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Proteinuria in several glomerular diseases results from dysfunction of the slit diaphragm, a cell-cell junction of glomerular epithelial cells (podocytes). Ephrin-B1 and its related molecule NHERF 2 are novel essential components of the slit diaphragm. Ephrin-B1 interacts with nephrin via the extra-cellular domain and interacts with NHERF2 via the cytoplasmic site. In the proteinuric state induced by the stimulation to nephrin, nephrin and ephrin-B1 are phosphorylated, and NHERF2 is de- phosphorylated and consequent disruption of the linkage and downregulation of nephrin, ephrin-B1 and NHERF2 are a critical pathogenic event of podocyte injury. Keywords:Podocyte; Slit Diaphragm; Ephrin-B1; Nephrin; NHERF2 https://www.raftpubs.com/cjn-nephrology/articles/cjn_raft1004.php

Gastrulation is a critical event in vertebrate morphogenesis driven by cellular processes, and characterized by coordinated multi-cellular movements that form the robust morphological structures. How these structures emerge in a developing organism and vary across vertebrates remains unclear. Inspired by experiments on the chick, we derive a theoretical framework that couples actomyosin activity to tissue flow, and provides a basis for the dynamics of gastrulation morphologies. Our model predicts the onset and development of observed experimental patterns of wild-type and perturbations of chick gastrulation as a spontaneous instability of a uniform state. Varying the initial conditions and a parameter in our model, allows us to recapitulate the phase space of gastrulation morphologies seen across vertebrates, consistent with experimental observations in the accompanying paper. All together, this suggests that early embryonic self-organization follows from a minimal predictive theory of active mechano-sensitive flows.

BACKGROUND AND AIM: Ongoing climate variability and change is altering the timing of spring onset, a critical event that signifies the start of tree pollen season in North America. There is a pauci...

Uniparentally-inherited markers on mitochondrial DNA (mtDNA) and the non-recombining regions of the Y chromosome (NRY), have been used for the past 30 years to investigate the history of humans from a maternal and paternal perspective. Researchers have preferred mtDNA due to its abundance in the cells, and comparatively high substitution rate. Conversely, the NRY is less susceptible to back mutations and saturation, and is potentially more informative than mtDNA owing to its longer sequence length. However, due to comparatively poor NRY coverage via shotgun sequencing, and the relatively low and biased representation of Y-chromosome variants on capture assays such as the 1240 k, ancient DNA studies often fail to utilize the unique perspective that the NRY can yield. Here we introduce a new DNA enrichment assay, coined YMCA (Y-mappable capture assay), that targets the "mappable" regions of the NRY. We show that compared to low-coverage shotgun sequencing and 1240 k capture, YMCA significantly improves the mean coverage and number of sites covered on the NRY, increasing the number of Y-haplogroup informative SNPs, and allowing for the identification of previously undiscovered variants. To illustrate the power of YMCA, we show that the analysis of ancient Y-chromosome lineages can help to resolve Y-chromosomal haplogroups. As a case study, we focus on H2, a haplogroup associated with a critical event in European human history: the Neolithic transition. By disentangling the evolutionary history of this haplogroup, we further elucidate the two separate paths by which early farmers expanded from Anatolia and the Near East to western Europe., Open Access funding enabled and organized by Projekt DEAL. This study was funded by the Max Planck Society, the French (ANR) and German (DFG) Research Foundations under the INTERACT project (ANR-17-FRAL-0010, DFG-HA-5407/4-1, 2018-2021) to M.R. and W.H., the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program under Grant agreement no. 771234-PALEoRIDER to W.H., the award Praemium Academiae of the Czech Academy of Sciences to M.E. and the project RVO 67985912 of the Institute of Archaeology of the Czech Academy of Sciences, Prague to M.S.

Embryo implantation is one of the pivotal steps during mammalian pregnancy, since the quality of embryo implantation determines the outcome of ongoing pregnancy and fetal development. A large number of factors, including transcription factors, signalling transduction components, and lipids, have been shown to be indispensable for embryo implantation. Increasing evidence also suggests the important roles of epigenetic factors in this critical event. This review focuses on recent findings about the involvement of epigenetic regulators during embryo implantation.

Ferroptosis is a recently recognized cell death modality that is morphologically, biochemically and genetically distinct from other forms of cell death and that has emerged to play an important role in cancer biology. Recent discoveries have highlighted the metabolic plasticity of cancer cells and have provided intriguing insights into how metabolic rewiring is a critical event for the persistence, dedifferentiation and expansion of cancer cells. In some cases, this metabolic reprogramming has been linked to an acquired sensitivity to ferroptosis, thus opening up new opportunities to treat therapy-insensitive tumours. However, it is not yet clear what metabolic determinants are critical for therapeutic resistance and evasion of immune surveillance. Therefore, a better understanding of the processes that regulate ferroptosis sensitivity should ultimately aid in the discovery of novel therapeutic strategies to improve cancer treatment. In this Perspectives article, we provide an overview of the known mechanisms that regulate sensitivity to ferroptosis in cancer cells and how the modulation of metabolic pathways controlling ferroptosis might reshape the tumour niche, leading to an immunosuppressive microenvironment that promotes tumour growth and progression.

The protection of a multicellular organism from infection, at both cell and humoral levels, has been a tremendous driver of gene selection and cellular response strategies. Here we focus on a critical event in the development of humoral immunity: The transition from principally innate responses to a system of adaptive cell selection, with all the attendant mechanical problems that must be solved in order for it to work effectively. Here we review recent advances, but our major goal is to highlight that the development of adaptive immunity resulted from the adoption, reuse and repurposing of an ancient, autonomous cellular program that combines and exploits three titratable cellular fate timers. We illustrate how this common cell machinery recurs and appears throughout biology, and has been essential for the evolution of complex organisms, at many levels of scale., We argue that the development of adaptive immunity resulted from the adoption, reuse and repurposing of an ancient, autonomous cellular program. Signature features of this ancient program can be seen exploited in many arms of the immune response.

One of the formative narratives in Japanese martial arts is the bestowal of the mystical sword “Futsunomitama-no-tsurugi” upon Emperor Jinmu, the legendary founder of Japan. Within the Kashima Shinden Bujutsu lineage, this bestowal is attested as a critical event in the initiation of the principles of Bushidō martiality. However, the practical reasons for its significance has been unclear. Drawing on historical and archaeological records, in this paper we hypothesise that the physical conformation of the legendary sword Futsunomitama-no-tsurugi represented a comparatively incremental progression from the one-handed short swords imported from mainland Asia. These modifications, however, allowed for a new, two-handed style of swordsmanship, and therefore it was the combination of the physical conformation of Futsunomitama-no-tsurugi and the development of appropriate techniques for wielding it that formed the basis of the martial significance of the “Law of Futsu-no-mitama”. Drawing on various traditions and records linking Futsunomitama-no-tsurugi to the Kashima Grand Shrine, we also argue that this new tradition of swordsmanship was the nucleus around which the Kashima Shinden Bujutsu lineage would develop, and therefore represented a critical first step towards the later concepts of Bushidō. Based on the kabala of the Kashima Shinryū, we also present a working model of what the techniques for usage of Futsunomitama-no-tsurugi might have been, and provide an account of an experiment testing its application.

Reproduction is a critical event in the life cycle of animals, and a high amount of energy is allocated to it. The aim of this study was to characterize the reproductive biology of two recently des...

Gastric cancer (GC) is one of the leading causes of cancer-related deaths, with limited improvement in its clinical outcome worldwide. Aberrant mucin-type O-glycosylation is a critical event widespread in the development of GC. Polypeptide N-acetylgalactosaminyltransferases (GALNTs) regulate the initial step and determine the sites of mucin-type O-glycoprotein bio-synthesis. GALNT6 has considerable potential as a biomarker in various cancers. The roles of GALNT6 in GC were analyzed, and the results showed that GALNT6 expression markedly increased in GC tissues compared with those in adjacent gastric tissues. High intratumoral GALNT6 density was associated with the clinicopathological parameters of TNM stage and distant metastasis. GALNT6 was identified as an independent prognosticator for the poor prognosis of GC patients. Moreover, the high expression level of GALNT6 was significantly associated with the low expression levels of E-cadherin and β-catenin and the high expression levels of MMP9. These findings indicated that GALNT6 could provide new insights into the characterization of GC as well as contribute to the development of an efficient prognostic indicator and novel therapeutic modalities for GC.

The efficiency of somatic cell nuclear transfer (SCNT) reprogramming is extremely low in terms of production of cloned animals. Here, we found that telomere rejuvenation is a critical event for SCNT reprogramming. Through small-molecule screening, we identified that melatonin significantly improved the

Amyloid diseases make up a set of fatal disorders in which proteins aggregate to form fibrils that deposit in tissues throughout the body. Amyloid-associated diseases are challenging to study because amyloid formation occurs on time scales that span several orders of magnitude and involve heterogeneous, interconverting protein conformations. The development of more effective technologies to diagnose and treat amyloid disease requires both a map of the conformations sampled during amyloidogenesis and an understanding of the molecular mechanisms that drive this process. In prior molecular dynamics simulations of amyloid proteins, we observed the formation of a nonstandard type of secondary structure, called α-sheet, that we proposed is associated with the pathogenic conformers in amyloid disease, the soluble oligomers. However, the detailed molecular interactions that drive the conversion to α-sheet remain elusive. Here we use molecular dynamics simulations to interrogate a critical event in transthyretin aggregation, the formation of aggregation-competent, monomeric species. We show that conformational changes in one of the two β-sheets in transthyretin enable solvent molecules and polar side chains to form electrostatic interactions with main-chain peptide groups to facilitate and modulate conversion to α-sheet secondary structure. Our results shed light on the early conformational changes that drive transthyretin toward the α-sheet structure associated with toxicity. Delineation of the molecular events that lead to aggregation at atomic resolution can aid strategies to target the early, critical toxic soluble oligomers.

En las llamas la transferencia de la inmunidad pasiva a través del calostro es un evento crítico para la supervivencia de la cría (teke). El objetivo de este trabajo fue establecer la cinética de la concentración de inmunoglobulina G (IgG) en tekes durante los primeros 5 meses de vida y relacionar la concentración de IgG en suero y calostro de las llamas con la concentración en suero de los tekes. Se diseñó un estudio de cohorte, observacional y analítico. Se estudiaron 25 llamas y sus respectivas crías. Se determinó la concentración de IgG en calostro y suero de las madres y en tekes según una cinética establecida desde el nacimiento hasta los 150 días de vida, empleando la técnica de inmunodifusión radial simple. Los resultados mostraron una concentración media de IgG en suero de llamas de 4311,47 mg/dl y en calostro de 23254,9 mg/dl. En los tekes -a las 0 h posparto- la concentración de IgG fue no dosable, alcanzando valores máximos entre las 18 y 24 h (4094,06 y 4197,95 mg/dl respectivamente) no encontrando en este periodo diferencias con la concentración de la IgG sérica materna (p 0,694). Desde las 24 h hasta los 120 días se observó un descenso en los niveles de IgG (p

SummaryOne critical event in reprogramming to pluripotency is erasure of the somatic transcriptional program of starting cells. Here, we present the proof of principle of a strategy for reprogramming to pluripotency facilitated by small molecules that interfere with the somatic transcriptional memory. We show that mild chemical targeting of the acetyllysine-binding pockets of the BET bromodomains, the transcriptional bookmarking domains, robustly enhances reprogramming. Furthermore, we show that chemical targeting of the transcriptional bookmarking BET bromodomains downregulates or turns off the expression of somatic genes in both naive and reprogramming fibroblasts. Chemical blocking of the BET bromodomains also results in loss of fibroblast morphology early in reprogramming. We therefore experimentally demonstrate that cell fate conversion can be achieved by chemically targeting the transcriptional bookmarking BET bromodomains responsible for transcriptional memory.

The transition from the vegetative to the reproductive stage of growth is a critical event in the lifecycle of a plant and is required for the plant’s reproductive success. Flowering time is tightly regulated by an internal time-keeping system and external light conditions, including photoperiod, light quality, and light quantity. Other environmental factors, such as drought and temperature, also participate in the regulation of flowering time. Thus, flexibility in flowering time in response to environmental factors is required for the successful adaptation of plants to the environment. In this review, we summarize our current understanding of the molecular mechanisms by which internal and environmental signals are integrated to regulate flowering time in Arabidopsis thaliana and rice (Oryza sativa).

The disruption of blood–brain barrier (BBB) is a critical event in the formation of brain edema during early phases of ischemic brain injury. Poly(ADP-ribose) polymerase (PARP) activation, which contributes to BBB damage, has been reported in ischemia–reperfusion and traumatic brain injury. Here, we investigated the effect of 3-aminobenzamide (3-AB), a PARP-1 inhibitor, on the ultrastructure of BBB. Male Sprague Dawley rats were suffered from 90 minutes of middle cerebral artery occlusion, followed by 4.5 hours or 22.5 hours of reperfusion (R). The vehicle or 3-AB (10 mg/kg) was administered intraperitoneally (ip) 60 minutes after lacking of blood. Tissue Evans Blue (EB) levels, ultrastructures of astrocytes and microvessels, and areas of perivascular edema were examined in penumbra and core, at I 1.5 hours /R 4.5 hours and I 1.5 hours /R 22.5 hours, respectively. The severity of ultrastructural changes was graded with a scoring system in each group. We showed that 3-AB treatment significantly decreased tissue EB levels and ultrastructural scores, attenuated damages in astrocytes and microvessels, and reduced areas of perivascular edema. In conclusion, PARP inhibition may provide a novel therapeutic approach to ischemic brain injury.

We examine the initial emergence of genetics; that is, of an inherited chemical capability. The crucial actors are ribonucleotides, occasionally meeting in a prebiotic landscape. Previous work identified six influential variables during such random ribonucleotide pooling. Geochemical pools can be in periodic danger (e.g., from tides) or constant danger (e.g., from unfavorable weather). Such pools receive Gaussian nucleotide amounts sporadically, at random times, or get varying substrates simultaneously. Pools use cross-templated RNA synthesis (5′–5′ product from 5′–3′ template) or para-templated (5′–5′ product from 5′–5′ template) synthesis. Pools can undergo mild or strong selection, and be recently initiated (early) or late in age. Considering >80 combinations of these variables, selection calculations identify a superior route. Most likely, an early, sporadically fed, cross-templating pool in constant danger, receiving ≥1 mM nucleotides while under strong selection for a coenzyme-like product, will host selection of the first encoded biochemical functions. Predominantly templated products emerge from a critical event, the starting bloc selection, which exploits inevitable differences among early pools. Favorable selection has a simple rationale; it is increased by product dispersion (SD/mean), by selection intensity (mild or strong), or by combining these factors as stringency, reciprocal fraction of pools selected (1/sfsel). To summarize: chance utility, acting via a preference for disperse, templated coenzyme-like dinucleotides, uses stringent starting bloc selection to quickly establish majority encoded/genetic expression. Despite its computational origin, starting bloc selection is largely independent of specialized assumptions. This ribodinucleotide route to inheritance may also have facilitated 5′–3′ chemical RNA replication.

Mitochondrial fission is essential for distributing cellular energy throughout cells and for isolating damaged regions of the organelle that are targeted for degradation. Excessive fission is associated with the progression of cell death as well. Therefore, this multistep process is tightly regulated and several physiologic cues directly impact mitochondrial division. The double membrane structure of mitochondria complicates this process, and protein factors that drive membrane scission need to coordinate the separation of both the outer and inner mitochondrial membranes. In this review, we discuss studies that characterize distinct morphological changes associated with mitochondrial division. Specifically, coordinated partitioning and pinching of mitochondria have been identified as alternative mechanisms associated with fission. Additionally, we highlight the major protein constituents that drive mitochondrial fission and the role of connections with the endoplasmic reticulum in establishing sites of membrane division. Collectively, we review decades of research that worked to define the molecular framework of mitochondrial fission. Ongoing studies will continue to sort through the complex network of interactions that drive this critical event.

Target recognition by developing axons is one of the fundamental steps for establishing the proper pattern of neuronal connectivity during development. However, knowledge of the mechanisms that underlie this critical event is still limited. In this study, to examine how commissural axons in vertebrates recognize their targets after crossing the midline, we analyzed in detail the behavior of postcrossing commissural axons derived from the deep cerebellar nuclei (DCN) in the developing mouse cerebellum. For this, we employed a cell-type-specific genetic labeling approach to selectively visualize DCN axons during the time when these axons project to the red nucleus (RN), one of the well-characterized targets of DCN axons. We found that, when DCN axons initially entered the RN at its caudal end, these axons continued to grow rostrally through the RN without showing noticeable morphological signs of axon branching. Interestingly, after a delay, DCN axons started forming interstitial branches from the portion of the axon shaft selectively within the RN. Because commissural axons acquire responsiveness to several guidance cues when they cross the midline, we further addressed whether midline crossing is a prerequisite for subsequent targeting by using a Robo3 knockdown strategy. We found that DCN axons were still capable of forming interstitial branches within the RN even in the absence of midline crossing. These results therefore suggest that the mechanism of RN recognition by DCN axons involves a delayed interstitial branching, and that these axons possess an intrinsic ability to respond to the target-derived cues irrespective of midline crossing.

Crystallography is a powerful tool to determine the atomic structures of proteins and RNAs. X-ray crystallography has been used to determine the structure of many splicing related proteins and RNAs, making major contributions to our understanding of the molecular mechanism and regulation of pre-mRNA splicing. Compared to other structural methods, crystallography has its own advantage in the high-resolution structural information it can provide and the unique biological questions it can answer. In addition, two new crystallographic methods – the serial femtosecond crystallography and 3D electron crystallography – were developed to overcome some of the limitations of traditional X-ray crystallography and broaden the range of biological problems that crystallography can solve. This review discusses the theoretical basis, instrument requirements, troubleshooting, and exciting potential of these crystallographic methods to further our understanding of pre-mRNA splicing, a critical event in gene expression of all eukaryotes.

During the course of prion infection, the normally soluble and protease-sensitive mammalian prion protein (PrPC) is refolded into an insoluble, partially protease-resistant, and infectious form called PrPSc. The conformational conversion of PrPC to PrPSc is a critical event during prion infection and is essential for the production of prion infectivity. This chapter briefly summarizes the ways in which cell biological approaches have enhanced our understanding of how PrP contributes to different aspects of prion pathogenesis.

Angiogenesis is a critical event in tumour growth and secondary spread. The concept of inhibiting angiogenesis to control tumour growth and metastasis is not new. Several signalling pathways are involved in angiogenesis and are co-ordinated by mammalian target of rapamycin. The practical value of this is emphasised here in the context of evolving new treatment strategies. The biological effects of naturally occurring inhibitors, endogenously produced inhibitors and monoclonal antibodies raised against angiogenic agents are described together with clinical benefits of their deployment as therapeutic agents.

Article in Press; Weaning is a critical event in the pig's life cycle, frequently associated with severe enteric infections and overuse of antibiotics; this raises serious economic and public health concerns. In this review, we explain why gut microbiota dysbiosis, induced by abrupt changes in the diet and environment of piglets, emerges as a leading cause of post-weaning diarrhea, even if the exact underlying mechanisms remain unclear. Then, we focus on nonantimicrobial alternatives, such as zinc oxide, essential oils, and prebiotics or probiotics, which are currently evaluated to restore intestinal balance and allow a better management of the crucial weaning transition. Finally, we discuss how in vitro models of the piglet gut could be advantageously used as a complement to ex vivo and in vivo studies for the development and testing of new feed additives.

Human neurological disorders are associated with brain-enriched proteins in a major way. Homeostasis of such proteins is a critical event in brain functioning and development. Neuropathological studies of most common neurological disorders clearly show that accumulated, misfolded, mutant proteins are the preliminary causes for such disorders. Studies in the past few decades suggest that the ubiquitin proteasome system (UPS) network is a critical regulator of protein levels mammalian cells. To date, various proteins and substrates in UPS associated with neurological disorders have been identified, but molecular mechanisms and how they are associated with pathogenesis of neurological disorders are poorly understood. Understanding UPS network may set a new window to understand the pathogenesis of neurological disorders. Here we are reporting the current studies of UPS components in major neurological disorders, such as Parkinson's, Alzheimer's, autistic spectrum disorders, Huntington's, and multiple sclerosis.

The switch from vegetative growth to reproductive growth, i.e. flowering, is the critical event in a plant's life. Flowering is regulated either autonomously or by environmental factors; photoperiodic flowering, which is regulated by the duration of the day and night periods, and vernalization, which is regulated by low temperature, have been well studied. Additionally, it has become clear that stress also regulates flowering. Diverse stress factors can induce or accelerate flowering, or inhibit or delay it, in a wide range of plant species. This article focuses on the positive regulation of flowering via stress, i.e. the induction or acceleration of flowering in response to stress that is known as stress-induced flowering - a new category of flowering response. This review aims to clarify the concept of stress-induced flowering and to summarize the full range of characteristics of stress-induced flowering from a predominately physiological perspective.

DNA repair by homologous recombination is highly suppressed in G1 cells to ensure that mitotic recombination occurs solely between sister chromatids. Although many homologous recombination factors are cell-cycle regulated, the identity of the events that are both necessary and sufficient to suppress recombination in G1 cells is unknown. Here we report that the cell cycle controls the interaction of BRCA1 with PALB2-BRCA2 to constrain BRCA2 function to the S/G2 phases in human cells. We found that the BRCA1-interaction site on PALB2 is targeted by an E3 ubiquitin ligase composed of KEAP1, a PALB2-interacting protein, in complex with cullin-3 (CUL3)-RBX1 (ref. 6). PALB2 ubiquitylation suppresses its interaction with BRCA1 and is counteracted by the deubiquitylase USP11, which is itself under cell cycle control. Restoration of the BRCA1-PALB2 interaction combined with the activation of DNA-end resection is sufficient to induce homologous recombination in G1, as measured by RAD51 recruitment, unscheduled DNA synthesis and a CRISPR-Cas9-based gene-targeting assay. We conclude that the mechanism prohibiting homologous recombination in G1 minimally consists of the suppression of DNA-end resection coupled with a multi-step block of the recruitment of BRCA2 to DNA damage sites that involves the inhibition of BRCA1-PALB2-BRCA2 complex assembly. We speculate that the ability to induce homologous recombination in G1 cells with defined factors could spur the development of gene-targeting applications in non-dividing cells.

The onset of metastasis is a critical event in the natural history of cancer, and is generally associated with a poor clinical outcome. Mechanistically, the metastatic process is made of several steps that are biologically distinct and now rather well characterized. Several explanatory models have been proposed: selective models (clonal selection), adaptive models (initial oncogenesis), involvement of tumor "stem" cells, epithelial-mesenchymal transition… The next progresses are expected to come from the characterization of circulating and disseminated tumor cells, which are two recently opened windows on the metastatic process in patients.

Early studies of incubation behavior acknowledged the existence of a less regular form of incubation that can occur from the beginning of egg laying to shortly after clutch completion. It has been variously termed “partial incubation” (Putnam , Seel , Ashkenazie and Safriel ), “brooding” (Barth ), “intermittent incubation” (Samuel ), “irregular incubation” (Beer ), or “nonrhythmic incubation” (Morton et al. ). This form of incubation has been described from visual observations of adults sitting on the nest less regularly, and from egg temperatures that are lower and more variable than those typically attained after clutch completion (Barth , Brackbill , Kendeigh , Barrett , Morton and Pereyra ). We refer to this little-understood behavior as “partial incubation” because it is characterized by a reduced amount of time during egg laying that parents sit on and warm their eggs, compared with the amount and intensity of incubation they provide later in the nesting cycle after the clutch is complete. Partial incubation is a common way for birds to initiate incubation. The onset of incubation, the moment at which a bird begins to incubate a clutch, is a critical event in the avian nesting cycle because it has important effects on fitness, as noted more than half a century ago by David Lack (). Incubation onset can affect hatching success and hatching patterns (Nilsson and Svensson , Wang and Beissinger ), nestling growth and development (Slagsvold et al. , Bitton et al. ), fledging success (Hebert , Hebert and McNeil ), and postfledging survival and recruitment (Cam et al. ). Not only can the onset of incubation affect adult reproductive rates, but it also influences and is influenced by parental body condition and survival (Hanssen et al. ). Yet the onset of incubation is rarely described and even less commonly quantified, and methods of determining incubation onset have not been standardized among studies or species. In this review, we () clarify terminology for the onset of incubation, refine the concept of partial incubation, and summarize the prevalence of partial incubation. We then () examine the potential functions of partial incubation, () map individual-level patterns of partial incubation from previous studies onto a recently developed typology of patterns for the onset of incubation (Wang and Beissinger ), and examine intraspecific variability and compare interspecific data with respect to taxonomic and ecological diversity. We also () provide a standardized method for determining the individual onset of full incubation, using complete records of nest attendance or incubation from the start of laying to beyond clutch completion. Our goal is to show how data from disparate studies can be used to test hypotheses about the function of partial incubation. Finally, we () offer questions that may prove to be fertile areas of research and suggest ways to standardize future data collection and analysis to benefit common research goals. TERMINOLOGY FOR THE ONSET OF INCUBATION

• During plant development, the transition from a vegetative to reproductive state is a critical event. For decades, pea (Pisum sativum) has been used as a model species to study this transition. These studies have led to a conceptual, qualitative model for the control of flower initiation, referred to as the ‘classical’ model. This model involves many inputs, namely photoperiod, genetic states and two mobile signals which interact to determine the first node of flowering. • Here, we developed a computational model based on the hypotheses of the classical model. Accordingly, we converted qualitative hypotheses into quantitative rules. • We found that new hypotheses, in addition to those already described for the classical model, were required that explicitly described the signals. In particular, we hypothesized that the key flowering gene HR interacts with the photoperiod pathway to control flowering. The computational model was tested against a wide range of biological data, including pre-existing and new experimental results presented here, and was found to be accurate. • This computational model, together with ongoing experimental advances, will assist future modelling efforts to increase our understanding of flowering in pea.

While neuroimmune interactions are increasingly recognized as important in nociceptive processing, the nature and functional significance of these interactions is not well defined. There are multiple reports that the activation of spinal microglia is a critical event in the generation of neuropathic pain behaviors but the mediators of this activation remain disputed. Here we show that the chemokine CCL2, produced by both damaged and undamaged primary sensory neurons in neuropathic pain states in rats, is released in an activity dependent manner from the central terminals of these fibres. We also demonstrate that intraspinal CCL2 in naïve rats leads to activation of spinal microglia and neuropathic pain-like behavior. An essential role for spinal CCL2 is demonstrated by the inhibition of neuropathic pain behavior and microglial activation by a specific neutralising antibody to CCL2 administered intrathecally. Thus, the neuronal expression of CCL2 provides a mechanism for immune activation, which in turn regulates the sensitivity of pain signaling systems in neuropathic pain states.

Loss of aggrecan from articular cartilage is an early and critical event in the pathogenesis of osteoarthritis (OA) and is enzymatically mediated by aggrecanase activity. Since the discovery of aggrecanase-1 (ADAMTS-4) and aggrecanase-2 (ADAMTS-5), both members of the "a disintegrin and metalloproteinase with thrombospondin motif" family of proteinases, other members of the family have been reported to have aggrecanase activity, as currently defined, including ADAMTS-1, -8, -9, -15 and -16. Understanding whether these other ADAMTS members are in fact genuine in vivo aggrecanases will be important for the development of therapeutic agents that aim to block aggrecan degradation. The goal of this review is to look at the current definition of "aggrecanase activity", and define its strengths, weaknesses and suitability for determining which ADAMTS, are aggrecanases that participate in aggrecan catabolism in OA. In addition, we propose a more comprehensive definition of aggrecanase activity, based on 6 criteria that encompass both biochemical and biological characteristics of the endogenous aggrecanase activity detected in vitro and in vivo. Finally, using these criteria, we propose which ADAMTSs should be classified as aggrecanases and therefore be considered as drug targets for the development of chondroprotective OA treatments.

Summary Obtaining food following the transition from endogenous to exogenous feeding and during the first year of life is a critical event that strongly influences growth and survival of young-of-year fishes. For shovelnose sturgeon Scaphirhynchus platorynchus, limited information is available on food habits during the first year of life. The objective of this study was to quantify diet components of shovelnose sturgeon during the transition from endogenous to exogenous feeding and during the young-of-year life stage in the North Dakota and Montana portions of the Missouri River. Young-of-year shovelnose sturgeon were sampled between early August and early September 2003. Shovelnose sturgeon initiated exogenous feeding by 16 mm, and individuals 16–140 mm fed exclusively on two macroinvertebrate orders (Diptera and Ephemeroptera). Young-of-year shovelnose sturgeon exhibited an apparently high feeding success as 99 of 100 individuals contained food in the gut. The number of organisms in the gut increased exponentially with fish length for larval Diptera (r2 = 0.73, P

Megaphyll leaf evolution was a critical event in Earth history that had major consequences for the biotic regulation of the global environment. Zimmermann's telome theory has been widely accepted for over seventy years as the leading explanation for this evolutionary innovation. According to the telome theory, megaphylls evolved from the three-dimensional lateral branches of early vascular land plants in a hypothetical series of three transformations; first, the formation of determinate lateral branches (overtopping); second, the development of 'flattened' branch systems (planation); and third, the fusion of planated branches with lateral outgrowths of photosynthetic mesophyll tissue to form the leaf blade (webbing). A critical review of the molecular and cellular evidence identifies plausible genetic, cellular and physiological mechanisms in extant higher plants for overtopping and planation but more limited evidence for the process of webbing (lateral outgrowth fusion). We highlight key outstanding questions concerning the telome theory that are likely to be resolved when gene identification and functional analysis techniques are applied to photosynthetic organisms that have different evolutionary histories.

Lignin is a complex phenolic polymer that is deposited in the secondary cell wall of all vascular plants. The evolution of lignin is considered to be a critical event during vascular plant development, because lignin provides mechanical strength, rigidity, and hydrophobicity to secondary cell walls to allow plants to grow tall and transport water and nutrients over a long distance. In recent years, great research efforts have been made to genetically alter lignin biosynthesis to improve biomass degradability for the production of second-generation biofuels. This global focus on lignin research has significantly advanced our understanding of the lignification process. Based on these advances, here I provide an overview of lignin composition, the biosynthesis pathway and its regulation.

BACKGROUND AND AIMS When the orientation of the stems of conifers departs from the vertical as a result of environmental influences, conifers form compression wood that results in restoration of verticality. It is well known that intercellular spaces are formed between tracheids in compression wood, but the function of these spaces remains to be clarified. In the present study, we evaluated the impact of these spaces in artificially induced compression wood in Chamaecyparis obtusa seedlings. METHODS We monitored the presence or absence of liquid in the intercellular spaces of differentiating xylem by cryo-scanning electron microscopy. In addition, we analysed the relationship between intercellular spaces and the hydraulic properties of the compression wood. KEY RESULTS Initially, we detected small intercellular spaces with liquid in regions in which the profiles of tracheids were not rounded in transverse surfaces, indicating that the intercellular spaces had originally contained no gases. In the regions where tracheids had formed secondary walls, we found that some intercellular spaces had lost their liquid. Cavitation of intercellular spaces would affect hydraulic conductivity as a consequence of the induction of cavitation in neighbouring tracheids. CONCLUSIONS Our observations suggest that cavitation of intercellular spaces is the critical event that affects not only the functions of intercellular spaces but also the hydraulic properties of compression wood.

Targeting of the Gag polyprotein to the plasma membrane (PM) for assembly is a critical event in the late phase of immunodeficiency virus type-1 (HIV-1) infection. Gag binding to the PM is mediated by interactions between the myristoylated matrix (MA) domain and PM lipids. Despite the extensive biochemical and in vitro studies of Gag and MA binding to membranes over the last two decades, the discovery of the role of phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] in Gag binding to the PM has sparked a string of studies aimed at elucidating the molecular mechanism of retroviral Gag–PM binding. Electrostatic interactions between a highly conserved basic region of MA and acidic phospholipids have long been thought to be the main driving force for Gag–membrane interactions. However, recent studies suggest that the mechanism is rather complex since other factors such as the hydrophobicity of the membrane interior represented by the acyl chains and cholesterol also play important roles. Here we summarize the current understanding of HIV-1 Gag–membrane interactions at the molecular and structural levels and briefly discuss the underlying forces governing interactions of other retroviral MA proteins with the PM.

Early cardiogenesis including myofibrillogenesis is a critical event during development. -Recently we showed that prospective cardiomyocytes reside in the posterior lateral blastoderm in the chick embryo. Here we cultured the posterior region of the chick blastoderm in serum-free medium and observed the process of myofibrillogenesis by immunohistochemistry. After 48 hours, explants expressed sarcomeric proteins (sarcomeric alpha-actinin, 61%; smooth muscle alpha-actin, 95%; Z-line titin, 56%; sarcomeric myosin, 48%); however, they did not yet show a mature striation. After 72 hours, more than 92% of explants expressed I-Z-I proteins, which were incorporated into the striation in 75% of explants or more (sarcomeric alpha-actinin, 75%; smooth muscle alpha-actin, 81%; Z-line titin, 83%). Sarcomeric myosin was -expressed in 63% of explants and incorporated into A-bands in 37%. The percentage incidence of expression or striation of I-Z-I proteins was significantly higher than that of sarcomeric myosin. Results suggested that the nascent I-Z-I components appeared to be generated independently of A-bands in the cultured posterior blastoderm, and that the process of myofibrillogenesis observed in our culture model faithfully reflected that in vivo. Our blastoderm culture model appeared to be useful to investigate the mechanisms regulating the early cardiogenesis.

The onset of exogenous feeding, when juveniles emerge from the gravel, is a critical event for salmonids where early emergence and large size provide a competitive advantage in the wild. Studying 131 farmed, hybrid and wild Norwegian Atlantic salmon families, originating from four wild populations and two commercial strains, we investigated whether approximately 10 generations of selection for faster growth has also resulted in increased somatic growth prior to the onset of exogenous feeding. In addition, we tested whether relaxed selection in farms has allowed for alterations in hatching time between farmed and wild salmon. Across three cohorts, wild salmon families hatched earlier than farmed salmon families, while hybrid families displayed intermediate hatching times. While the observed differences were small, i.e., 1–15 degree-days (0–3 days, as water temperatures were c. 5–6°C), these data suggest additive genetic variation for hatching time. Alevin length prior to exogenous feeding was positively related to egg size. After removal of egg size effects, no systematic differences in alevin length were observed between the wild and farmed salmon families. While these results indicate additive genetic variation for egg development timing, and wild salmon families consistently hatched earlier than farmed salmon families, these differences were so small they are unlikely to significantly influence early life history competition of farmed and wild salmon in the natural environment. This is especially the case given that the timing of spawning among females can vary by several weeks in some rivers. The general lack of difference in size between farmed and wild alevins, strongly suggest that the documented differences in somatic growth rate between wild and farmed Norwegian Atlantic salmon under hatchery conditions are first detectable after the onset of exogenous feeding. publishedVersion

During membrane fusion, the outer leaflets of the two membranes merge first, whereas the distal membrane leaflets remain separate until the opening of a fusion pore. This intermediate stage, called hemifusion, is a critical event shared by exocytosis, protein trafficking, and viral entry.

The amyloid hypothesis of Alzheimer's disease (AD) maintains that the accumulation of the amyloid β protein (Aβ) is a critical event in disease pathogenesis. A great deal of both academic and commercial research has focused on the mechanisms by which Aβ is generated. However, investigations into the mechanisms underlying Aβ clearance have blossomed over the last several years. This minireview will summarize pathways involved in the removal of cerebral Aβ, including enzymatic degradation and receptor-mediated efflux out of the brain.

Hepatic stellate cell (HSC) activation is the critical event of liver fibrosis. Abnormality of miR-16 expression induces their activation. However, the action model of miR-16 remains to be elucidated because of its multiple-targeted manner. Here, we report that miR-16 restoration exerted a wide-range impact on transcriptome (2,082 differentially expressed transcripts) of activated HSCs. Integrative analysis of both targetome (1,195 targets) and transcriptome uncovered the miR-16 regulatory network based upon bio-molecular interaction databases (BIND, BioGrid, Tranfac, and KEGG), cross database searching with iterative algorithm, Dijkstra's algorithm with greedy method, etc. Eight targets in the targetome (Map2k1, Bmpr1b, Nf1, Pik3r3, Ppp2r1a, Prkca, Smad2, and Sos2) served as key regulatory network nodes that mediate miR-16 action. A set of TFs (Sp1, Jun, Crebl, Arnt, Fos, and Nf1) was recognized to be the functional layer of key nodes, which mapped the signal of miR-16 to transcriptome. In result, the comprehensive action of miR-16 abrogated transcriptomic characteristics that determined the phenotypes of activated HSCs, including active proliferation, ECM deposition, and apoptosis resistance. Therefore, a multi-layer regulatory network based upon the integration of targetome and transcriptome may underlie the global action of miR-16, which suggesting it plays an inhibitory role in HSC activation.

The release of neurotransmitters from synaptic vesicles exocytosing at presynaptic nerve terminals is a critical event in the initiation of synaptic transmission. This event occurs at specialized sites known as active zones. The task of faithfully executing various steps in the process is undertaken by careful orchestration of overlapping sets of molecular nano-machineries upon a core macromolecular scaffold situated at active zones. However, their composition remains incompletely elucidated. This review provides an overview of the role of the active zone in mediating neurotransmitter release and summarizes the recent progress using neuroproteomic approaches to decipher their composition. Key proteins of these nano-machineries are highlighted.

The transition from vegetative to reproductive growth is a critical event in the life cycle of plants. Previous physiological studies have deduced that hormone-like substances mediate this important transition but the biochemical nature of the putative signaling molecules has remained elusive. Recent molecular and genetic studies of key flowering-time genes offer new approaches to understanding the mechanisms underlying the initiation of flowering.

The proper targeting and fusion of transport vesicles with the correct membrane is a critical event in the determination of the identity of different compartments within the cell. Work over the last decade has made tremendous progress toward determining a general mechanism by which this occurs. The

The assembly of vascular endothelial cells (ECs) and smooth muscle cells is a critical event in the development of the cardiovascular system. Although the role of ECs in this event has been studied intensively, the cross-talk between the two cell components remains poorly understood. In this study, we blocked platelet-derived growth factor receptor (PDGFR) pathways in mice by antagonistic rat monoclonal antibody APB5 against murine PDGFR-beta and examined glomerular capillary formation.

The breaking of tolerance to self-antigens, involving the activation of self-reactive lymphocytes, is a critical event leading to autoimmune disease. The precise mechanisms by which this occurs are unknown, but among other etiological factors, viruses have been implicated. Recent results with animal models of insulin-dependent diabetes provide insight into how viruses induce autoimmune disease.

The steroidogenesis in the granulosa-thecal layers of fish ovarian follicles undergo a distinct shift from the production of estradiol-17β (E2) to 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP, maturation-inducing hormone, MIH) prior to meiotic maturation. This review attempts to explain the underlying mechanisms of steroidogenic shift.

A hypoxic microenvironment plays a critical role in the development and progression of tumors. The epithelial to mesenchymal transition (EMT) is a process by which epithelial cells lose their polarity and are converted to a mesenchymal phenotype, which is regarded as a critical event in morphogenetic changes during embryonic development, wound healing, and cancer metastasis. Recent advances in our understanding of the molecular pathways that govern the association of hypoxia with malignant tumors point to the epithelial to mesenchymal transition (EMT). The hypoxic microenvironment common to cancer cells emerges as an important factor in the induction of a pathological EMT, which is a key link in cancer progression. This review presents the potential molecular mechanisms underlying the hypoxia/HIF-dependent regulation of the EMT in cancer.

Ciliary movement is powered by axonemal dynein. This article considers how a signal transduction cascade initiated at the cell membrane may activate outer dynein arms to change the velocity of microtubule sliding and the swimming speed of ciliated cells. For Paramecium, a critical event in the cascade is the cAMP-dependent phosphorylation of a 29 kDa polypeptide that is associated with the outer dynein arm.