoration, provided that semantic adaptations and further validations are set in place. This study highlights the need for more validation studies to increase the robustness of self-report instruments and outlines a theoretical approach to achieve this scope.

Cyclical fate restriction: a new view of neural crest cell fate specification

ABSTRACT Neural crest cells are crucial in development, not least because of their remarkable multipotency. Early findings stimulated two hypotheses for how fate specification and commitment from fully multipotent neural crest cells might occur, progressive fate restriction (PFR) and direct fate restriction, differing in whether partially restricted intermediates were involved. Initially hotly debated, they remain unreconciled, although PFR has become favoured. However, testing of a PFR hypothesis of zebrafish pigment cell development refutes this view. We propose a novel ‘cyclical fate restriction’ hypothesis, based upon a more dynamic view of transcriptional states, reconciling the experimental evidence underpinning the traditional hypotheses.

A Matter of Transition: Authenticity Judgments and Attracting Employees to Hybridized Organizations

Category-spanning organizations have been shown to face a number of penalties compared with organizations occupying a single category. The assumption seems to be, however, that organizations spanning the same categories will be evaluated similarly. Yet, this is not always the case. We know far less about why evaluations may differ within category-spanners, largely due to existing studies’ focus on comparing single-category to category-spanning organizations in equilibrium states at a fixed point in time. Instead, this paper investigates audience judgments of organizations as they transition from single to multiple categories. We rely on the empirical setting of social-commercial hybrids—an intriguing context in which to explore category-spanning across market and nonmarket domains associated with distinct values, norms, and expectations. In a series of two experimental studies, we investigate how hybridization affects audience judgments of organizational authenticity and the ability to attract potential employees. We find that across organizational fields associated with nonprofit (communal) and for-profit (market exchange) norms, hybridization—more than hybridity itself—triggers audience cynicism and leads to decreased judgments of authenticity. However, the penalties for hybridizing are only observed when organizations also move away from field-level profit-status norms. The findings contribute to the category-spanning and authenticity literatures by integrating social psychological and organizational theory perspectives to offer a dynamic view of spanning beyond for-profit, market contexts. They also offer empirical support for the theorized multidirectionality of mission drift in hybrid organizations, while suggesting that drifting need not always be detrimental.

Microscopic and transcriptomic analyses of Dalbergoid legume peanut reveal a divergent evolution leading to Nod Factor dependent epidermal crack-entry and terminal bacteroid differentiation.

Root nodule symbiosis (RNS) is the pillar behind sustainable agriculture and plays a pivotal role in the environmental nitrogen cycle. Most of the genetic, molecular, and cell-biological knowledge on RNS come from model legumes that exhibit a root-hair mode of bacterial infection in contrast to the Dalbergoid legumes exhibiting crack-entry of rhizobia. As a step towards understanding this important group of legumes, we have combined microscopic analysis and temporal transcriptome to obtain a dynamic view of plant gene expression during Arachis hypogaea (peanut) nodule development. We generated a comprehensive transcriptome data by mapping the reads to A. hypogaea, and two diploid progenitor genomes. Additionally, we performed BLAST searches to identify nodule-induced yet-to-be annotated peanut genes. Comparison between peanut, Medicago truncatula, Lotus japonicus, and Glycine max showed upregulation of 61 peanut orthologs among 111 tested known RNS-related genes, indicating conservation in mechanisms of nodule development among members of the Papilionoid family. Unlike model legumes, recruitment of class 1 phytoglobin derived symbiotic hemoglobin (SymH) in peanut indicates diversification of oxygen scavenging mechanisms in the Papilionoid family. Finally, absence of cysteine-rich motif-1 containing-NCRs, but the recruitment of defensin like NCRs suggest a diverse molecular mechanism of terminal bacteroid differentiation. In summary, our work describes genetic conservation and diversification in legume-rhizobial symbiosis in the Papilionoid family, as well as among members of the Dalbergoid legumes.