skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Flat mount preparation for whole-mount fluorescent imaging of zebrafish embryos
ABSTRACT The zebrafish is a widely used model organism for biomedical research due to its ease of maintenance, external fertilization of embryos, rapid embryonic development, and availability of established genetic tools. One notable advantage of using zebrafish is the transparency of the embryos, which enables high-resolution imaging of specific cells, tissues, and structures through the use of transgenic and knock-in lines. However, as the embryo develops, multiple layers of tissue wrap around the lipid-enriched yolk, which can create a challenge to image tissues located deep within the embryo. While various methods are available, such as two-photon imaging, cryosectioning, vibratome sectioning, and micro-surgery, each of these has limitations. In this study, we present a novel deyolking method that allows for high-quality imaging of tissues that are obscured by other tissues and the yolk. Embryos are lightly fixed in 1% PFA to remove the yolk without damaging embryonic tissues and are then refixed in 4% PFA and mounted on custom-made bridged slides. This method offers a simple way to prepare imaging samples that can be subjected to further preparation, such as immunostaining. Furthermore, the bridged slides described in this study can be used for imaging tissue and organ preparations from various model organisms.  more » « less
Award ID(s):
2054512
PAR ID:
10480574
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
Biol Open
Date Published:
Journal Name:
Biology Open
Volume:
12
Issue:
7
ISSN:
2046-6390
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract We evaluated the elasticity of live tissues of zebrafish embryos using label‐free optical elastography. We employed a pair of custom‐built elastic microcantilevers to gently compress a zebrafish embryo and used optical‐tracking analysis to obtain the induced internal strain. We then built a finite element method (FEM) model and matched the strain with the optical analysis. The elastic moduli were found by minimizing the root‐mean‐square errors between the optical and FEM analyses. We evaluated the average elastic moduli of a developing somite, the overlying ectoderm, and the underlying yolk of seven zebrafish embryos during the early somitogenesis stages. The estimation results showed that the average elastic modulus of the somite increased from 150 to 700 Pa between 4‐ and 8‐somite stages, while those of the ectoderm and the yolk stayed between 100 and 200 Pa, and they did not show significant changes. The result matches well with the developmental process of somitogenesis reported in the literature. This is among the first attempts to quantify spatially‐resolved elasticity of embryonic tissues from optical elastography. 
    more » « less
  2. Boury, Nancy Maroushek (Ed.)
    ABSTRACT Embryonic development is fascinating to follow and highly engaging and, therefore, lends itself for undergraduate students’ first steps in experimental science. We developed the “Trails to Research” inquiry-based course, which exposes students to life science research using zebrafish as model organism. Zebrafish are ideal in the classroom: they are easy to maintain, their embryos develop rapidly, and they are easily manipulated. Further, they lend themselves to teach about embryo development and experimental design. We developed the course for undergraduates at 2-year colleges and, therefore, for students with little or no research experience. In this 5-day intensive course (which is taught during summers as a stand-alone course), students design treatment experiments for zebrafish embryos with known teratogens and with substances they select. The course comprises three modules that overlap over the 5 days: (i) introduction to developmental biology, model organisms, toxicology, and experimental design, (ii) zebrafish embryo experimental setup, and (iii) collecting, analyzing, and presenting data. Student learning was significant in the areas of experimental design, working with model systems, working with zebrafish embryos, using laboratory equipment, and presenting the results of their experiments using effective methods. 
    more » « less
  3. The choice of fixation method significantly impacts tissue morphology and visualization of gene expression and proteins after in situ hybridization chain reaction (HCR) or immunohistochemistry (IHC), respectively. In this study, we compared the effects of paraformaldehyde (PFA) and trichloroacetic acid (TCA) fixation techniques prior to HCR and IHC on chicken embryos. Our findings underscore the importance of optimizing fixation methods for accurate visualization and subsequent interpretation of HCR and IHC results, with implications for probe and antibody validation and tissue-specific protein localization studies. We found that TCA fixation resulted in larger and more circular nuclei and neural tubes compared to PFA fixation. Additionally, TCA fixation altered the subcellular fluorescence signal intensity of various proteins, including transcription factors, cytoskeletal proteins, and cadherins. Notably, TCA fixation revealed protein signals in tissues that may be inaccessible with PFA fixation. In contrast, TCA fixation proved ineffective for mRNA visualization. These results highlight the need for optimization of fixation protocols depending on the target and model system, emphasizing the importance of methodological considerations in biological analyses. 
    more » « less
  4. Embryonic development is a complex phenomenon that integrates genetic regulation and biomechanical cellular behaviors. However, the relative influence of these factors on spatiotemporal morphogen distributions is not well understood. Bone Morphogenetic Proteins (BMPs) are the primary morphogens guiding the dorsal-ventral (DV) patterning of the early zebrafish embryo, and BMP signaling is regulated by a network of extracellular and intracellular factors that impact the range and signaling of BMP ligands. Recent advances in understanding the mechanism of pattern formation support a source-sink mechanism, however, it is not clear how the source-sink mechanism shapes the morphogen patterns in three-dimensional (3D) space, nor how sensitive the pattern is to biophysical rates and boundary conditions along both the anteroposterior (AP) and DV axes of the embryo, nor how the patterns are controlled over time. Throughout blastulation and gastrulation, major cell movement, known as epiboly, happens along with the BMP-mediated DV patterning. The layer of epithelial cells begins to thin as they spread toward the vegetal pole of the embryo until it has completely engulfed the yolk cell. This dynamic domain may influence the distributions of BMP network members through advection. We developed a Finite Element Model (FEM) that incorporates all stages of zebrafish embryonic development data and solves the advection-diffusion-reaction Partial Differential Equations (PDE) in a growing domain. We use the model to investigate mechanisms in underlying BMP-driven DV patterning during epiboly. Solving the PDE is computationally expensive for parameter exploration. To overcome this obstacle, we developed a Neural Network (NN) metamodel of the 3D embryo that is accurate and fast and provided a nonlinear map between high-dimensional input and output that replaces the direct numerical simulation of the PDEs. From the modeling and acceleration by the NN metamodels, we identified the impact of advection on patterning and the influence of the dynamic expression level of regulators on the BMP signaling network. 
    more » « less
  5. Abstract Implantation of the human embryo begins a critical developmental stage that comprises profound events including axis formation, gastrulation and the emergence of haematopoietic system1,2. Our mechanistic knowledge of this window of human life remains limited due to restricted access to in vivo samples for both technical and ethical reasons3–5. Stem cell models of human embryo have emerged to help unlock the mysteries of this stage6–16. Here we present a genetically inducible stem cell-derived embryoid model of early post-implantation human embryogenesis that captures the reciprocal codevelopment of embryonic tissue and the extra-embryonic endoderm and mesoderm niche with early haematopoiesis. This model is produced from induced pluripotent stem cells and shows unanticipated self-organizing cellular programmes similar to those that occur in embryogenesis, including the formation of amniotic cavity and bilaminar disc morphologies as well as the generation of an anterior hypoblast pole and posterior domain. The extra-embryonic layer in these embryoids lacks trophoblast and shows advanced multilineage yolk sac tissue-like morphogenesis that harbours a process similar to distinct waves of haematopoiesis, including the emergence of erythroid-, megakaryocyte-, myeloid- and lymphoid-like cells. This model presents an easy-to-use, high-throughput, reproducible and scalable platform to probe multifaceted aspects of human development and blood formation at the early post-implantation stage. It will provide a tractable human-based model for drug testing and disease modelling. 
    more » « less