Axis formation in annual killifish: Nodal and β-catenin regulate morphogenesis without Huluwa prepatterning.

Axis formation in fish and amphibians typically begins with a prepattern of maternal gene products. Annual killifish embryogenesis, however, challenges prepatterning models as blastomeres disperse and then aggregate to form the germ layers and body axes. We show that , a prepatterning factor thought to break symmetry by stabilizing β-catenin, is truncated and inactive in .

A new dawn for the study of cell type evolution.

Animal evolution is influenced by the emergence of new cell types, yet our understanding of this process remains elusive. This prompts the need for a broader exploration across diverse research organisms, facilitated by recent breakthroughs, such as gene editing tools and single-cell genomics. Essential to our understanding of cell type evolution is the accurate identification of homologous cells.

Fluorescent In Situ Hybridization in Embryos of the African Turquoise Killifish .

Precisely where and when a given gene is expressed is crucial for our understanding of developmental and cell biology but determining this is often constrained by detection limits. Here, we describe a technique for visualization of low-copy mRNA in embryos using tyramide signal amplification (TSA). In this protocol, an anti-sense digoxigenin-labeled RNA probe is hybridized to mRNA in situ.

The pattern of nodal morphogen signaling is shaped by co-receptor expression.

Embryos must communicate instructions to their constituent cells over long distances. These instructions are often encoded in the concentration of signals called morphogens. In the textbook view, morphogen molecules diffuse from a localized source to form a concentration gradient, and target cells adopt fates by measuring the local morphogen concentration.

The pre-vertebrate origins of neurogenic placodes.

The sudden appearance of the neural crest and neurogenic placodes in early branching vertebrates has puzzled biologists for over a century. These embryonic tissues contribute to the development of the cranium and associated sensory organs, which were crucial for the evolution of the vertebrate "new head". A previous study suggests that rudimentary neural crest cells existed in ancestral chordates.

Ephrin-mediated restriction of ERK1/2 activity delimits the number of pigment cells in the Ciona CNS.

Recent evidence suggests that ascidian pigment cells are related to neural crest-derived melanocytes of vertebrates. Using live-imaging, we determine a revised cell lineage of the pigment cells in Ciona intestinalis embryos. The neural precursors undergo successive rounds of anterior-posterior (A-P) oriented cell divisions, starting at the blastula 64-cell stage.

Identification of a rudimentary neural crest in a non-vertebrate chordate.

Neural crest arises at the neural plate border, expresses a core set of regulatory genes and produces a diverse array of cell types, including ectomesenchyme derivatives that elaborate the vertebrate head. The evolution of neural crest has been proposed to be a key event leading to the appearance of new cell types that fostered the transition from filter feeding to active predation in ancestral vertebrates. However, the origin of neural crest remains controversial, as homologous cell types have not been unambiguously identified in non-vertebrate chordates.

The planar cell polarity effector Fuz is essential for targeted membrane trafficking, ciliogenesis and mouse embryonic development.

The planar cell polarity (PCP) signalling pathway is essential for embryonic development because it governs diverse cellular behaviours, and 'core PCP' proteins, such as Dishevelled and Frizzled, have been extensively characterized. By contrast, the 'PCP effector' proteins, such as Intu and Fuz, remain largely unstudied. These proteins are essential for PCP signalling, but they have never been investigated in mammals and their cell biological activities remain entirely unknown.

Dishevelled controls apical docking and planar polarization of basal bodies in ciliated epithelial cells.

The planar cell polarity (PCP) signaling system governs many aspects of polarized cell behavior. Here, we use an in vivo model of vertebrate mucociliary epithelial development to show that Dishevelled (Dvl) is essential for the apical positioning of basal bodies. We find that Dvl and Inturned mediate the activation of the Rho GTPase specifically at basal bodies, and that these three proteins together mediate the docking of basal bodies to the apical plasma membrane.

Identification of novel ciliogenesis factors using a new in vivo model for mucociliary epithelial development.

Mucociliary epithelia are essential for homeostasis of many organs and consist of mucus-secreting goblet cells and ciliated cells. Here, we present the ciliated epidermis of Xenopus embryos as a facile model system for in vivo molecular studies of mucociliary epithelial development. Using an in situ hybridization-based approach, we identified numerous genes expressed differentially in mucus-secreting cells or in ciliated cells.