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Ascidian papillae (palps) constitute a transient sensory adhesive organ that assures larval settlement and the onset of metamorphosis to the filterfeeding adult. Despite the importance of papillae for the ascidian development, their cellular composition is only roughly described. For Ciona intestinalis/robusta, a clear definition of cell numbers and discriminative molecular markers for the different cell types is missing. While some attention was given to neural cell types and their connectivity little is known about the adhesive producing collocytes. We converge serial-section electron microscopy and confocal imaging with various marker combinations to document the 3D organization of the Ciona papillae. We show the papillar development with 4 axial columnar cells (ACCs), 4 lateral primary sensory neurons (PSNs) and 12 central collocytes (CCs). We propose molecular markers for each cell type including novel ones for collocytes. The subcellular characteristics are suggestive of their role in papillar function: the ACCs featuring apical protrusions and microvilli, also contain neuroactive and endocytic vesicles indicative of a chemosensory role. They are clearly distinct from the ciliated glutamatergic PSNs. CCs encircle the ACCs and contain microvilli, small endocytic vesicles and notably a large numbers of adhesive granules that, according to element analysis and histochemistry, contain glycoproteins. Interestingly, we detect two different types of collocyte granules, one of them containing fibrous material and larger quantities of polysaccharides. Consistently, carbohydrate specific lectins label the papillar apex, the granules within CCs and the adhesive plaques upon larval attachment. We further propose CCs to derive from an evolutionary ancient neurosecretory cell type. Our findings contribute to understanding the development of the anterior ('new head') region of the Ciona larva and notably the adhesive secreting cells which has implications for developmental biology, cell differentiation and evolution, but also bioadhesion., (Copyright © 2018. Published by Elsevier Inc.)

Temporal and spatial characterization of gene expression is a prerequisite for the understanding of cell-, tissue-, and organ-differentiation. In a multifaceted approach to investigate gene expression in the tail plate of the free-living marine flatworm Macrostomum lignano, we performed a posterior-region-specific in situ hybridization screen, RNA sequencing (RNA-seq) of regenerating animals, and functional analyses of selected tail-specific genes. The in situ screen revealed transcripts expressed in the antrum, cement glands, adhesive organs, prostate glands, rhabdite glands, and other tissues. Next we used RNA-seq to characterize temporal expression in the regenerating tail plate revealing a time restricted onset of both adhesive organs and copulatory apparatus regeneration. In addition, we identified three novel previously unannotated genes solely expressed in the regenerating stylet. RNA interference showed that these genes are required for the formation of not only the stylet but the whole male copulatory apparatus. RNAi treated animals lacked the stylet, vesicula granulorum, seminal vesicle, false seminal vesicle, and prostate glands, while the other tissues of the tail plate, such as adhesive organs regenerated normally. In summary, our findings provide a large resource of expression data during homeostasis and regeneration of the morphologically complex tail regeneration and pave the way for a better understanding of organogenesis in M. lignano., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Apical-basal and planar cell polarities are hallmarks of metazoan epithelia required to separate internal and external environments and to regulate trans- and intracellular transport, cytoskeletal organization, and morphogenesis. Mechanisms of cell polarization have been intensively studied in bilaterian model organisms, particularly in early embryos and cultured cells, while cell polarity in pre-bilaterian tissues is poorly understood. Here, we have studied apical-basal and planar polarization in regenerating (aggregating) clusters of epitheliomuscular cells of Hydra, a simple representative of the ancestral, pre-bilaterian phylum Cnidaria. Immediately after dissociation, single epitheliomuscular cells do not exhibit cellular polarity, but they polarize de novo during aggregation. Reestablishment of the Hydra-specific epithelial bilayer is a result of short-range cell sorting. In the early phase of aggregation, apical-basal polarization starts with an enlargement of the epithelial apical-basal diameter and by the development of belt-like apical septate junctions. Specification of the basal pole of epithelial cells occurs shortly later and is linked to synthesis of mesoglea, development of hemidesmosome-like junctions, and formation of desmosome-like junctions connecting the basal myonemes of neighbouring cells. Planar polarization starts, while apical-basal polarization is already ongoing. It is executed gradually starting with cell-autonomous formation, parallelization, and condensation of myonemes at the basal end of each epithelial cell and continuing with a final planar alignment of epitheliomuscular cells at the tissue level. Our findings reveal that epithelial polarization in Hydra aggregates occurs in defined steps well accessible by histological and ultrastructural techniques and they will provide a basis for future molecular studies., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Mutations in the homeobox transcription factor MNX1 are the major cause of dominantly inherited sacral agenesis. Studies in model organisms revealed conserved mnx gene requirements in neuronal and pancreatic development while Mnx activities that could explain the caudal mesoderm specific agenesis phenotype remain elusive. Here we use the zebrafish pronephros as a simple yet genetically conserved model for kidney formation to uncover a novel role of Mnx factors in nephron morphogenesis. Pronephros formation can formally be divided in four stages, the specification of nephric mesoderm from the intermediate mesoderm (IM), growth and epithelialisation, segmentation and formation of the glomerular capillary tuft. Two of the three mnx genes in zebrafish are dynamically transcribed in caudal IM in a time window that proceeds segmentation. We show that expression of one mnx gene, mnx2b, is restricted to the pronephric lineage and that mnx2b knock-down causes proximal pronephric tubule dilation and impaired pronephric excretion. Using expression profiling of embryos transgenic for conditional activation and repression of Mnx regulated genes, we further identified irx1b as a direct target of Mnx factors. Consistent with a repression of irx1b by Mnx factors, the transcripts of irx1b and mnx genes are found in mutual exclusive regions in the IM, and blocking of Mnx functions results in a caudal expansion of the IM-specific irx1b expression. Finally, we find that knock-down of irx1b is sufficient to rescue proximal pronephric tubule dilation and impaired nephron function in mnx-morpholino injected embryos. Our data revealed a first caudal mesoderm specific requirement of Mnx factors in a non-human system and they demonstrate that Mnx-dependent restriction of IM-specific irx1b activation is required for the morphogenesis and function of the zebrafish pronephros., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

Due to the rapidly rising production and usage of nano-enabled products, aquatic environments are increasingly exposed to engineered nanoparticles (ENPs), causing concerns about their potential negative effects. In this study we assessed the effects of uncoated titanium dioxide nanoparticles (TiO2NPs) on the growth and activity of bacterial communities of three Swedish lakes featuring different chemical characteristics such as dissolved organic carbon (DOC) concentration, pH and elemental composition. TiO2NP exposure concentrations were 15, 100, and 1000 μg L(-1), and experiments were performed in situ under three light regimes: darkness, photosynthetically active radiation (PAR), and ambient sunlight including UV radiation (UVR). The nanoparticles were most stable in lake water with high DOC and low chemical element concentrations. At the highest exposure concentration (1000 μg L(-1) TiO2NP) the bacterial abundance was significantly reduced in all lake waters. In the medium and high DOC lake waters, exposure concentrations of 100 μg L(-1) TiO2NP caused significant reductions in bacterial abundance. The cell-specific bacterial activity was significantly enhanced at high TiO2NP exposure concentrations, indicating the loss of nanoparticle-sensitive bacteria and a subsequent increased activity by tolerant ones. No UV-induced phototoxic effect of TiO2NP was found in this study. We conclude that in freshwater lakes with high DOC and low chemical element concentrations, uncoated TiO2NPs show an enhanced stability and can significantly reduce bacterial abundance at relatively low exposure concentrations., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Members of the DAZ (Deleted in AZoospermia) gene family are important players in the process of gametogenesis and their dysregulation accounts for 10% of human male infertility. Boule, the ancestor of the family, is mainly involved in male meiosis in most organisms. With the exception of Drosophila and C. elegans, nothing is known on the function of boule in non-vertebrate animals. In the present study, we report on three boule orthologues in the flatworm Macrostomum lignano. We demonstrate that macbol1 and macbol2 are expressed in testes whilst macbol3 is expressed in ovaries and developing eggs. Macbol1 RNAi blocked spermatocyte differentiation whereas macbol2 showed no effect upon RNAi treatment. Macbol3 RNAi resulted in aberrant egg maturation and led to female sterility. We further demonstrated the evolutionary functional conservation of macbol1 by introducing this gene into Drosophila bol(1) mutants. Macbol1 was able to rescue the progression of fly meiotic divisions. In summary, our findings provide evidence for an involvement of boule genes in male and female gamete development in one organism. Furthermore, boule gene function is shown here for the first time in a lophotrochozoan. Our results point to a more diverse functional assignment of boule genes. Therefore, a better understanding of boule function in flatworms can help to elucidate the molecular mechanisms of and concomitant infertility in higher organisms including humans., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Nanoparticles as potential carriers for local drug transfer are an alternative to systemic drug delivery into the inner ear. We report on the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic(®) F127 (PF127) copolymer. Pluronic copolymers possess a unique viscosity-adjustable property that makes PF127 gels easy to handle compared to conventional cross-linked hydrogels. This ferrogel was successfully tested in cadaver human temporal bones as well as in organotypic explant cultures of mouse inner ears. SPIONs were identified by light microscopy and localized with different imaging modes in energy-filtered transmission electron microscopy. Our approach shows a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels., From the Clinical Editor: The authors report the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic® F127 (PF127) copolymer for drug delivery in the inner ear, demonstrasting a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The flatworm stem cell system is exceptional within the animal kingdom, as totipotent stem cells (neoblasts) are the only dividing cells within the organism. In contrast to most organisms, piwi-like gene expression in flatworms is extended from germ cells to somatic stem cells. We describe the isolation and characterization of the piwi homologue macpiwi in the flatworm Macrostomum lignano. We use in situ hybridization, antibody staining and RNA interference to study macpiwi expression and function in adults, during postembryonic development, regeneration and upon starvation. We found novelties regarding piwi function and observed differences to current piwi functions in flatworms. First, macpiwi was essential for the maintenance of somatic stem cells in adult animals. A knock-down of macpiwi led to a complete elimination of stem cells and death of the animals. Second, the regulation of stem cells was different in adults and regenerates compared to postembryonic development. Third, sexual reproduction of M. lignano allowed to follow germline formation during postembryonic development, regeneration, and starvation. Fourth, piwi expression in hatchlings further supports an embryonic formation of the germline in M. lignano. Our findings address new questions in flatworm stem cell research and provide a basis for comparison with higher organisms.

Background: Apolipoprotein A-IV (ApoA-IV) is a 46 kD glycoprotein thought to protect against atherosclerosis. It is synthesized primarily in epithelial cells of the small intestine. Elevated plasma concentrations of ApoA-IV in patients with chronic kidney disease suggest that the human kidney is involved in ApoA-IV metabolism., Methods: To investigate whether the human kidney directly metabolizes ApoA-IV and which kidney tissue compartment is involved therein, ApoA-IV was localized by immunohistochemistry in 28 healthy kidney tissue samples obtained from patients undergoing nephrectomy. ApoA-IV mRNA expression was analyzed by real-time polymerase chain reaction (PCR) to exclude de novo synthesis in the kidney., Results: ApoA-IV immunostaining was detected in proximal and distal tubular cells, capillaries and blood vessels but not inside glomeruli. ApoA-IV was predominantly found in the brush border of proximal tubules and in intracellular granules and various plasma membrane domains of both proximal and distal tubules. mRNA expression analysis revealed that no ApoA-IV was produced in the kidney., Conclusion: The immunoreactivity of ApoA-IV observed in kidney tubular cells suggests a direct role of the human kidney in ApoA-IV metabolism. The granular staining pattern probably represents lysosomes degrading ApoA-IV. The additional ApoA-IV localization in distal tubules suggests a rescue function to reabsorb otherwise escaping ApoA-IV in case proximal tubules cannot reabsorb all ApoA-IV. Since no mRNA expression could be detected in any kidney cells, the observed ApoA-IV immunoreactivity represents uptake and not de novo synthesis of ApoA-IV.