Embryonic Development of the Gastrodermis in the Coral .

Due to limited spawning seasons, embryogenesis of corals has not fully been studied and the embryonic origin of gastrodermis remains uncertain in . We herein examined how embryonic endodermal cells develop into the gastrodermis and mesentery of polyps in . In juvenile polyps, the gastrodermis invaginates to form mesenteries, both of which were stained with rhodamine-phalloidin, an anti-myocyte-specific enhancer factor 2 (anti-AtMef2) antibody, and an anti-lipoxygenase homology domain-containing protein 1 (anti-AtLoxhd1) antibody.

Stat stimulates histone H3K4 methylation via KDM5 inhibition in adult stem cells of budding tunicates.

Background: The branchial epithelium is one of the main tissues in which histone H3K4 trimethylation (H3K4me3) occurs in the budding tunicate, Polyandrocarpa misakiensis. It contains proliferating and undifferentiated cell aggregates at the bottom of each pharyngeal cleft, providing the nest for the adult stem cell niche. We examined the sustainable mechanism enabling epigenetic histone methylation in adult stem cells.

In Vitro Phagocytosis of Different Dinoflagellate Species by Coral Cells.

Coral-dinoflagellate symbiosis is a unique biological phenomenon, in which animal cells engulf single-celled photosynthetic algae and maintain them in their cytoplasm mutualistically. Studies are needed to reveal the complex mechanisms involved in symbiotic processes, but it is difficult to answer these questions using intact corals. To tackle these issues, our previous studies established an in vitro system of symbiosis between cells of the scleractinian coral and the dinoflagellate , and showed that corals direct phagocytosis, while algae are likely engulfed by coral cells passively.

The transcription factor AP2 and downstream genes shared by asexual reproduction and zooidal regeneration in the tunicate, Polyandrocarpa misakiensis.

Epithelial outpocketing, tunic softening, mesenchymal cell death, dedifferentiation/transdifferentiation, and resistance to environmental stress are major events that occur during asexual reproduction by budding in the tunicate, Polyandrocarpa misakiensis. To identify the molecules underlying these events and compare them with those operating in regeneration, differential gene expression profiles were developed in buds and zooids. Among approximately 40,000 contigs, 21 genes were identified as potentially being involved in asexual reproduction.

Establishing Sustainable Cell Lines of a Coral, Acropora tenuis.

Planula larvae of the scleractinian coral, Acropora tenuis, consist of elongated ectodermal cells and developing inner endodermal cells. To establish in vitro cell lines for future studies of cellular and developmental potential of coral cells, larvae were successfully dissociated into single cells by treating them with a tissue dissociation solution consisting of trypsin, EDTA, and collagenase. Brown-colored cells, translucent cells, and pale blue cells were the major components of dissociated larvae.

YAF2-Mediated YY1-Sirtuin6 Interactions Responsible for Mitochondrial Downregulation in Aging Tunicates.

In budding tunicates, aging accompanies a decrease in the gene expression of mitochondrial transcription factor A (), and the transfection of mRNA stimulates the mitochondrial respiratory activity of aged animals. The gene expression of both the transcriptional repressor Yin-Yang-1 () and corepressor Sirtuin6 () increased during aging, and the cotransfection of synthetic mRNA of and synergistically downregulated gene expression. Pulldown assays of proteins indicated that YY1-associated factor 2 (YAF2) was associated with both YY1 and SIRT6.

Autophagic dedifferentiation induced by cooperation between TOR inhibitor and retinoic acid signals in budding tunicates.

Asexual bud development in the budding tunicate Polyandrocarpa misakiensis involves transdifferentiation of multipotent epithelial cells, which is triggered by retinoic acid (RA), and thrives under starvation after bud isolation from the parent. This study aimed to determine cell and molecular mechanisms of dedifferentiation that occur during the early stage of transdifferentiation. During dedifferentiation, the numbers of autophagosomes, lysosomes, and secondary lysosomes increased remarkably.

Regulatory cis- and trans-elements of mitochondrial D-loop-driven reporter genes in budding tunicates.

To unveil the underlying mechanism of mitochondrial gene regulation associated with ageing and budding in the tunicate Polyandrocarpa misakiensis, mitochondrial non-coding-region (NCR)-containing reporter genes were constructed. PmNCR2.3K/GFP was expressed spatiotemporally in a pattern quite similar to mitochondrial 16SrRNA.

Histone methylation codes involved in stemness, multipotency, and senescence in budding tunicates.

We examined the dynamics of nuclear histone H3 trimethylation related to cell differentiation and aging in a budding tunicate, Polyandrocarpa misakiensis. Throughout zooidal life, multipotent epithelial and coelomic cell nuclei showed strong trimethylation signals at H3 lysine27 (H3K27me3), consistent with the results of western blotting. Epidermal H3K27me3 repeatedly appeared in protruding buds and disappeared in senescent adult zooids.

Interactive histone acetylation and methylation in regulating transdifferentiation-related genes during tunicate budding and regeneration.

Background: In the budding tunicate Polyandrocarpa misakiensis, retinoic acid (RA)-triggered transdifferentiation occurs during bud development and zooid regeneration. We aimed to reveal how and to what extent epigenetic histone modifications are involved in transdifferentiation-related gene expression.

Results: Acetylated histone H3 lysine 9 (H3K9ac) was observed in transdifferentiating bud tissues and regenerating zooid tissues, where a histone acetyltransferase (HAT) gene, PmGCN5, was strongly expressed.

Retinoid X receptor-mediated transdifferentiation cascade in budding tunicates.

In the budding tunicate, Polyandrocarpa misakiensis, retinoic acid (RA) applied to buds promotes transdifferentiation of somatic cells to form the secondary body axis. This study investigated the gene cascade regulating such RA-triggered transdifferentiation in tunicates. Genes encoding retinoic acid receptor (RAR) and retinoid X receptor (RXR) were induced during transdifferentiation, and they responded to all-trans RA or 13-cis RA in vivo, whereas 9-cis RA had the least effects, demonstrating differences in the ligand preference between budding tunicates and vertebrates.

Senescence-associated superoxide dismutase influences mitochondrial gene expression in budding tunicates.

A recent study has shown that in the budding tunicate Polyandrocarpa misakiensis, the mitochondrial respiratory chain (MRC) dramatically attenuates the gene activity during senescence. In this study, we examined the possible involvement of superoxide dismutase (SOD) in the attenuation of gene expression of cytochrome c oxidase subunit 1 (COX1) in aged zooids. By RT-PCR and in situ hybridization, Cu/Zn-SOD (SOD1) was found to be expressed in most cells and tissues of buds and juvenile zooids but showed a conspicuous decline in senescent adult zooids, except in the gonad tissue in which the cytoplasm of juvenile oocytes was stained heavily.

Molecular anatomy of tunicate senescence: reversible function of mitochondrial and nuclear genes associated with budding cycles.

Zooids of the asexual strain of Polyandrocarpa misakiensis have a lifespan of 4-5 months; before dying, they produce many buds, enabling continuation of the strain. This study was designed to investigate the nature of gene inactivation and reactivation during this continuous process of senescence and budding. During senescence, the zooidal epidermis showed acid β-galactosidase activity, lost proliferating cell nuclear antigen immunoreactivity and became ultrastructurally worn, indicating that the epidermis is a major tissue affected by the ageing process.

RACK1 regulates mesenchymal cell recruitment during sexual and asexual reproduction of budding tunicates.

A homolog of receptor for activated protein kinase C1 (RACK1) was cloned from the budding tunicate Polyandrocarpa misakiensis. By RT-PCR and in situ hybridization analyses, PmRACK1 showed biphasic gene expression during asexual and sexual reproduction. In developing buds, the signal was exclusively observed in the multipotent atrial epithelium and undifferentiated mesenchymal cells that contributed to morphogenesis by the mesenchymal-epithelial transition (MET).

Tunicate cytostatic factor TC14-3 induces a polycomb group gene and histone modification through Ca(2+) binding and protein dimerization.

Background: As many invertebrate species have multipotent cells that undergo cell growth and differentiation during regeneration and budding, many unique and interesting homeostatic factors are expected to exist in those animals. However, our understanding of such factors and global mechanisms remains very poor. Single zooids of the tunicate, Polyandrocarpa misakiensis, can give off as many as 40 buds during the life span.

Role of Vasa, Piwi, and Myc-expressing coelomic cells in gonad regeneration of the colonial tunicate, Botryllus primigenus.

In the colonial tunicate, Botryllus primigenus Oka, gonads consist of indifferent germline precursor cells, the primordial testis and ovary, and mature gonads, of which the immature gonad components can be reconstructed de novo in vascular buds that arise from the common vascular system, although the mechanism is uncertain. In this study, we investigated how and what kinds of cells regenerated the gonad components. We found that few Vasa-positive cells in the hemocoel entered the growing vascular bud, where their number increased, and finally developed exclusively into female germ cells.

Germline cell formation and gonad regeneration in solitary and colonial ascidians.

The morphology of ascidian gonad is very similar among species. The testis consists of variable number of testicular follicles; the ovary consists of ovarian tubes that are thickened forming the germinal epithelium with stem cells for female germ cells with the exception of botryllid ascidians. Peculiar accessory cells that would be germline in origin accompany the oocytes.

Hemoblasts in colonial tunicates: are they stem cells or tissue-restricted progenitor cells?

Colonial tunicates have hemoblasts, which are undifferentiated coelomic cells that play a key role in tissue renewal during reproduction and regeneration. Some hemoblasts differentiate into somatic lineage cells such as endodermal multipotent epithelial, cardiac and body-wall muscle, and blood cells. There is no well established evidence that somatic hemoblasts are stem cells.

An ascidian homologue of the gonadotropin-releasing hormone receptor is a retinoic acid target gene.

Transdifferentiation of the multipotent atrial epithelium is a key event during budding of the ascidian Polyandrocarpa misakiensis. The transdifferentiation is induced by mesenchyme cells that were stimulated by retinoic acid. The fluorescent differential display identified a few cDNA fragments for retinoic acid-inducible genes.