Comparative analysis of neural crest development in the chick and mouse.

A core framework of the gene regulatory network (GRN) governing neural crest (NC) cell development has been generated by integrating separate inputs from diverse model organisms rather than direct comparison. This has limited insights into the diversity of genes in the NC cell GRN and extent of conservation of newly identified transcriptional signatures in cell differentiation and invasion. Here, we address this by leveraging the strengths and accessibility of the avian embryo to precise developmental staging by egg incubation and use an integrated analysis of chick (HH13) and mouse (E9.

Comparative Analysis of Neural Crest Development in the Chick and Mouse.

A core framework of the gene regulatory network (GRN) governing neural crest (NC) cell development has been generated by integrating separate inputs from diverse model organisms rather than direct comparison. This has limited insights into the diversity of genes in the NC cell GRN and extent of conservation of newly identified transcriptional signatures in cell differentiation and invasion. Here, we address this by leveraging the strengths and accessibility of the avian embryo to precise developmental staging by egg incubation and use an integrated analysis of chick (HH13) and mouse (E9.

Characterization of Multicellular Niches Supporting Hematopoietic Stem Cells Within Distinct Zones.

Previous studies of hematopoietic stem cells (HSCs) primarily focused on single cell-based niche models, yielding fruitful but conflicting findings . Here we report our investigation on the fetal liver (FL) as the primary fetal hematopoietic site using spatial transcriptomics. Our study reveals two distinct niches: the portal-vessel (PV) niche and the sinusoidal niche.

A PAK family kinase and the Hippo/Yorkie pathway modulate WNT signaling to functionally integrate body axes during regeneration.

Successful regeneration of missing tissues requires seamless integration of positional information along the body axes. Planarians, which regenerate from almost any injury, use conserved, developmentally important signaling pathways to pattern the body axes. However, the molecular mechanisms which facilitate cross talk between these signaling pathways to integrate positional information remain poorly understood.

Cell extrusion - a novel mechanism driving neural crest cell delamination.

Neural crest cells (NCC) comprise a heterogeneous population of cells with variable potency, that contribute to nearly every tissue and organ system throughout the body. Considered unique to vertebrates, NCC are transiently generated within the dorsolateral region of the neural plate or neural tube, during neurulation. Their delamination and migration are crucial events in embryo development as the differentiation of NCC is heavily influenced by their final resting locations.

Graded FGF activity patterns distinct cell types within the apical sensory organ of the sea anemone Nematostella vectensis.

Bilaterian animals have evolved complex sensory organs comprised of distinct cell types that function coordinately to sense the environment. Each sensory unit has a defined architecture built from component cell types, including sensory cells, non-sensory support cells, and dedicated sensory neurons. Whether this characteristic cellular composition is present in the sensory organs of non-bilaterian animals is unknown.

Starvation-resistant cavefish reveal conserved mechanisms of starvation-induced hepatic lipotoxicity.

Starvation causes the accumulation of lipid droplets in the liver, a somewhat counterintuitive phenomenon that is nevertheless conserved from flies to humans. Much like fatty liver resulting from overfeeding, hepatic lipid accumulation (steatosis) during undernourishment can lead to lipotoxicity and atrophy of the liver. Here, we found that although surface populations of undergo this evolutionarily conserved response to starvation, the starvation-resistant cavefish larvae of the same species do not display an accumulation of lipid droplets upon starvation.

Starvation resistant cavefish reveal conserved mechanisms of starvation-induced hepatic lipotoxicity.

Starvation causes the accumulation of lipid droplets in the liver, a somewhat counterintuitive phenomenon that is nevertheless conserved from flies to humans. Much like fatty liver resulting from overfeeding, hepatic lipid accumulation (steatosis) during undernourishment can lead to lipotoxicity and atrophy of the liver. Here, we found that while surface populations of Astyanax mexicanus undergo this evolutionarily conserved response to starvation, the starvation-resistant cavefish larvae of the same species do not display an accumulation of lipid droplets upon starvation.

rRNA transcription is integral to phase separation and maintenance of nucleolar structure.

Transcription of ribosomal RNA (rRNA) by RNA Polymerase (Pol) I in the nucleolus is necessary for ribosome biogenesis, which is intimately tied to cell growth and proliferation. Perturbation of ribosome biogenesis results in tissue specific disorders termed ribosomopathies in association with alterations in nucleolar structure. However, how rRNA transcription and ribosome biogenesis regulate nucleolar structure during normal development and in the pathogenesis of disease remains poorly understood.

Dynamic fibronectin assembly and remodeling by leader neural crest cells prevents jamming in collective cell migration.

Collective cell migration plays an essential role in vertebrate development, yet the extent to which dynamically changing microenvironments influence this phenomenon remains unclear. Observations of the distribution of the extracellular matrix (ECM) component fibronectin during the migration of loosely connected neural crest cells (NCCs) lead us to hypothesize that NCC remodeling of an initially punctate ECM creates a scaffold for trailing cells, enabling them to form robust and coherent stream patterns. We evaluate this idea in a theoretical setting by developing an individual-based computational model that incorporates reciprocal interactions between NCCs and their ECM.

Modelling Cell Invasion: A Review of What JD Murray and the Embryo Can Teach Us.

Cell invasion and cell plasticity are critical to human development but are also striking features of cancer metastasis. By distributing a multipotent cell type from a place of birth to distal locations, the vertebrate embryo builds organs. In comparison, metastatic tumor cells often acquire a de-differentiated phenotype and migrate away from a primary site to inhabit new microenvironments, disrupting normal organ function.

Live Imaging of the Neural Crest Cell Epithelial-to-Mesenchymal Transition in the Chick Embryo.

Live embryo imaging may provide a wealth of information on intact cell and tissue dynamics, but can be technically challenging to sustain embryo orientation and health for long periods under a microscope. In this protocol, we describe an in vivo method to mount and image cell movements during the epithelial-to-mesenchymal transition (EMT) of neural crest cells within the chick dorsal neural tube. We focus on describing the collection of images and data preparation for image analysis throughout the developmental stages HH15-21 in the chick trunk.

Visualizing mesoderm and neural crest cell dynamics during chick head morphogenesis.

Vertebrate head morphogenesis involves carefully-orchestrated tissue growth and cell movements of the mesoderm and neural crest to form the distinct craniofacial pattern. To better understand structural birth defects, it is important that we characterize the dynamics of these processes and learn how they rely on each other. Here we examine this question during chick head morphogenesis using time-lapse imaging, computational modeling, and experiments.

Neural crest cells bulldoze through the microenvironment using Aquaporin 1 to stabilize filopodia.

Neural crest migration requires cells to move through an environment filled with dense extracellular matrix and mesoderm to reach targets throughout the vertebrate embryo. Here, we use high-resolution microscopy, computational modeling, and and cell invasion assays to investigate the function of Aquaporin 1 (AQP-1) signaling. We find that migrating lead cranial neural crest cells express AQP-1 mRNA and protein, implicating a biological role for water channel protein function during invasion.

An interdisciplinary approach to investigate collective cell migration in neural crest.

The neural crest serves as a powerful and tractable model paradigm for understanding collective cell migration. The neural crest cell populations are well-known for their long-distance collective migration and contribution to diverse cell lineages during vertebrate development. If neural crest cells fail to reach a target or populate an incorrect location, then improper cell differentiation or uncontrolled cell proliferation can result.

Predicting neuroblastoma using developmental signals and a logic-based model.

Genomic information from human patient samples of pediatric neuroblastoma cancers and known outcomes have led to specific gene lists put forward as high risk for disease progression. However, the reliance on gene expression correlations rather than mechanistic insight has shown limited potential and suggests a critical need for molecular network models that better predict neuroblastoma progression. In this study, we construct and simulate a molecular network of developmental genes and downstream signals in a 6-gene input logic model that predicts a favorable/unfavorable outcome based on the outcome of the four cell states including cell differentiation, proliferation, apoptosis, and angiogenesis.

Single-cell transcriptome analysis of avian neural crest migration reveals signatures of invasion and molecular transitions.

Neural crest cells migrate throughout the embryo, but how cells move in a directed and collective manner has remained unclear. Here, we perform the first single-cell transcriptome analysis of cranial neural crest cell migration at three progressive stages in chick and identify and establish hierarchical relationships between cell position and time-specific transcriptional signatures. We determine a novel transcriptional signature of the most invasive neural crest Trailblazer cells that is consistent during migration and enriched for approximately 900 genes.

Resolving in vivo gene expression during collective cell migration using an integrated RNAscope, immunohistochemistry and tissue clearing method.

During collective cell migration individual cells display diverse behaviors that complicate our understanding of group cell decisions of direction and cohesion. In vivo gene and protein expression analyses would shed light on the underlying molecular choreography. However, this information has been limited due to difficulties to integrate single cell detection methods and the simultaneous readout of multiple signals deep within the embryo.

Angiopoietin 2 signaling plays a critical role in neural crest cell migration.

Background: Collective neural crest cell migration is critical to the form and function of the vertebrate face and neck, distributing bone, cartilage, and nerve cells into peripheral targets that are intimately linked with head vasculature. The vasculature and neural crest structures are ultimately linked, but when and how these patterns develop in the early embryo are not well understood.

Results: Using in vivo imaging and sophisticated cell behavior analyses, we show that quail cranial neural crest and endothelial cells share common migratory paths, sort out in a dynamic multistep process, and display multiple types of motion.

Quantitative single cell gene expression profiling in the avian embryo.

Background: Single cell gene profiling has been successfully applied to cultured cells. However, isolation and preservation of a cell's native gene expression state from an intact embryo remain problematic.

Results: Here, we present a strategy for in vivo single cell profiling that optimizes cell identification, isolation and amplification of nucleic acids with nominal bias and sufficient material detection.

Developmental imaging: the avian embryo hatches to the challenge.

The avian embryo provides a multifaceted model to study developmental mechanisms because of its accessibility to microsurgery, fluorescence cell labeling, in vivo imaging, and molecular manipulation. Early two-dimensional planar growth of the avian embryo mimics human development and provides unique access to complex cell migration patterns using light microscopy. Later developmental events continue to permit access to both light and other imaging modalities, making the avian embryo an excellent model for developmental imaging.

Evidence for dynamic rearrangements but lack of fate or position restrictions in premigratory avian trunk neural crest.

Neural crest (NC) cells emerge from the dorsal trunk neural tube (NT) and migrate ventrally to colonize neuronal derivatives, as well as dorsolaterally to form melanocytes. Here, we test whether different dorsoventral levels in the NT have similar or differential ability to contribute to NC cells and their derivatives. To this end, we precisely labeled NT precursors at specific dorsoventral levels of the chick NT using fluorescent dyes and a photoconvertible fluorescent protein.

CycleTrak: a novel system for the semi-automated analysis of cell cycle dynamics.

Cell proliferation is crucial to tissue growth and form during embryogenesis, yet dynamic tracking of cell cycle progression and cell position presents a challenging roadblock. We have developed a fluorescent cell cycle indicator and single cell analysis method, called CycleTrak, which allows for better spatiotemporal resolution and quantification of cell cycle phase and cell position than current methods. Our method was developed on the basis of the existing Fucci method.

Rspo1/Wnt signaling promotes angiogenesis via Vegfc/Vegfr3.

Here, we show that a novel Rspo1-Wnt-Vegfc-Vegfr3 signaling pathway plays an essential role in developmental angiogenesis. A mutation in R-spondin1 (rspo1), a Wnt signaling regulator, was uncovered during a forward-genetic screen for angiogenesis-deficient mutants in the zebrafish. Embryos lacking rspo1 or the proposed rspo1 receptor kremen form primary vessels by vasculogenesis, but are defective in subsequent angiogenesis.

In vivo calcium dynamics during neural crest cell migration and patterning using GCaMP3.

Examining calcium dynamics within the neural crest (NC) has the potential to shed light on mechanisms that regulate complex cell migration and patterning events during embryogenesis. Unfortunately, typical calcium indicators are added to culture media or have low signal to noise after microinjection into tissue that severely limit analyses to cultured cells or superficial events. Here, we studied in vivo calcium dynamics during NC cell migration and patterning, using a genetically encoded calcium sensor, GCaMP3.