Positional information modulates transient regeneration-activated cell states during vertebrate appendage regeneration.

Injury is common in the life of organisms. Because the extent of damage cannot be predicted, injured organisms must determine how much tissue needs to be restored. Although it is known that amputation position affects the regeneration speed of appendages, mechanisms conveying positional information remain unclear.

Sea lamprey enlightens the origin of the coupling of retinoic acid signaling to vertebrate hindbrain segmentation.

Retinoic acid (RA) is involved in antero-posterior patterning of the chordate body axis and, in jawed vertebrates, has been shown to play a major role at multiple levels of the gene regulatory network (GRN) regulating hindbrain segmentation. Knowing when and how RA became coupled to the core hindbrain GRN is important for understanding how ancient signaling pathways and patterning genes can evolve and generate diversity. Hence, we investigated the link between RA signaling and hindbrain segmentation in the sea lamprey Petromyzon marinus, an important jawless vertebrate model providing clues to decipher ancestral vertebrate features.

Chromatin accessibility in the Drosophila embryo is determined by transcription factor pioneering and enhancer activation.

Chromatin accessibility is integral to the process by which transcription factors (TFs) read out cis-regulatory DNA sequences, but it is difficult to differentiate between TFs that drive accessibility and those that do not. Deep learning models that learn complex sequence rules provide an unprecedented opportunity to dissect this problem. Using zygotic genome activation in Drosophila as a model, we analyzed high-resolution TF binding and chromatin accessibility data with interpretable deep learning and performed genetic validation experiments.

Cell-type profiling of the sympathetic nervous system using spatial transcriptomics and spatial mapping of mRNA.

Background: The molecular identification of neural progenitor cell populations that connect to establish the sympathetic nervous system (SNS) remains unclear. This is due to technical limitations in the acquisition and spatial mapping of molecular information to tissue architecture.

Results: To address this, we applied Slide-seq spatial transcriptomics to intact fresh frozen chick trunk tissue transversely cryo-sectioned at the developmental stage prior to SNS formation.

Single-cell reconstruction with spatial context of migrating neural crest cells and their microenvironments during vertebrate head and neck formation.

The dynamics of multipotent neural crest cell differentiation and invasion as cells travel throughout the vertebrate embryo remain unclear. Here, we preserve spatial information to derive the transcriptional states of migrating neural crest cells and the cellular landscape of the first four chick cranial to cardiac branchial arches (BA1-4) using label-free, unsorted single-cell RNA sequencing. The faithful capture of branchial arch-specific genes led to identification of novel markers of migrating neural crest cells and 266 invasion genes common to all BA1-4 streams.

The embryonic trunk neural crest microenvironment regulates the plasticity and invasion of human neuroblastoma via TrkB signaling.

Mistakes in trunk neural crest (NC) cell migration may lead to birth defects of the sympathetic nervous system (SNS) and neuroblastoma (NB) cancer. Receptor tyrosine kinase B (TrkB) and its ligand BDNF critically regulate NC cell migration during normal SNS development and elevated expression of TrkB is correlated with high-risk NB patients. However, in the absence of a model with in vivo interrogation of human NB cell and gene expression dynamics, the mechanistic role of TrkB in NB disease progression remains unclear.

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.

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.

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.

NGF reprograms metastatic melanoma to a bipotent glial-melanocyte neural crest-like precursor.

Melanoma pathogenesis from normal neural crest-derived melanocytes is often fatal due to aggressive cell invasion throughout the body. The identification of signals that reprogram de-differentiated, metastatic melanoma cells to a less aggressive and stable phenotype would provide a novel strategy to limit disease progression. In this study, we identify and test the function of developmental signals within the chick embryonic neural crest microenvironment to reprogram and sustain the transition of human metastatic melanoma to a neural crest cell-like phenotype.

DAN (NBL1) promotes collective neural crest migration by restraining uncontrolled invasion.

Neural crest cells are both highly migratory and significant to vertebrate organogenesis. However, the signals that regulate neural crest cell migration remain unclear. In this study, we test the function of differential screening-selected gene aberrant in neuroblastoma (DAN), a bone morphogenetic protein (BMP) antagonist we detected by analysis of the chick cranial mesoderm.

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.

TrkB/BDNF signalling patterns the sympathetic nervous system.

The sympathetic nervous system is essential for maintaining mammalian homeostasis. How this intricately connected network, composed of preganglionic neurons that reside in the spinal cord and post-ganglionic neurons that comprise a chain of vertebral sympathetic ganglia, arises developmentally is incompletely understood. This problem is especially complex given the vertebral chain of sympathetic ganglia derive secondarily from the dorsal migration of 'primary' sympathetic ganglia that are initially located several hundred microns ventrally from their future pre-synaptic partners.

VEGF signals induce trailblazer cell identity that drives neural crest migration.

Embryonic neural crest cells travel in discrete streams to precise locations throughout the head and body. We previously showed that cranial neural crest cells respond chemotactically to vascular endothelial growth factor (VEGF) and that cells within the migratory front have distinct behaviors and gene expression. We proposed a cell-induced gradient model in which lead neural crest cells read out directional information from a chemoattractant profile and instruct trailers to follow.

Neural crest migration is driven by a few trailblazer cells with a unique molecular signature narrowly confined to the invasive front.

Neural crest (NC) cell migration is crucial to the formation of peripheral tissues during vertebrate development. However, how NC cells respond to different microenvironments to maintain persistence of direction and cohesion in multicellular streams remains unclear. To address this, we profiled eight subregions of a typical cranial NC cell migratory stream.

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.

The neural crest and cancer: a developmental spin on melanoma.

Neural crest (NC) cells undergo an epithelial to mesenchymal transition (EMT) in order to exit from the dorsal neural tube. Similarly, ancestrally related melanoma cells employ an EMT-like event during the initial stages of metastasis to dissociate from surrounding keratinocytes. Whether or not the molecular pathogenesis and cellular dynamics of melanoma metastasis resemble the embryonic NC invasion program is unclear.

Gene profiling in the avian embryo using laser capture microdissection and RT-qPCR.

The dynamic nature of the developing embryo makes it challenging to understand complex morphogenetic events using information from large-scale gene expression patterns. What would be more insightful is molecular profiling of small numbers of cells selectively surveyed at specific developmental stages. However, detecting gene expression profile information from small numbers of cells (<10) in homogenous tissue has remained a major challenge.

Multiscale mechanisms of cell migration during development: theory and experiment.

Long-distance cell migration is an important feature of embryonic development, adult morphogenesis and cancer, yet the mechanisms that drive subpopulations of cells to distinct targets are poorly understood. Here, we use the embryonic neural crest (NC) in tandem with theoretical studies to evaluate model mechanisms of long-distance cell migration. We find that a simple chemotaxis model is insufficient to explain our experimental data.

Melanoma revives an embryonic migration program to promote plasticity and invasion.

Cancer cells must regulate plasticity and invasion to survive and metastasize. However, the identification of targetable mechanisms to inhibit metastasis has been slow. Signaling programs that drive stem and progenitor cells during normal development offer an inroad to discover mechanisms common to metastasis.

Multi-position photoactivation and multi-time acquisition for large-scale cell tracing in avian embryos.

Vertebrate development is a complex orchestration of cell and tissue movements. Tracing individual cell positions can rapidly become a large-scale problem because cell numbers often grow exponentially in the early embryo. A typical approach consists of fluorescently marking small numbers of cells within a large number of embryos, followed by comprehensive three-dimensional static or time-lapse imaging to map cell positions.

Developmental cues and persistent neurogenic potential within an in vitro neural niche.

Background: Neurogenesis, the production of neural cell-types from neural stem cells (NSCs), occurs during development as well as within select regions of the adult brain. NSCs in the adult subependymal zone (SEZ) exist in a well-categorized niche microenvironment established by surrounding cells and their molecular products. The components of this niche maintain the NSCs and their definitive properties, including the ability to self-renew and multipotency (neuronal and glial differentiation).

Detection of calcium transients in embryonic stem cells and their differentiated progeny.

A central issue in stem cell biology is the determination of function and activity of differentiated stem cells, features that define the true phenotype of mature cell types. Commonly, physiological mechanisms are used to determine the functionality of mature cell types, including those of the nervous system. Calcium imaging provides an indirect method of determining the physiological activities of a mature cell.

Treatment of lysosomal storage disorders: focus on the neuronal ceroid-lipofuscinoses.

Recent advances in our understanding of lysosomal storage disorders (LSDs) may lead to new therapies to treat the neuronal ceroid-lipofuscinoses (NCLs). In this review, enzyme replacement therapy, gene therapy, cell-mediated therapy and pharmaceutical treatments are considered across the LSDs and extended to therapies for the NCLs. It is likely that a combination of approaches will produce the most beneficial clinical outcome for treatment of pathologies displayed by the NCLs.