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.

Colec12 and Trail signaling confine cranial neural crest cell trajectories and promote collective cell migration.

Background: Collective and discrete neural crest cell (NCC) migratory streams are crucial to vertebrate head patterning. However, the factors that confine NCC trajectories and promote collective cell migration remain unclear.

Results: Computational simulations predicted that confinement is required only along the initial one-third of the cranial NCC migratory pathway.

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.

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.

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.

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.

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.

The neural crest cell cycle is related to phases of migration in the head.

Embryonic cells that migrate long distances must critically balance cell division in order to maintain stream dynamics and population of peripheral targets. Yet details of individual cell division events and how cell cycle is related to phases of migration remain unclear. Here, we examined these questions using the chick cranial neural crest (NC).

Multispectral fingerprinting for improved in vivo cell dynamics analysis.

Background: Tracing cell dynamics in the embryo becomes tremendously difficult when cell trajectories cross in space and time and tissue density obscure individual cell borders. Here, we used the chick neural crest (NC) as a model to test multicolor cell labeling and multispectral confocal imaging strategies to overcome these roadblocks.

Results: We found that multicolor nuclear cell labeling and multispectral imaging led to improved resolution of in vivo NC cell identification by providing a unique spectral identity for each cell.

Vascular endothelial growth factor (VEGF) regulates cranial neural crest migration in vivo.

The neural crest is an excellent model to study embryonic cell migration, since cell behaviors can be studied in vivo with advanced optical imaging and molecular intervention. What is unclear is how molecular signals direct neural crest cell (NCC) migration through multiple microenvironments and into specific targets. Here, we tested the hypothesis that the invasion of cranial NCCs, specifically the rhombomere 4 (r4) migratory stream into branchial arch 2 (ba2), is due to chemoattraction through neuropilin-1-vascular endothelial growth factor (VEGF) interactions.

Reprogramming multipotent tumor cells with the embryonic neural crest microenvironment.

The embryonic microenvironment is an important source of signals that program multipotent cells to adopt a particular fate and migratory path, yet its potential to reprogram and restrict multipotent tumor cell fate and invasion is unrealized. Aggressive tumor cells share many characteristics with multipotent, invasive embryonic progenitors, contributing to the paradigm of tumor cell plasticity. In the vertebrate embryo, multiple cell types originate from a highly invasive cell population called the neural crest.

Neural crest invasion is a spatially-ordered progression into the head with higher cell proliferation at the migratory front as revealed by the photoactivatable protein, KikGR.

Neural crest cell (NCC) invasion is a complex sculpting of individual cells into organized migratory streams that lead to organ development along the vertebrate axis. Key to our understanding of how molecular mechanisms modulate the NCC migratory pattern is information about cell behaviors, yet it has been challenging to selectively mark and analyze migratory NCCs in a living embryo. Here, we apply an innovative in vivo strategy to investigate chick NCC behaviors within the rhombomere 4 (r4) migratory stream by combining photoactivation of KikGR and confocal time-lapse analysis of H2B-mRFP1 transfected NCCs.

Reprogramming metastatic melanoma cells to assume a neural crest cell-like phenotype in an embryonic microenvironment.

Human metastatic melanoma cells express a dedifferentiated, plastic phenotype, which may serve as a selective advantage, because melanoma cells invade various microenvironments. Over the last three decades, there has been an increased focus on the role of the tumor microenvironment in cancer progression, with the goal of reversing the metastatic phenotype. Here, using an embryonic chick model, we explore the possibility of reverting the metastatic melanoma phenotype to its cell type of origin, the neural-crest-derived melanocyte.

Four-color, 4-D time-lapse confocal imaging of chick embryos.

Our understanding of the molecular mechanisms that direct cell motility, cell division, and cell shaping has benefited from innovations in cell labeling and the ability to resolve intracellular dynamics with multispectral, high-resolution imaging. However, due to difficulties with in vivo cell marking and monitoring, most studies have been restricted to fixed tissue or cells in culture. Here, we report the delivery of multiple (up to four), multicolor fluorescent protein (FP) constructs and four-dimensional (4-D), multispectral time-lapse confocal imaging of cell movements in living chick embryos.

In vivo evidence for short- and long-range cell communication in cranial neural crest cells.

The proper assembly of craniofacial structures and the peripheral nervous system requires neural crest cells to emerge from the neural tube and navigate over long distances to the branchial arches. Cell and molecular studies have shed light on potential intrinsic and extrinsic cues, which, in combination, are thought to ensure the induction and specification of cranial neural crest cells. However, much less is known about how migrating neural crest cells interpret and integrate signals from the microenvironment and other neural crest cells to sort into and maintain the stereotypical pattern of three spatially segregated streams.