Mammalian oocytes store proteins for the early embryo on cytoplasmic lattices.

Mammalian oocytes are filled with poorly understood structures called cytoplasmic lattices. First discovered in the 1960s and speculated to correspond to mammalian yolk, ribosomal arrays, or intermediate filaments, their function has remained enigmatic to date. Here, we show that cytoplasmic lattices are sites where oocytes store essential proteins for early embryonic development. Using super-resolution light microscopy and cryoelectron tomography, we show that cytoplasmic lattices are composed of filaments with a high surface area, which contain PADI6 and subcortical maternal complex proteins. The lattices associate with many proteins critical for embryonic development, including proteins that control epigenetic reprogramming of the preimplantation embryo. Loss of cytoplasmic lattices by knocking out PADI6 or the subcortical maternal complex prevents the accumulation of these proteins and results in early embryonic arrest. Our work suggests that cytoplasmic lattices enrich maternally provided proteins to prevent their premature degradation and cellular activity, thereby enabling early mammalian development.

Maintenance of appropriate size scaling of the C. elegans pharynx by YAP-1.

Even slight imbalance between the growth rate of different organs can accumulate to a large deviation from their appropriate size during development. Here, we use live imaging of the pharynx of C. elegans to ask if and how organ size scaling nevertheless remains uniform among individuals. Growth trajectories of hundreds of individuals reveal that pharynxes grow by a near constant volume per larval stage that is independent of their initial size, such that undersized pharynxes catch-up in size during development. Tissue-specific depletion of RAGA-1, an activator of mTOR and growth, shows that maintaining correct pharynx-to-body size proportions involves a bi-directional coupling between pharynx size and body growth. In simulations, this coupling cannot be explained by limitation of food uptake alone, and genetic experiments reveal an involvement of the mechanotransducing transcriptional co-regulator yap-1. Our data suggests that mechanotransduction coordinates pharynx growth with other tissues, ensuring body plan uniformity among individuals.

Biological factors and self-perception of stress in relation to freeze-like response in humans.

Many animals react to threatening stimuli such as a predator attacks by freezing. However, little experimental research investigated freeze response in humans. Here, we have employed practices commonly used in self-defense training to create two unique scenarios simulating armed physical threat. Sixty healthy men volunteers divided into three groups of twenty (untrained, trained but unexperienced, trained and experienced) underwent these scenarios accompanied by measurement of biochemical, physiological, and psychological markers of stress. Our results show that untrained individuals exhibit stronger freezing reactions, while highly skilled participants display the lowest propensity for freezing, especially in high-intensity scenarios. Moreover, the study shows variations in anxiety levels and selected biomarkers, with cortisol and osteocalcin showing different patterns in low and high-intensity scenarios, and suggests a complex interplay between these factors, electrodermal activity, and stress perception.

Learning mitigates genetic drift.

Genetic drift is a basic evolutionary principle describing random changes in allelic frequencies, with far-reaching consequences in various topics ranging from species conservation efforts to speciation. The conventional approach assumes that genetic drift has the same effect on all populations undergoing the same changes in size, regardless of different non-reproductive behaviors and history of the populations. However, here we reason that processes leading to a systematic increase of individuals` chances of survival, such as learning or immunological memory, can mitigate loss of genetic diversity caused by genetic drift even if the overall mortality rate in the population does not change. We further test this notion in an agent-based model with overlapping generations, monitoring allele numbers in a population of prey, either able or not able to learn from successfully escaping predators' attacks. Importantly, both these populations start with the same effective size and have the same and constant overall mortality rates. Our results demonstrate that even under these conditions, learning can mitigate loss of genetic diversity caused by drift, by creating a pool of harder-to-die individuals that protect alleles they carry from extinction. Furthermore, this effect holds regardless if the population is haploid or diploid or whether it reproduces sexually or asexually. These findings may be of importance not only for basic evolutionary theory but also for other fields using the concept of genetic drift.

TACSTD2 upregulation is an early reaction to lung infection.

TACSTD2 encodes a transmembrane glycoprotein Trop2 commonly overexpressed in carcinomas. While the Trop2 protein was discovered already in 1981 and first antibody-drug conjugate targeting Trop2 were recently approved for cancer therapy, the physiological role of Trop2 is still not fully understood. In this article, we show that TACSTD2/Trop2 expression is evolutionarily conserved in lungs of various vertebrates. By analysis of publicly available transcriptomic data we demonstrate that TACSTD2 level consistently increases in lungs infected with miscellaneous, but mainly viral pathogens. Single cell and subpopulation based transcriptomic data revealed that the major source of TACSTD2 transcript are lung epithelial cells and their progenitors and that TACSTD2 is induced directly in lung epithelial cells following infection. Increase in TACSTD2 expression may represent a mechanism to maintain/restore epithelial barrier function and contribute to regeneration process in infected/damaged lungs.

Proteomic Signatures of Human Visceral and Subcutaneous Adipocytes.

CONTEXT: Adipose tissue distribution is a key factor influencing metabolic health and risk in obesity-associated comorbidities. OBJECTIVE: Here we aim to compare the proteomic profiles of mature adipocytes from different depots. METHODS: Abdominal subcutaneous (SA) and omental visceral adipocytes (VA) were isolated from paired adipose tissue biopsies obtained during bariatric surgery on 19 severely obese women (body mass index > 30 kg/m2) and analyzed using state-of-the-art mass spectrometry. Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were performed to investigate proteome signature properties and to examine a possible association of the protein expression with the clinical data. RESULTS: We identified 3686 protein groups and found 1140 differentially expressed proteins (adj. P value < 0.05), of which 576 proteins were upregulated in SA and 564 in VA samples. We provide a global protein profile of abdominal SA and omental VA, present the most differentially expressed pathways and processes distinguishing SA from VA, and correlate them with clinical and body composition data. We show that SA are significantly more active in processes linked to vesicular transport and secretion, and to increased lipid metabolism activity. Conversely, the expression of proteins involved in the mitochondrial energy metabolism and translational or biosynthetic activity is higher in VA. CONCLUSION: Our analysis represents a valuable resource of protein expression profiles in abdominal SA and omental VA, highlighting key differences in their role in obesity.

Homeostatic model of human thermoregulation with bi-stability.

All homoiothermic organisms are capable of maintaining a stable body temperature using various negative feedback mechanisms. However, current models cannot satisfactorily describe the thermal adaptation of homoiothermic living systems in a physiologically meaningful way. Previously, we introduced stress entropic load, a novel variable designed to quantify adaptation costs, i.e. the stress of the organism, using a thermodynamic approach. In this study, we use stress entropic load as a starting point for the construction of a novel dynamical model of human thermoregulation. This model exhibits bi-stable mechanisms, a physiologically plausible features which has thus far not been demonstrated using a mathematical model. This finding allows us to predict critical points at which a living system, in this case a human body, may proceed towards two stabilities, only one of which is compatible with being alive. In the future, this may allow us to quantify not only the direction but rather the extent of therapeutic intervention in critical care patients.

Predation has small, short-term, and in certain conditions random effects on the evolution of aging.

BACKGROUND: The pace of aging varies considerably in nature. The best-known explanation of the evolution of specific rates of aging is the Williams' hypothesis suggesting that the aging rate should correlate with the level of extrinsic mortality. However, the current evidence is inconclusive with various examples where the Williams' hypothesis seems to be correct and where it doesn't. Here we explore the relationship between extrinsic mortality and aging rate by developing a simulation model of the evolution of aging rate in prey subject to predation. RESULTS: Our results suggest that more intense predation leads to the evolution of faster pace of aging in prey. However, this effect slowly vanishes when the predator diet breadth is allowed to evolve, too. Furthermore, in our model, the evolution of a specific aging rate is driven mainly by a single parameter, the strength of a trade-off between aging and fecundity. Indeed, in the absence of this trade-off the evolutionary impacts of predation on the prey aging rate appear random. CONCLUSIONS: We show that the William's hypothesis appears valid when there is a trade-off between aging and fecundity and predators and prey do not coevolve. However, we also show that when the prey and predators coevolve or if there is no trade-off between aging and fecundity the William`s hypothesis is no longer applicable.

Trop2: Jack of All Trades, Master of None.

Trophoblast cell surface antigen 2 (Trop2) is a widely expressed glycoprotein and an epithelial cell adhesion molecule (EpCAM) family member. Although initially identified as a transmembrane protein, other subcellular localizations and processed forms were described. Its congenital mutations cause a gelatinous drop-like corneal dystrophy, a disease characterized by loss of barrier function in corneal epithelial cells. Trop2 is considered a stem cell marker and its expression associates with regenerative capacity in various tissues. Trop2 overexpression was described in tumors of different origins; however, functional studies revealed both oncogenic and tumor suppressor roles. Nevertheless, therapeutic potential of Trop2 was recognized and clinical studies with drug-antibody conjugates have been initiated in various cancer types. One of these agents, sacituzumab govitecan, has been recently granted an accelerated approval for therapy of metastatic triple-negative breast cancer. In this article, we review the current knowledge about the yet controversial function of Trop2 in homeostasis and pathology.

Eustress and Distress: Neither Good Nor Bad, but Rather the Same?

The terms "eustress" and "distress" are widely used throughout the scientific literature. As of February 2020, 203 items in the Web of Science show up in a search for "eustress," however, there are almost 16 400 items found in a search for the term "distress." Based on the reasoning in this article, however, it is believed there is no such thing as eustress or distress. The adaptation reaction of an organism under stress is not intrinsically good or bad, and its effect on health or performance depends on a plethora of other interactions of the body with the environment as well as on the history of such interactions. The vagueness of the terms "eustress/distress" has historically led to vast differences in the perception and application of the terms across disciplines. While psychology or sociology perceive eustress as something inextricably linked to positive perception and enhanced cognition, biomedicine perceives eustress as generally associated with better survival, health, or increased longevity, no matter how the event is perceived. In this paper, the authors review the current understanding of the term "eustress" in different fields, discuss possible implications of its misleading use, and suggest that the term may be replaced by "stress" only.

Centriole foci persist in starfish oocytes despite Polo-like kinase 1 inactivation or loss of microtubule nucleation activity.

Centrioles must be eliminated or inactivated from the oocyte to ensure that only the two functional centrioles contributed by the sperm are present in the zygote. Such removal can occur during oogenesis, as in Drosophila, where departure of Polo kinase from centrosomes leads to loss of microtubule nucleating activity and centriole removal. In other species, oocyte-derived centrioles are removed around the time of fertilization through incompletely understood mechanisms. Here, we use confocal imaging of live starfish oocytes and zygotes expressing markers of microtubule nucleating activity and centrioles to investigate this question. We first assay the role of Polo-like kinase 1 (Plk1) in centriole elimination. We find that although Plk1 localizes around oocyte-derived centrioles, kinase impairment with BI-2536 does not protect centrioles from removal in the bat star Patiria miniata. Moreover, we uncover that all four oocyte-derived centrioles lose microtubule nucleating activity when retained experimentally in the zygote of the radiate star Asterias forbesi. Interestingly, two such centrioles nevertheless retain the centriolar markers mEGFP::PACT and pmPoc1::mEGFP. Together, these findings indicate that centrioles can persist when Plk1 activity is impaired, as well as when microtubule nucleating activity is lacking, uncovering further diversity in the mechanisms governing centriole removal.

Actin assembly ruptures the nuclear envelope by prying the lamina away from nuclear pores and nuclear membranes in starfish oocytes.

The nucleus of oocytes (germinal vesicle) is unusually large and its nuclear envelope (NE) is densely packed with nuclear pore complexes (NPCs) that are stockpiled for embryonic development. We showed that breakdown of this specialized NE is mediated by an Arp2/3-nucleated F-actin 'shell' in starfish oocytes, in contrast to microtubule-driven tearing in mammalian fibroblasts. Here, we address the mechanism of F-actin-driven NE rupture by correlated live-cell, super-resolution and electron microscopy. We show that actin is nucleated within the lamina, sprouting filopodia-like spikes towards the nuclear membranes. These F-actin spikes protrude pore-free nuclear membranes, whereas the adjoining stretches of membrane accumulate NPCs that are associated with the still-intact lamina. Packed NPCs sort into a distinct membrane network, while breaks appear in ER-like, pore-free regions. We reveal a new function for actin-mediated membrane shaping in nuclear rupture that is likely to have implications in other contexts, such as nuclear rupture observed in cancer cells.

Nanoscopy reveals the layered organization of the sarcomeric H-zone and I-band complexes.

Sarcomeres are extremely highly ordered macromolecular assemblies where structural organization is intimately linked to their functionality as contractile units. Although the structural basis of actin and Myosin interaction is revealed at a quasiatomic resolution, much less is known about the molecular organization of the I-band and H-zone. We report the development of a powerful nanoscopic approach, combined with a structure-averaging algorithm, that allowed us to determine the position of 27 sarcomeric proteins in Drosophila melanogaster flight muscles with a quasimolecular, ∼5- to 10-nm localization precision. With this protein localization atlas and template-based protein structure modeling, we have assembled refined I-band and H-zone models with unparalleled scope and resolution. In addition, we found that actin regulatory proteins of the H-zone are organized into two distinct layers, suggesting that the major place of thin filament assembly is an M-line-centered narrow domain where short actin oligomers can form and subsequently anneal to the pointed end.

Male mortality rates mirror mortality rates of older females.

Women on average live longer than men, which seems to suggest that women also age slower than men. However, the potential difference in the pace of aging between the sexes is a relatively controversial topic, and both positions, i.e. "men age faster" and "men and women age at the same pace", have found some support. We therefore employ parametric models previously established in model organisms as well as two nonparametric approaches to compare the pace of aging between the sexes using freely available mortality data from 13 high-income countries. Our results support the hypothesis that men age faster than women while also suggesting that the difference is small and that from a practical standpoint male mortality rates behave similarly to the mortality rates of women approximately eight years their senior.

Sibling relatedness rather than father absence predicts earlier age at menarche in ELSPAC cohort.

Many studies during the past 50 years have found an association between father absence and earlier menarche. In connection with these findings, several evolutionary theories assume that father absence is a causal factor accelerating reproductive development. However, a recent study analysing data from the Avon Longitudinal Study of Parents and Children (ALSPAC) found that father absence does not predict age at menarche when adjusted for sibling relatedness. In this study, we have replicated these results in the Czech section of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC), which used the same questionnaires as ALSPAC to study a geographically distinct population. Our results support the conclusion that sibling relatedness rather than father absence predicts age at menarche. Furthermore, our results show that age at menarche in 1990s UK and Czech cohorts is very similar despite socioeconomic differences between the two countries.

The Pathosome: A Dynamic Three-Dimensional View of Disease-Environment Interaction.

Most contemporary models of disease development consider the interaction between genotype and environment as static. The authors argue that because time is a key factor in genotype-environment interaction, this approach oversimplifies the pathology analysis and may lead to wrong conclusions. In reviewing the field, the authors suggest that the history of genotype-environment interactions plays an important role in the development of diseases and that this history may be analyzed using the phenotype as a proxy. Furthermore, a theoretical and experimental framework is proposed based on the assumption that phenotypes do not change from one to another randomly but are interconnected and follow certain phenotype trajectories. It then follows that analysis of such phenotype trajectories might be useful to predict the future phenotypes including the onset of disease. In addition, an analysis of phenotype trajectories can be subsequently used to choose better control subjects in comparative studies reducing noise and bias in studies investigating disease mechanisms.

Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions.

Cytoplasmic flows are an ubiquitous feature of biological systems, in particular in large cells, such as oocytes and eggs in early animal development. Here we show that cytoplasmic flows in starfish oocytes, which can be imaged well with transmission light microscopy, are fully determined by the cortical dynamics during surface contraction waves. We first show that the dynamics of the oocyte surface is highly symmetric around the animal-vegetal axis. We then mathematically solve the Stokes equation for flows inside a deforming sphere using the measured surface displacements as boundary conditions. Our theoretical predictions agree very well with the intracellular flows quantified by particle image velocimetry, proving that during this stage the starfish cytoplasm behaves as a simple Newtonian fluid on the micrometer scale. We calculate the pressure field inside the oocyte and find that its gradient is too small as to explain polar body extrusion, in contrast to earlier suggestions. Myosin II inhibition by blebbistatin confirms this conclusion, because it diminishes cell shape changes and hydrodynamic flow, but does not abolish polar body formation.

Stress entropic load: New stress measurement method?

While stress is a widely utilized concept, no direct methods facilitating its measurement are currently available. In our previous work we proposed stress entropic load (SEL) as a potential new marker of stress response in the human body. However, at that time no method for SEL measurement existed. In this pilot study we devised and then tested methodology for SEL measurement. Healthy male participants were monitored by indirect calorimetry and thermography while resting and subsequently while under prolonged mental effort. The acquired data was then used to calculate the temporal development of SEL for each participant. Our results show that SEL production increased significantly in participants subjected to prolonged mental effort. Furthermore, we observed that the calculated development of SEL over time may be used to accurately determine the time point at which participants started performing stressful tasks.

Evolution favours aging in populations with assortative mating and in sexually dimorphic populations.

Since aging seems omnipresent, many authors regard it as an inevitable consequence of the laws of physics. However, recent research has conclusively shown that some organisms do not age, or at least do not age on a scale comparable with other aging organisms. This begets the question why aging evolved in some organisms yet not in others. Here we present a simulation model of competition between aging and non-aging individuals in a sexually reproducing population. We find that the aging individuals may outcompete the non-aging ones if they have a sufficiently but not excessively higher initial fecundity or if individuals mate assortatively with respect to their own phenotype. Furthermore, the aging phenotype outcompetes the non-aging one or resists dominance of the latter for a longer period in populations composed of genuine males and females compared to populations of simultaneous hermaphrodites. Finally, whereas sterilizing parasites promote non-aging, the effect of mortality-enhancing parasites is to enable longer persistence of the aging phenotype relative to when parasites are absent. Since the aging individuals replace the non-aging ones in diverse scenarios commonly found in nature, our study provides important insights into why aging has evolved in most, but not all organisms.

Correlated light and electron microscopy of cell division in large marine oocytes, eggs, and embryos.

The rapid and synchronous divisions of large and transparent oocytes, eggs, and embryos of marine species are exceptionally well suited for microscopic observation. Consequently, these cells have been models for cell division research since its beginnings and contributed some of its first and most fundamental discoveries. While large size and rapid transitions render these cells ideal specimens for light microscopy, the same features constitute a challenge for electron microscopy. Here, we describe example protocols from our work on starfish oocyte meiosis, where we overcome these challenges by using live imaging of fluorescently labeled structures in combination with correlated electron microscopy. In this work, we demonstrate how: (i) to capture a rapid, transient event in time and (ii) to localize a small structure within the large oocyte. These techniques are applicable with minor modifications to oocytes and embryos of other species and, possibly, to other cell types.