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Introductions of non-indigenous ascidian species are highly common nowadays due to their ability to establish successfully on artificial substrates. Didemnid species are of particular concern because of their rapid a-sexual growth and high fecundity. The colonial ascidian Didemnum perlucidum Monniot F., 1983 was first described from Guadeloupe Island in the Caribbean, although its native range remains unknown. To date, it has been recorded from numerous sites across the Indo-Pacific and Atlantic oceans. Here, having employed both classic taxonomy and genetic tools to verify its identification, we document for the first time its occurrence in the Mediterranean Sea – on two artificial substrates along the Israeli coast. The ability of D. pelucidum to establish reproductive populations despite the harsh environmental conditions of this region, with temperature fluctuations between 16-31°C and a salinity of 38-39 ppt, raises concern regarding this species’ potential for introductions at numerous sites across the Mediterranean.

The increasing use of pharmaceuticals in human and veterinary medicine, along with their poor removal rates at wastewater treatment facilities is resulting in the chronic release of pharmaceutically-active compounds (PhACs) into the marine environment, where they pose a threat to non-target organisms. A useful approach, as applied in the current study for assessing the effects of PhACs on non-target organisms, is the proteomic approach: the large-scale study of an organism's proteins. Using ‘shotgun’ proteomics, we identified differentially-expressed proteins based on peptide fragments in the solitary ascidian, Herdmania momus, following a 14-day laboratory experimental exposure to the PhAC carbamazepine (CBZ), an anticonvulsant and antidepressant medication, frequently detected in the aquatic environment. Individuals were exposed to environmentally relevant concentrations: 5 or 10 µg/L of CBZ, in addition to a control treatment. Out of 199 identified proteins, 24 were differentially expressed (12%) between the treatment groups, and thus can potentially be developed as biomarkers for CBZ contamination. Ascidians’ phylogenetic position within the closest sister group to vertebrates presents an advantage in examining the pathological effects of PhACs on vertebrate-related organs and systems. Together with the world-wide distribution of some model ascidian species, and their ability to flourish in pristine and polluted sites, they provide a promising tool through which to study the extent and effects of PhAC contamination on marine organisms.

Ascidians (Chordata, Ascidiacea) are considered to be prominent marine invaders, able to tolerate highly polluted environments and fluctuations in salinity and temperature. Here, we examined the seasonal and spatial dynamics of the microbial communities in the inner-tunic of two invasive ascidians, Styela plicata (Lesueur 1823) and Herdmania momus (Savigny 1816), in order to investigate the changes that occur in the microbiome of non-indigenous ascidians in different environments. Microbial communities were characterized using next-generation sequencing of partial (V4) 16S rRNA gene sequences. A clear differentiation between the ascidian-associated microbiome and bacterioplankton was observed, and two distinct sets of operational taxonomic units (OTUs), one core and the other dynamic, were recovered from both species. The relative abundance of the dynamic OTUs in H. momus was higher than in S. plicata, for which core OTU structure was maintained independently of location. Ten and seventeen core OTUs were identified in S. plicata and H. momus, respectively, including taxa with reported capabilities of carbon fixing, ammonia oxidization, denitrification, and heavy-metal processing. The ascidian-sourced dynamic OTUs clustered in response to site and season but significantly differed from the bacterioplankton community structure. These findings suggest that the associations between invasive ascidians and their symbionts may enhance host functionality while maintaining host adaptability to changing environmental conditions.

The incidence of transitional cell carcinoma (TCC), the fourth most common neoplasm diagnosed in men, is rising. Despite the development of several noninvasive diagnostic tests, none have gained full recognition by the clinicians. Gene expression profiling of tumors can identify new molecular markers for early diagnosis and disease follow-up. It also allows the classification of tumors into subclasses assisting in disease diagnosis and prognosis, as well as in treatment selection. In this paper, we employed expression profiling for molecular analysis of TCC. A TCC-derived cDNA microarray was constructed and hybridized with 19 probes from normal urothelium and TCC tissues. Hierarchical clustering analysis identified all normal urothelium samples to be tightly clustered and separated from the TCC samples, with 29 of the genes significantly induced (t-test, P10(-5)) in noninvasive TCC compared to normal urothelium. The identified genes are involved in epithelial cells' functions, tumorigenesis or apoptosis, and could become molecular tools for noninvasive TCC diagnosis. Principal components analysis of the noninvasive and invasive TCC expression profiles further revealed sets of genes that are specifically induced in different tumor subsets, thus providing molecular fingerprints that expand the information gained from classical staging and grading.

Styela plicata (Lesueur, 1823) (Tunicata; Stolidobranchia; Styelidae) is a solitary ascidian with a global distribution. Until recently it had not been observed along the Mediterranean coast of Israel, but is now to be found in many harbors attached to suspended ropes and other artificial structures. In order to monitor the populations of S. plicata, we surveyed eight harbors along the Israeli Mediterranean coast. Our results show that the condition and maintenance of each harbor significantly affected the presence of S. plicata. We also characterized the microbial communities in the tunic of three individuals using 16S rRNA gene tag pyrosequencing and compared them to those in the surrounding seawater, in order to determine whether the symbiotic bacteria may contribute to the successful establishment of this ascidian species. We found 15 bacterial phyla in total, of which 14 were present in the animal hosts: 6 were present in all of the individuals and 4 in two of the individuals. Three of the 15 phyla observed were absent in the surrounding seawater. The high variability among the three hosts suggests a mechanism of horizontal transmission and may play a role in the process of invading new and less tolerant niches.

Peptide epitopes presented through class I major histocompatability complex (MHC class I) on the cell surface, are generated by proteolytic processing of protein-antigens in the cytoplasm. The length and amino acid sequence determine whether a given peptide can fit into the peptide binding groove of class I heavy chain molecules and subsequently be presented to the immune system. The mode of action of the processing pathway is therefore of great interest. To study the processing mechanism of MHC class I-restricted intracellular antigens, we reconstituted the proteolytic processing of a model antigen in a cell-free system. Incubation of oxidized and urea-treated OVA in lymphocyte lysate resulted in partial degradation of the antigen. Degradation of the antigen depended on the presence of ATP. Addition of methylated ubiquitin abolished the reaction which was then restored by addition of an excess of native ubiquitin, indicating that the breakdown of the antigen in lymphocyte lysate is mediated by the ubiquitin proteolytic system. Upon incubation of modified OVA in lymphocyte lysate, a specific antigenic peptide was generated. The peptide was recognized by cytotoxic T lymphocytes directed against OVA-derived, H-2Kb-restricted peptide (SIINFEKL), and by a monoclonal antibody that recognizes cell-bound Kb-SIINFEKL complexes. Formation of the peptide epitope depended on the presence of ATP and ubiquitin. These results indicate that proteolytic processing of modified OVA is carried out by the ubiquitin-mediated degradation system. The experimental system described provides a tool to analyze the molecular mechanisms underlying the generation of specific, MHC class I-restricted peptide epitopes.