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Stem cells (SCs) in vertebrates typically reside in “stem cell niches” (SCNs), morphologically restricted tissue microenvironments that are important for SC survival and proliferation. SCNs are broadly defined by properties including physical location, but in contrast to vertebrates and other “model” organisms, aquatic invertebrate SCs do not have clearly documented niche outlines or properties. Life strategies such as regeneration or asexual reproduction may have conditioned the niche architectural variability in aquatic or marine animal groups. By both establishing the invertebrates SCNs as independent types, yet allowing inclusiveness among them, the comparative analysis will allow the future functional characterization of SCNs.

The Sundarbans, a highly biodiverse tropical ecosystem stretching across India and Bangladesh, is also the largest mangrove forest in the world. Organochlorine compounds (OCs) have been extensively used for agriculture and sanitary purposes in the region. OCs can accumulate in biological tissues and biomagnify in organisms through food webs, for which reason they reach high concentrations in top predators. Because marine food webs are long and marine predators are extensively used in the region as human food, assessment of potential health-related risks caused by OC pollution is in order. This study is the first to determine the concentration of PCBs in fish and crustaceans from the Sundarbans mangroves, their accumulation trends through the food web, and the potential toxicological risk that their consumption poses to humans. DDT concentrations, which had already been assessed in the region, were also determined. The median concentrations ranged from below detection limits to 176.3 ng g−1 lipid weight for tDDT and 275.9 ng g−1 for PCBs. Overall, these concentrations were lower than those usually observed in other regions of the world, apparently as a result of the interplay of several factors: low environmental organochlorine inputs, the physical and climatic characteristics of an ecosystem dominated by high temperatures in a highly flushed ecosystem that dilutes and rapidly disperses pollutants, and the comparatively short food chain lengths that, similarly to other mangrove ecosystems, characterize the Sundarbans. Organochlorine concentrations were 2-3 orders of magnitude lower than commonly accepted tolerance levels, so their consumption do not pose a sensible risk to the population. However, concentrations of DDT in dry fish from retail markets were higher because this compound is used for pest control during fish processing. Potential risks involved in this practice likely outweigh potential benefits, so it is recommended that this compound is substituted by less hazardous alternatives.

Editorial on the Research Topic Marine Aquaculture Impacts on Marine Biota

Nowadays, the industry is quite commonly using nanoparticles of titanium dioxide (nTiO2) especially in sunscreens, due to its higher reflective index in comparison to micron size TiO2. Its high demand causes its widespread environmental occurrence, thus damaging the environment. The aquatic ecosystems are the most vulnerable to contamination by nTiO2. Like other engineered nanoparticles, nTiO2 has demonstrated generation of reactive oxygen species (ROS) and reactive halogen species (RHS) in the aquatic environment under UV radiation. This study investigated the toxicity of nTiO2 towards two aquatic indicator organisms, one from freshwater (Daphnia magna) and the other from seawater (Artemia sp.), under simulated solar radiation (SSR). Daphnia magna and Artemia sp. were co-exposed in 16 h SSR and 8 h darkness cycles to different concentrations of nTiO2. The estimated EC50 at 48 h for D. magna was 3.16 mg nTiO2/L, whereas for A. sp. no toxic effects were observed. When we exposed these two organisms simultaneously to 48 h of prolonged SSR using higher nTiO2 concentrations, EC50 values of 7.60 mg/L and 5.59 mg/L nTiO2 for D. magna and A. sp., respectively, were obtained. A complementary bioassay was carried out with A. sp., by exposing this organism to a mixture of nTiO2 and organic UV filters (benzophenone 3 (oxybenzone, BP3), octocrylene (OC), and ethyl 4-aminobenzoate (EtPABA)), and then exposed to SSR. The results suggested that nTiO2 could potentially have negative impacts on these organisms, also this work outlines the different characteristics and interactions that may contribute to the mechanisms of environmental (in salted and freshwater) phototoxicity of nTiO2 and UV radiation, besides their interaction with organic compounds., Authors acknowledge the financial support of the Spanish Ministry of Science and Innovation, for projects ROUSSEAU (CTM2017-89767-C3-1-R), CEX2018-000794-S, and CTQ2017-86466-R., and AGAUR-Gencat project 2017SGR131. A.C. Soler acknowledges Mexican CONACyT for her doctoral grant (Ref. 409154).

[cat] El creixent nombre de genomes seqüenciats està posant de manifest que la pèrdua gènica és un fenomen recurrent que pot haver generat diversitat al llarg de la història evolutiva dels diferents grups d’organismes. En aquest sentit, un dels grans reptes en el camp de la EvoDevo és entendre l’impacte de la pèrdua gènica en l’evolució dels mecanismes del desenvolupament animal considerant diferents escenaris evolutius. En escenaris de selecció positiva, la pèrdua hauria comportat canvis morfològics o fisiològics que haurien permès l’adaptació de les espècies a noves condicions ambientals. En escenaris de selecció neutre (o quasi neutre), la pèrdua hauria afectat a gens que haurien esdevingut prescindibles per l’existència de robustesa mutacional o perquè les condicions ambientals haurien canviat. Saber si una pèrdua gènica ha estat adaptativa o neutre és generalment molt complex ja que molts cops es difícil establir relacions directes de causalitat entre la pèrdua d’un gen i l’aparició d’una nova característica evolutivament avantatjosa. Malgrat aquesta dificultat, en aquesta tesi doctoral vàrem voler estudiar l’impacte de la pèrdua gènica en l’EvoDevo a partir d’analitzar l’evolució de les vies de senyalització de l’àcid retinoic (RA) i de Wnt -vies essencials pel desenvolupament de tots els cordats- a l’urocordat Oikopleura. dioica com a sistema model de referència. Per establir O. dioica com a model animal, però, a més de les característiques biològiques que la fan atractiva per aquests tipus estudis –desenvolupament embrionari i cicle de vida extremadament ràpid, simplicitat i transparència corporal, genoma reduït i totalment seqüenciat, possibilitat de manipulació gènica per estudis funcionals– ha estat fonamental desenvolupar unes instal·lacions per cultivar-la en el laboratori, així com protocols de manteniment assequibles (low-cost) per qualsevol grup d’investigació. Gràcies a aquest sistema de cultiu, em pogut analitzar els components de la xarxa gènica del metabolisme de l’RA (RA-MGN), així com els lligands de la via de senyalització per Wnt. En referència a la RA-MGN, el nostre treball ens permet concloure que les pèrdues gèniques que han afectat a aquesta via durant l’evolució de O. dioica han tingut lloc en un sistema genètic no robust, on el desballestament de la via no han tingut un impacte dramàtic en el pla corporal típic de cordats que preserva aquest organisme. Per altre banda, l’anàlisi de la família Wnt a cordats, ens ha permès concloure que a més de la duplicació gènica o de la redundància funcional per processos d’evolució convergent, els fenòmens de reassignació de funcions (function shuffling) augmenten també la robustesa mutacional i faciliten les pèrdues gèniques en les famílies de gens. En resum, els resultats d’aquesta tesi doctoral posen de manifest que O. dioica és un model animal atractiu per estudiar tant aspectes bàsics de l’impacte de les pèrdues gèniques en l’evolució dels mecanismes del desenvolupament, com en aspectes aplicats en que certes pèrdues confereixen a O. dioica la condició de knockout evolutiu que pot ser interessant per l’estudi de mecanismes moleculars concrets com la toxicitat de les PUAs en el desenvolupament embrionari d’organismes marins., [eng] The bloom of genomics is revealing gene loss as a pervasive evolutionary force generating genetic diversity that shapes the evolution of species. In this sense, one of the great challenges in the field of EvoDevo is to understand the impact of gene loss on the evolution of animal developmental mechanisms. In this doctoral thesis we wanted to study the impact of gene loss in EvoDevo, using the analysis of the evolution of retinoic acid (RA) and Wnt signaling pathways - essential pathways in the development of all the chordates- in the urochordate Oikopleura. dioica as a model reference system. To establish O. dioica as an animal model, in addition to the biological characteristics that make it attractive for his type of studies-embryonic development and extremely fast life cycle, simplicity and body transparency, reduced and fully sequenced genome, possibility of gene manipulation for functional studies - It has been essential to develop a facility to grow O. dioica in the laboratory, as well as low-cost maintenance protocols affordable for any research group. Thanks to this culture system, we were able to analyze the components of the RA metabolic gene network (RA-MGN), as well as the ligands of the Wnt signaling pathway. In reference to the RA-MGN, our work allows us to conclude that the gene losses that have affected this pathway during the evolution of O. dioica have taken place in a non-robust genetic system, where the dismantling of the network has not had a dramatic impact on the typical body plan of chordates that preserves this organism. On the other hand, the analysis of the Wnt family in chordates, has allowed us to conclude that in addition to gene duplication or functional redundancy due to processes of convergent evolution, function shuffling also increase the mutational robustness and facilitate gene losses in gene families. In summary, the results of this doctoral thesis show that O. dioica is an attractive animal model for studying both basic aspects of the impact of gene losses in the evolution of development mechanisms, and in applied aspects. For instance, certain losses give to O. dioica an evolutionary knockout condition that may be interesting for the study of concrete molecular mechanisms such as the toxicity of PUAs in the embryonic development of marine organisms.

Antarctic benthos was prospected in search for anti-inflammatory activity in polar benthic invertebrates, in two different geographical areas: deep-bottoms of the Eastern Weddell Sea and shallow-waters of the South Shetland Islands. A total of 36 benthic algae and invertebrate species were selected to perform solubility tests in order to obtain extracts that were soluble at an innocuous ethanol concentration (0.2%) for cell culture, and further test them for anti-inflammatory activity. From these, ethanol extracts of ten species from five different phyla resulted suitable to be studied in cell macrophage cultures (RAW 264.7). Cytotoxicity (MTT method) and production of inflammatory mediators (prostaglandin E2, leukotriene B4, interleukin-1β) were determined at three extract concentrations (50, 125, 250 μg/mL). Bioassays resulted in four different species showing anti-inflammatory activity corresponding to three sponges: Mycale (Oxymycale) acerata, Isodictya erinacea, and I. toxophila; and one hemichordate: Cephalodiscus sp. These results show that Antarctic sessile invertebrates may have great value as a source of lead compounds with potential pharmaceutical applications.

Aquesta tesi comença amb la presentació de la família de Lamel·larines, uns productes naturals d'orígen marí amb interessants activitats biològiques. En el Capítol 1 se'n descriuen els últims avanços quant al seu aïllament, nova metodologia sintètica i estudis sobre l'activitat biològica i el seu mode d'acció. La consecució d'aquests mètodes sintètics ha obert la porta a la preparació del producte natural, i de molècules anàlogues. Així, en el Capítol 3 es descriu la síntesi de la Lamel·larina D amb una metodologia d'acoblaments creuats successius de Suzuki amb catàlisi de Pd(0). Amb la preparació descrita al Capítol 2 dels bromopolialcòxibenzens s'ha pogut realitzar la síntesi d'una quimioteca d'anàlegs sense lactona de la Lamel·larina D i amb la introducció de diferents patrons de substitució (es descriu al Capítol 4). S'ha assajat l'activitat biològica i estudiat les relacions estructura-activitat d'aquests compostos, cosa que ha permès posar de manifest aquells grups estructuralment importants quant a activitat. Al Capítol 5 es descriu la síntesi d'uns conjugats amb polietilenglicol de la Lamel·larina D, i més enllà al Capítol 6 es descriu la síntesi de conjugats estructuralment més complexos amb una seqüència peptídica de localització nuclear i un dendrímer. Amb els productes sintetitzats s'ha procedit a fer-ne una avaluació de la seva internalització i distribució cel·lulars, estudis co-localització dels productes amb marcatges selectius de membrana, mitocòndries i topoisomerasa.Per l'estudi del mode d'acció de la Lamel·larina D com a inhibidor de la topoisomerasa, s'ha fet ús de biosensors de pinzes òptiques i microscòpia de forces atòmiques. Aquest treball es descriu al Capítol 7 i cal destacar que aquestes novedoses tecnologies amb sensibilitats de pN i resolució nanomètrica es mostren d'elevada utilitat per a l'estudi de l'activitat de la topoisomerasa, i de la seva inhibició., Lamellarin D (Lam-D) is a marine alkaloid with antiproliferative activity against various tumor cells in the low nanomolar range. The inhibition of topoisomerase-I, a mitochondrial transmembrane potential disruption as well as promotion of apoptosis are its modes of action. Topoisomerase is an especially interesting chemotherapy target, namely because of the topoisomerase-DNA complex, which undergoes mechanical motions essential to its function (Chapter 1). The present research summary highlights the synthetic methodologies used for the synthesis of Lam-D and its related derivatives. Two synthetic strategies (A, B) had been employed for the total synthesis of Lam-D, which enable high versatility and robust methodologies for the preparation of the natural product, regioselective conjugation on its free phenolic groups and its structurally simplified derivatives.Methyl 8-isopropoxy-9-methoxy-5,6-dihydropyrrolo[2,1-a]isoquinoline-3-carboxylate was used as scaffold of strategy A. Regioselective and sequential introduction of aryl groups followed by Pd(0)-catalyzed cross coupling reactions, aromatization and ether deprotection provided the final compounds in 18-61% yields (Chapter 3). Boronic acids and borolanes were used as building blocks for the synthesis. Its preparation through regioselective bromination under mild conditions of highly activated benzenes and Pd(0)-catalyzed borylation gave the non-commercial polialcoxy synthons (7 compounds, 43-80% yields over 2 steps) for the diverted combinatorial synthesis (Chapter 2).A combinatorial library of 45 analogues of the privileged lead Lam-D was prepared using strategy A in which removal of the lactone ring were implemented in order to improve solubility, and modifications on the OMe/OH substitution pattern were explored for structure activity relationship studies. Lam-D and its analogues were obtained in 18-44% overall yields. A panel of three human tumor cell lines was used to evaluate their cytotoxic potential: A-549 lung carcinoma NSCL, HT-29 colon carcinoma cells, and MDA-MB-231 breast adenocarcinoma. Cytotoxicity was observed for numerous compounds at low micromolar concentrations, and clear SAR patterns were determined. SAR study concluded that more than 75% of the 45 open-chain Lam-D analogs tested showed cytotoxicity in a low micromolar GI50 range (Chapter 4). Strategy B, based on quaternization of the isoquinoline, further cycloaddition on the alquine and aromatization, readily gave the pentacyclic structure in good yields. A good choice of orthogonally removable protectors has been developed for the regioselective attachment of well-defined water-soluble polymeric and peptidic nuclear location signal sequence carriers to Lam-D. These chemical modifications can significantly improve both drug delivery and therapeutic efficacy due to the enhanced permeability and retention effect observed in tumor tissue. Mono-, di-, and tri-Lam-D conjugates were regioselectively synthesized through ester bond linkages in the phenolic sites. Polymeric and peptidic conjugates, respectively, have been obtained in 18-84% (2 steps) and 8-20% (2 or 3 steps) overall yields from the corresponding Lam-D protected phenolic derivatives (Chapter 5, 6).Further studies on the mechanism of action of Lamellarin D by innovative optical tweezers biosensors, served to gain a novel insight in the biological engineering of topoisomerase I enzyme and its inhibition by small drugs. Topoisomerase is an especially interesting chemotherapy target, namely because of the topoisomerase-DNA complex, which undergoes mechanical motions essential to its function during the cleavage and religation of a single strand within a duplex DNA (Chapter 7).Here we show the use of optical tweezers to study topoisomerase activity, evidenced by a large increase in the hysteresis of the force cycles resulting from the generation of ssDNA-like domains inside dsλDNA, and subsequent strand religation indicated by recovery of the characteristic dsDNA force fingerprint. In contrast, the presence of the topoisomerase inhibitor Lamellarin D results in a large increase in force hysteresis due to the initial nicking activity of Topo I and a subsequent absence of religation. These results highlight the potential of optical tweezers biosensors for the mechanistic study of DNA-modifying enzymes and for the screening of their inhibitors, and foresee profound implications in drug discovery and medical nanotechnology.

Investigating environmental hazards than could affect appendicularians is of prime ecological interest because they are among the most abundant components of the mesozooplankton. This work shows that embryo development of the appendicularian Oikopleura dioica is compromised by diatom bloom-derived biotoxins, even at concentrations in the same range as those measured after blooms. Developmental gene expression analysis of biotoxin-treated embryos uncovers an aberrant golf ball-like phenotype affecting morphogenesis, midline convergence, and tail elongation. Biotoxins induce a rapid upregulation of defensome genes, and considerable delay and silencing of zygotic transcription of developmental genes. Upon a possible future intensification of blooms associated with ocean warming and acidification, our work puts an alert on the potential impact that an increase of biotoxins may have on marine food webs, and points to defensome genes as molecular biosensors that marine ecologists could use to monitor the genetic stress of natural populations exposed to microalgal blooms.