Egg Development After In Vitro Insemination in Japanese Quail (Coturnix japonica)

In vitro fertilization has been widely used to produce offspring in several mammalian species. We previously successfully produced Japanese quail chicks using intracytoplasmic sperm injection (ICSI), whereas in vitro insemination was not successful. This may be due to the difficulties associated with mimicking the sperm-egg fusion process and subsequent events in physiological polyspermic fertilization in vitro. In the present study, we observed egg development after in vitro insemination and investigated the inactivation of metaphase-promoting factor (MPF) and cytostatic factor (CSF), which are downstream of the Ca²⁺ signaling pathway in the egg, due to fertilizing sperm. We found a sperm number-dependent increase in hole formation caused by sperm penetration of the perivitelline membrane, the extracellular coat surrounding the egg. Egg development was observed following in vitro insemination; however, the developmental rate and stages after 24-h culture were inferior to those of ICSI eggs, even when insemination was performed with a high number of sperm (2 × 10⁴). We also noted the downregulation of inositol 1,4,5-trisphosphate receptor-1, ryanodine receptor-3, cyclin B1, and c-MOS, which are important regulatory components of MPF and CSF in the egg, which was dependent on the number of sperm used for insemination. However, the decreases observed in these components did not reach the levels observed in the ICSI eggs. Collectively, the present results suggest that a sperm number higher than 2 × 10⁴ is required for the progression of the Ca²⁺ signaling pathway, which initiates subsequent egg development in Japanese quail.

Transcriptome analysis of blastoderms exposed to prolonged egg storage and short periods of incubation during egg storage

BACKGROUND

Cool temperature egg storage prior to incubation is a common practice in the broiler industry; however, prolonged egg storage causes increased embryonic mortality and decreased hatchability and growth in surviving chicks. Exposing eggs to short periods of incubation during egg storage (SPIDES) reduces the adverse consequences of prolonged storage. SPIDES increases blastodermal cell viability by reducing apoptosis, though the counteracting mechanisms are unclear. To define the impact of prolonged storage and SPIDES, transcriptome analysis compared gene expression from blastoderms isolated from eggs exposed to the following treatments: control (CR, stored at 17 °C for 4 days), prolonged storage (NSR, stored at 17 °C for 21 days), SPIDES (SR, stored at 17 °C for 21 days with SPIDES), and incubated control (C2, stored at 17 °C for 4 days followed by incubation to HH (Hamburger-Hamilton) stage 2, used as the ideal standard development) (n = 3/group). Data analysis was performed using the CLC Genomics Workbench platform. Functional annotation was performed using DAVID and QIAGEN Ingenuity Pathway Analysis.

RESULTS

In total, 4726 DEGs (differentially expressed genes) were identified across all experimental group comparisons (q < 0.05, FPKM> 20, |fold change| > 1.5). DEGs common across experimental comparisons were involved in cellular homeostasis and cytoskeletal protein binding. The NSR group exhibited activation of ubiquitination, apoptotic, and cell senescence processes. The SR group showed activation of cell viability, division, and metabolic processes. Through comparison analysis, cellular respiration, tRNA charging, cell cycle control, and HMBG1 signaling pathways were significantly impacted by treatment and potential regulatory roles for ribosomal protein L23a (RPL23A) and MYC proto-oncogene, BHLH transcription factor (MYC) were identified.

CONCLUSIONS

Prolonged egg storage (NSR) resulted in enriched cell stress and death pathways; while SPIDES (SR) resulted in enriched basic cell and anti-apoptotic pathways. New insights into DNA repair mechanisms, RNA processing, shifts in metabolism, and chromatin dynamics in relation to egg storage treatment were obtained through this study. Although egg storage protocols have been examined through targeted gene expression approaches, this study provided a global view of the extensive molecular networks affected by prolonged storage and SPIDES and helped to identify potential upstream regulators for future experiments to optimize egg storage parameters.

Labeling and Tracking Mitochondria with Photoactivation in Drosophila Embryos

Mitochondria are relatively small, fragmented, and abundant in the large embryos of Drosophila, Xenopus and zebrafish. It is essential to study their distribution and dynamics in these embryos to understand the mechanistic role of mitochondrial function in early morphogenesis events. Photoactivation of mitochondrially tagged GFP (mito-PA-GFP) is an attractive method to highlight a specific population of mitochondria in living embryos and track their distribution during development. Drosophila embryos contain large numbers of maternally inherited mitochondria, which distribute differently at specific stages of early embryogenesis. They are enriched basally in the syncytial division cycles and move apically during cellularization. Here, we outline a method for highlighting a population of mitochondria in discrete locations using mito-PA-GFP in the Drosophila blastoderm embryo, to follow their distribution across syncytial division cycles and cellularization. Photoactivation uses fluorophores, such as PA-GFP, that can change their fluorescence state upon exposure to ultraviolet light. This enables marking a precise population of fluorescently tagged molecules of organelles at selected regions, to visualize and systematically follow their dynamics and movements. Photoactivation followed by live imaging provides an effective way to pulse label a population of mitochondria and follow them through the dynamic morphogenetic events during Drosophila embryogenesis.

The evolution of the gene regulatory networks patterning the Drosophila Blastoderm

The Drosophila blastoderm gene regulatory network is one of the best studied networks in biology. It is composed of a series of tiered sub-networks that act sequentially to generate a primary segmental pattern. Many of these sub-networks have been studied in other arthropods, allowing us to reconstruct how each of them evolved over the transition from the arthropod ancestor to the situation seen in Drosophila today. I trace the evolution of each of these networks, showing how some of them have been modified significantly in Drosophila relative to the ancestral state while others are largely conserved across evolutionary timescales. I compare the putative ancestral arthropod segmentation network with that found in Drosophila and discuss how and why it has been modified throughout evolution, and to what extent this modification is unusual.

The early Drosophila embryo as a model system for quantitative biology

With the rise of new tools, from controlled genetic manipulations and optogenetics to improved microscopy, it is now possible to make clear, quantitative and reproducible measurements of biological processes. The humble fruit fly Drosophila melanogaster, with its ease of genetic manipulation combined with excellent imaging accessibility, has become a major model system for performing quantitative in vivo measurements. Such measurements are driving a new wave of interest from physicists and engineers, who are developing a range of testable dynamic models of active systems to understand fundamental biological processes. The reproducibility of the early Drosophila embryo has been crucial for understanding how biological systems are robust to unavoidable noise during development. Insights from quantitative in vivo experiments in the Drosophila embryo are having an impact on our understanding of critical biological processes, such as how cells make decisions and how complex tissue shape emerges. Here, to highlight the power of using Drosophila embryogenesis for quantitative biology, I focus on three main areas: (1) formation and robustness of morphogen gradients; (2) how gene regulatory networks ensure precise boundary formation; and (3) how mechanical interactions drive packing and tissue folding. I further discuss how such data has driven advances in modelling.

Derivation and characterization of putative embryonic stem cells isolated from blastoderms of Taiwan Country chicken for the production of chimeric chickens

The conservation of Taiwan Country chicken (TCC) is important due to concerns for the local breed's adaptability to the area and disease resistance. Furthermore, the genetic resource base of native chickens can be used to improve egg and meat production efficiency in commercial TCC. As the embryonic stem cells (ESCs) hold great potential for regenerative medicine and species conservation, the aims of this study were to isolate and characterize ESCs of TCC. The blastodermal cells (BCs) were isolated from the zona pellucida of stage X chicken embryos and cultured in conditioned medium for the proliferation and maintenance of BCs in vitro. The quantitative real-time polymerase chain reaction (qPCR) results showed that POUV, SOX2 and NANOG were expressed in the putative ESCs. In addition, the expression of pluripotent markers, SSEA-1 and SSEA-4, was detected. The DiI-stained ESCs were injected into the dorsal aorta of the E3.5 recipient fetuses soon after staining and the injected embryos were continuously incubated and checked on day 7 of incubation. It was shown that some DiI-positive cells were found in the 7-d-old chimeric embryos. The results demonstrated that some pluripotent cells existed in the cultured BCs for the production of germline chimeric embryos from TCC.

Signaling events regulating embryonic polarity and formation of the primitive streak in the chick embryo

The avian embryo is a key experimental model system for early development of amniotes. One key difference with invertebrates and "lower" vertebrates like fish and amphibians is that amniotes do not rely so heavily on maternal messages because the zygotic genome is activated very early. Early development also involves considerable growth in volume and mass of the embryo, with cell cycles that include G1 and G2 phases from very early cleavage. The very early maternal to zygotic transition also allows the embryo to establish its own polarity without relying heavily on maternal determinants. In many amniotes including avians and non-rodent mammals, this enables an ability of the embryo to "regulate": a single multicellular embryo can give rise to more than one individual-monozygotic twins. Here we discuss the embryological, cellular, molecular and evolutionary underpinnings of gastrulation in avian embryos as a model amniote embryo. Many of these properties are shared by human embryos.

Positional Information and Cell Fate Determination in the Early Drosophila Embryo

During early development in Drosophila, the spatial information of maternal gradients is translated into discrete transcriptional states determining cell fate. Information transfer depends on reproducibility of the gradients themselves, as well as the ability of cells to accurately measure and utilize morphogen concentrations in biologically meaning ways. In the following essay, these issues are discussed in context of the Bicoid gradient.

A study of embryonic development in eriophyoid mites (Acariformes, Eriophyoidea) with the use of the fluorochrome DAPI and confocal microscopy

The embryonic development of four eriophyoid mite species, Cecidophyopsis ribis, Phytoptus avellanae, Oziella liroi and Loboquintus subsquamatus, has been studied with the use of fluorochrome DAPI and confocal microscopy. The first three nuclear divisions occur on the egg periphery (the groups of 2, 4, and 6 nuclei have been recorded), while the biggest part of yolk remains undivided. After four or five nuclear divisions all nuclei are situated only in one sector of the embryo, while other sectors contain only yolk suggesting possible meroblastic cleavage. Later, the formation of superficial blastoderm takes place. A few large yolk cells are situated inside the embryo. Germ band formation initiates as funnel-like cell invagination and leads to formation of a typical stage with four paired prosomal buds (chelicerae, palps, legs I and II). Each palp contains two lobes (anterior and posterior), the adult subcapitulum is presumably a fusion product of the anterior pair of the lobes. Neither rudiments of legs III and IV, traces of opisthosomal segments nor remnants of the prelarval exuvium under the egg shell were detected. Overall, the pattern of embryonic development in eriophyoids re-emphasizes the peculiarity of this ancient group of miniaturized phytoparasitic animals, and invites researches to pursue a deeper investigation of various fundamental aspects of this aberrant group of Acari. Further studies using various fluorescent dyes and transmission electron microscopy are needed to visualize plasma membranes and clarify the pattern of early cleavage of eriophyoids.

Function and dynamics of slam in furrow formation in early Drosophila embryo

The Drosophila embryo undergoes a developmental transition in the blastoderm stage switching from syncytial to cellular development. The cleavage furrow, which encloses nuclei into cells, is a prominent morphological feature of this transition. It is not clear how the pattern of the furrow array is defined and how zygotic genes trigger the formation and invagination of interphase furrows. A key to these questions is provided by the gene slam, which has been previously implicated in controlling furrow invagination. Here we investigate the null phenotype of slam, the dynamics of Slam protein, and its control by the recycling endosome. We find that slam is essential for furrow invagination during cellularisation and together with nullo, for specification of the furrow. During cellularisation, Slam marks first the furrow, which is derived from the metaphase furrow of the previous mitosis. Slightly later, Slam accumulates at new furrows between daughter cells early in interphase. Slam is stably associated with the furrow canal except for the onset of cellularisation as revealed by FRAP experiments. Restriction of Slam to the furrow canal and Slam mobility during cellularisation is controlled by the recycling endosome and centrosomes. We propose a three step model. The retracting metaphase furrow leaves an initial mark. This mark and the border between corresponding daughter nuclei are refined by vesicular transport away from pericentrosomal recycling endosome towards the margins of the somatic buds. Following the onset of zygotic gene expression, Slam and Nullo together stabilise this mark and Slam triggers invagination of the cleavage furrow.

Spontaneous self-assembly of DNA fragments into nucleus-like structures from yolk granules of fertilized chicken eggs: Antoine Béchamp meets Bong Han Kim via Olga Lepeshinskaya

We found evidence that spontaneous self-assembly of DNA molecules from yolk granules occurred during the very early stage of egg fertilization. In order to find solid evidence for self-assembly of DNA molecules, we collected many available data in different stages of fertilized eggs, making a data table. At first by using acridine orange vital staining to demonstrate DNA, we noticed that some yolk granules emitted DNA signals that gradually increased with increasing incubation time from very small sizes to much larger nucleus-like structures. For convincing evidence, we also used another vital dye, Hoechst 33258 DNA-specific dye, to trace the changes in the yolk granules. The patterns of the DNA signals from yolk granules stained with Hoechst 33258 were the same as those from the yolk granules stained with acridine orange. A partial phase contrast microscopic image of the changes in the yolk granules showed some liquid-like material around the granules before the formation of the nucleus-like structures. Concomitant use of fluorescence and partial phase contrast microscopy suggested that these liquid-like materials may have been released from yolk granules in which spontaneous self-assembly of DNA molecules had occurred. Finally, in order to verify whether the DNA signals came from real DNA molecules or not, by using deoxyribonuclease I (DNAse), we confirmed that the nucleus-like structures were really assembled DNA molecules. Thus, in this article, we report evidence for the self-assembly of DNA molecules toward cell-like structures and discuss our findings, comparing them with those in the works of other pioneers, especially Antoine Béchamp, Olga Lepeshinskaya and Bong Han Kim, who insisted on the existence of a mitosis-free alternative pathway for generating new cells.