Phylogenetic analysis and expression patterns of p16 and p19 in Paracentrotus lividus embryos

Automated, high-throughput in-situ hybridization of Lytechinus pictus embryos

Despite the reach of in situ hybridization (ISH) in developmental biology, it has rarely been used at scale. The major limitation has been the throughput of the assay, which typically relies upon labor intensive manual steps. The goal of this study was to develop a fully automated hybridization chain reaction (HCR) pipeline capable of large-scale gene expression pattern profiling, with dramatically reduced cost and effort, in the sea urchin Lytechinus pictus. Our resulting pipeline, which we term high throughput (HT)-HCR, can process 192 gene probe sets on whole-mount embryos within 32 hours. The unique qualities of the sea urchin embryo enabled us to automate the entire HCR assay in a 96-well plate format, and utilize highly miniaturized reaction volumes, a general purpose robotic liquid handler, and automated confocal microscopy. From this approach we produced high quality localization data for 101 target genes across three developmental stages of L. pictus. The results reveal the localization of previously undescribed physiological genes, as well as canonical developmental transcription factors. HT-HCR represents a log order increase in the rate at which spatial transcriptomic data can be resolved in the sea urchin. This study paves the way for localization of understudied genes and for sophisticated perturbation analysis.

Gene, Protein, and in Silico Analyses of FoxO, an Evolutionary Conserved Transcription Factor in the Sea Urchin Paracentrotus lividus

FoxO is a member of the evolutionary conserved family of transcription factors containing a Forkhead box, involved in many signaling pathways of physiological and pathological processes. In mammals, mutations or dysfunctions of the FoxO gene have been implicated in diverse diseases. FoxO homologs have been found in some invertebrates, including echinoderms. We have isolated the FoxO cDNA from the sea urchin Paracentrotus lividus (Pl-foxo) and characterized the corresponding gene and mRNA. In silico studies showed that secondary and tertiary structures of Pl-foxo protein corresponded to the vertebrate FoxO3 isoform, with highly conserved regions, especially in the DNA-binding domain. A phylogenetic analysis compared the Pl-foxo deduced protein with proteins from different animal species and confirmed its evolutionary conservation between vertebrates and invertebrates. The increased expression of Pl-foxo mRNA following the inhibition of the PI3K signaling pathway paralleled the upregulation of Pl-foxo target genes involved in apoptosis or cell-cycle arrest events (BI-1, Bax, MnSod). In silico studies comparing molecular data from sea urchins and other organisms predicted a network of Pl-foxo protein-protein interactions, as well as identified potential miRNAs involved in Pl-foxo gene regulation. Our data may provide new perspectives on the knowledge of the signaling pathways underlying sea urchin development.

Carbonic anhydrases in development: morphological observations and gene expression profiling in sea urchin embryos exposed to acetazolamide

Carbonic anhydrases (CANs) are conserved metalloenzymes catalysing the reversible hydration of carbon dioxide into protons and bicarbonate, with important roles in cells physiology. Some CAN-coding genes were found in sea urchin genome, although only one involved in embryonic skeletogenesis was described in Paracentrotus lividus. Here, we investigated gene expression patterns of P. lividus embryos cultured in the presence of acetazolamide (AZ), a CAN inhibitor, to combine morphological defects with their molecular underpinning. CAN inhibition blocked skeletogenesis, affected the spatial/temporal expression of some biomineralization-related genes, inhibited embryos swimming. A comparative analysis on the expression of 127 genes in control and 3 h/24 h AZ-treated embryos, using NanoString technology, showed the differential expression of genes encoding for structural/regulatory proteins, with different embryonic roles: biomineralization, transcriptional regulation, signalling, development and defence response. The study of the differentially expressed genes and the signalling pathways affected, besides in silico analyses and a speculative 'interactomic model', leads to predicting the presence of various CAN isoforms, possibly involved in different physiological processes/activities in sea urchin embryo, and their potential target genes/proteins. Our findings provide new valuable molecular data for further studies in several biological fields: developmental biology (biomineralization, axes patterning), cell differentiation (neural development) and drug toxicology (AZ effects on embryos/tissues).

Assessing the eco-compatibility of new generation sunscreen products through a combined microscopic-molecular approach

There is now unequivocal evidence that sunscreen can severely affect marine ecosystems. However, so far, most studies have focused on the impact of single sunscreen ingredients rather than on the whole sunscreen products, which are released into the marine environment. In the present work, we investigated the ecological impact of six formulations, which represent the "new generation" organic UV filters such as diethylamino hydroxybenzoyl hexyl benzoate (DHHB), methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), ethylhexyl triazone (EHT), and bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT), which are progressively replacing the "old generation" organic UV filters (e.g., oxybenzone, octinoxate) banned in several countries of the world. The six formulations tested were characterized by a different combination of ingredients, on a model species particularly sensitive to environmental alterations: the sea urchin, Paracentrotus lividus. We investigated the sea urchin responses both in terms of gene expression and anomalies in embryonic development. We found that all sunscreen products containing only MBBT, DHHB, BEMT, and EHT as UV filters, are more eco-compatible than those also containing also ES, or other ingredients such as emollients and texturizing compounds, which may act synergistically causing molecular stress, morphological anomalies, and ultimately possible death. Overall, the results presented here provide new insights on the effects of sunscreen products based on "new generation" UV filters, and highlights the urgency of testing complete formulations, rather than just specific UV filters to ascertain the eco-compatibility of sunscreen products, to effectively minimize their impact on marine ecosystems.

Gene Expression Analysis of the Stress Response to Lithium, Nickel, and Zinc in Paracentrotus lividus Embryos

Many anthropogenic pollutants such as metals are discharged into the marine environment through modern sources. Among these, lithium (Li), nickel (Ni), and zinc (Zn) can interfere with biological processes in many organisms when their concentration rises. These metals are toxic to sea urchin embryos, affecting their development. Indeed, animal/vegetal and dorso/ventral embryonic axes are differently perturbed: Li is a vegetalizing agent, Ni can disrupt dorso-ventral axis, Zn can be animalizing. To address the molecular response adopted by embryos to cope with these metals or involved in the gene networks regulating embryogenesis, and to detect new biomarkers for evaluating hazards in polluted environments in a well-known in vivo model, we applied a high-throughput screening approach to sea urchin embryos. After fertilization, Paracentrotus lividus embryos were exposed to Li, Ni, and Zn for 24/48 h. At both endpoints, RNAs were analyzed by NanoString nCounter technology. By in silico analyses, we selected a panel of 127 transcripts encoding for regulatory and structural proteins, ranked in categories: Apoptosis, Defense, Immune, Nervous, Development, and Biomineralization. The data analysis highlighted the dysregulation of many genes in a metal-dependent manner. A functional annotation analysis was performed by the KEEG Orthology database. This study provides a platform for research on metals biomarkers in sea urchins.

A preliminary gene expression analysis on Paracentrotus lividus embryos exposed to UVB, Cadmium and their combination

Paracentrotus lividus is a Mediterranean and Eastern Atlantic sea urchin species, very sensitive to chemical and physical environmental changes and widely used in eco-toxicological studies. Here, we applied a high throughput screening approach on P. lividus embryos exposed to UVB radiation (UV), Cadmium Chloride (Cd) and their combination (Cd/UV), to deeply characterize the molecular responses adopted by embryos to cope with these stressors. in vitro eco-toxicological assays were performed by exposing embryos to Cd (10-4 M) soon after fertilization, to UV (200 and 400J/m2) at early stage of development, while in co-exposure experiments, Cd-exposed embryos were irradiated with UV at 200 J/m2. By NanoString nCounter technology, custom-made probes were developed and hybridized on total RNA extracted from exposed embryos at 51h after fertilization. By in silico analyses, we selected and retrieved at the NCBI nucleotide database a panel of P. lividus transcripts encoding for many regulatory and structural proteins that we ranked in categories, i.e., Apoptosis, Biomineralization, Defense, Development, Immunity, Signaling and Transcription Factors. The analysis of 127 transcripts highlighted the dysregulation of many genes, some specifically activated to cope with stress agents, others involved in the complex molecular network of genes that regulate embryo development. We revealed the downregulation of Biomineralization and Development genes and the upregulation of Defensive genes in Cd and Cd/UV embryos. Our approach, using sea urchin embryo as an in vivomodel, contributes to advance our knowledge about cellular responses to UV, Cd and their combination.

Diatom-Derived Polyunsaturated Aldehydes Activate Similar Cell Death Genes in Two Different Systems: Sea Urchin Embryos and Human Cells

Programmed cell death, such as apoptosis and autophagy, are key processes that are activated early on during development, leading to remodelling in embryos and homeostasis in adult organisms. Genomic conservation of death factors has been largely investigated in the animal and plant kingdoms. In this study, we analysed, for the first time, the expression profile of 11 genes involved in apoptosis (extrinsic and intrinsic pathways) and autophagy in sea urchin Paracentrotus lividus embryos exposed to antiproliferative polyunsaturated aldehydes (PUAs), and we compared these results with those obtained on the human cell line A549 treated with the same molecules. We found that sea urchins and human cells activated, at the gene level, a similar cell death response to these compounds. Despite the evolutionary distance between sea urchins and humans, we observed that the activation of apoptotic and autophagic genes in response to cytotoxic compounds is a conserved process. These results give first insight on death mechanisms of P. lividus death mechanisms, also providing additional information for the use of this marine organism as a useful in vitro model for the study of cell death signalling pathways activated in response to chemical compounds.

Titanium dioxide nanoparticles temporarily influence the sea urchin immunological state suppressing inflammatory-relate gene transcription and boosting antioxidant metabolic activity

Titanium dioxide nanoparticles (TiO₂NPs) are revolutionizing biomedicine due to their potential application as diagnostic and therapeutic agents. However, the TiO₂NP immune-compatibility remains an open issue, even for ethical reasons. In this work, we investigated the immunomodulatory effects of TiO₂NPs in an emergent proxy to human non-mammalian model for in vitro basic and translational immunology: the sea urchin Paracentrotus lividus. To highlight on the new insights into the evolutionarily conserved intracellular signaling and metabolism pathways involved in immune-TiO₂NP recognition/interaction we applied a wide-ranging approach, including electron microscopy, biochemistry, transcriptomics and metabolomics. Findings highlight that TiO₂NPs interact with immune cells suppressing the expression of genes encoding for proteins involved in immune response and apoptosis (e.g. NF-κB, FGFR2, JUN, MAPK14, FAS, VEGFR, Casp8), and boosting the immune cell antioxidant metabolic activity (e.g. pentose phosphate, cysteine-methionine, glycine-serine metabolism pathways). TiO₂NP uptake was circumscribed to phagosomes/phagolysosomes, depicting harmless vesicular internalization. Our findings underlined that under TiO₂NP-exposure sea urchin innate immune system is able to control inflammatory signaling, excite antioxidant metabolic activity and acquire immunological tolerance, providing a new level of understanding of the TiO₂NP immune-compatibility that could be useful for the development in Nano medicines.

MITF: an evolutionarily conserved transcription factor in the sea urchin Paracentrotus lividus

Microphthalmia-associated transcription factor (MITF) is a member of MYC superfamily, associated with melanocyte cells, as it was discovered in depigmented mice. However, over the last years it was found to be involved in many cellular signaling pathways, among which oncogenesis, osteoclast differentiation, and stress response. In mammals, Mitf gene mutations can cause diverse syndromes affecting pigmentation of eyes or skin, bone defects and melanomas. As MITF protein homologs were also found in some invertebrates, we have isolated and characterized the MITF cDNAs from the sea urchin Paracentrotus lividus, referred to as Pl-Mitf. The in silico study of the secondary and tertiary structure of Pl-Mitf protein showed high conserved regions mostly lying in the DNA binding domain. To understand the degree of evolutionary conservation of MITF, a phylogenetic analysis was performed comparing the Pl-Mitf deduced protein with proteins from different animal species. Moreover, the analysis of temporal and spatial expression pattern of Pl-Mitf mRNA showed that it was expressed from the onset of gastrulation of the sea urchin embryo to the pluteus larva, specifically in primary mesenchymes cells (PMCs), the sea urchin skeletogenic cells, and in the forming archenteron, the larval gut precursor. In silico protein-protein interactions analysis was used to understand the association of MITF with other proteins. Our results put in evidence the conservation of the MITF protein among vertebrates and invertebrates and may provide new perspectives on the pathways underlying sea urchin development, even if further functional analyses are needed.

PI3K inhibition highlights new molecular interactions involved in the skeletogenesis of Paracentrotus lividus embryos

The sea urchin embryo develops a well-defined biomineralized endoskeleton, synthesized exclusively by the skeletogenic cells, supported by ectodermal cues for the correct skeleton patterning. The biomineralization process is tightly regulated via a hierarchical order of gene expression, including transcription and growth factors, biomineralization proteins. Recently, the role of kinases and intracellular signaling pathways in sea urchin skeletogenesis has been addressed, although the downstream components still remain unknown. In this study, we investigated the role of phosphatidylinositide 3-kinase (PI3K)-mediated signaling pathway in Paracentrotus lividus, to identify its genes/proteins targets. The effects of LY294002 (LY), a PI3K-specific inhibitor, were evaluated at morphological and molecular levels. Treatment with 40 μM LY from the blastula stage completely blocked skeleton deposition, which was reversed by wash out experiments. Besides, LY caused a slight delay in the tripartite gut development. Despite the skeleton absence, a few skeleton-specific proteins/mRNAs were regularly expressed and localized in LY-treated embryos, as shown for MSP130 and SM50 by immunofluorescence and in situ hybridization experiments. QPCR analyses showed that LY differently affected the expression of genes coding for other biomineralization proteins, transcription and growth factors. SM30 and carbonic anhydrase expression was severely downregulated, while almost all the transcription factors analyzed were upregulated. Based on the present results and in silico analyses, we propose an "interactomic" model simulating PI3K connections in P. lividus embryos. Our findings define a novel regulatory step in the embryonic skeletogenesis, and provide valuable molecular data for further studies on the role of PI3K signaling in invertebrate biomineralization.

First molecular evidence of the toxicogenetic effects of copper on sea urchin Paracentrotus lividus embryo development

Bioassays with sea urchin embryos are widely used to define the environmental quality of marine waters. Anomalies during embryogenesis are generally considered as end-points, whereas a toxigenomic approach, despite it is wide use in other species, is yet in its infancy. In the present study we evaluated toxigenic effects induced by copper on the sea urchin Paracentrotus lividus embryo, combining morphological observations with gene expression analysis. Many anthropogenic activities release copper in the marine environment, with harmful effects on aquatic organisms. In the present study P. lidivus embryos were exposed to different concentrations of copper (24, 36, 48 μg/L) and the activation of fifty specific marker genes, involved in different biological processes (stress, skeletogenesis, development/differentiation, detoxification) was investigated at early blastula, late gastrula and pluteus stage. At blastula stage no morphological anomalies were found, with early down-regulation of genes involved in development/differentiation and a moderate up-regulation of some detoxification genes. At gastrula stage a slight increase in developmental anomalies (up to 19% of malformed embryos) was followed by an increased number of targeted genes belonging to the same two classes, relative to the blastula stage. At pluteus stage morphological anomalies increased in a dose dependent manner. All the analyzed genes were strongly up-regulated, stress and skeletogenic genes showing a "late response" and almost all genes were targeted by copper at all the concentrations tested. The present study represents the first molecular report on the potential negative effect of copper on P. lividus embryos in the environment. Gene expression analysis should be considered as a promising tool for future environmental biomonitoring programs.

Noxious effects of the benthic diatoms Cocconeis scutellum and Diploneis sp. on sea urchin development: Morphological and de novo transcriptomic analysis

Diatoms are often the dominating group of benthic microalgae living on different types of bottom substrates. Their effects on invertebrate consumers is not well-documented. We here investigate the effects of feeding on another two benthic diatoms, Cocconeis scutellum and Diploneis sp., isolated from leaves of the seagrass Posidonia oceanica, on the sea urchin Paracentrotus lividus. Our results indicate a noxious effect on sea urchin embryos spawned from adults fed on Diploneis sp., with an increasing number of malformed embryos with respect to those spawned from adults fed on Ulva rigida (used as a feeding control). In contrast C. scutellum did not induce any morphological effect on embryos, similar to control non-diatom diets. Moreover, de novo obtained transcriptome indicated that oxidation-reduction process, translation, proton and electron transmembrane transport, ATP/RNA/GTP/heme/calcium and metal ion binding, NADH dehydrogenase activity, cytochrome c oxidase were affected by feeding of sea urchins on Diploneis sp. Our findings have considerable ecological significance considering that diatom biomass ingested by the sea urchin in these experiments is within the range of cell densities characterizing P. oceanica leaves where sea urchins live and spawn.

Identification of Cell Death Genes in Sea Urchin Paracentrotus lividus and Their Expression Patterns during Embryonic Development

Apoptosis and autophagy are fundamental mechanisms of programed cell death activated during protostome and deuterostome embryonic development, contributing to the creation and remodeling of different anatomical structures. Programed cell death has been investigated at morphological and biochemical levels, but there is a lack of information concerning gene expression of death factors during deuterostome embryonic development. In this study, we analyze the expression patterns of 13 genes involved in autophagy, extrinsic and intrinsic apoptosis during blastula, gastrula, and pluteus stages of the sea urchin Paracentrotus lividus embryonic development. Results suggested the occurrence of all death mechanisms investigated, highlighting the simultaneous involvement of apoptosis and autophagy during embryonic development. In particular, gastrula was the developmental stage where the majority of death genes were highly expressed. During gastrulation apoptotic processes are fundamental for tissue remodeling, such as cavity formation and removal of inner ectodermal cells. This is the first report that identifies a panel of cell death genes in the P. lividus genome and analyzes their expression variations during ontogenesis.

Molecular and Morphological Toxicity of Diatom-Derived Hydroxyacid Mixtures to Sea Urchin Paracentrotus lividus Embryos

Oxylipins such as polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) are signaling molecules derived from the oxidation of polyunsaturated fatty acids. They are common in diatoms that constitute a major group of microalgae in freshwater and oceanic ecosystems. Although HEPEs represent the most common oxylipins produced by diatoms, little information is available on their effects on marine invertebrates, and most of the information has been obtained by testing individual HEPEs. Our previous studies reported that four hydroxyacids, i.e., 5-, 9-, 11-, and 15-HEPE, were able to induce malformations and a marked developmental delay in sea urchin Paracentrotus lividus embryos, which had not been reported for other oxylipins. Here, we tested a mixture of 5-, 9-, 11-, and 15-HEPE at different concentrations for the first time. The results showed that mixtures of HEPEs have synergistic effects that are much more severe compared to those of individual HEPEs: The HEPE mixtures induced malformations in sea urchin embryos at lower concentrations. Increasing HEPE mixture concentrations induced a marked increase in the number of delayed embryos, until all embryos were delayed at the highest concentration tested. At the molecular level, the HEPE mixtures induced variations in the expression of 50 genes involved in different functional processes, mainly down-regulating these genes at the earliest stages of embryonic development. These findings are ecologically significant, considering that during diatom blooms, sea urchins could accumulate HEPEs in concentrations comparable to those tested in the present study.

Toxicity of diatom-derived polyunsaturated aldehyde mixtures on sea urchin Paracentrotus lividus development

Diatom-derived polyunsaturated aldehydes (PUAs), decadienal, heptadienal and octadienal, derive from the oxidation of fatty acids and have cytotoxic and anticancer effects. PUAs, tested separately, induce malformations in sea urchin Paracentrotus lividus embryos. Decadienal induces the worst malformations and lowest survival rates. Interestingly, decadienal, heptadienal and octadienal place in motion several genes to counteract their negative effects. To date, no studies are available reporting on the effects of PUA mixtures on marine invertebrates. Here we test binary and ternary mixtures on embryonic development of P. lividus. Our findings demonstrate that mixtures of PUAs act (i) at morphological level in synergistic way, being much more severe compared to individual PUAs; (ii) at molecular level also reveal an additive effect, affecting almost all fifty genes, previously tested using individual PUAs. This study is relevant from an ecological point of view since diatoms are a major food source for both pelagic and benthic organisms. This work opens new perspectives for understanding the molecular mechanisms that marine organisms use in reacting to environmental natural toxin mixtures such as diatom PUAs.

Nickel toxicity in P. lividus embryos: Dose dependent effects and gene expression analysis

Many industrial activities release Nickel (Ni) in the environment with harmful effects for terrestrial and marine organisms. Despite many studies on the mechanisms of Ni toxicity are available, the understanding about its toxic effects on marine organisms is more limited. We used Paracentrotus lividus as a model to analyze the effects on the stress pathways in embryos continuously exposed to different Ni doses, ranging from 0.03 to 0.5 mM. We deeply examined the altered embryonic morphologies at 24 and 48 h after Ni exposure. Some different phenotypes have been classified, showing alterations at the expenses of the dorso-ventral axis as well as the skeleton and/or the pigment cells. At the lowest dose used, Ni mainly induced a multi-spicule phenotype observed at 24 h after treatment. On the contrary, at the highest dose of Ni (0.5 mM), 90% of embryos showed no skeleton and no pigment cells. Therefore, we focused on this dose to study protein and gene expression patterns at 24 and 48 h after exposure. Among the proteins analyzed, i.e. p38MAPK, Grp78 and Mn-SOD, only p38MAPK was induced by Ni treatment. Moreover, we analyzed the mRNA profiles of a pool of genes that are involved in stress response and in development mechanisms, i.e. the transcription factors Pl-NFkB and Pl-FOXO; a marker of DNA repair, Pl-XPB/ERCC3; a mitogen-activated protein kinase (MAPK), Pl-p38; an ER stress gene, Pl-grp78; an adapter protein, Pl-14-3-3ε; two markers of pigment cells, Pl-PKS1 and Pl-gcm. The spatial expression of mesenchymal marker genes has been evaluated in Ni-treated embryos at both 24 and 48 h after exposure. Our results indicated that Ni acts at several levels in P. lividus sea urchin, by affecting embryo development, influencing the embryonic immune response and activating stress response pathways to counteract the suffered injury and to promote embryos surviving.

Response to metals treatment of Fra1, a member of the AP-1 transcription factor family, in P. lividus sea urchin embryos

Lithium (Li), Nickel (Ni), and Zinc (Zn) are metals normally present in the seawater, although they can have adverse effects on the marine ecosystem at high concentrations by interfering with many biological processes. These metals are toxic for sea urchin embryos, affecting their morphology and developmental pathways. In particular, they perturb differently the correct organization of the embryonic axes (animal-vegetal, dorso-ventral): Li is a vegetalizing agent and Ni disrupts the dorso-ventral axis, while Zn has an animalizing effect. To deeply address the response of Paracentrotus lividus embryos to these metals, we studied the expression profiling of Pl-Fra transcription factor (TF), relating it to Pl-jun, a potential partner for AP-1 complex formation, and to Pl-MT, known to be an AP-1 target and to have a protective role against heavy metals. The AP-1 TFs are found throughout the animal kingdom and are involved in many cellular events, i.e. cell proliferation and differentiation, immune and stress responses, cancer growth. Here, we isolated the complete Pl-Fra cDNA and showed that Pl-Fra transcript, already present in the unfertilized eggs, was newly synthesized from the blastula stage, while its spatial distribution was mainly observed in skeletogenic cells, similarly to Pl-jun. Interestingly, Pl-Fra expression was induced by the different metals and the induction kinetics revealed its persistent expression during treatments. Moreover, its temporal and spatial behavior in response to the three metals was comparable to that of Pl-jun and Pl-MT. The understanding of AP-1 functions in invertebrates may provide new knowledge about the mechanisms of response to metal injuries, as well as it might lead to acknowledge the TFs as new type of biomarkers for the evaluation of hazards in polluted environment.

Toxigenic effects of two benthic diatoms upon grazing activity of the sea urchin: morphological, metabolomic and de novo transcriptomic analysis

Diatoms are unicellular algae playing a key role as photosynthetic organisms in the world's ocean food webs. The chemical ecology of planktonic diatoms is well documented, but few studies have reported on the effects of benthic diatoms on their consumers, also due to difficulties in the collection, quantification and massive culturing of benthic species. Here for the first time we investigate the effects of feeding on two abundantly occurring benthic diatoms, Nanofrustulum shiloi and Cylindrotheca closterium, isolated from the leaves of the seagrass Posidonia oceanica, on the sea urchin Paracentrotus lividus. Adult P. lividus were fed for one month on diets of either one of the two diatoms and on the green alga Ulva rigida, used as a feeding control. By combining morphological, metabolomic and de novo transcriptomic approaches, we demonstrate toxigenic effect on embryos generated by females fed with these benthic diatoms. Furthermore, chemical analysis reveal the presence of polyunsaturated aldehydes only for N. shiloi, and a high production of other oxylipins (cytotoxic compounds on their grazers and on cancer cell lines) for both diatoms, including some additional peaks not correlated to the canonic oxylipins commonly observed in planktonic diatoms. These findings open new perspectives in the study of diatom secondary metabolites influencing their grazers.

Gadolinium perturbs expression of skeletogenic genes, calcium uptake and larval development in phylogenetically distant sea urchin species

Chelates of Gadolinium (Gd), a lanthanide metal, are employed as contrast agents for magnetic resonance imaging and are released into the aquatic environment where they are an emerging contaminant. We studied the effects of environmentally relevant Gd concentrations on the development of two phylogenetically and geographically distant sea urchin species: the Mediterranean Paracentrotus lividus and the Australian Heliocidaris tuberculata. We found a general delay of embryo development at 24h post-fertilization, and a strong inhibition of skeleton growth at 48h. Total Gd and Ca content in the larvae showed a time- and concentration-dependent increase in Gd, in parallel with a reduction in Ca. To investigate the impact of Gd on the expression of genes involved in the regulation of skeletogenesis, we performed comparative RT-PCR analysis and found a misregulation of several genes involved in the skeletogenic and left-right axis specification gene regulatory networks. Species-specific differences in the biomineralization response were evident, likely due to differences in the skeletal framework of the larvae and the amount of biomineral produced. Our results highlight the hazard of Gd for marine organisms.

Developmental effects of the protein kinase inhibitor kenpaullone on the sea urchin embryo

The selection and validation of bioactive compounds require multiple approaches, including in-depth analyses of their biological activity in a whole-animal context. We exploited the sea urchin embryo in a rapid, medium-scale range screening to test the effects of the small synthetic kinase inhibitor kenpaullone. We show that sea urchin embryos specifically respond to this molecule depending on both dose and timing of administration. Phenotypic effects of kenpaullone are not immediately visible, since this molecule affects neither the fertilization nor the spatial arrangement of blastomeres at early developmental stages. Nevertheless, kenpaullone exposure from the beginning of embryogenesis profoundly perturbs specification, detachment from the epithelium, and migration of the primary mesenchyme cells, thus affecting the whole embryonic epithelial mesenchymal transition process. Our results reaffirm the sea urchin embryo as an excellent and sensitive in vivo system, which provides straightforward and rapid response to external stimuli.

New inter-correlated genes targeted by diatom-derived polyunsaturated aldehydes in the sea urchin Paracentrotus lividus

The marine environment is continually subjected to the action of stressors (including natural toxins), which represent a constant danger for benthic communities. In the present work using network analysis we identified ten genes on the basis of associated functions (FOXA, FoxG, GFI-1, nodal, JNK, OneCut/Hnf6, TAK1, tcf4, TCF7, VEGF) in the sea urchin Paracentrotus lividus, having key roles in different processes, such as embryonic development and asymmetry, cell fate specification, cell differentiation and morphogenesis, and skeletogenesis. These genes are correlated with three HUB genes, Foxo, Jun and HIF1A. Real Time qPCR revealed that during sea urchin embryonic development the expression levels of these genes were modulated by three diatom-derived polyunsaturated aldehydes (PUAs), decadienal, heptadienal and octadienal. Our findings show how changes in gene expression levels may be used as an early indicator of stressful conditions in the marine environment. The identification of key genes and the molecular pathways in which they are involved represents a fundamental tool in understanding how marine organisms try to afford protection against toxicants, to avoid deleterious consequences and irreversible damages. The genes identified in this work as targets for PUAs can be considered as possible biomarkers to detect exposure to different environmental pollutants.

A sea urchin in vivo model to evaluate Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) is an evolutionarily conserved cellular program, which is a prerequisite for the metastatic cascade in carcinoma progression. Here, we evaluate the EMT process using the sea urchin Paracentrotus lividus embryo. In sea urchin embryos, the earliest EMT event is related to the acquisition of a mesenchymal phenotype by the spiculogenetic primary mesenchyme cells (PMCs) and their migration into the blastocoel. We investigated the effect of inhibiting the epidermal growth factor (EGF) signaling pathway on this process, and we observed that mesenchyme cell differentiation was blocked. In order to extend and validate our studies, we investigated the migratory capability and the level of potential epidermal growth factor receptor (EGFr) targets in a breast cancer cell line after EGF modulation. Altogether, our data highlight the sensitivity of the sea urchin embryo to anti-EMT drugs and pinpoint the sea urchin embryo as a valuable in vivo model system for studying EMT and the screening of anti-EMT candidates.

New insights into negative effects of lithium on sea urchin Paracentrotus lividus embryos

The diffuse use of lithium in a number of industrial processes has produced a significant contamination of groundwater and surface water with it. The increased use of lithium has generated only scarce studies on its concentrations in ambient waters and on its effects on aquatic organisms. Only few contributions have focused on the toxicity of lithium in marine organisms (such as marine animals, algae and vegetables), showing that the toxic effect depends on the animal species. In the present study we describe the morphological and the molecular effects of lithium chloride (LiCl), using the sea urchin Paracentrotus lividus as a model organism. We show that LiCl, if added to the eggs before fertilization, induces malformations in the embryos in a dose-dependent manner. We have also followed by RT qPCR the expression levels of thirty seven genes (belonging to different classes of functional processes, such as stress, development, differentiation, skeletogenesis and detoxifications) to identify the molecular targets of LiCl. This study opens new perspectives for the understanding of the mechanism of action of lithium on marine organisms. The findings may also have relevance outside the world of marine organisms since lithium is widely prescribed for the treatment of human bipolar disorders.

Characterization of an Alpha Type Carbonic Anhydrase from Paracentrotus lividus Sea Urchin Embryos

Carbonic anhydrases (CA) are zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide to bicarbonate. In the sea urchin, CA has a role in the formation of the calcitic skeleton during embryo development. Here, we report a newly identified mRNA sequence from embryos of the sea urchin Paracentrotus lividus, referred to as Pl-can. The complete coding sequence was identified with the aid of both EST databases and experimental procedures. Pl-CAN is a 447 aa-long protein, with an estimated molecular mass of 48.5 kDa and an isoelectric point of 6.83. The in silico study of functional domains showed, in addition to the alpha type CA-specific domain, the presence of an unexpected glycine-rich region at the N-terminal of the molecule. This is not found in any other species described so far, but probably it is restricted to the sea urchins. The phylogenetic analysis indicated that Pl-CAN is evolutionarily closer to human among chordates than to other species. The putative role(s) of the identified domains is discussed. The Pl-can temporal and spatial expression profiles, analyzed throughout embryo development by comparative qPCR and whole-mount in situ hybridization (WMISH), showed that Pl-can mRNA is specifically expressed in the primary mesenchyme cells (PMC) of the embryo and levels increase along with the growth of the embryonic skeleton, reaching a peak at the pluteus stage. A recombinant fusion protein was produced in E. coli and used to raise specific antibodies in mice recognized the endogenous Pl-CAN by Western blot in embryo extracts from gastrula and pluteus.

Subtle reproductive impairment through nitric oxide-mediated mechanisms in sea urchins from an area affected by harmful algal blooms

The health of the sea urchin Paracentrotus lividus, a key species in the Mediterranean Sea, is menaced by several pressures in coastal environments. Here, we aimed at assessing the reproductive ability of apparently healthy P. lividus population in a marine protected area affected by toxic blooms of Ostreospsis cf. ovata. Wide-ranging analyses were performed in animals collected prior to and during the bloom, as well as at several times thereafter, during the reproductive season. Adults showed a low fertilization rate, along with high nitric oxide (NO) levels in the gonads and the nitration of the major yolk protein toposome, which is an important player in sea urchin development. Serious developmental anomalies were observed in the progeny, which persist several months after the bloom. NO levels were high in the different developmental stages, which also showed variations in the transcription of several genes that were found to be directly or indirectly modulated by NO. These results highlight subtle but important reproductive flaws transmitted from the female gonads to the offspring with the NO involvement. Despite a recovery along time after the bloom, insidious damages can be envisaged in the local sea urchin population, with possible reverberation on the whole benthic system.

First Morphological and Molecular Evidence of the Negative Impact of Diatom-Derived Hydroxyacids on the Sea Urchin Paracentrotus lividus

Oxylipins (including polyunsaturated aldehydes [PUAs], hydoxyacids, and epoxyalcohols) are the end-products of a lipoxygenase/hydroperoxide lyase metabolic pathway in diatoms. To date, very little information is available on oxylipins other than PUAs, even though they represent the most common oxylipins produced by diatoms. Here, we report, for the first time, on the effects of 2 hydroxyacids, 5- and 15-HEPE, which have never been tested before, using the sea urchin Paracentrotus lividus as a model organism. We show that HEPEs do induce developmental malformations but at concentrations higher when compared with PUAs. Interestingly, HEPEs also induced a marked developmental delay in sea urchin embryos, which has not hitherto been reported for PUAs. Recovery experiments revealed that embryos do not recover following treatment with HEPEs. Finally, we report the expression levels of 35 genes (involved in stress, development, differentiation, skeletogenesis, and detoxification processes) to identify the molecular targets affected by HEPEs. We show that the 2 HEPEs have very few common molecular targets, specifically affecting different classes of genes and at different times of development. In particular, 15-HEPE switched on fewer genes than 5-HEPE, upregulating mainly stress-related genes at a later pluteus stage of development. 5-HEPE was stronger than 15-HEPE, targeting 24 genes, mainly at the earliest stages of embryo development (at the blastula and swimming blastula stages). These findings highlight the differences between HEPEs and PUAs and also have important ecological implications because many diatom species do not produce PUAs, but rather these other chemicals are derived from the oxidation of fatty acids.

Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: A quantitative proteomics approach

Marine bioadhesives have unmatched performances in wet environments, being an inspiration for biomedical applications. In sea urchins specialized adhesive organs, tube feet, mediate reversible adhesion, being composed by a disc, producing adhesive and de-adhesive secretions, and a motile stem. After tube foot detachment, the secreted adhesive remains bound to the substratum as a footprint. Sea urchin adhesive is composed by proteins and sugars, but so far only one protein, Nectin, was shown to be over-expressed as a transcript in tube feet discs, suggesting its involvement in sea urchin adhesion. Here we use high-resolution quantitative mass-spectrometry to perform the first study combining the analysis of the differential proteome of an adhesive organ, with the proteome of its secreted adhesive. This strategy allowed us to identify 163 highly over-expressed disc proteins, specifically involved in sea urchin reversible adhesion; to find that 70% of the secreted adhesive components fall within five protein groups, involved in exocytosis and microbial protection; and to provide evidences that Nectin is not only highly expressed in tube feet discs but is an actual component of the adhesive. These results give an unprecedented insight into the molecular mechanisms underlying sea urchin adhesion, and opening new doors to develop wet-reliable, reversible, and ecological biomimetic adhesives.

SIGNIFICANCE

Sea urchins attach strongly but in a reversible manner to substratum, being a valuable source of inspiration for industrial and biomedical applications. Yet, the molecular mechanisms governing reversible adhesion are still poorly studied delaying the engineering of biomimetic adhesives. We used the latest mass spectrometry techniques to analyze the differential proteome of an adhesive organ and the proteome of its secreted adhesive, allowing us to uncover the key players in sea urchin reversible adhesion. We demonstrate, that Nectin, a protein previously pointed out as potentially involved in sea urchin adhesion, is not only highly expressed in tube feet discs, but is a genuine component of the secreted adhesive.

Experimental Approach Reveals the Role of alx1 in the Evolution of the Echinoderm Larval Skeleton

Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acquisition of the larval skeleton. In the present study, we compared expression patterns of Alx genes among echinoderm classes to further explore the factors involved in the acquisition of a larval skeleton. We found that the alx1 gene, originally described as crucial for sea urchin skeletogenesis, may have also played an essential role in the evolution of the larval skeleton. Unlike those echinoderms that have a larval skeleton, we found that alx1 of starfish was barely expressed in early larvae that have no skeleton. When alx1 overexpression was induced via injection of alx1 mRNA into starfish eggs, the expression patterns of certain genes, including those possibly involved in skeletogenesis, were altered. This suggested that a portion of the skeletogenic program was induced solely by alx1. However, we observed no obvious external phenotype or skeleton. We concluded that alx1 was necessary but not sufficient for the acquisition of the larval skeleton, which, in fact, requires several genetic events. Based on these results, we discuss how the larval expression of alx1 contributed to the acquisition of the larval skeleton in the putative ancestral lineage of echinoderms.

Large-scale gene expression study in the ophiuroid Amphiura filiformis provides insights into evolution of gene regulatory networks

Background

The evolutionary mechanisms involved in shaping complex gene regulatory networks (GRN) that encode for morphologically similar structures in distantly related animals remain elusive. In this context, echinoderm larval skeletons found in brittle stars and sea urchins provide an ideal system. Here, we characterize for the first time the development of the larval skeleton in the ophiuroid Amphiura filiformis and compare it systematically with its counterpart in sea urchin.

Results

We show that ophiuroids and euechinoids, that split at least 480 Million years ago (Mya), have remarkable similarities in tempo and mode of skeletal development. Despite morphological and ontological similarities, our high-resolution study of the dynamics of genetic regulatory states in A. filiformis highlights numerous differences in the architecture of their underlying GRNs. Importantly, the A.filiformispplx, the closest gene to the sea urchin double negative gate (DNG) repressor pmar1, fails to drive the skeletogenic program in sea urchin, showing important evolutionary differences in protein function. hesC, the second repressor of the DNG, is co-expressed with most of the genes that are repressed in sea urchin, indicating the absence of direct repression of tbr, ets1/2, and delta in A. filiformis. Furthermore, the absence of expression in later stages of brittle star skeleton development of key regulatory genes, such as foxb and dri, shows significantly different regulatory states.

Conclusion

Our data fill up an important gap in the picture of larval mesoderm in echinoderms and allows us to explore the evolutionary implications relative to the recently established phylogeny of echinoderm classes. In light of recent studies on other echinoderms, our data highlight a high evolutionary plasticity of the same nodes throughout evolution of echinoderm skeletogenesis. Finally, gene duplication, protein function diversification, and cis-regulatory element evolution all contributed to shape the regulatory program for larval skeletogenesis in different branches of echinoderms.

Electronic supplementary material

The online version of this article (doi:10.1186/s13227-015-0039-x) contains supplementary material, which is available to authorized users.

Heterologous expression of newly identified galectin-8 from sea urchin embryos produces recombinant protein with lactose binding specificity and anti-adhesive activity

Galectin family members specifically bind beta-galactoside derivatives and are involved in different cellular events, including cell communication, signalling, apoptosis, and immune responses. Here, we report a tandem-repeat type galectin from the Paracentrotus lividus sea urchin embryo, referred to as Pl-GAL-8. The 933nt sequence encodes a protein of 34.73 kDa, containing the conserved HFNPRF and WGxExR motifs in the two highly similar carbohydrate-recognition domains (CRD). The three-dimensional protein structure model of the N-CRD confirms the high evolutionary conservation of carbohydrate binding sites. The temporal gene expression is regulated during development and transcripts localize at the tip of the archenteron at gastrula stage, in a subset of the secondary mesenchyme cells that differentiate into blastocoelar (immune) cells. Functional studies using a recombinant Pl-GAL-8 expressed in bacteria demonstrate its hemo-agglutinating activity on human red blood cells through the binding to lactose, as well as its ability in inhibiting the adhesion of human Hep-G2 cells to the substrate. The recent implications in autoimmune diseases and inflammatory disorders make Gal-8 an attractive candidate for therapeutic purposes. Our results offer a solid basis for addressing the use of the new Pl-GAL-8 in functional and applicative studies, respectively in the developmental and biomedical fields.

Mechanisms of the epithelial-to-mesenchymal transition in sea urchin embryos

Sea urchin mesenchyme is composed of the large micromere-derived spiculogenetic primary mesenchyme cells (PMC), veg2-tier macromere-derived non-spiculogenetic mesenchyme cells, the small micromere-derived germ cells, and the macro- and mesomere-derived neuronal mesenchyme cells. They are formed through the epithelial-to-mesenchymal transition (EMT) and possess multipotency, except PMCs that solely differentiate larval spicules. The process of EMT is associated with modification of epithelial cell surface property that includes loss of affinity to the apical and basal extracellular matrices, inter-epithelial cell adherens junctions and epithelial cell surface-specific proteins. These cell surface structures and molecules are endocytosed during EMT and utilized as initiators of cytoplasmic signaling pathways that often initiate protein phosphorylation to activate the gene regulatory networks. Acquisition of cell motility after EMT in these mesenchyme cells is associated with the expression of proteins such as Lefty, Snail and Seawi. Structural simplicity and genomic database of this model will further promote detailed EMT research.

Titanium dioxide nanoparticles stimulate sea urchin immune cell phagocytic activity involving TLR/p38 MAPK-mediated signalling pathway

Titanium dioxide nanoparticles (TiO2NPs) are one of the most widespread-engineered particles in use for drug delivery, cosmetics, and electronics. However, TiO2NP safety is still an open issue, even for ethical reasons. In this work, we investigated the sea urchin Paracentrotus lividus immune cell model as a proxy to humans, to elucidate a potential pathway that can be involved in the persistent TiO2NP-immune cell interaction in vivo. Morphology, phagocytic ability, changes in activation/inactivation of a few mitogen-activated protein kinases (p38 MAPK, ERK), variations of other key proteins triggering immune response (Toll-like receptor 4-like, Heat shock protein 70, Interleukin-6) and modifications in the expression of related immune response genes were investigated. Our findings indicate that TiO2NPs influence the signal transduction downstream targets of p38 MAPK without eliciting an inflammatory response or other harmful effects on biological functions. We strongly recommend sea urchin immune cells as a new powerful model for nano-safety/nano-toxicity investigations without the ethical normative issue.

A member of the Tlr family is involved in dsRNA innate immune response in Paracentrotus lividus sea urchin

The innate immune response involves proteins such as the membrane receptors of the Toll-like family (TLRs), which trigger different intracellular signalling pathways that are dependent on specific stimulating molecules. In sea urchins, TLR proteins are encoded by members of a large multigenic family composed of 60-250 genes in different species. Here, we report a newly identified mRNA sequence encoding a TLR protein (referred to as Pl-Tlr) isolated from Paracentrotus lividus immune cells. The partial protein sequence contained the conserved Toll/IL-1 receptor (TIR) domain, the transmembrane domain and part of the leucine repeats. Phylogenetic analysis of the Pl-Tlr protein was accomplished by comparing its sequence with those of TLRs from different classes of vertebrates and invertebrates. This analysis was suggestive of an evolutionary path that most likely represented the course of millions of years, starting from simple organisms and extending to humans. Challenge of the sea urchin immune system with poly-I:C, a chemical compound that mimics dsRNA, caused time-dependent Pl-Tlr mRNA up-regulation that was detected by QPCR. In contrast, bacterial LPS injury did not affect Pl-Tlr transcription. The study of the Tlr genes in the sea urchin model system may provide new perspectives on the role of Tlrs in the invertebrate immune response and clues concerning their evolution in a changing world.

Maternal Exposure to Cadmium and Manganese Impairs Reproduction and Progeny Fitness in the Sea Urchin Paracentrotus lividus

Metal contamination represents one of the major sources of pollution in marine environments. In this study we investigated the short-term effects of ecologically relevant cadmium and manganese concentrations (10(-6) and 3.6 x 10(-5) M, respectively) on females of the sea urchin Paracentrotus lividus and their progeny, reared in the absence or presence of the metal. Cadmium is a well-known heavy metal, whereas manganese represents a potential emerging contaminant, resulting from an increased production of manganese-containing compounds. The effects of these agents were examined on both P. lividus adults and their offspring following reproductive state, morphology of embryos, nitric oxide (NO) production and differential gene expression. Here, we demonstrated that both metals differentially impaired the fertilization processes of the treated female sea urchins, causing modifications in the reproductive state and also affecting NO production in the ovaries. A detailed analysis of the progeny showed a high percentage of abnormal embryos, associated to an increase in the endogenous NO levels and variations in the transcriptional expression of several genes involved in stress response, skeletogenesis, detoxification, multi drug efflux processes and NO production. Moreover, we found significant differences in the progeny from females exposed to metals and reared in metal-containing sea water compared to embryos reared in non-contaminated sea water. Overall, these results greatly expanded previous studies on the toxic effects of metals on P. lividus and provided new insights into the molecular events induced in the progeny of sea urchins exposed to metals.

Stress response to cadmium and manganese in Paracentrotus lividus developing embryos is mediated by nitric oxide

Increasing concentrations of contaminants, often resulting from anthropogenic activities, have been reported to occur in the marine environment and affect marine organisms. Among these, the metal ions cadmium and manganese have been shown to induce developmental delay and abnormalities, mainly reflecting skeleton elongation perturbation, in the sea urchin Paracentrotus lividus, an established model for toxicological studies. Here, we provide evidence that the physiological messenger nitric oxide (NO), formed by l-arginine oxidation by NO synthase (NOS), mediates the stress response induced by cadmium and manganese in sea urchins. When NO levels were lowered by inhibiting NOS, the proportion of abnormal plutei increased. Quantitative expression of a panel of 19 genes involved in stress response, skeletogenesis, detoxification and multidrug efflux processes was followed at different developmental stages and under different conditions: metals alone, metals in the presence of NOS inhibitor, NO donor and NOS inhibitor alone. These data allowed the identification of different classes of genes whose metal-induced transcriptional expression was directly or indirectly mediated by NO. These results open new perspectives on the role of NO as a sensor of different stress agents in sea urchin developing embryos.

Accumulation and embryotoxicity of polystyrene nanoparticles at early stage of development of sea urchin embryos Paracentrotus lividus

Nanoplastic debris, resulted from runoff and weathering breakdown of macro- and microplastics, represents an emerging concern for marine ecosystems. The aim of the present study was to investigate disposition and toxicity of polystyrene nanoparticles (NPs) in early development of sea urchin embryos (Paracentrotus lividus). NPs with two different surface charges where chosen, carboxylated (PS-COOH) and amine (PS-NH2) polystyrene, the latter being a less common variant, known to induce cell death in several in vitro cell systems. NPs stability in natural seawater (NSW) was measured while disposition and embryotoxicity were monitored within 48 h of postfertilization (hpf). Modulation of genes involved in cellular stress response (cas8, 14-3-3ε, p-38 MAPK, Abcb1, Abcc5) was investigated. PS-COOH forms microaggregates (PDI > 0.4) in NSW, whereas PS-NH2 results are better dispersed (89 ± 2 nm) initially, though they also aggregated partially with time. Their respectively anionic and cationic nature was confirmed by ζ-potential measurements. No embryotoxicity was observed for PS-COOH up to 50 μg mL(-1) whereas PS-NH2 caused severe developmental defects (EC50 3.85 μg mL(-1) 24 hpf and EC50 2.61 μg mL(-1) 48 hpf). PS-COOH accumulated inside embryo's digestive tract while PS-NH2 were more dispersed. Abcb1 gene resulted up-regulated at 48 hpf by PS-COOH whereas PS-NH2 induced cas8 gene at 24 hpf, suggesting an apoptotic pathway. In line with the results obtained with the same PS NPs in several human cell lines, also in sea urchin embryos, differences in surface charges and aggregation in seawater strongly affect their embryotoxicity.

Molecular response to toxic diatom-derived aldehydes in the sea urchin Paracentrotus lividus

Diatoms are dominant photosynthetic organisms in the world’s oceans and represent a major food source for zooplankton and benthic filter-feeders. However, their beneficial role in sustaining marine food webs has been challenged after the discovery that they produce secondary metabolites, such as polyunsaturated aldehydes (PUAs), which negatively affect the reproductive success of many invertebrates. Here, we report the effects of two common diatom PUAs, heptadienal and octadienal, which have never been tested before at the molecular level, using the sea urchin, Paracentrotus lividus, as a model organism. We show that both PUAs are able to induce teratogenesis (i.e., malformations), as already reported for decadienal, the better-studied PUA of this group. Moreover, post-recovery experiments show that embryos can recover after treatment with all three PUAs, indicating that negative effects depend both on PUA concentrations and the exposure time of the embryos to these metabolites. We also identify the time range during which PUAs exert the greatest effect on sea urchin embryogenesis. Finally, we report the expression levels of thirty one genes (having a key role in a broad range of functional responses, such as stress, development, differentiation, skeletogenesis and detoxification processes) in order to identify the common targets affected by PUAs and their correlation with morphological abnormalities. This study opens new perspectives for understanding how marine organisms afford protection from environmental toxicants through an integrated network of genes.

Time- and dose-dependent gene expression in sea urchin embryos exposed to UVB

The increase of UVB radiation reaching marine environment has harmful effects on living organisms. Paracentrotus lividus sea urchin embryos living in shallow water are exposed to radiations, providing a good model for studying the molecular mechanisms activated upon UV stress. Here, we report the modulated time- and dose-dependent expression of six genes, known to be involved in stress response, in embryos exposed at cleavage to 400 and 800 J/m(2) UVB, and collected at early (morula) and later (gastrula) stages. We analyzed their mRNA levels by QPCR and found that Pl-14-3-3 showed a dose-dependent induction, both early and late in development; Pl-c-jun was up-regulated proportionally to the UVB dose at early stages and only at 800 J/m(2) UVB at later stages; Pl-XPB-ERCC3, Pl-MT and Pl-NF-kB were highly up-regulated later in development at the high dose, with the exception of Pl-XPB-ERCC3 whose mRNA levels were high also at the lower dose; Pl-FOXO expression was not affected by UVB radiation. We believe that the identification of UVB-responsive genes in irradiated sea urchin embryos, reported for the first time in this study, will be helpful for the understanding of the involved molecular pathways. The correlation between the impaired morphogenesis, affecting endo-mesoderm differentiation, and gene modulations described herewith is also discussed.

Tissue-specificity and phylogenetics of Pl-MT mRNA during Paracentrotus lividus embryogenesis

Metallothioneins (MTs) constitute a family of cysteine-rich, low molecular weight proteins, which generally provide protection against metal toxicity and oxidative stress counteracting the cell damage caused by essential and non-essential heavy metals. Equally important is the physiological role of MTs in the homeostasis of essential metals, which are involved in a wide variety of cellular processes. The aim of this work was to investigate the expression and the territorial localization of Paracentrotus lividus MT (Pl-MT) mRNA during sea urchin development by Quantitative Polymerase Chain Reaction (QPCR) and Whole Mount In Situ Hybridization (WMISH), as well as the phylogenetic comparison with selected MT homologs present in different phyla. We found that Pl-MT mRNA is accumulated in unfertilized eggs and constitutively expressed during development, with very low levels of maternal mRNA at cleavage stages, followed by a significant rise during gastrulation with a peak at the prism stage. Pl-MT mRNA was expressed in the vegetative plate at mesenchyme blastula, later restricted to the endoderm of gastrula embryos and finally to the gut of plutei. Indirect immunofluorescence (IF) using a specific antibody for the endoderm marker Endo1 demonstrated a co-localization with the Pl-MT transcripts in the midgut and hindgut after the intestine differentiation occurs and when larval feeding begins. Our results show for the first time the constitutive temporal and tissue-specific expression of MT in P. lividus embryos, providing new information for studies on the mechanisms controlling basal and induced MT gene expression. The analysis of the phylogenetic relationship of Pl-MT with homologs from different phyla, ranging from yeast to vertebrates, suggests the evolutionary process of these proteins, which could have been selected not only on the basis of their ability to bind metals but also by their tissue-specificity.