Project description:The neural crest is an embryonic cell population that contributes to key vertebrate-specific features including the craniofacial skeleton and peripheral nervous system. Here we examine the transcriptional profiles and chromatin accessibility of neural crest cells in the basal sea lamprey, in order to gain insight into the ancestral state of the neural crest gene regulatory network (GRN) at the dawn of vertebrates. Transcriptome analyses reveal clusters of co-regulated genes during neural crest specification and migration that show high conservation across vertebrates for dynamic programmes like Wnt modulation during the epithelial to mesenchymal transition, but also reveal novel transcription factors and cell-adhesion molecules not previously implicated in neural crest migration. ATAC-seq analysis refines the location of known cis-regulatory elements at the Hox-α2 locus and uncovers novel cis-regulatory elements for Tfap2B and SoxE1. Moreover, cross-species deployment of lamprey elements in zebrafish reveals that the lamprey SoxE1 enhancer activity is deeply conserved, mediating homologous expression in jawed vertebrates. Together, our data provide new insight into the core elements of the GRN that are conserved to the base of the vertebrates, as well as expose elements that are unique to lampreys.
Project description:Neural crest development is orchestrated by a complex and still poorly understood gene regulatory network. Premigratory neural crest is induced at the lateral border of the neural plate by the combined action of signaling molecules and transcription factors such as AP2, Gbx2, Pax3 and Zic1. Among them, Pax3 and Zic1 are both necessary and sufficient to trigger a complete neural crest developmental program. However, their gene targets in the neural crest regulatory network remain unknown. Here, through a transcriptome analysis of frog microdissected neural border, we identified an extended gene signature for the premigratory neural crest, and we defined novel potential members of the regulatory network. This signature includes 34 novel genes, as well as 44 known genes expressed at the neural border. Using another microarray analysis which combined Pax3 and Zic1 gain-of-function and protein translation blockade, we uncovered 25 Pax3 and Zic1 direct targets within this signature. We demonstrated that the neural border specifiers Pax3 and Zic1 are direct upstream regulators of neural crest specifiers Snail1/2, Foxd3, Twist1, and Tfap2b. In addition, they may modulate the transcriptional output of multiple signaling pathways involved in neural crest development (Wnt, Retinoic Acid) through the induction of key pathway regulators (Axin2 and Cyp26c1). We also found that Pax3 could maintain its own expression through a positive autoregulatory feedback loop. These hierarchical inductions, feedback loops, and pathway modulation provide novel tools to understand the neural crest induction network. The transcriptomes of neural border samples (stage 14 and 18) were compared to the transcriptome of anterior neural fold (stage 18), early neural plate (stage 12), and animal cap explants (stage14) to identify genes expressed specifically in neural border samples. Tissue samples from Xenopus laevis embryos were dissected, then total RNA was extracted and hybridized on Affymetrix microarrays. Selected tissue samples encompass the neural crest at different stages of its induction (early neural plate at stage 12, neural border at stage 14, neural border at stage 18), as well as reference tissues (anterior neural fold at stage 18, a tissue that belongs to the neural border but does not produce neural crest, and animal cap grown until stage 14 that differentiates into epidermis).
Project description:Neural crest development is orchestrated by a complex and still poorly understood gene regulatory network. Premigratory neural crest is induced at the lateral border of the neural plate by the combined action of signaling molecules and transcription factors such as AP2, Gbx2, Pax3 and Zic1. Among them, Pax3 and Zic1 are both necessary and sufficient to trigger a complete neural crest developmental program. However, their gene targets in the neural crest regulatory network remain unknown. Here, through a transcriptome analysis of frog microdissected neural border, we identified an extended gene signature for the premigratory neural crest, and we defined novel potential members of the regulatory network. This signature includes 34 novel genes, as well as 44 known genes expressed at the neural border. Using another microarray analysis which combined Pax3 and Zic1 gain-of-function and protein translation blockade, we uncovered 25 Pax3 and Zic1 direct targets within this signature. We demonstrated that the neural border specifiers Pax3 and Zic1 are direct upstream regulators of neural crest specifiers Snail1/2, Foxd3, Twist1, and Tfap2b. In addition, they may modulate the transcriptional output of multiple signaling pathways involved in neural crest development (Wnt, Retinoic Acid) through the induction of key pathway regulators (Axin2 and Cyp26c1). We also found that Pax3 could maintain its own expression through a positive autoregulatory feedback loop. These hierarchical inductions, feedback loops, and pathway modulation provide novel tools to understand the neural crest induction network. Transcriptomes of animal caps overexpressing Pax3+/-Zic1 in the presence/absence of cycloheximide, a translation inhibitor, were compared to control animal caps to identify direct Pax3 and Zic1 targets 2-4 cells stage embryos were injected with inducible Pax3-GR+/-Zic1-GR constructs. Animal caps were cut at stage 9. Cycloheximide (Chx, 0.1mg/ml) was then applied to the healed animal caps, from stage 10 to 10.5 (i.e. for 30 min at 23*C), then dexamethasone (Dex) was added at stage 10.5 to the cycloheximide-containing medium. Explants were rinced and lysed after two additional hours at 23*C, i.e. when sibling embryos reached stage 11.5-12. Total RNA was then extracted and hybridized on Affymetrix microarrays. Transcriptomes were compared to determine Pax3 and Zic1 targets.
Project description:Neural crest development is orchestrated by a complex and still poorly understood gene regulatory network. Premigratory neural crest is induced at the lateral border of the neural plate by the combined action of signaling molecules and transcription factors such as AP2, Gbx2, Pax3 and Zic1. Among them, Pax3 and Zic1 are both necessary and sufficient to trigger a complete neural crest developmental program. However, their gene targets in the neural crest regulatory network remain unknown. Here, through a transcriptome analysis of frog microdissected neural border, we identified an extended gene signature for the premigratory neural crest, and we defined novel potential members of the regulatory network. This signature includes 34 novel genes, as well as 44 known genes expressed at the neural border. Using another microarray analysis which combined Pax3 and Zic1 gain-of-function and protein translation blockade, we uncovered 25 Pax3 and Zic1 direct targets within this signature. We demonstrated that the neural border specifiers Pax3 and Zic1 are direct upstream regulators of neural crest specifiers Snail1/2, Foxd3, Twist1, and Tfap2b. In addition, they may modulate the transcriptional output of multiple signaling pathways involved in neural crest development (Wnt, Retinoic Acid) through the induction of key pathway regulators (Axin2 and Cyp26c1). We also found that Pax3 could maintain its own expression through a positive autoregulatory feedback loop. These hierarchical inductions, feedback loops, and pathway modulation provide novel tools to understand the neural crest induction network. The transcriptomes of neural border samples (stage 14 and 18) were compared to the transcriptome of anterior neural fold (stage 18), early neural plate (stage 12), and animal cap explants (stage14) to identify genes expressed specifically in neural border samples.
Project description:Neural crest development is orchestrated by a complex and still poorly understood gene regulatory network. Premigratory neural crest is induced at the lateral border of the neural plate by the combined action of signaling molecules and transcription factors such as AP2, Gbx2, Pax3 and Zic1. Among them, Pax3 and Zic1 are both necessary and sufficient to trigger a complete neural crest developmental program. However, their gene targets in the neural crest regulatory network remain unknown. Here, through a transcriptome analysis of frog microdissected neural border, we identified an extended gene signature for the premigratory neural crest, and we defined novel potential members of the regulatory network. This signature includes 34 novel genes, as well as 44 known genes expressed at the neural border. Using another microarray analysis which combined Pax3 and Zic1 gain-of-function and protein translation blockade, we uncovered 25 Pax3 and Zic1 direct targets within this signature. We demonstrated that the neural border specifiers Pax3 and Zic1 are direct upstream regulators of neural crest specifiers Snail1/2, Foxd3, Twist1, and Tfap2b. In addition, they may modulate the transcriptional output of multiple signaling pathways involved in neural crest development (Wnt, Retinoic Acid) through the induction of key pathway regulators (Axin2 and Cyp26c1). We also found that Pax3 could maintain its own expression through a positive autoregulatory feedback loop. These hierarchical inductions, feedback loops, and pathway modulation provide novel tools to understand the neural crest induction network. Transcriptomes of animal caps overexpressing Pax3+/-Zic1 in the presence/absence of cycloheximide, a translation inhibitor, were compared to control animal caps to identify direct Pax3 and Zic1 targets
Project description:Ectoderm-derived neural crest is a transient structure arising during early embryogenesis in vertebrates. Neural crest consists of four derivatives based on their anterior- to posterior location along the body axis; cranial, vagal, trunk and sacral, respectively. We recently showed that trunk neural crest-specific gene MOXD1 functions as a tumor suppressor in trunk neural crest-derived childhood cancer form neuroblastoma and is essential for proper development of healthy adrenal glands. However, the role of MOXD1 during early embryogenesis is not known. Here, we conditionally knocked out MOXD1 in trunk neural crest cells before they become lineage-committed, using a CRISPR/Cas9 approach in chick embryos. Assessment of embryo growth showed that knockout of MOXD1 delayed development with knockout embryos being smaller. RNA sequencing of trunk-derived neural crest cells from control and knockout embryos showed enrichment of genes connected to gland development, copper ion metabolism and neuroblastoma progression. In conclusion, MOXD1 is important during early and prolonged embryonic development with effects on gland formation, possibly mediated via its role in copper metabolism.
Project description:The neural crest is a migratory stem cell population that gives rise to a wide array of cell types. The formation and differentiation of neural crest cells are controlled by a complex transcriptional network, which endows these cells with unique features such as multipotency and stemness. During migration, signaling systems modulate subcircuits within this network to ensure that neural crest cells differentiate at the right time and place. The wingless (Wnt) signaling pathway, in particular, plays an important role in defining developmental potential of these cells but, surprisingly few direct Wnt-target genes have been identified in the neural crest transcriptional network. To address this, we generated a high-resolution contact map of active enhancers in the neural crest and identified the direct targets of Wnt signaling in the neural crest genome via CUT&RUN for its nuclear effectors LEF1 and CTNNB1 (bCat).
Project description:Neural crest cells exemplify cellular diversification from a multipotent progenitor population. However, the full sequence of molecular choices governing the emergence of neural crest heterogeneity from the ectoderm remains elusive. Gene regulatory networks govern these steps of embryonic development and cell specification towards definitive neural crest. Here, we combine ultra-dense single cell transcriptomes with machine-learning strategies and experimental validation to provide a comprehensive gene regulatory network driving vertebrate neural crest fate diversification, from induction to early migration stages. Transcription factor connectome and bifurcation analyses demonstrate emergence of early neural crest fates at the neural plate stage, alongside an unbiased multipotent neural crest lineage persisting until after epithelial-mesenchymal transition. We also define a new and transient neural border zone state, preceding choice between neural crest and placodes during gastrulation. Theis combination of experimental tests, with Machine Learning broadly applicable to single cell transcriptomics, deciphers the circuits driving cranial and vagal neural crest formation and provides a general model for investigating vertebrate GRNs in development, evolution and disease.
Project description:Neural crest cells exemplify cellular diversification from a multipotent progenitor population. However, the full sequence of molecular choices governing the emergence of neural crest heterogeneity from the ectoderm remains elusive. Gene regulatory networks govern these steps of embryonic development and cell specification towards definitive neural crest. Here, we combine ultra-dense single cell transcriptomes with machine-learning strategies and experimental validation to provide a comprehensive gene regulatory network driving vertebrate neural crest fate diversification, from induction to early migration stages. Transcription factor connectome and bifurcation analyses demonstrate emergence of early neural crest fates at the neural plate stage, alongside an unbiased multipotent neural crest lineage persisting until after epithelial-mesenchymal transition. We also define a new and transient neural border zone state, preceding choice between neural crest and placodes during gastrulation. Theis combination of experimental tests, with Machine Learning broadly applicable to single cell transcriptomics, deciphers the circuits driving cranial and vagal neural crest formation and provides a general model for investigating vertebrate GRNs in development, evolution and disease.