Light-modulated neural control of sphincter regulation in the evolution of through-gut.

The development of a continuous digestive tract, or through-gut, represents a key milestone in bilaterian evolution. However, the regulatory mechanisms in ancient bilaterians (urbilaterians) are not well understood. Our study, using larval sea urchins as a model, reveals a sophisticated system that prevents the simultaneous opening of the pylorus and anus, entry and exit points of the gut.

Nonmuscular Troponin-I is required for gastrulation in sea urchin embryos.

Background: Gastrulation is one of the most important events in our lives (Barresi and Gilbert, 2020, Developmental Biology, 12th ed.). The molecular mechanisms of gastrulation in multicellular organisms are not yet fully understood, since many molecular, physical, and chemical factors are involved in the event.

Rx and its downstream factor, Musashi1, is required for establishment of the apical organ in sea urchin larvae.

Acetylcholine, a vital neurotransmitter, plays a multifarious role in the brain and peripheral nervous system of various organisms. Previous research has demonstrated the proximity of cholinergic neurons to serotonergic neurons in the apical organ of sea urchin embryos. While several transcription factors have been identified as playing a role in the development of serotonergic neurons in this region of a sea urchin, , comparatively little is known about the specific transcription factors and their spatiotemporal expression patterns that regulate the development of cholinergic neurons.

Temnopleurus reevesii as a new sea urchin model in genetics.

Echinoderms, including sea urchins and starfish, have played important roles in cell, developmental and evolutionary biology research for more than a century. However, since most of them take a long time to mature sexually and their breeding seasons are limited, it has been difficult to obtain subsequent generations in the laboratory, resulting in them not being recognized as model organisms in recent genetics research. To overcome this issue, we maintained and obtained gametes from several nonmodel sea urchins in Japan and finally identified Temnopleurus reevesii as a suitable model for sea urchin genetics.

Human disease-associated extracellular matrix orthologs ECM3 and QBRICK regulate primary mesenchymal cell migration in sea urchin embryos.

Sea urchin embryos have been one of model organisms to investigate cellular behaviors because of their simple cell composition and transparent body. They also give us an opportunity to investigate molecular functions of human proteins of interest that are conserved in sea urchin. Here we report that human disease-associated extracellular matrix orthologues ECM3 and QBRICK are necessary for mesenchymal cell migration during sea urchin embryogenesis.

Sea urchin larvae utilize light for regulating the pyloric opening.

Background: Light is essential for various biological activities. In particular, visual information through eyes or eyespots is very important for most of animals, and thus, the functions and developmental mechanisms of visual systems have been well studied to date. In addition, light-dependent non-visual systems expressing photoreceptor Opsins have been used to study the effects of light on diverse animal behaviors.

Establishment of homozygous knock-out sea urchins.

Yaguchi et al. establish a homozygous knock-out sea urchin line by applying the CRISPR-Cas9 system to a new model species, Temnopleurus reevesii, whose breeding cycle takes about half a year.

cis-Regulatory analysis for later phase of anterior neuroectoderm-specific foxQ2 expression in sea urchin embryos.

The specification of anterior neuroectoderm is controlled by a highly conserved molecular mechanism in bilaterians. A forkhead family gene, foxQ2, is known to be one of the pivotal regulators, which is zygotically expressed in this region during embryogenesis of a broad range of bilaterians. However, what controls the expression of this essential factor has remained unclear to date.

Evolution of nitric oxide regulation of gut function.

Although morphologies are diverse, the common pattern in bilaterians is for passage of food in the gut to be controlled by nerves and endodermally derived neuron-like cells. In vertebrates, nitric oxide (NO) derived from enteric nerves controls relaxation of the pyloric sphincter. Here, we show that in the larvae of sea urchins, there are endoderm-derived neuronal nitric oxide synthase (nNOS)-positive cells expressing pan-neural marker, Synaptotagmin-B (SynB), in sphincters and that NO regulates the relaxation of the pyloric sphincter.

Microinjection methods for sea urchin eggs and blastomeres.

Methods for microinjection into sea urchin eggs have become relatively easier because of the technical improvements by a number of researchers in the past decades. However, the size and the characteristics, such as the elasticity and toughness, of the eggs and embryos differ in species, so that we still need to modify the details of methods to adapt to each target. In this section, I list microinjection methods for three species: Hemicentrotus pulcherrimus, which has relatively tough eggs, Temnopleurus reevesii, which has slightly weak eggs, and Strongylocentrotus purpuratus, which is the most used species in sea urchin biology.

Meis transcription factor maintains the neurogenic ectoderm and regulates the anterior-posterior patterning in embryos of a sea urchin, Hemicentrotus pulcherrimus.

Precise body axis formation is an essential step in the development of multicellular organisms, for most of which the molecular gradient and/or specifically biased localization of cell-fate determinants in eggs play important roles. In sea urchins, however, any biased proteins and mRNAs have not yet been identified in the egg except for vegetal cortex molecules, suggesting that sea urchin development is mostly regulated by uniformly distributed maternal molecules with contributions to axis formation that are not well characterized. Here, we describe that the maternal Meis transcription factor regulates anterior-posterior axis formation through maintenance of the most anterior territory in embryos of a sea urchin, Hemicentrotus pulcherrimus.

Calaxin establishes basal body orientation and coordinates movement of monocilia in sea urchin embryos.

Through their coordinated alignment and beating, motile cilia generate directional fluid flow and organismal movement. While the mechanisms used by multiciliated epithelial tissues to achieve this coordination have been widely studied, much less is known about regulation of monociliated tissues such as those found in the vertebrate node and swimming planktonic larvae. Here, we show that a calcium sensor protein associated with outer arm dynein, calaxin, is a critical regulator for the coordinated movements of monocilia.

Troponin-I is present as an essential component of muscles in echinoderm larvae.

The troponin complex, composed of Troponin-I, Troponin-T and Troponin-C, is an essential mediator of the contraction of striated muscle downstream of calcium signaling in almost all bilaterians. However, in echinoderms and hemichordates, collectively termed Ambulacraria, the components of the troponin complex have never been isolated, thus suggesting that these organisms lost the troponin system during evolution. Here, by analyzing genomic information from sea urchins, we identify the troponin-I gene and isolate its complete mRNA sequence.

Cooperative Wnt-Nodal Signals Regulate the Patterning of Anterior Neuroectoderm.

When early canonical Wnt is experimentally inhibited, sea urchin embryos embody the concept of a Default Model in vivo because most of the ectodermal cell fates are specified as anterior neuroectoderm. Using this model, we describe here how the combination of orthogonally functioning anteroposterior Wnt and dorsoventral Nodal signals and their targeting transcription factors, FoxQ2 and Homeobrain, regulates the precise patterning of normal neuroectoderm, of which serotonergic neurons are differentiated only at the dorsal/lateral edge. Loss-of-function experiments revealed that ventral Nodal is required for suppressing the serotonergic neural fate in the ventral side of the neuroectoderm through the maintenance of foxQ2 and the repression of homeobrain expression.

Early development and neurogenesis of Temnopleurus reevesii.

Sea urchins are model non-chordate deuterostomes, and studying the nervous system of their embryos can aid in the understanding of the universal mechanisms of neurogenesis. However, despite the long history of sea urchin embryology research, the molecular mechanisms of their neurogenesis have not been well investigated, in part because neurons appear relatively late during embryogenesis. In this study, we used the species Temnopleurus reevesii as a new sea urchin model and investigated the detail of its development and neurogenesis during early embryogenesis.

bicaudal-C is required for the formation of anterior neurogenic ectoderm in the sea urchin embryo.

bicaudal-C (bicC) mRNA encodes a protein containing RNA-binding domains that is reported to be maternally present with deflection in the oocytes/eggs of some species. The translated protein plays a critical role in the regulation of cell fate specification along the body axis during early embryogenesis in flies and frogs. However, it is unclear how it functions in eggs in which bicC mRNA is uniformly distributed, for instance, sea urchin eggs.

Imaging neural development in embryonic and larval sea urchins.

Imaging is a critical tool in neuroscience, and our understanding of the structure and function of sea urchin nervous systems owes much to this approach. In particular, studies of neural development have been facilitated by methods that enable the accurate identification of specific types of neurons. Here we describe methods that have been successfully employed to study neural development in sea urchin embryos.

Glutathione transferase theta in apical ciliary tuft regulates mechanical reception and swimming behavior of Sea Urchin Embryos.

An apical tuft, which is observed in a wide range of embryos/larvae of marine invertebrates, is composed of a group of cilia that are longer and less motile than the abundant lateral cilia covering the rest of the embryonic surface. Although the apical tuft has been thought to function as a sensory organ, its molecular composition and roles are poorly understood. Here, we identified a glutathione transferase theta (GSTT) as an abundant and specific component of the apical tuft in sea urchin embryos.

Zinc finger homeobox is required for the differentiation of serotonergic neurons in the sea urchin embryo.

Serotonergic neurons differentiate in the neurogenic animal plate ectoderm of the sea urchin embryo. The regulatory mechanisms that control the specification or differentiation of these neurons in the sea urchin embryo are not yet understood, although, after the genome was sequenced, many genes encoding transcription factors expressed in this region were identified. Here, we report that zinc finger homeobox (zfhx1/z81) is expressed in serotonergic neural precursor cells, using double in situ hybridization screening with a serotonergic neural marker, tryptophan 5-hydroxylase (tph) encoding a serotonin synthase that is required for the differentiation of serotonergic neurons.

Fez function is required to maintain the size of the animal plate in the sea urchin embryo.

Partitioning ectoderm precisely into neurogenic and non-neurogenic regions is an essential step for neurogenesis of almost all bilaterian embryos. Although it is widely accepted that antagonism between BMP and its inhibitors primarily sets up the border between these two types of ectoderm, it is unclear how such extracellular, diffusible molecules create a sharp and precise border at the single-cell level. Here, we show that Fez, a zinc finger protein, functions as an intracellular factor attenuating BMP signaling specifically within the neurogenic region at the anterior end of sea urchin embryos, termed the animal plate.

CIPRO 2.5: Ciona intestinalis protein database, a unique integrated repository of large-scale omics data, bioinformatic analyses and curated annotation, with user rating and reviewing functionality.

The Ciona intestinalis protein database (CIPRO) is an integrated protein database for the tunicate species C. intestinalis. The database is unique in two respects: first, because of its phylogenetic position, Ciona is suitable model for understanding vertebrate evolution; and second, the database includes original large-scale transcriptomic and proteomic data.

ankAT-1 is a novel gene mediating the apical tuft formation in the sea urchin embryo.

In sea urchin embryos, the apical tuft forms within the neurogenic animal plate. When FoxQ2, one of the earliest factors expressed specifically in the animal plate by early blastula stage, is knocked down, the structure of the apical tuft is altered. To determine the basis of this phenotype, we identified FoxQ2-dependent genes using microarray analysis.

TGFβ signaling positions the ciliary band and patterns neurons in the sea urchin embryo.

The ciliary band is a distinct region of embryonic ectoderm that is specified between oral and aboral ectoderm. Flask-shaped ciliary cells and neurons differentiate in this region and they are patterned to form an integrated tissue that functions as the principal swimming and feeding organ of the larva. TGFβ signaling, which is known to mediate oral and aboral patterning of the ectoderm, has been implicated in ciliary band formation.

Development of a dopaminergic system in sea urchin embryos and larvae.

The mechanisms that regulate the organized swimming movements of sea urchin blastulae are largely unknown. Using immunohistochemistry, we found that dopamine (DA) and the Hemicentrotus pulcherrimus homolog of the dopamine receptor D1 (Hp-DRD1) were strongly co-localized in 1-2 microm diameter granules (DA/DRD1 granules). Furthermore, these granules were arranged across the entire surface of blastulae as they developed locomotory cilia before hatching, and remained evident until metamorphosis.