Search

One of the first organizing processes during animal development is the assembly of embryonic cells into epithelia. Common features unite epithelialization across select bilaterians, however, we know less about the molecular and cellular mechanisms that drive epithelial emergence in early branching nonbilaterians. In sea anemones, epithelia emerge both during embryonic development and after cell aggregation of dissociated tissues. Although adhesion is required to keep cells together, it is not clear whether cell polarization plays a role as epithelia emerge from disordered aggregates. Here, we use the embryos of the sea anemone Nematostella vectensis to investigate the evolutionary origins of epithelial development. We demonstrate that lateral cell polarization is essential for epithelial organization in both embryos and aggregates. With disrupted lateral polarization, cell contact in the aggregate is not sufficient to trigger epithelialization and further tissue development. Specifically, knockdown of the conserved lateral polarity and tumor suppressor protein Lethal giant larvae (Lgl) disrupts epithelia in developing embryos and impairs the capacity of dissociated cells to epithelialize from aggregates. In contrast to other systems, cells in Nematostella lgl knockdown embryos do not undergo excessive proliferation. Cells with reduced Lgl levels lose their columnar shape and proper positioning of their mitotic spindles and basal bodies. Due to misoriented divisions and aberrant shapes, cells arrange nonuniformly without forming a monolayer. Together our data show that, in Nematostella, Lgl drives epithelialization in embryos and cell aggregates through its effect on cell shape and organelle localization., Competing Interests: Competing interests statement:The authors declare no competing interest.

Early amniote development is highly self-organized, capable of adapting to interference through local and long-range cell-cell interactions. This process, called embryonic regulation 1 , has been well illustrated in experiments on avian embryos, in which subdividing the epiblast disk into different parts not only redirects cell fates to eventually form a complete and well-proportioned embryo at its original location, but also leads to the self-organization of additional, fully formed embryos 2,3 in the other separated parts. The cellular interactions underlying embryonic self-organization are widely believed to be mediated by molecular signals, yet the identity of such signals is unclear. Here, by analysing intact and mechanically perturbed quail embryos, we show that the mechanical forces that drive embryogenesis self-organize, with contractility locally self-activating and the ensuing tension acting as a long-range inhibitor. This mechanical feedback governs the persistent pattern of tissue flows that shape the embryo 4-6 and also steers the concomitant emergence of embryonic territories by modulating gene expression, ensuring the formation of a single embryo under normal conditions, yet allowing the emergence of multiple, well-proportioned embryos after perturbations. Thus, mechanical forces act at the core of embryonic self-organization, shaping both tissues and gene expression to robustly yet plastically canalize early development., (© 2024. The Author(s).)

We established a normal embryonic development table for the Anji salamander Hynobius amjiensis, a critically endangered tailed amphibian of the family Hynobiidae with a very limited distribution in East China, following the standards set by the early developmental table of vertebrates. Put together 32 embryonic stages for the Anji salamander was defined. The total embryonic period from oviposition to hatching is approximately 30 days at 9 °C. Stages 1-16 represent early development from cleavage to neurulation. Stages 17-32 represent organogenesis documenting later developmental events such as tail, gill, and limb formation, and hatching (Stage 32). We provided a detailed description of the external morphology and color changes of the head, trunk, limbs, tail, external gills, and balancers at various stages from egg-laying to hatching. We also described several cases of abnormal embryonic development. The establishment of the embryonic development table in H. amjiensis contributes to better understanding of the ontogeny in tailed amphibians, distinguishing closely related species, and identifying abnormal embryonic amphibians., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Angioblasts that form the major axial blood vessels of the dorsal aorta and cardinal vein migrate toward the embryonic midline from distant lateral positions. Little is known about what controls the precise timing of angioblast migration and their final destination at the midline. Using zebrafish, we found that midline angioblast migration requires neighboring tissue rearrangements generated by somite morphogenesis. The somitic shape changes cause the adjacent notochord to separate from the underlying endoderm, creating a ventral midline cavity that provides a physical space for the angioblasts to migrate into. The anterior to posterior progression of midline angioblast migration is facilitated by retinoic acid-induced anterior to posterior somite maturation and the subsequent progressive opening of the ventral midline cavity. Our work demonstrates a critical role for somite morphogenesis in organizing surrounding tissues to facilitate notochord positioning and angioblast migration, which is ultimately responsible for creating a functional cardiovascular system., Competing Interests: EP, NP, JW, BM No competing interests declared, (© 2022, Paulissen et al.)

Somitogenesis, the segmentation of the antero-posterior axis in vertebrates, is thought to result from the interactions between a genetic oscillator and a posterior-moving determination wavefront. The segment (somite) size is set by the product of the oscillator period and the velocity of the determination wavefront. Surprisingly, while the segmentation period can vary by a factor three between 20 °C and 32 °C, the somite size is constant. How this temperature independence is achieved is a mystery that we address in this study. Using RT-qPCR we show that the endogenous fgf8 mRNA concentration decreases during somitogenesis and correlates with the exponent of the shrinking pre-somitic mesoderm (PSM) size. As the temperature decreases, the dynamics of fgf8 and many other gene transcripts, as well as the segmentation frequency and the PSM shortening and tail growth rates slows down as T-T c (with T c  = 14.4 °C). This behavior characteristic of a system near a critical point may account for the temperature independence of somitogenesis in zebrafish., (© 2022. The Author(s).)

Morphogenesis is a precise and robust dynamic process during metazoan embryogenesis, consisting of both cell proliferation and cell migration. Despite the fact that much is known about specific regulations at molecular level, how cell proliferation and migration together drive the morphogenesis at cellular and organismic levels is not well understood. Using Caenorhabditis elegans as the model animal, we present a phase field model to compute early embryonic morphogenesis within a confined eggshell. With physical information about cell division obtained from three-dimensional time-lapse cellular imaging experiments, the model can precisely reproduce the early morphogenesis process as seen in vivo, including time evolution of location and morphology of each cell. Furthermore, the model can be used to reveal key cell-cell attractions critical to the development of C. elegans embryo. Our work demonstrates how genetic programming and physical forces collaborate to drive morphogenesis and provides a predictive model to decipher the underlying mechanism., Competing Interests: The authors declare that no competing interests exist.

Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s)., Competing Interests: BG, RD, CH, AM No competing interests declared, (© 2021, Godard et al.)

How force generated by the morphogenesis of one tissue impacts the morphogenesis of other tissues to achieve an elongated embryo axis is not well understood. The notochord runs along the length of the somitic compartment and is flanked on either side by somites. Vacuolating notochord cells undergo a constrained expansion, increasing notochord internal pressure and driving its elongation and stiffening. Therefore, the notochord is appropriately positioned to play a role in mechanically elongating the somitic compartment. We used multi-photon cell ablation to remove specific regions of the zebrafish notochord and quantify the impact on axis elongation. We show that anterior expansion generates a force that displaces notochord cells posteriorly relative to adjacent axial tissues, contributing to the elongation of segmented tissue during post-tailbud stages. Unexpanded cells derived from progenitors at the posterior end of the notochord provide resistance to anterior notochord cell expansion, allowing for stress generation along the anterior-posterior axis. Therefore, notochord cell expansion beginning in the anterior, and addition of cells to the posterior notochord, act as temporally coordinated morphogenetic events that shape the zebrafish embryo anterior-posterior axis., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Sea urchin embryos have been one of model organisms to investigate cellular behaviors because of their simple cell composition and transparent body. They also give us an opportunity to investigate molecular functions of human proteins of interest that are conserved in sea urchin. Here we report that human disease-associated extracellular matrix orthologues ECM3 and QBRICK are necessary for mesenchymal cell migration during sea urchin embryogenesis. Immunofluorescence has visualized the colocalization of QBRICK and ECM3 on both apical and basal surface of ectoderm. On the basal surface, QBRICK and ECM3 constitute together a mesh-like fibrillar structure along the blastocoel wall. When the expression of ECM3 was knocked down by antisense-morpholino oligonucleotides, the ECM3-QBRICK fibrillar structure completely disappeared. When QBRICK was knocked down, the ECM3 was still present, but the basally localized fibers became fragmented. The ingression and migration of primary mesenchymal cells were not critically affected, but their migration at later stages was severely affected in both knock-down embryos. As a consequence of impaired primary mesenchymal cell migration, improper spicule formation was observed. These results indicate that ECM3 and QBRICK are components of extracellular matrix, which play important role in primary mesenchymal cell migration, and that sea urchin is a useful experimental animal model to investigate human disease-associated extracellular matrix proteins.

Diapause is a reversible developmental arrest faced by many organisms in harsh environments. Annual killifish present this mechanism in three possible stages of development. Killifish are freshwater teleosts from Africa and America that live in ephemeral ponds, which dry up in the dry season. The juvenile and adult populations die, and the embryos remain buried in the bottom mud until the next rainy season. Thus, species survival is entirely embryo-dependent, and they are perhaps the most remarkable extremophile organisms among vertebrates. The aim of the present study was to gather information about embryonic diapauses with the use of a "shotgun" proteomics approach in diapause III and prehatching Austrolebias charrua embryos. Our results provide insight into the molecular mechanisms of diapause III. Data are available via ProteomeXchange with identifier PXD025196. We detected a diapause-dependent change in a large group of proteins involved in different functions, such as metabolic pathways and stress tolerance, as well as proteins related to DNA repair and epigenetic modifications. Furthermore, we observed a diapause-associated switch in cytoskeletal proteins. This first glance into global protein expression differences between prehatching and diapause III could provide clues regarding the induction/maintenance of this developmental arrest in A. charrua embryos. There appears to be no single mechanism underlying diapause and the present data expand our knowledge of the molecular basis of diapause regulation. This information will be useful for future comparative approaches among different diapauses in annual killifish and/or other organisms that experience developmental arrest., Competing Interests: The authors have declared that no competing interests exist.

The first dinosaur embryos found inside megaloolithid eggs from Auca Mahuevo, Patagonia, were assigned to sauropod dinosaurs that lived approximately 80 million years ago. Discovered some 25 years ago, these considerably flattened specimens still remain the only unquestionable embryonic remains of a sauropod dinosaur providing an initial glimpse into titanosaurian in ovo ontogeny. Here we describe an almost intact embryonic skull, which indicates the early development of stereoscopic vision, and an unusual monocerotic face for a sauropod. The new fossil also reveals a neurovascular sensory system in the premaxilla and a partly calcified braincase, which potentially refines estimates of its prenatal stage. The embryo was found in an egg with thicker eggshell and a partly different geochemical signature than those from the egg-bearing layers described in Auca Mahuevo. The cranial bones are comparably ossified as in previously described specimens but differ in facial anatomy and size. The new specimen reveals significant heterochrony in cranial ossifications when compared with non-sauropod sauropodomorph embryos, and demonstrates that the specialized craniofacial morphology preceded the postnatal transformation of the skull anatomy in adults of related titanosaurians., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Nuclear size plays pivotal roles in gene expression, embryo development, and disease. A central hypothesis in organisms ranging from yeast to vertebrates is that nuclear size scales to cell size. This implies that nuclei may reach steady-state sizes set by limiting cytoplasmic pools of size-regulating components. By monitoring nuclear dynamics in early sea urchin embryos, we found that nuclei undergo substantial growth in each interphase, reaching a maximal size prior to mitosis that declined steadily over the course of development. Manipulations of cytoplasmic volume through multiple chemical and physical means ruled out cell size as a major determinant of nuclear size and growth. Rather, our data suggest that the perinuclear endoplasmic reticulum, accumulated through dynein activity, serves as a limiting membrane pool that sets nuclear surface growth rate. Partitioning of this local pool at each cell division modulates nuclear growth kinetics and dictates size scaling throughout early development., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The degradation of maternally provided molecules is a very important process during early embryogenesis. However, the vast majority of studies deals with mRNA degradation and protein degradation is only a very little explored process yet. The aim of this article was to summarize current knowledge about the protein degradation during embryogenesis of mammals. In addition to resuming of known data concerning mammalian embryogenesis, we tried to fill the gaps in knowledge by comparison with facts known about protein degradation in early embryos of non-mammalian species. Maternal protein degradation seems to be driven by very strict rules in terms of specificity and timing. The degradation of some maternal proteins is certainly necessary for the normal course of embryonic genome activation (EGA) and several concrete proteins that need to be degraded before major EGA have been already found. Nevertheless, the most important period seems to take place even before preimplantation development-during oocyte maturation. The defects arisen during this period seems to be later irreparable.

A laboratory flume was constructed to examine substrate effects on aquatic development. The flume was designed as a once-through system with a submerged cobble-filled corebox. Lake whitefish (Coregonus clupeaformis) embryos and temperature probes were deployed at multiple sites within the cobble and in the open water channel. Embryos were incubated in the flume for two different experimental periods: one to examine substrate impacts during natural lake cooling (37 days: 5 December 2016 to 10 January 2017) and the second to investigate substrate effects while administering a twice weekly 1 h heat shock (51 days: 11 January to 2 March 2017). During incubation, no significant difference was found in the average temperature between locations; however, temperatures were more stable within the cobble. Following both incubation periods, embryos retrieved from the cobble were significantly smaller in both dry mass and body length by up to 20%. These results demonstrate differences between embryos submerged in a cobble substrate and in the open water column, highlighting the need to consider the physical influences from the incubation environment when assessing development effects as part of any scientific study or environmental assessment., (© 2020 The Fisheries Society of the British Isles.)

Understanding the biological function of amyloid beta (Aβ) precursor protein (APP) beyond its role in Alzheimer's disease is emerging. Yet, its function during embryonic development is poorly understood. The zebrafish APP orthologue, Appb, is strongly expressed during early development but thus far has only been studied via morpholino-mediated knockdown. Zebrafish enables analysis of cellular processes in an ontogenic context, which is limited in many other vertebrates. We characterized zebrafish carrying a homozygous mutation that introduces a premature stop in exon 2 of the appb gene. We report that appb mutants are significantly smaller until 2 dpf and display perturbed enveloping layer (EVL) integrity and cell protrusions at the blastula stage. Moreover, appb mutants surviving beyond 48 hpf exhibited no behavioral defects at 6 dpf and developed into healthy and fertile adults. The expression of the app family member, appa, was also found to be altered in appb mutants. Taken together, we show that appb is involved in the initial development of zebrafish by supporting the integrity of the EVL, likely by mediating cell adhesion properties. The loss of Appb might then be compensated for by other app family members to maintain normal development.

Marine angelfish (family: Pomacanthidae) are among the most sought-after fish species in the saltwater aquarium trade. However, there is a lack of information in the literature on their early ontogeny. The objective of this study was to describe the embryonic and early larval development of two dwarf angelfish, the bicolour angelfish, Centropyge bicolor and the coral beauty angelfish, Centropyge bispinosa. The eggs of these two species were obtained from spontaneous spawning of the broodstock fish in captivity and incubated at 26.0 ± 0.2°C throughout the study. Fertilized eggs (n = 15) of both species are transparent, pelagic and spherical; the mean diameters of the eggs were measured at 703.6 ± 7.8 μm for C. bicolor and 627.6 ± 7.8 μm for C. bispinosa. The eggs of both species possessed a narrow perivitelline space, smooth and thin chorion, a homogenous and non-segmented yolk as well as a single oil globule. Overall, the observed embryonic development pattern of C. bicolor and C. bispinosa was very similar, and the main difference was the embryonic pigmentation pattern, which only became evident close to hatching. Larvae of both species started hatching at 13 h 30 min after fertilization, and the larval characteristics of both species also showed high levels of similarities. However, the mouth opening time for C. bicolor was 72 h after hatching (AH) and 96 AH for C. bispinosa. In general, the observed early ontogeny of C. bicolor and C. bispinosa also resembled that of other Centropyge species documented in the literature.

The co-occurrence of hypoxia and xenobiotics is extremely common in natural environments, highlighting the necessity to elicit their interaction on aquatic toxicities. In the present study, marine medaka embryos were exposed to various concentrations (nominal 0, 1, 3.3 and 10 mg/L) of perfluorobutane sulfonate (PFBS), an environmental pollutant of emerging concern, under either normoxia (6.9 mg/L) or hypoxia (1.7 mg/L) condition. After acute exposure till 15 days post-fertilization, single or combined toxicities of PFBS and hypoxia on embryonic development (e.g., mortality, hatching and heartbeat) and endocrine systems were investigated. Sex and thyroid hormones were measured by enzyme-linked immunosorbent assay. Transcriptional changes of endocrine genes were determined by quantitative real-time PCR assays. Co-exposure to 10 mg/L PFBS and hypoxia caused a further reduction in survival rate and heart beat compared to single exposure. PFBS induced a precocious hatching, while no larvae hatched under hypoxia condition. By disturbing the balance of sex hormones, either PFBS or hypoxia single exposure produced an anti-estrogenic activity in medaka larvae. However, PFBS and hypoxia combinations reversed to estrogenic activity in co-exposed larvae. Variation in disrupting pattern may be attributed to the interactive effects on steroidogenic pathway involving diverse cytochrome P450 enzymes. Regarding thyroid system, PFBS exposure caused detriments of multiple processes along thyroidal axis (e.g., feedback regulation, synthesis and transport of thyroid hormones, receptor-mediated signaling and thyroid gland development), while hypoxia potently impaired the development and function of thyroid gland. Combinations of PFBS and hypoxia interacted to dysregulate the function of thyroid endocrine system. In summary, the present study revealed the dynamic interaction of PFBS pollutant and hypoxia on aquatic developmental toxicities and endocrine disruption. Considering the frequent co-occurrence of xenobiotics and hypoxia, current results would be beneficial to improve our understanding about their interactive mechanisms and provide baseline evidences for accurate ecological risk evaluation., Competing Interests: Declaration of Competing Interest There is no conflict of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In spite of its toxic effects, N-acetyl-p-aminophenol (APAP), also commonly known as acetaminophen or paracetamol, is one of the most widely used analgesic and antipyretic agents. It can be obtained without a medical prescription. To test the effect over the zebrafish embryonic development, a Fish Embryo acute Toxicity (FET) test was carried out with acetaminophen to establish the range of concentrations that cause a harmful effect on the zebrafish development. Diminished pigmentation (in embryos treated from 0 h post-fertilization) and blockage of melanin synthesis (in larvae treated from 72 h post-fertilization) were detected, suggesting the involvement of this compound in the development of black pigment cells as described recently for human epidermal melanocytes. Morphological abnormalities such as aberrant craniofacial structures, pericardial edemas, and blood accumulation were also found. All these effects could be due to higher levels of apoptotic cells detected in treated embryos. Therefore, teratogenic effects of acetaminophen cannot be ruled out, and its wide use should be taken with caution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Multicellular rosettes are transient epithelial structures that serve as intermediates during diverse organ formation. We have identified a unique contributor to rosette formation in zebrafish Kupffer's vesicle (KV) that requires cell division, specifically the final stage of mitosis termed abscission. KV utilizes a rosette as a prerequisite before forming a lumen surrounded by ciliated epithelial cells. Our studies identify that KV-destined cells remain interconnected by cytokinetic bridges that position at the rosette's center. These bridges act as a landmark for directed Rab11 vesicle motility to deliver an essential cargo for lumen formation, CFTR (cystic fibrosis transmembrane conductance regulator). Here we report that premature bridge cleavage through laser ablation or inhibiting abscission using optogenetic clustering of Rab11 result in disrupted lumen formation. We present a model in which KV mitotic cells strategically place their cytokinetic bridges at the rosette center, where Rab11-associated vesicles transport CFTR to aid in lumen establishment.

Predicting how interactions between transcription factors and regulatory DNA sequence dictate rates of transcription and, ultimately, drive developmental outcomes remains an open challenge in physical biology. Using stripe 2 of the even-skipped gene in Drosophila embryos as a case study, we dissect the regulatory forces underpinning a key step along the developmental decision-making cascade: the generation of cytoplasmic mRNA patterns via the control of transcription in individual cells. Using live imaging and computational approaches, we found that the transcriptional burst frequency is modulated across the stripe to control the mRNA production rate. However, we discovered that bursting alone cannot quantitatively recapitulate the formation of the stripe and that control of the window of time over which each nucleus transcribes even-skipped plays a critical role in stripe formation. Theoretical modeling revealed that these regulatory strategies (bursting and the time window) respond in different ways to input transcription factor concentrations, suggesting that the stripe is shaped by the interplay of 2 distinct underlying molecular processes., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

The role of epigenetics in development has garnered attention in recent years due to their ability to modulate the embryonic developmental gene expression in response to the environmental cues. The epigenetic mechanisms - DNA methylation, histone modification, and non-coding RNAs have a unique impact on vertebrate development. Zebrafish, a model vertebrate organism is being used widely in developmental studies due to their high fecundability and rapid organogenesis. With increased studies on various aspects of epigenetics in development, this review gives a glimpse of the major epigenetic modifications and their role in zebrafish development. In this review, the basic mechanism behind each modification followed by their status in zebrafish has been reviewed. Further, recent advancements in the epigenetic aspect of zebrafish development have been discussed., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Embryonic poly(A)-binding protein (EPAB) is an RNA-binding protein that binds to the poly(A) tails and AU-rich element at the 3' ends of messenger RNA (mRNAs). The main functions of EPAB are to protect stored mRNAs from undergoing deadenylation and subsequent degradation and to be involved in their translational regulation during spermatogenesis, oogenesis, and early embryogenesis. Following the first characterization of Epab in the Xenopus oocytes and early embryos, spatial and temporal expression and potential roles of the Epab gene have been determined in the vertebrate germ cells and early embryos. In this review, we have comprehensively evaluated all studies in this field and discussed the particular functions of EPAB in the spermatogenic cells, oocytes, early embryos, and somatic cells in vertebrates., (© 2019 Wiley Periodicals, Inc.)

lncRNAs, genes transcribed but not translated, longer than 200 nucleotides, are classified as a separate class of nonprotein coding genes. Since their discovery, largely from RNAseq data, a number of pioneer studies have begun to unravel its myriad functions, centered on gene expression regulation, suggesting developmental and evolutionary conservation. Since they do not code for proteins and have no open reading frames, their functional constraints likely differ from that of protein coding genes, or of genes where the majority of the nucleotide sequence is required for function, like tRNAs. This has complicated assessment of both developmental and evolutionary conservation, and the identification of homologs in different species. Here we argue that other characteristics: general synteny and particular chromosomal placement regardless of sequence, sequence micro-motifs, and secondary structure allow for "homologs" to be identified and compared, confirming developmental and evolutionary conservation of lncRNAs. We conclude exemplifying a case in point: that of the evolutionarily conserved lncRNA acal, characterized and required for embryogenesis in Drosophila., (© 2019 Wiley Periodicals, Inc.)

Background: One goal of evolutionary developmental biology is to understand the role of development in the origin of phenotypic novelty and convergent evolution. Geckos are an ideal system to study this topic, as they are species-rich and exhibit a suite of diverse morphologies-many of which have independently evolved multiple times within geckos., Results: We characterized and discretized the embryonic development of Lepidodactylus lugubris-an all-female, parthenogenetic gecko species. We also used soft-tissue μCT to characterize the development of the brain and central nervous system, which is difficult to visualize using traditional microscopy techniques. Additionally, we sequenced and assembled a de novo transcriptome for a late-stage embryo as a resource for generating future developmental tools. Herein, we describe the derived and conserved patterns of L. lugubris development in the context of squamate evolution and development., Conclusions: This embryonic staging series, μCT data, and transcriptome together serve as critical enabling resources to study morphological evolution and development, the evolution and development of parthenogenesis, and other questions concerning vertebrate evolution and development in an emerging gecko model., (© 2019 Wiley Periodicals, Inc.)

The maternal-to-zygotic transition (MZT) is a conserved and fundamental process during which the maternal environment is converted to an environment of embryonic-driven development through dramatic reprogramming. However, how maternally supplied transcripts are dynamically regulated during MZT remains largely unknown. Herein, through genome-wide profiling of RNA 5-methylcytosine (m 5 C) modification in zebrafish early embryos, we found that m 5 C-modified maternal mRNAs display higher stability than non-m 5 C-modified mRNAs during MZT. We discovered that Y-box binding protein 1 (Ybx1) preferentially recognizes m 5 C-modified mRNAs through π-π interactions with a key residue, Trp45, in Ybx1's cold shock domain (CSD), which plays essential roles in maternal mRNA stability and early embryogenesis of zebrafish. Together with the mRNA stabilizer Pabpc1a, Ybx1 promotes the stability of its target mRNAs in an m 5 C-dependent manner. Our study demonstrates an unexpected mechanism of RNA m 5 C-regulated maternal mRNA stabilization during zebrafish MZT, highlighting the critical role of m 5 C mRNA modification in early development., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Late embryogenesis abundant (LEA) proteins are intrinsically disordered proteins (IDPs) commonly found in anhydrobiotic organisms and are frequently correlated with desiccation tolerance. Herein we report new findings on AfrLEA6, a novel group 6 LEA protein from embryos of Artemia franciscana. Assessment of secondary structure in aqueous and dried states with circular dichroism (CD) reveals 89% random coil in the aqueous state, thus supporting classification of AfrLEA6 as an IDP. Removal of water from the protein by drying or exposure to trifluoroethanol (a chemical de-solvating agent) promotes a large gain in secondary structure of AfrLEA6, predominated by α-helix and exhibiting minimal β-sheet structure. We evaluated the impact of physiological concentrations (up to 400 mM) of the disaccharide trehalose on the folding of LEA proteins in solution. CD spectra for AfrLEA2, AfrLEA3m, and AfrLEA6 are unaffected by this organic solute noted for its ability to drive protein folding. AfrLEA6 exhibits its highest concentration in vivo during embryonic diapause, drops acutely at diapause termination, and then declines during development to undetectable values at the larval stage. Maximum cellular titer of AfrLEA6 was 10-fold lower than for AfrLEA2 or AfrLEA3, both group 3 LEA proteins. Acute termination of diapause with H 2 O 2 (a far more effective terminator than desiccation in this Great Salt Lake, UT, population) fostered a rapid 38% decrease in AfrLEA6 content of embryos. While the ultimate mechanism of diapause termination is unknown, disruption of key macromolecules could initiate physiological signaling events necessary for resumption of development and metabolism.

Serotonin (5-HT) is a key player in many physiological processes in both the adult organism and developing embryo. One of the mechanisms for 5-HT-mediated effects is covalent binding of 5-HT to the target proteins catalyzed by transglutaminases (serotonylation). Despite the implication in a variety of physiological processes, the involvement of serotonylation in embryonic development remains unclear. Here we tested the hypothesis that 5-HT serves as a substrate for transglutaminase-mediated transamidation of the nuclear proteins in the early embryos of both vertebrates and invertebrates. For this, we demonstrated that the level of serotonin immunoreactivity (5-HT-ir) in cell nuclei increases upon the elevation of 5-HT concentration in embryos of sea urchins, mollusks, and teleost fish. Consistently, pharmacological inhibition of transglutaminase activity resulted in the reduction of both brightness and nuclear localization of anti-5-HT staining. We identified specific and bright 5-HT-ir within nuclei attributed to a subset of different cell types: ectodermal and endodermal, macro- and micromeres, and blastoderm. Western blot and dot blot confirmed the presence of 5-HT-ir epitopes in the normal embryos of all the species examined. The experimental elevation of 5-HT level led to the enhancement of 5-HT-ir-related signal on blots in a species-specific manner. The obtained results demonstrate that 5-HT is involved in transglutaminase-dependent monoaminylation of nuclear proteins and suggest nuclear serotonylation as a possible regulatory mechanism during early embryonic development. The results reveal that this pathway is conserved in the development of both vertebrates and invertebrates.

Migrasomes are recently identified vesicular organelles that form on retraction fibres behind migrating cells. Whether migrasomes are present in vivo and, if so, the function of migrasomes in living organisms is unknown. Here, we show that migrasomes are formed during zebrafish gastrulation and signalling molecules, such as chemokines, are enriched in migrasomes. We further demonstrate that Tspan4 and Tspan7 are required for migrasome formation. Organ morphogenesis is impaired in zebrafish MZtspan4a and MZtspan7 mutants. Mechanistically, migrasomes are enriched on a cavity underneath the embryonic shield where they serve as chemoattractants to ensure the correct positioning of dorsal forerunner cells vegetally next to the embryonic shield, thereby affecting organ morphogenesis. Our study shows that migrasomes are signalling organelles that provide specific biochemical information to coordinate organ morphogenesis.

Temperature during the prenatal period is an important factor for developing embryos. Extensive human and animal research indicate embryos are sensitive to small fluctuations in temperature which has profound effects on phenotype development. Much of this research has focused on survivability, morphology, and incubation duration, but comparatively less in known about how prenatal temperature influences the development of motor coordination. In this study, we experimentally tested whether exposure to naturally occurring cool (36.9 °C) or warm (38.1 °C) thermal conditions for a brief period (4 days) during early incubation can influence postnatal motor performance in neonatal bobwhite quail hatchlings. We compared gait spatiotemporal parameters, body kinematics, and locomotive behaviors of control chicks incubated in an optimal thermal environment (37.5 °C) with thermally manipulated chicks. Experimental temperature treatment began on embryonic day five (E5) and ended on E8. Chicks were tested 24-h after hatching. Cool thermal exposure during incubation delayed hatching, reduced body mass, and increased fall frequency, intertarsal joint angle and stride length variability during the gait task compared to optimally incubated chicks. Warm thermal exposure during incubation delayed bone growth and increased fall frequency relative to controls. We discuss the relationship between motor development and thermal regulatory processes and provide insight into how spatiotemporal parameters aid in elucidating subtle differences in coordinated movement which may contribute to atypical motor development and be associated with neural developmental disorders. We provide the first spatiotemporal evidence for the importance of optimal thermal microclimates for typical prenatal motor development., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Actinotrichia are the first exoskeletal elements formed during zebrafish fin development. These rigid fibrils serve as skeletal support for the fin fold and as substrates for mesenchymal cell migration. In the adult intact fins, actinotrichia are restricted to the distal domain of the fin. Following fin amputation, actinotrichia also reform during regeneration. The actinodin gene family codes for structural proteins of actinotrichia. We have previously identified cis-acting regulatory elements in a 2kb genomic region upstream of the first exon of actinodin1, termed 2P, required for tissue-specific expression in the fin fold ectoderm and mesenchyme during embryonic development. Indeed, 2P contains an ectodermal enhancer in a 150bp region named epi. Deletion of epi from 2P results in loss of ectodermal-specific activity. In the present study, we sought to further characterize the activity of these regulatory sequences throughout fin development and during adult fin regeneration. Using a reporter transgenic approach, we show that a site within the epi region, termed epi3, contains an early mesenchymal-specific repressor. We also show that the larval fin fold ectodermal enhancer within epi3 remains functional in the basal epithelial layer during fin regeneration. We show that the first non-coding exon and first intron of actinodin1 contains a transcriptional enhancer and an alternative promoter that are necessary for the persistence of reporter expression reminiscent of actinodin1 expression during adulthood. Altogether, we have identified cis-acting regulatory elements that are required for tissue-specific expression as well as full recapitulation of actinodin1 expression during adulthood. Furthermore, the characterization of these elements provides us with useful molecular tools for the enhancement of transgene expression in adulthood., Competing Interests: The authors have declared that no competing interests exist.

The cadherin-catenin complex is a conserved, calcium-dependent cell-cell adhesion module that is necessary for normal development and the maintenance of tissue integrity in bilaterian animals. Despite longstanding evidence of a deep ancestry of calcium-dependent cell adhesion in animals, the requirement of the cadherin-catenin complex to coordinate cell-cell adhesion has not been tested directly in a non-bilaterian organism. Here, we provide the first analysis of classical cadherins and catenins in the Starlet Sea Anemone, Nematostella vectensis. Gene expression, protein localization, siRNA-mediated knockdown of α-catenin, and calcium-dependent cell aggregation assays provide evidence that a bonafide cadherin-catenin complex is present in the early embryo, and that α-catenin is required for normal embryonic development and the formation of cell-cell adhesions between cells dissociated from whole embryos. Together these results support the hypothesis that the cadherin-catenin complex was likely a complete and functional cell-cell adhesion module in the last common cnidarian-bilaterian ancestor. SUMMARY STATEMENT: Embryonic manipulations and ex vivo adhesion assays in the sea anemone, Nematostella vectensis, indicate that the necessity of the cadherin-catenin complex for mediating cell-cell adhesion is deeply conserved in animal evolution., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Organ regeneration occurs in anamniotes (fish and amphibians) while is absent in amniotes (reptiles, birds and mammals). An evolutionary hypothesis is presented to explain the loss of organ regeneration in amniotes. The aquatic life in fish or the initial aquatic and later terrestrial life in amphibians requires complex life cycles after embryonic development. One or more larval stages that occupy different ecological niches are necessary in fish to reach the final adult stage, generally through metamorphosis. This is a post-embryonic process determined by genes that are constitutive of the genome of fish and amphibians, and that can also be re-utilized during adult life to regenerate injured or lost organs. During the adaptation to terrestrial niches, the larval stages disappeared and a direct development evolved with the formation of the amniote egg in reptiles and birds or the blastocysts in mammals. The genome for developing larvae and metamorphosis was therefore eliminated from the life cycle of amniotes. The loss of genes utilized for metamorphosis determined also the loss of the capability to regenerate organs in adults, especially of the neural organization of the nervous system. The cellular immune system that in anamniotes was operating in metamorphic destruction of larval tissues, in amniotes became no longer tolerant to embryonic-larval antigens. The loss of genes operating during metamorphosis and presence of intolerant immune cells determined the inability to regenerate organs in amniotes. Efforts of regenerative medicine must overcome these genetic and immune barriers to induce organ regeneration., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Three theoretical models have been proposed to explain lifespan extension resulting from exposure to extreme conditions in microscopic animals: individuals become completely dormant and stop aging, continue to age or age but at a diminished rate. Here we show that the earliest life history stages, embryonic cell divisions, in the tardigrade species Hypsibius dujardini are retarded when eggs are reared at 0 °C. Compared to control specimens reared at 22 °C, juveniles that hatched from eggs exposed to 0 °C for 4 days and returned to 22 °C experienced a three-day lag, indicating that their biological age was less than their chronological age. As cold exposure duration increased (days = 10, 20, 40), incubation period at 22 °C decreased incrementally (days = 3, 2, 1), suggesting that tardigrades involve a threshold-determined, quantum-like, energetic-based system for controlling embryogenesis.

Identifying functional enhancer elements in metazoan systems is a major challenge. Large-scale validation of enhancers predicted by ENCODE reveal false-positive rates of at least 70%. We used the pregrastrula-patterning network of Drosophila melanogaster to demonstrate that loss in accuracy in held-out data results from heterogeneity of functional signatures in enhancer elements. We show that at least two classes of enhancers are active during early Drosophila embryogenesis and that by focusing on a single, relatively homogeneous class of elements, greater than 98% prediction accuracy can be achieved in a balanced, completely held-out test set. The class of well-predicted elements is composed predominantly of enhancers driving multistage segmentation patterns, which we designate segmentation driving enhancers (SDE). Prediction is driven by the DNA occupancy of early developmental transcription factors, with almost no additional power derived from histone modifications. We further show that improved accuracy is not a property of a particular prediction method: after conditioning on the SDE set, naïve Bayes and logistic regression perform as well as more sophisticated tools. Applying this method to a genome-wide scan, we predict 1,640 SDEs that cover 1.6% of the genome. An analysis of 32 SDEs using whole-mount embryonic imaging of stably integrated reporter constructs chosen throughout our prediction rank-list showed >90% drove expression patterns. We achieved 86.7% precision on a genome-wide scan, with an estimated recall of at least 98%, indicating high accuracy and completeness in annotating this class of functional elements., Competing Interests: The authors declare no conflict of interest., (Copyright © 2019 the Author(s). Published by PNAS.)

The goldfish (Carassius auratus auratus) is a useful species for embryonic micromanipulations because of its large egg size and wide temperature tolerance. Here, we describe in detail the rate of development and morphological characteristics of goldfish embryos incubated at temperatures between 10 °C and 30 °C. The cleavage speed increased rapidly as temperature increased. Synchronized cell divisions occurred at 131 min intervals at 10 °C, at 33 min intervals at 20 °C, and at 19 min intervals at 30 °C during the cleavage period. The rate of hatched abnormal embryos significantly increased at temperatures of 26 °C and above, while there was no change in the number of abnormal embryos at temperatures less than 24 °C. Moreover, the blastomeres around the center of the blastodisc rose in the direction of the animal pole at temperatures less than 14 °C. At the lower temperatures, clusters of maternally-supplied germplasm were visualized both at the ends of the first three cleavage furrows and at the border between the lower and upper tiers at the 16- to 32-cell stage, with injection of artificial mRNA and vasa in situ hybridization. This study showed that temperature affects not only developmental speed but also the shape of the blastodisc and the distribution of maternally-supplied materials in the blastodisc. By controlling the temperature, it is possible for researchers to prepare many stages of embryos and shapes of the blastodisc from a single batch of eggs.

During development metazoan embryos have to establish the molecular coordinates for elaboration of the embryonic body plan. Typically, bilaterian (bilaterally symmetric animals) embryos establish anterior-posterior (AP) and dorsal-ventral (DV) axes, and in most cases the AP axis is established first. For over a century it has been known that formation of the AP axis is strongly influenced by the primary axis of the egg, the animal-vegetal (AV) axis. The molecular basis for how the AV axis influences AP polarity remains poorly understood, but sea urchins have proven to be important for elucidating the molecular basis for this process. In fact, it is the first model system where a critical role for Wnt signaling in specification and patterning the AV and AP axis was first established. One current area of research is focused on identifying the maternal factors that regulate localized activation of Wnt/β-catenin signaling at the vegetal pole during development. An essential tool for this work is the means to identify the AV polarity in oocytes and eggs. This permits investigation into how polarity is established and allows development of experimental strategies to identify maternal factors that contribute to and control axial polarity. This chapter provides protocols to accomplish this in sea urchin eggs and early embryos. We describe simple methods to visualize polarity including direct observation of eggs and oocytes, using a microscope for overt morphological signs of polarity, and more extensive methods involving localization of known factors indicative of inherent embryonic polarity, such as the upstream regulators of the Wnt/β-catenin pathway., (© 2019 Elsevier Inc. All rights reserved.)

A simultaneous analysis of the pre and postnatal growth data obtained for five exemplary animals (zebra, rat, guinea pig, chicken, tilapia) is performed. To this aim, the generalized von Bertalanffy (VB) model is employed in which one of the fitted parameters is related to the gestation or incubation period of the system under consideration. The results obtained reveal a descriptive power of the VB model in both the pre and postnatal stages for a wide range of the data analyzed using several goodness-of-fit metrics and biologically meaningful parameters fitted. It has been proved that generalized VB function with one parameter constrained to the experimental value of the gestation (incubation) period and other parameters fitted only to the postnatal data predicts with high accuracy the growth of animals in the developmental prenatal stages. Hence, the VB model features not only descriptive but also retro-predictive power to reproduce the prenatal growth patterns of the animals considered. Three main sources of the problems with the fit stability reported for the VB function are identified: nonlinear nature of the scaling n-exponent, its strong correlation with remaining parameters defining the model and n-value placed in the vicinity of the discontinuity point n = 1 or outside the standard range 0 ≤ n < 1 usually applied in the data analysis., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In oviparous species, the embryonic environment-particularly temperature-can alter phenotype and survival of an individual by affecting its size as well as its metabolic rate. Previous studies have shown that incubation temperatures can affect sex ratio in birds; specifically, low incubation temperatures were shown to produce a male-biased sex ratio in zebra finches (Taeniopygia guttata) possibly because of a higher pre- or postnatal mortality rate in females. We hypothesized that sexes respond differently to suboptimal incubation temperature, leading to a male-biased sex ratio. To test this hypothesis, zebra finch eggs were incubated at 36.1°, 37.5°, or 38.5°C and hatching success, hatchling mass, residual yolk mass, and pectoralis mass were measured. We found that while hatchling mass was similar between the sexes at 37.5°C, female hatchlings were heavier at 36.1°C, and male hatchlings were heavier at 38.5°C. Pectoralis muscle mass was similar between the sexes at 36.1°C; however, at 37.5°C, female pectoralis mass was heavier at hatching than that of males. Females at 37.5°C also had lower residual yolk at hatching compared with males, reflecting a higher use of energy by female embryos compared with male embryos at this temperature. In contrast, residual yolk was similar between the sexes at 36.1° and 38.5°C. Our results suggest that there are sex differences in how incubation temperature alters organ mass and yolk energy reserve; this can lead to a difference in survival at different incubation temperatures between the sexes. Taken together with previous studies showing that females alter incubation behavior with ambient temperature, rising ambient temperatures could impact phenotype and survival of avian offspring in a sex-specific manner.

Light inducible protein-protein interactions have been used to manipulate protein localization and function in the cell with utmost spatial and temporal precision. In this technical report, we use a recently developed optogenetic approach to manipulate protein localization in the developing sea urchin embryo. A photosensitive LOV domain from Avena sativa phototropin1 cages a small peptide that binds the engineered PDZ domain (ePDZ) upon blue light irradiation. Using this system, mCherry tagged proteins fused with the LOV domain were recruited to ectopic sub-cellular regions such as the membrane, microtubules, or actin by GFP tagged proteins fused with the ePDZ domain upon blue light irradiation within 1-3 min in the sea urchin embryo. The efficiency and speed of recruitment of each protein to its respective subcellular region appeared to be dependent on the power and duration of laser irradiation, as well as the respective level of affinity to the tagged location. Controlled laser irradiation allowed partial recruitment of the spindle to the membrane, and resulted in cell blebbing. Vasa, a cell cycle and germline factor that localizes on the spindle and enriches in the micromeres at 8-16 cell stage was recruited to ectopic sites, preventing normal enrichment. Continuous blue light activation with a regular blue aquarium light over two days of culture successfully induced LOV-ePDZ binding in the developing embryos, resulting in continued ectopic recruitment of Vasa and failure in gastrulation at Day 2. Although some cytotoxicity was observed with prolonged blue light irradiation, this optogenetic system provides a promising approach to test the sub-cellular activities of developmental factors, as well as to alter protein localization and development during embryogenesis., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Egg activation is essential for the successful transition from a mature oocyte to a developmentally competent egg. It consists of a series of events including the resumption and completion of meiosis, initiation of translation of some maternal mRNAs and destruction of others, and changes to the vitelline envelope. This major change of cell state is accompanied by large scale alteration in the oocyte's phosphoproteome. We hypothesize that the cohort of proteins that are subject to phosphoregulation during egg activation are functionally important for processes before, during, or soon after this transition, potentially uniquely or as proteins carrying out essential cellular functions like those they do in other (somatic) cells. In this study, we used germline-specific RNAi to examine the function of 189 maternal proteins that are phosphoregulated during egg activation in Drosophila melanogaster We identified 53 genes whose knockdown reduced or abolished egg production and caused a range of defects in ovarian morphology, as well as 51 genes whose knockdown led to significant impairment or abolishment of the egg hatchability. We observed different stages of developmental arrest in the embryos and various defects in spindle morphology and aberrant centrosome activities in the early arrested embryos. Our results, validated by the detection of multiple genes with previously-documented maternal effect phenotypes among the proteins we tested, revealed 15 genes with newly discovered roles in egg activation and early embryogenesis in Drosophila. Given that protein phosphoregulation is a conserved characteristic of this developmental transition, we suggest that the phosphoregulated proteins may provide a rich pool of candidates for the identification of important players in the egg-to-embryo transition., (Copyright © 2018 Zhang et al.)

N-acetylcysteine, a precursor molecule of glutathione, is an antioxidant. Ketamine, a pediatric anesthetic, has been implicated in cardiotoxicity and neurotoxicity including modulation of monoaminergic systems in mammals and zebrafish. Here, we show that N-acetylcysteine prevents ketamine's adverse effects on development and monoaminergic neurons in zebrafish embryos. The effects of ketamine and N-acetylcysteine alone or in combination were measured on the heart rate, body length, brain serotonergic neurons and tyrosine hydroxylase-immunoreactive (TH-IR) neurons. In the absence of N-acetylcysteine, a concentration of ketamine that produces an internal embryo exposure level comparable to human anesthetic plasma concentrations significantly reduced heart rate and body length and those effects were prevented by N-acetylcysteine co-treatment. Ketamine also reduced the areas occupied by serotonergic neurons in the brain, whereas N-acetylcysteine co-exposure counteracted this effect. TH-IR neurons in the embryo brain and TH-IR cells in the trunk were significantly reduced with ketamine treatment, but not in the presence of N-acetylcysteine. In our continued search for compounds that can prevent ketamine toxicity, this study using specific endpoints of developmental toxicity, cardiotoxicity and neurotoxicity, demonstrates protective effects of N-acetylcysteine against ketamine's adverse effects. This is the first study that shows the protective effects of N-acetylcysteine on ketamine-induced developmental defects of monoaminergic neurons as observed in a whole organism., (Published by Elsevier B.V.)

The metabolic and redox state changes during the transition from an arrested oocyte to a totipotent embryo remain uncharacterized. Here, we applied state-of-the-art, integrated methodologies to dissect these changes in Drosophila We demonstrate that early embryos have a more oxidized state than mature oocytes. We identified specific alterations in reactive cysteines at a proteome-wide scale as a result of this metabolic and developmental transition. Consistent with a requirement for redox change, we demonstrate a role for the ovary-specific thioredoxin Deadhead (DHD). dhd -mutant oocytes are prematurely oxidized and exhibit meiotic defects. Epistatic analyses with redox regulators link dhd function to the distinctive redox-state balance set at the oocyte-to-embryo transition. Crucially, global thiol-redox profiling identified proteins whose cysteines became differentially modified in the absence of DHD. We validated these potential DHD substrates by recovering DHD-interaction partners using multiple approaches. One such target, NO66, is a conserved protein that genetically interacts with DHD, revealing parallel functions. As redox changes also have been observed in mammalian oocytes, we hypothesize a link between developmental control of this cell-cycle transition and regulation by metabolic cues. This link likely operates both by general redox state and by changes in the redox state of specific proteins. The redox proteome defined here is a valuable resource for future investigation of the mechanisms of redox-modulated control at the oocyte-to-embryo transition., Competing Interests: The authors declare no conflict of interest., (Copyright © 2018 the Author(s). Published by PNAS.)

Evidence has shown that triphenyltin (TPT) triggers severe malformations in Xenopus tropicalis embryos, partly due to activation of PPARγ (peroxisome proliferator activated receptor γ) protein. In the present study, we investigated how abundance of pparγ and TPT exposure interact and affect X. tropicalis embryonic development. We observed pparγ expression signals appeared in the neural crest and neural fold, as well as in the brain, eyes and spinal cord organs. Both pparγ overexpression and its Morpholino (MO) knockdown inhibited pax6 (paired box 6) expression, a marker of eye development, and significantly up- and down-regulated lipid and glucose homeostasis related genes, such as lpl (lipoprotein lipase), slc2a4 (solute carrier family 2 (facilitated glucose transporter), member 4) and pck1 (phosphoenolpyruvate carboxykinase 1, cytosolic), thus inducing eye phenotypes. Overexpression of pparγ induced small eye phenotype, while pparγ MO induced small eye plus turbid eye lens microencephaly and enlarged trunk. In contrast, 5-20μgSn/L (stannum/L) TPT exposure reversed some impacts induced by pparγ overexpression, i.e., no small eye, up-regulation of pax6 and down-regulation of pparγ, lpl, slc2a4 and pck1. Meanwhile, microinjection of pparγ MO combined with exposure to 20μgSn/L TPT caused 85% mortality. In brief, our work clearly indicates that pparγ is essential to eye development and inhibition of its expression combined with TPT exposure can be extremely harmful to X. tropicalis embryo., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Based on functional evidence, we have previously demonstrated that early ventral Notch1 activity restricts dorsoanterior development in Xenopus We found that Notch1 has ventralizing properties and abolishes the dorsalizing activity of β-catenin by reducing its steady state levels, in a process that does not require β-catenin phosphorylation by glycogen synthase kinase 3β. In the present work, we demonstrate that Notch1 mRNA and protein are enriched in the ventral region from the beginning of embryogenesis in Xenopus This is the earliest sign of ventral development, preceding the localized expression of wnt8a , bmp4 and Ventx genes in the ventral center and the dorsal accumulation of nuclear β-catenin. Knockdown experiments indicate that Notch1 is necessary for the normal expression of genes essential for ventral-posterior development . These results indicate that during early embryogenesis ventrally located Notch1 promotes the development of the ventral center. Together with our previous evidence, these results suggest that ventral enrichment of Notch1 underlies the process by which Notch1 participates in restricting nuclear accumulation of β-catenin to the dorsal side., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

Development is a process precisely coordinated in both space and time. Spatial precision has been quantified in a number of developmental systems, and such data have contributed significantly to our understanding of, for example, morphogen gradient interpretation. However, comparatively little quantitative analysis has been performed on timing and temporal coordination during development. Here, we use Drosophila to explore the temporal robustness of embryonic development within physiologically normal temperatures. We find that development is temporally very precise across a wide range of temperatures in the three Drosophila species investigated. However, we find temperature dependence in the timing of developmental events. A simple model incorporating history dependence can explain the developmental temporal trajectories. Interestingly, history dependence is temperature-specific, with either effective negative or positive feedback at different temperatures. We also find that embryos are surprisingly robust to shifting temperatures during embryogenesis. We further identify differences between tropical and temperate species, potentially due to different mechanisms regulating temporal development that depend on the local environment. Our data show that Drosophila embryonic development is temporally robust across a wide range of temperatures. This robustness shows interesting species-specific differences that are suggestive of different sensitivity to temperature fluctuations between Drosophila species., (© 2018 The Authors.)

The description of the cell spatial pattern and characteristic distances is fundamental in a wide range of physio-pathological biological phenomena, from morphogenesis to cancer growth. Discrete particle models are widely used in this field, since they are focused on the cell-level of abstraction and are able to preserve the identity of single individuals reproducing their behavior. In particular, a fundamental role in determining the usefulness and the realism of a particle mathematical approach is played by the choice of the intercellular pairwise interaction kernel and by the estimate of its parameters. The aim of the paper is to demonstrate how the concept of H-stability, deriving from statistical mechanics, can have important implications in this respect. For any given interaction kernel, it in fact allows to a priori predict the regions of the free parameter space that result in stable configurations of the system characterized by a finite and strictly positive minimal interparticle distance, which is fundamental when dealing with biological phenomena. The proposed analytical arguments are indeed able to restrict the range of possible variations of selected model coefficients, whose exact estimate however requires further investigations (e.g., fitting with empirical data), as illustrated in this paper by series of representative simulations dealing with cell colony reorganization, sorting phenomena and zebrafish embryonic development., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Atypical cadherin Dachsous (Dchs) is a conserved regulator of planar cell polarity, morphogenesis, and tissue growth during animal development. Dchs functions in part by regulating microtubules by unknown molecular mechanisms. Here we show that maternal zygotic (MZ) dchs1b zebrafish mutants exhibit cleavage furrow progression defects and impaired midzone microtubule assembly associated with decreased microtubule turnover. Mechanistically, Dchs1b interacts via a conserved motif in its intracellular domain with the tetratricopeptide motifs of Ttc28 and regulates its subcellular distribution. Excess Ttc28 impairs cleavages and decreases microtubule turnover, while ttc28 inactivation increases turnover. Moreover, ttc28 deficiency in dchs1b mutants suppresses the microtubule dynamics and midzone microtubule assembly defects. Dchs1b also binds to Aurora B, a known regulator of cleavages and microtubules. Embryonic cleavages in MZdchs1b mutants exhibit increased, and in MZttc28 mutants decreased, sensitivity to Aurora B inhibition. Thus, Dchs1b regulates microtubule dynamics and embryonic cleavages by interacting with Ttc28 and Aurora B., (Copyright © 2018 Elsevier Inc. All rights reserved.)

During gastrulation, one of the most important morphogenetic events in sea urchin embryogenesis, the gut bends toward the ventral side to form an open mouth. Although the involvement of transforming growth factor-β (TGF-β) signals in the cell-fate specification of the ectoderm and endoderm along the dorsal-ventral axis has been well reported, it remains unclear what controls the morphogenetic behavior of gut bending. Here, using two sea urchin species, Hemicentrotus pulcherrimus and Temnopleurus reevesii, we show that TGF-β signals are required for gut bending toward the ventral side. To search for the common morphogenetic cue in these two species, we initially confirmed the expression patterns of the dorsal-ventral regulatory TGF-β members, nodal, lefty, bmp2/4, and chordin, in T. reevesii because these factors are appropriate candidates to investigate the cue that starts gut bending, although genetic information about the body axes is entirely lacking in this species. Based on their expression patterns and a functional analysis of Nodal, the dorsal-ventral axis formation of T. reevesii is likely regulated by these TGF-β members, as in other sea urchins. When the Alk4/5/7 signal was inhibited by its specific inhibitor, SB431542, before the late gastrula stage of T. reevesii, the gut was extended straight toward the anterior tip region, although the ectodermal dorsal-ventral polarity was normal. By contrast, H. pulcherrimus gut bending was sensitive to SB431542 until the prism stage. These data clearly indicate that gut bending is commonly dependent on a TGF-β signal in sea urchins, but the timing of the response varies in different species., (© 2018 Japanese Society of Developmental Biologists.)

Several chemokine molecules control cell movements during early morphogenesis. However, it is unclear whether chemokine molecules affect cell fate. Here, we identified and characterized the CXC-type chemokine ligand in Xenopus laevis, Xenopus CXCLh (XCXCLh), during early embryogenesis. XCXCLh is expressed in the dorsal vegetal region at the gastrula stage. Both overexpression and knockdown of XCXCLh in the dorsal region inhibited gastrulation. XCXCLh contributed to the attraction of mesendodermal cells and accelerated the reassembly of scratched culture cells. Also, XCXCLh contributed to early endodermal induction. Overexpression of VegTmRNA or high concentrations of calcium ions induced XCXCLh expression. XCXCLh may play roles in both cell movements and differentiation during early Xenopus embryogenesis., (© 2018 Japanese Society of Developmental Biologists.)

The growth and dynamics of epithelial tissues govern many morphogenetic processes in embryonic development. A recent quantitative transition in data acquisition, facilitated by advances in genetic and live-imaging techniques, is paving the way for new insights to these processes. Computational models can help us understand and interpret observations, and then make predictions for future experiments that can distinguish between hypothesised mechanisms. Increasingly, cell-based modelling approaches such as vertex models are being used to help understand the mechanics underlying epithelial morphogenesis. These models typically seek to reproduce qualitative phenomena, such as cell sorting or tissue buckling. However, it remains unclear to what extent quantitative data can be used to constrain these models so that they can then be used to make quantitative, experimentally testable predictions. To address this issue, we perform an in silico study to investigate whether vertex model parameters can be inferred from imaging data, and explore methods to quantify the uncertainty of such estimates. Our approach requires the use of summary statistics to estimate parameters. Here, we focus on summary statistics of cellular packing and of laser ablation experiments, as are commonly reported from imaging studies. We find that including data from repeated experiments is necessary to generate reliable parameter estimates that can facilitate quantitative model predictions., (Copyright © 2018 Elsevier Ltd. All rights reserved.)