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Neural crest (NC) specification comprises an early phase, initiating immature NC progenitors formation at neural plate stage, and a later phase at neural fold stage, resulting in a functional premigratory NC that is able to delaminate and migrate. We found that the NC gene regulatory network triggers upregulation of pfkfb4 (6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4) during this late specification phase. As shown in previous studies, PFKFB4 controls AKT signaling in gastrulas and glycolysis rate in adult cells. Here, we focus on PFKFB4 function in NC during and after neurulation, using time-controlled or hypomorph depletions in vivo We find that PFKFB4 is essential both for specification of functional premigratory NC and for its migration. PFKFB4-depleted embryos fail to activate n-cadherin and late NC specifiers, and exhibit severe migration defects resulting in craniofacial defects. AKT signaling mediates PFKFB4 function in NC late specification, whereas both AKT signaling and glycolysis regulate migration. These findings highlight novel and essential roles of PFKFB4 activity in later stages of NC development that are wired into the NC gene regulatory network., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)

During vertebrate neurulation, the embryonic ectoderm is patterned into lineage progenitors for neural plate, neural crest, placodes and epidermis. Here, we use Xenopus laevis embryos to analyze the spatial and temporal transcriptome of distinct ectodermal domains in the course of neurulation, during the establishment of cell lineages. In order to define the transcriptome of small groups of cells from a single germ layer and to retain spatial information, dorsal and ventral ectoderm was subdivided along the anterior-posterior and medial-lateral axes by microdissections. Principal component analysis on the transcriptomes of these ectoderm fragments primarily identifies embryonic axes and temporal dynamics. This provides a genetic code to define positional information of any ectoderm sample along the anterior-posterior and dorsal-ventral axes directly from its transcriptome. In parallel, we use nonnegative matrix factorization to predict enhanced gene expression maps onto early and mid-neurula embryos, and specific signatures for each ectoderm area. The clustering of spatial and temporal datasets allowed detection of multiple biologically relevant groups (e.g., Wnt signaling, neural crest development, sensory placode specification, ciliogenesis, germ layer specification). We provide an interactive network interface, EctoMap, for exploring synexpression relationships among genes expressed in the neurula, and suggest several strategies to use this comprehensive dataset to address questions in developmental biology as well as stem cell or cancer research.

Wnt proteins form a family of highly conserved secreted molecules that are critical mediators of cell-cell signaling during embryogenesis. Partial data on Wnt activity in different tissues and at different stages have been reported in frog embryos. Our objective here is to provide a coherent and detailed description of Wnt activity throughout embryo development. Using a transgenic Xenopus tropicalis line carrying a Wnt-responsive reporter sequence, we depict the spatial and temporal dynamics of canonical Wnt activity during embryogenesis. We provide a comprehensive series of in situ hybridization in whole-mount embryos and in cross-sections, from gastrula to tadpole stages, with special focus on neural tube, retina and neural crest cell development. This collection of patterns will thus constitute a valuable resource for developmental biologists to picture the dynamics of Wnt activity during development. [ABSTRACT FROM AUTHOR]