Lateral cell polarization drives organization of epithelia in sea anemone embryos and embryonic cell aggregates.

One of the first organizing processes during animal development is the assembly of embryonic cells into epithelia. Common features unite epithelialization across select bilaterians, however, we know less about the molecular and cellular mechanisms that drive epithelial emergence in early branching nonbilaterians. In sea anemones, epithelia emerge both during embryonic development and after cell aggregation of dissociated tissues.

Lateral cell polarization drives organization of epithelia in sea anemone embryos and embryonic cell aggregates.

One of the first organizing processes during animal development is the assembly of embryonic cells into epithelia. In certain animals, including Hydra and sea anemones, epithelia also emerge when cells from dissociated tissues are aggregated back together. Although cell adhesion is required to keep cells together, it is not clear whether cell polarization plays a role as epithelia emerge from disordered aggregates.

Topological structures and syntenic conservation in sea anemone genomes.

There is currently little information about the evolution of gene clusters, genome architectures and karyotypes in early branching animals. Slowly evolving anthozoan cnidarians can be particularly informative about the evolution of these genome features. Here we report chromosome-level genome assemblies of two related anthozoans, the sea anemones Nematostella vectensis and Scolanthus callimorphus.

Origin and development of primary animal epithelia.

Epithelia are the first organized tissues that appear during development. In many animal embryos, early divisions give rise to a polarized monolayer, the primary epithelium, rather than a random aggregate of cells. Here, we review the mechanisms by which cells organize into primary epithelia in various developmental contexts.

Cell polarity oscillations in mitotic epithelia.

Epithelial organization and function depend on coordinated cell polarity. In developing tissues, proliferative epithelia maintain whole tissue polarity as individual cells undergo symmetric divisions. However, recent work has shown that cells in diverse epithelia remodel their polarity in a cell cycle-dependent manner.

Cell-Cycle-Coupled Oscillations in Apical Polarity and Intercellular Contact Maintain Order in Embryonic Epithelia.

Throughout animals, embryonic cells must ultimately organize into polarized epithelial layers that provide the structural basis for gastrulation or subsequent developmental events [1]. Precisely how this primary epithelium maintains continuous integrity during rapid and repeated cell divisions has never been directly addressed, particularly in cases where early cleavages are driven in synchrony. Representing the early-branching non-bilaterian phylum Cnidaria, embryos of the sea anemone Nematostella vectensis undergo rapid synchronous cell divisions and ultimately give rise to a diploblastic epithelial body plan after gastrulation [2, 3].

Cell division and the maintenance of epithelial order.

Epithelia are polarized layers of adherent cells that are the building blocks for organ and appendage structures throughout animals. To preserve tissue architecture and barrier function during both homeostasis and rapid growth, individual epithelial cells divide in a highly constrained manner. Building on decades of research focused on single cells, recent work is probing the mechanisms by which the dynamic process of mitosis is reconciled with the global maintenance of epithelial order during development.

A single GATA factor plays discrete, lineage specific roles in ascidian heart development.

GATA family transcription factors are core components of the vertebrate heart gene network. GATA factors also contribute to heart formation indirectly through regulation of endoderm morphogenesis. However, the precise impact of GATA factors on vertebrate cardiogenesis is masked by functional redundancy within multiple lineages.

The Bacillus subtilis spore coat provides "eat resistance" during phagocytic predation by the protozoan Tetrahymena thermophila.

Bacillus spores are highly resistant to many environmental stresses, owing in part to the presence of multiple "extracellular" layers. Although the role of some of these extracellular layers in resistance to particular stresses is known, the function of one of the outermost layers, the spore coat, is not completely understood. This study sought to determine whether the spore coat plays a role in resistance to predation by the ciliated protozoan Tetrahymena, which uses phagocytosis to ingest and degrade other microorganisms.

Cooperativity between different nutrient receptors in germination of spores of Bacillus subtilis and reduction of this cooperativity by alterations in the GerB receptor.

The GerA nutrient receptor alone triggers germination of Bacillus subtilis spores with L-alanine or L-valine, and these germinations were stimulated by glucose and K+ plus the GerK nutrient receptor. The GerB nutrient receptor alone did not trigger spore germination with any nutrients but required glucose, fructose, and K+ (GFK) (termed cogerminants) plus GerK for triggering of germination with a number of L-amino acids. GerB and GerA also triggered spore germination cooperatively with l-asparagine, fructose, and K+ and either L-alanine or L-valine.

Transglutaminase-mediated cross-linking of GerQ in the coats of Bacillus subtilis spores.

The spores of Bacillus subtilis show remarkable resistance to many environmental stresses, due in part to the presence of an outer proteinaceous structure known as the spore coat. GerQ is a spore coat protein essential for the presence of CwlJ, an enzyme involved in the hydrolysis of the cortex during spore germination, in the spore coat. Here we show that GerQ is cross-linked into higher-molecular-mass forms due in large part to a transglutaminase.

Identification of a new gene essential for germination of Bacillus subtilis spores with Ca2+-dipicolinate.

Bacillus subtilis spores can germinate with a 1:1 chelate of Ca(2+) and dipicolinic acid (DPA), a compound present at high levels in the spore core. Using a genetic screen to identify genes encoding proteins that are specifically involved in spore germination by Ca(2+)-DPA, three mutations were identified. One was in the gene encoding the cortex lytic enzyme, CwlJ, that was previously shown to be essential for spore germination by Ca(2+)-DPA.