Almiramide D,cytotoxic peptide from the marine cyanobacterium Oscillatoria nigroviridis

Marine benthic cyanobacteria are widely known as a source of toxic and potentially useful compounds. These microorganisms have been studied from many Caribbean locations, which recently include locations in the Colombian Caribbean Sea. In the present study, six lipopeptides named almiramides D to H, together with the known almiramide B are identified from a mat characterized as Oscillatoria nigroviridis collected at the Island of Providence (Colombia, S.W. Caribbean Sea). The most abundant compounds, almiramides B and D were characterized by NMR and HRESIMS, while the structures of the minor compounds almiramides E to H were proposed by the analysis of their HRESIMS and MS² spectra. Almiramides B and D were tested against six human cell lines including a gingival fibroblast cell line and five human tumor cell lines (A549, MDA-MB231, MCF-7, HeLa and PC3) showing a strong but not selective toxicity.     

Population Genetics of a Trochid Gastropod Broadens Picture of Caribbean Sea Connectivity

Background

Regional genetic connectivity models are critical for successful conservation and management of marine species. Even though rocky shore invertebrates have been used as model systems to understand genetic structure in some marine environments, our understanding of connectivity in Caribbean communities is based overwhelmingly on studies of tropical fishes and corals. In this study, we investigate population connectivity and diversity of Cittarium pica, an abundant rocky shore trochid gastropod that is commercially harvested across its natural range, from the Bahamas to Venezuela.

Methodology/Principal Findings

We tested for genetic structure using DNA sequence variation at the mitochondrial COI and 16S loci, AMOVA and distance-based methods. We found substantial differentiation among Caribbean sites. Yet, genetic differentiation was associated only with larger geographic scales within the Caribbean, and the pattern of differentiation only partially matched previous assessments of Caribbean connectivity, including those based on larval dispersal from hydrodynamic models. For instance, the Bahamas, considered an independent region by previous hydrodynamic studies, showed strong association with Eastern Caribbean sites in our study. Further, Bonaire (located in the east and close to the meridional division of the Caribbean basin) seems to be isolated from other Eastern sites.

Conclusions/Significance

The significant genetic structure and observed in C. pica has some commonalities in pattern with more commonly sampled taxa, but presents features, such as the differentiation of Bonaire, that appear unique. Further, the level of differentiation, together with regional patterns of diversity, has important implications for the application of conservation and management strategies in this commercially harvested species.     

Nearshore coral growth declining on the Mesoamerican Barrier Reef System

Anthropogenic global change and local stressors are impacting coral growth and survival worldwide, altering the structure and function of coral reef ecosystems. Here, we show that skeletal extension rates of nearshore colonies of two abundant and widespread Caribbean corals (Siderastrea siderea, Pseudodiploria strigosa) declined across the Belize Mesoamerican Barrier Reef System (MBRS) over the past century, while offshore coral conspecifics exhibited relatively stable extension rates over the same temporal interval. This decline has caused nearshore coral extension rates to converge with those of their historically slower growing offshore coral counterparts. For both species, individual mass coral bleaching events were correlated with low rates of skeletal extension within specific reef environments, but no single bleaching event was correlated with low skeletal extension rates across all reef environments. We postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long‐term ocean warming and increasing exposure to higher levels of land‐based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role. If these declining trends in skeletal growth of nearshore S. siderea and P. strigosa continue into the future, the structure and function of these critical nearshore MBRS coral reef systems is likely to be severely impaired.     

Phylogenetic relationships of the family Axinellidae (Porifera: Demospongiae) using morphological and molecular data

Alvarez, B., Crisp, M.D., Driver, F., Hooper, J.N.A. & Van Soest, R.W.M. (2000). Phylogenetic relationships of the family Axinellidae (Porifera: Demospongiae) using morphological and molecular data. —Zoologica Scripta, 29, 169–198. Twenty‐seven species of marine sponges belonging to Axinellidae and related groups (Halichondriidae, Dictyonellidae, Agelasida) were selected to test the monophyly of Axinellidae and investigate their phylogenetic relationships using parsimony and maximum likelihood methods. Partial 28S rDNA sequences, including the D3 domain, and traditional morphological characters (mainly skeletal ones) were used independently to construct phylogenetic trees. Sequences were aligned using the appropriate model of secondary structure of the RNA and compared to that produced by the multiple sequence alignment program, ClustalW. The alignment using secondary structure constraints produced a better estimate of the phylogeny and was demonstrated to be an effective and objective method. Results of the cladistic analyses of the molecular and morphological data sets were not fully congruent; the morphological data suggest that Axinellidae is monophyletic, however, the molecular data suggest that it is nonmonophyletic. The single most‐parsimonious tree derived from the molecular data showed that species of Axinella (except A. polypoides) are united in a clade that is more closely related to members of Agelasida than to other species of Axinellidae; the remaining members of Axinellidae form a monophyletic group that is closely related to the families Dictyonellidae and Halichondriidae. The consensus tree of 20 most‐parsimonious trees from the morphological analysis, on the other hand, showed that all the sampled species of Axinellidae belong to a monophyletic group which is closely related to the species of Dictyonellidae and Halichondriidae. Only two branches were identical in both cladograms, the one uniting the species of Ptilocaulis and Reniochalina and the one with the species of Dictyonellidae. The robustness of the molecular and morphological trees (or parts of the trees), was tested using bootstrap, jack‐knife, PTP and T‐PTP tests. The results of the PTP test were significant indicating significant cladistic structure in both data sets. The bootstrap and jack‐knife values indicate that the molecular tree is in general better supported than the morphological one. The lack of morphological characters and the homoplastic nature of some may explain the weak support of the morphological tree. A T‐PTP test of nonmonophyly showed that the nonmonophyly of Axinellidae, as indicated by the results of the molecular analysis, is not significant; however, a T‐PTP test of monophyly of Axinellidae, as indicated by the morphological tree, produced significant results. This indicates that the monophyly of Axinellidae based on morphological data cannot be rejected; the family however, cannot be defined in terms of a unique diagnostic character common to all members of the ingroup. Tests of heterogeneity (reciprocal T‐PTP and partition homogeneity test) indicated that the data partitions are heterogeneous, which could be due to sampling errors (in either data set) or differences in the underlying phylogenies; therefore data were not combined in a single analysis. Further, both data sets are unequally sized (95 informative molecular characters vs. 16 informative morphological characters), which means that the molecular signal could swamp the morphological signal if the data is combined. Nonmonophyly of Axinellidae is supported by chemical and genetic evidence available in the literature and DNA sequences data of axinellid species from New Zealand. However, this needs to be confirmed using independent evidence from different genes (or gene regions), biochemistry, histology or cell ultrastructure. Therefore, no changes to the taxonomic position of the family in the higher classification are proposed at this stage.     

Demographic history of Diadema antillarum, a keystone herbivore on Caribbean reefs.

The sea urchin Diadema antillarum was the most important herbivore on Caribbean reefs until 1983, when mass mortality reduced its populations by more than 97%. Knowledge of its past demography is essential to reconstruct reef ecology as it was before human impact, which has been implicated as having caused high pre-mortality Diadema abundance. To determine the history of its population size, we sequenced the ATPase 6 and 8 region of mitochondrial DNA from populations in the Caribbean and in the eastern Atlantic (which was not affected by the mass mortality), as well as from the eastern Pacific D. mexicanum. The Caribbean population harbours an order of magnitude more molecular diversity than those of the eastern Pacific or the eastern Atlantic and, despite the recent mass mortality, its DNA sequences bear the genetic signature of a previous population expansion. By estimating mutation rates from divergence between D. antillarum and D. mexicanum, that were separated at a known time by the Isthmus of Panama, and by using estimates of effective population size derived from mismatch distributions and a maximum likelihood coalescence algorithm, we date the expansion as having occurred no more recently than 100 000 years before the present. Thus, Diadema was abundant in the Caribbean long before humans could have affected ecological processes; the genetic data contain no evidence of a recent, anthropogenically caused, population increase.     

FIRST RECORD OF THE INDO‐PACIFIC REEF CORAL GENUS ISOPORA IN THE CARIBBEAN REGION: TWO NEW SPECIES FROM THE NEOGENE OF CURAÇAO,NETHERLANDS ANTILLES

Abstract: The coral genus Isopora, a sister group of the modern dominant Acropora until now only known from the Pliocene to Recent of the Indo‐Pacific, is recorded in the Caribbean for the first time. Two new species, Isopora ginsburgi and Isopora curacaoensis, are described from the Neogene Seroe Domi Formation of Curaçao, Netherlands Antilles. Study of large collections made systematically through the sequence indicates that Isopora first occurred in the Caribbean during the Mio–Pliocene, at approximately the same time as the origination of many modern Caribbean reef coral dominants including Acropora cervicornis. It last occurred in the region during the late Pliocene as part of a pulse of extinction, in which several genera that live today in the Indo‐Pacific became extinct in the Caribbean. Throughout its Caribbean duration, Isopora co‐occurred with the two abundant modern Caribbean species of Acropora, A. cervicornis and A. palmata. Comparisons with Neogene collections made elsewhere in the Caribbean indicate that Isopora was restricted in distribution to the southern Caribbean. Isopora species are viviparous, while Acropora are oviparous, and this difference in reproductive strategy may have played a role in the extinction of Isopora in the Caribbean. The occurrences of Isopora reported in this study are the oldest records to date of Isopora worldwide, and are important for understanding the biogeographic separation between reef coral faunas in the Caribbean and Indo‐Pacific regions.     

Eryloside W,a triterpenoid saponin from the sponge Dictyonella marsilii

A new saponin derivative named eryloside W was isolated from the marine sponge Dictyonella marsilii (Demospongiae, Halichondrida, Dictyonellidae). The structure of the compound was elucidated through extensive use of 1D and 2D nuclear magnetic resonance and mass spectrometry. Determination of the absolute configuration was performed using electronic circular dichroism (ECD) by comparison of experimental and time dependent density functional theory (TDDFT) calculated spectra. This is the first occurrence of a saponin derivative produced by a marine sponge present in the Mediterranean.     

AAMP, a Newly Identified Protein, Shares a Common Epitope with α-Actinin and a Fast Skeletal Muscle Fiber Protein

AAMP (angio-associated migratory cell protein) shares a common epitope with α-actinin and a fast-twitch skeletal muscle fiber protein. An antigenic peptide, P189, derived from the sequence of AAMP was synthesized. Polyclonal antibodies generated to P189 readily react with AAMP (52 kDa) in brain and activated T lymphocyte lysates, α-actinin (100 kDa) in all tissues tested, and a 23-kDa protein in skeletal muscle lysates. The antibody's reactivity for α-actinin can be competed with the purified protein. Activation of T lymphocytes does not alter the degree of α-actinin reactivity with anti-P189 as it does for AAMP's reactivity in these lysates. Competition studies with peptide variants show that six amino acid residues, ESESES, constitute a common epitope in all three proteins in human tissues. The antigenic determinant is continuous in AAMP but discontinuous (or assembled) in α-actinin. α-Actinin does not contain this epitope in its linear sequence so reactivity is attributed to an epitope formed by its secondary structure. Limited digestion of the reactive proteins with thermolysin destroys anti-P189’s reactivity for α-actinin while reactivity for recombinant AAMP is retained. Specificity of anti-P189 for human skeletal muscle fast fibers seen on immunoperoxidase staining may be explained by anti-P189’s reactivity with a 23-kDa protein found only in skeletal muscle lysates. Its pattern of reactivity is the same as that obtained using monoclonal anti-skeletal muscle myosin heavy chain in type II (fast-twitch) fibers.     

CARP,a Myostatin-downregulated Gene in CFM Cells,Is a Novel Essential Positive Regulator of Myogenesis

Myostatin, a member of the TGF-β superfamily, has been shown to act as a negative regulator of myogenesis. Although its role in myogenesis has been clearly documented through genetic analysis, few gene cascades that respond to myostatin signaling and regulate myogenesis have been characterized, especially in avian species. In a previous study, we screened for such genes in chicken fetal myoblasts (CFMs) using the differential display PCR method and found that cardiac ankyrin repeat protein (CARP) was downregulated by myostatin and specifically expressed in chicken skeletal muscle. However, little is known about the potential functions of CARP in chicken skeletal myogenesis. In this study, the expression patterns of chicken CARP and the possible function of this gene in skeletal muscle growth were characterized. Our data showed that CARP was predominantly expressed in postnatal skeletal muscle, and its expression increased during myogenic differentiation in CFM cells. When CARP was overexpressed, CFM cell growth was enhanced by accelerating the cell cycle at the G1 to S phase transition and increasing cyclin D1 expression. CARP knockdown had the opposite effect: while myoblasts underwent differentiation, knockdown of CARP expression induced extensive cell death, suppressed the formation of myotubes, and markedly decreased the expression of differentiation-related genes such as myosin heavy chain (MHC), myoD, and caveolin-3. Our findings indicate that CARP may play a key role in the myostatin signaling cascade that governs chicken skeletal myogenesis through promoting proliferation and avoiding apoptosis during CFM cell differentiation.     

Skeletal muscle stem cell birth and properties

Development and maintenance of an abundant tissue such as skeletal muscle poses several challenges. Curiously, not all skeletal muscle stem cells are born alike, since diverse genetic pathways can specify their birth. Stem and progenitor cells that establish the tissue during development, those that maintain its homeostasis, as well as participate in its regeneration have generated considerable interest. The ability to distinguish stem cells from more committed progenitors throughout prenatal and postnatal life has guided researchers to identify stem cell properties and characterise their niche. These properties include markers that influence cell behaviour and mode of division during normal development, after trauma and cell transplantations. This review addresses these issues from a developmental perspective.     

Population Genetic Structure of the Magnificent Frigatebird Fregata magnificens (Aves,Suliformes) Breeding Colonies in the Western Atlantic Ocean

The Magnificent Frigatebird Fregata magnificens has a pantropical distribution, nesting on islands along the Atlantic and Pacific coasts. In the Caribbean, there is little genetic structure among colonies; however, the genetic structure among the colonies off Brazil and its relationship with those in the Caribbean are unknown. In this study, we used mtDNA and microsatellite markers to infer population structure and evolutionary history in a sample of F. magnificens individuals collected in Brazil, Grand Connétable (French Guyana), and Barbuda. Virtually all Brazilian individuals had the same mtDNA haplotype. There was no haplotype sharing between Brazil and the Caribbean, though Grand Connétable shared haplotypes with both regions. A Bayesian clustering analysis using microsatellite data found two genetic clusters: one associated with Barbuda and the other with the Brazilian populations. Grand Connétable was more similar to Barbuda but had ancestry from both clusters, corroborating its “intermediate” position. The Caribbean and Grand Connétable populations showed higher genetic diversity and effective population size compared to the Brazilian population. Overall, our results are in good agreement with an effect of marine winds in isolating the Brazilian meta-population.     

Circular dichroism spectra show abundance of beta-sheet structure in connectin, a muscle elastic protein

Circular dichroism spectra of native connectin from chicken breast muscle strongly suggested the abundant presence of beta-sheet structure, as much as 70% in 0.5 M KCl and 50 mM phosphate buffer, pH 7.5. alpha-Helix was not detected. These results are in contradiction with the conclusion that native connectin from rabbit skeletal muscle consists entirely of random coil [(1984) J. Mol. Biol. 180, 331-356].     

Slr4, a newly identified S-layer protein from marine Gammaproteobacteria,is a major biofilm matrix component

S-layers are paracrystalline proteinaceous lattices that surround prokaryotic cells, forming a critical interface between the cells and their extracellular environment. Here, we report the discovery of a novel S-layer protein present in the Gram-negative marine organism, Pseudoalteromonas tunicata D2. An uncharacterized protein (EAR28894) was identified as the most abundant protein in planktonic cultures and biofilms. Bioinformatic methods predicted a beta-helical structure for EAR28894 similar to the Caulobacter S-layer protein, RsaA, despite sharing less than 20% sequence identity. Transmission electron microscopy revealed that purified EAR28894 protein assembled into paracrystalline sheets with a unique square lattice symmetry and a unit cell spacing of ~9.1 nm. An S-layer was found surrounding the outer membrane in wild-type cells and completely removed from cells in an EAR28894 deletion mutant. S-layer material also appeared to be “shed” from wild-type cells and was highly abundant in the extracellular matrix where it is associated with outer membrane vesicles and other matrix components. EAR28894 and its homologs form a new family of S-layer proteins that are widely distributed in Gammaproteobacteria including species of Pseudoalteromonas and Vibrio, and found exclusively in marine metagenomes. We propose the name Slr4 for this novel protein family.     

Genomic organization,alternative splicing,and expression of human and mouse N-RAP,a nebulin-related LIM protein of striated muscle

Linkage analysis identifies 10q24-26 as a disease locus for dilated cardiomyopathy (DCM), a region including the N-RAP gene. N-RAP is a nebulin-like LIM protein that may mediate force transmission and myofibril assembly in cardiomyocytes. We describe the sequence, genomic structure, and expression of human N-RAP, as well as an initial screen to determine whether N-RAP mutations cause cardiomyopathy. Human expressed sequence tag databases were searched with the published 3,528-bp mouse N-RAP open reading frame (ORF). Putative cDNA sequences were interrogated by direct sequencing from cardiac and skeletal muscle RNA. We identified two human N-RAP isoforms with ORFs of 5,085 bp (isoform C) and 5,190 bp (isoform S), encoding products of 193-197 kDa. Genomic database searches localize N-RAP to human chromosome 10q25.3 and match isoforms C and S to 41 and 42 exons. Only isoform C is detected in human cardiac RNA; in skeletal muscle, approximately 10% is isoform C and approximately 90% is isoform S. We investigated apparent differences between human N-RAP cDNA and mouse sequences. Two mouse N-RAP isoforms with ORFs of 5,079 and 5,184 bp were identified with approximately 85% similarity to human isoforms; published mouse sequences include cloning artifacts truncating the ORF. Murine and human isoforms have similar gene structure, tissue specificity, and size. N-RAP is especially conserved within its nebulin-like and LIM domains. We expressed both N-RAP isoforms and the previously described truncated N-RAP in embryonic chick cardiomyocytes. All constructs targeted to myofibril precursors and the cell periphery, and inhibited myofibril assembly. Several human N-RAP polymorphisms were detected, but none were unique to cardiomyopathy patients. N-RAP is highly conserved and exclusively expressed in cardiac and skeletal muscle. Genetic abnormalities remain excellent candidate causes for cardiac and skeletal myopathies.     

Eastern Caribbean Circulation and Island Mass Effect on St. Croix,US Virgin Islands: A Mechanism for Relatively Consistent Recruitment Patterns

The northeastern Caribbean Sea is under the seasonal influence of the Trade Winds but also of the Orinoco/Amazon freshwater plume. The latter is responsible for intensification of the Caribbean Current in general and of its eddy activity in the northern part of the Caribbean Sea. More importantly, we show in this study that the front of the freshwater plume drives a northward flow that impinges directly on the island of St. Croix in the United States Virgin Islands. The angle of incidence of the incoming flow controls the nature of the wake on both sides and ends of the island, which changes from cyclonic to anticylonic wake flow, with either attached or shed eddies. Using an off-line bio-physical model, we simulated the dispersal and recruitment of an abundant Caribbean coral reef fish, the bluehead wrasse (Thalassoma bifasciatum) in the context of the wake flow variability around St. Croix. Our results revealed the role played by the consistent seasonal forcing of the wake flow on the recruitment patterns around the island at the interannual scale. The interannual variability of the timing of arrival and northward penetration of the plume instead controls the nature of the wake, hence the regional spatial recruitment patterns.     

SRP-35, a newly identified protein of the skeletal muscle sarcoplasmic reticulum, is a retinol dehydrogenase

In the present study we provide evidence that SRP-35, a protein we identified in rabbit skeletal muscle sarcoplasmic reticulum, is an all-trans-retinol dehydrogenase. Analysis of the primary structure and tryptic digestion revealed that its N-terminus encompasses a short hydrophobic sequence bound to the sarcoplasmic reticulum membrane, whereas its C-terminal catalytic domain faces the myoplasm. SRP-35 is also expressed in liver and adipocytes, where it appears in the post-microsomal supernatant; however, in skeletal muscle, SRP-35 is enriched in the longitudinal sarcoplasmic reticulum. Sequence comparison predicts that SRP-35 is a short-chain dehydrogenase/reductase belonging to the DHRS7C [dehydrogenase/reductase (short-chain dehydrogenase/reductase family) member 7C] subfamily. Retinol is the substrate of SRP-35, since its transient overexpression leads to an increased production of all-trans-retinaldehyde. Transfection of C2C12 myotubes with a fusion protein encoding SRP-35-EYFP (enhanced yellow fluorescent protein) causes a decrease of the maximal Ca2? released via RyR (ryanodine receptor) activation induced by KCl or 4-chloro-m-chresol. The latter result could be mimicked by the addition of retinoic acid to the C2C12 cell tissue culture medium, a treatment which caused a significant reduction of RyR1 expression. We propose that in skeletal muscle SRP-35 is involved in the generation of all-trans-retinaldehyde and may play an important role in the generation of intracellular signals linking Ca2+ release (i.e. muscle activity) to metabolism.     

Early (Series 2) Cambrian archaeocyathan reefs of southern Labrador as a locus for skeletal carbonate production

Pruss, S.B., Clemente, H. & Laflamme, M. 2012: Early (Series 2) Cambrian archaeocyathan reefs of southern Labrador as a locus for skeletal carbonate production. Lethaia, Vol. 45, pp. 401–410. Archaeocyathan reefs, the first reefs produced by animals, are prominent, global features of early Cambrian successions. However, microbialites – the dominant reef components of the Proterozoic – were still abundant in most archaeocyathan reefs. Although such reefs were a locus for carbonate production, it is unclear how much carbonate was produced skeletally. This analysis of well‐known early Cambrian archaeocyathan patch reefs of the Forteau Formation, southern Labrador, demonstrates that skeletal carbonate was abundantly produced in these archaeocyathan reefs, although only about half was produced by archaeocyathans. Trilobites, echinoderms and brachiopods contributed substantially to the total carbonate budget, particularly in grainstone facies flanking the reefs. Through point count analysis of samples collected from the reef core and flanking grainstones, it can be demonstrated that skeletal material was most abundant in grainstone facies, where animals such as trilobites and echinoderms contributed significantly to carbonate production. In contrast, microbial fabrics were more abundant than skeletal fabrics in the reef core, although archaeocyathan material was more abundant than other skeletal debris. Similar to modern reefs, these reefs created a variety of habitats that allowed for the proliferation of skeletal organisms living on and around the reef, thereby promoting skeletal carbonate production through ecosystem engineering. □Archaeocyatha, bioherms, carbonates, calcification, point count analysis     

Population structure and connectivity of the mountainous star coral,Orbicella faveolata,throughout the wider Caribbean region

As coral reefs continue to decline worldwide, it becomes ever more necessary to understand the connectivity between coral populations to develop efficient management strategies facilitating survival and adaptation of coral reefs in the future. Orbicella faveolata is one of the most important reef‐building corals in the Caribbean and has recently experienced severe population reductions. Here, we utilize a panel of nine microsatellite loci to evaluate the genetic structure of O. faveolata and to infer connectivity across ten sites spanning the wider Caribbean region. Populations are generally well‐mixed throughout the basin (F_ST = 0.038), although notable patterns of substructure arise at local and regional scales. Eastern and western populations appear segregated with a genetic break around the Mona Passage in the north, as has been shown previously in other species; however, we find evidence for significant connectivity between Curaçao and Mexico, suggesting that the southern margin of this barrier is permeable to dispersal. Our results also identify a strong genetic break within the Mesoamerican Barrier Reef System associated with complex oceanographic patterns that promote larval retention in southern Belize. Additionally, the diverse genetic signature at Flower Garden Banks suggests its possible function as a downstream genetic sink. The findings reported here are relevant to the ongoing conservation efforts for this important and threatened species, and contribute to the growing understanding of large‐scale coral reef connectivity throughout the wider Caribbean.