Developmental Dynamics最新文献

Background: Mean linear intercept (MLI) is a method of evaluating lung structure and pathology that is widely used in clinical and research settings. Unfortunately, no widely available software for automation of this process is available, and many clinicians and scientists still perform these measurements manually.

Results: To increase the speed and accuracy of obtaining MLI measurements, we have developed a macro for Fiji is just ImageJ (Fiji) to semi-automate the acquisition of these measurements. Twenty to 25 images from each of 43 mouse lungs, a total of 1042 images, were analyzed manually and by macro (automated) to validate the accuracy of the MLI macro. No significant difference was recorded between the manual and automated methods in mouse lung tissue of either different age (P14, P21, 8 weeks) or different condition (healthy vs. emphysema). Optimization of MLI macro parameters showed that additional measurements beyond three lines per image did not further improve accuracy. We also provide an Excel macro that summarizes the airspace data for each image and averages all the image data in a given batch of images.

Conclusion: This Fiji macro can be used to automate MLI measurement in histological sections of lung tissue faster and with lower variance.

Background: During vertebrate development, p53 family members (p53, p63, and p73) play both discrete and redundant roles. While p63 gene mutations lead to various skeletal and organ birth defects, p63's role in muscle development is less considered. Muscles derive from embryonic mesoderm. However, head and heart muscle differentiation also depends on intrinsic cues and signals from adjacent epithelia. In p63 mutant mice, ectoderm- and endoderm-derived epithelia are defective, implying defective myogenesis. We review the evidence that p63 is important for the differentiation of striated muscles, including cardiopharyngeal field-derived head and heart musculature.

Results: Several p63 isoforms act during mesoderm induction, myoblast proliferation, cell cycle exit, and cell differentiation. Of particular interest, TAp63γ is expressed in embryonic myoblasts and endoderm. In striated muscles, TAp63γ functions in myogenic proliferation and differentiation and participates in sarcomere development and myofibril assembly.

Conclusions: p63 is active during all muscle development stages, from mesoderm induction to myocyte differentiation. Different p53 family members, including several p63 isoforms, have overlapping functions. This redundancy could explain the limited myopathies described in p63 mouse mutants. As these defects may be subtler and more age/stage-dependent than appreciated, they warrant further study.

Background: Gene transcription is crucial for embryo and postnatal development and is regulated by the Mediator complex. Mediator is comprised of four submodules, including the kinase submodule (CKM). The CKM consists of MED13, MED12, CDK8, and CCNC. In mammals, there are paralogs for CKM components, including MED13L, MED12L, and CDK19. Neurological disorders have been associated with mutations in CKM genes including MED13L syndrome. MED13L syndrome is generally characterized as a haploinsufficiency of MED13L with a broad phenotypic response due in part to a wide range of de novo mutations.

Results: We developed a Med13l heterozygous (HET) mouse model with an exon 11 deletion to evaluate whether Med13l HET mice are a viable research tool to study human phenotypes. We characterized our mouse model using growth, cardiovascular, and skeletal readouts. We observed Med13l HET mice are smaller than wildtype (WT) littermates, and over 60% of them exhibited one of two craniofacial anomalies: a pug snout with midface hypoplasia or a crooked snout. We also observed discontinuous squamosal sutures in a subset of our Med13l HETs.

Conclusions: Med13l HET mice recapitulate MED13L syndrome phenotypes including a developmental growth delay and craniofacial anomalies. Med13l HET mice represent a novel research tool for MED13L syndrome.

Background: Jointed appendages represent one of the key innovations of arthropods, and thus understanding the development and evolution of these structures is important for the understanding of the evolutionary success of Arthropoda. In this paper, we analyze a cell cluster that was identified in a previous single-cell sequencing (SCS) experiment on embryos of the spider Parasteatoda tepidariorum. This cell cluster is characterized by marker genes that suggest a role in appendage patterning and joint development.

Results: We analyzed the expression profiles of these marker genes showing that they are expressed in the developing appendages and in a pattern that suggests a potential function during joint development. Several of the investigated genes represent new and unexpected factors such as dysfusion (dysf), spätzle3 (spz3), seven-up (svp). In order to study their evolutionary origin, we also investigated orthologs of the identified appendage-patterning genes in the harvestman Phalangium opilio, a distantly related chelicerate.

Conclusion: Our work highlights the usefulness of SCS experiments for the identification of potential new genetic factors that are involved in specific developmental processes. The current data provide potential new insights into the gene regulatory networks that underlie arthropod joint development.

The word symmetry is a derivative of symmetria and symmetros in Latin and Greek, meaning to have agreement in dimensions, proportion, and arrangement. The correct development of multicellular organisms depends on the establishment of symmetry both at the whole-body level and within individual tissues and organs. In biology, symmetry comes in many forms and is associated with beauty and functional necessity, which can have evolutionary or fitness advantages. Starfish are a classic example of radial symmetry, which can be halved in any plane to produce identical parts. In contrast, bilateral symmetry is defined by a single plane that divides an organism into two identical mirror-image halves. This is typical of the majority of animals on Earth, such as butterflies, for example. It would therefore be convenient to think of symmetry as a natural state for vertebrates and their embryos. However, there is also considerable evolutionary pressure to develop asymmetry in structures with high complexity, which drives variation, diversification, and adaptation. The breaking of symmetry is therefore also a fundamental feature of normal vertebrate development and is necessary to establish the anterior–posterior, dorsal–ventral, and left–right axes of the body plan. But how is symmetry established and maintained, and what are the evolutionary and developmental consequences of repeatedly breaking symmetry? Defining the mechanisms that establish, maintain, and break symmetry is fundamental to an improved understanding of development, evolution, and disease.

This Special Issue on “The Establishment, Maintenance and Breaking of Symmetry” contains a diverse selection of articles that explore some of the basic mechanisms that break symmetry during anterior–posterior axis formation and left–right patterning, including morphological structures such as the node and cilia, and the molecular pathways that drive asymmetric signaling, particularly the Nodal pathway. Asymmetry is a frequent feature of developmental disorders and the development and application of new tools for quantifying asymmetry can help reveal the genetic and environmental factors that drive the establishment, maintenance, and breaking of symmetry.

Breaking radial symmetry to establish anterior–posterior axis formation is a key developmental step in vertebrate gastrulation. The transient longitudinally oriented primitive streak is representative of the emerging anterior–posterior axis of birds and mammals. Pre-gastrulation pig embryos develop as a flat disc, the ancestral form of amniotes, and in this study,¹ Ploger and colleagues explore the expression and possible evolutionarily conserved function of Eomes, Tbx6, Wnt3, and Pkdcc in anterior–posterior axis formation. Similarities in expression patterns in pig embryos as compared to rabbit provide the first evidence for equivalence in the number of transient axial domains.

Background: Biomineralization is a vital biological process through which organisms produce mineralized structures such as shells, skeletons, and teeth. Microtubules are essential for biomineralization in various eukaryotic species; however, their specific roles in this process remain unclear.

Results: Here, we investigated the structure and function of microtubule filaments and their co-localization with matrix and focal adhesion proteins during the elongation of the calcite spicules of the sea urchin larva. First, we show that inhibiting microtubule polymerization using Nocodazole in whole embryos and isolated skeletogenic cell cultures results in a significant reduction of skeletal growth and affects skeletal morphology. Next, we demonstrate that microtubule filaments elongate from around the skeletogenic nuclei to the biomineralization compartment where they overlap with active focal adhesion kinase. The expression of spicule matrix proteins overlaps with microtubule filaments around the nuclei and with microtubule filaments that elongate to the spicule cavity.

Conclusions: We propose that vesicles bearing matrix proteins are trafficked on microtubules to the spicule cavity where their exocytosis is assisted by focal adhesions. The role of microtubules in biomineralization from unicellular algae to human bones suggests that the proposed microtubule-guided vesicle transport into the biomineralization compartment could be a common mechanism in Eukaryotes' biomineralization.

Background: The International Mouse Phenotyping Consortium (IMPC) has generated thousands of knockout mouse lines, many of which exhibit embryonic or perinatal lethality. Using micro-computed tomography (micro-CT), the IMPC has created and publicly released three-dimensional image data sets of embryos from these lethal and subviable lines. In this study, we leveraged this data set to screen homozygous null mutants for anomalies in secondary palate development. We analyzed optical sections from 2987 embryos at embryonic days E15.5 and E18.5, representing 484 homozygous mutant lines.

Results and conclusions: Our analysis identified 44 novel genes implicated in palatogenesis. Gene set enrichment analysis highlighted biological processes and pathways relevant to palate development and uncovered 18 genes jointly regulating the development of the eye and the palate. These findings present a valuable resource for further research, offer novel insights into the molecular mechanisms underlying palatogenesis, and provide important context for understanding the etiology of rare human congenital disorders involving malformations of the palate and other organs.

Background: To understand cellular morphology, biologists have relied on traditional optical microscopy of tissues combined with tissue clearing protocols to image structures deep within tissues. Unfortunately, these protocols often struggle to retain cell boundary markers, especially at high enough resolutions necessary for precise cell segmentation. This limitation affects the ability to study changes in cell shape during major developmental events.

Results: We introduce a method that preserves cell boundary markers and matches the refractive index of tissues with water. This technique enables the use of high-magnification, long working distance water-dipping objectives that provide sub-micron resolution images. We subsequently segment individual cells using a trained neural network segmentation model. These segmented images facilitate quantification of cell properties of the entire three-dimensional tissue. As a demonstration, we examine mandibles of transgenic mice that express fluorescent proteins in their cell membranes and extend this technique to a non-model animal, the catshark, investigating its dental lamina and dermal denticles-invaginating and evaginating ectodermal structures, respectively. This technique provides insight into the mechanical environment that cells experience during developmental transitions.

Conclusions: This pipeline, named MORPHOVIEW, provides a powerful tool to quantify in high throughput the 3D structures of cells and tissues during organ morphogenesis.

Background: Diabetes is a group of diseases characterized by loss of β cell mass and/or function, resulting in hyperglycemia. With no established curative treatment, this has initiated research in β cell regeneration. Current animal models have either limited regenerative capacity (mice) or small size and evolutionary distance from humans (zebrafish). There is a need for new models to study endogenous regeneration pathways. This study proposes the axolotl salamander (Ambystoma mexicanum) as a model for studying the regeneration of β cells and aims to establish a protocol for STZ-induced hyperglycemia to mimic a diabetic state.

Results: In this pilot study, five streptozotocin (STZ) protocols were tested, and the most effective one was identified on the basis of glucose tolerance tests. Blood glucose levels were monitored to track both disease progression and remission. Histological examination of the pancreas and systemic effects of STZ treatment were also evaluated.

Conclusion: Induction of a diabetes-like state (hyperglycemia) in axolotls was possible with STZ, but variability among animals suggests the need for a higher degree of normalization or larger sample sizes. Histological regeneration was not observed, though blood glucose levels normalized over time. Some STZ-treated animals developed edema, but its cause remains unknown.