The genome of the sea urchin Strongylocentrotus purpuratus

We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes

Radiocesium concentrations and DNA strand breakage in two species of amphibians from the Chornobyl exclusion zone

Relatively few studies have considered impacts of the 1986 nuclear accident at Chornobyl on lower vertebrate populations. Amphibians are recognized as sensitive indicators of environmental degradation and pollution, and some amphibian population declines may be associated with contaminant-induced stress. Amphibians also utilize both aquatic and terrestrial habitats, which facilitates comparison of radionuclide accumulation and effects in different environments. We sampled sympatric frog species from a highly contaminated area within the Chornobyl exclusion zone and from a nearby, less contaminated area in August - September 1999. Radiocesium was measured in whole frogs and in muscle samples. Whole body mean radiocesium for Rana esculenta from Gluboke Lake, a highly contaminated area, was 22.3 Bq/g wet mass; R. terrestris from the same area contained 53.4 Bq/g wet mass. Radiocesium levels in frogs from Emerald Camp, a less contaminated area, were about an order of magnitude lower. In both locations, whole body radiocesium concentrations were higher in R. terrestris than in R. esculenta, probably reflecting dietary differences between species. Mean muscle radiocesium concentrations were generally lower than whole body concentrations, and muscle and whole body concentrations were highly correlated within individuals. We used pulsed field-gel electrophoresis to examine the size distribution of DNA fragments in muscle tissue from a subsample of R. terrestris from both locations. Increased proportions of smaller DNA fragments, suggesting DNA strand breakage, occurred in R. terrestris from the more contaminated location. Results support the concept that amphibians are useful in assessing radionuclide accumulation and effects in contaminated areas. However, differences among species must be considered in evaluating contaminant concentrations and potential effects

Localization and diversity of 185/333 proteins from the purple sea urchin - unexpected protein-size range and protein expression in a new coelomocyte type

The current paradigm proposes that the innate immune systems of invertebrates are much more complex than previously thought. The highly diverse 185/333 gene family in the purple sea urchin encodes a family of closely related proteins of varying length and sequence composition. Subsets of small phagocytes and polygonal cells express 185/333 proteins with localization on the surface of the small phagocytes and within perinuclear vesicles in both cell types. In short-term cultures, coelomocytes form small aggregates that progress to syncytia that are thought to be equivalent to encapsulation in vivo. These aggregates were found to be enriched for 185/333-positive (185/333+) small phagocytes. In response to lipopolysaccharide challenge, coelomocytes transiently increased, including frequencies of both 185/333+ and 185/333-negative (185/333-) small phagocytes and 185/333+ polygonal cells. The 185/333 proteins were present in a broad array of sizes, most of which were larger than that predicted from the cDNAs. Recombinant 185/333 proteins expressed in bacteria and insect cells were also larger than expected, suggesting that the proteins dimerize and multimerize. The diversity of the 185/333 proteins, their expression in response to immune challenge, and their cellular localization suggests this protein family and the small phagocytes have an important immunological role in the sea urchin.10 page(s

Sp185/333 : a novel family of genes and proteins involved in the purple sea urchin immune response

The Sp185/333 system of genes, messages and proteins are expressed in the coelomocytes of the purple sea urchin, Strongylocentrotus purpuratus, and is an extraordinary example of diversification of a putative innate immune response system in an invertebrate. Reviewed here, is the current understanding of this complex system as illustrated by sequence comparisons of the genes, messages and deduced proteins with descriptions of diversity, including preliminary results on genomic organization and descriptions of 185/333 in other echinoids. Sp185/333 gene expression in adults and embryos occurs in response to immune challenge and includes changes in the frequencies of Sp185/333-positive coelomocytes in the adults. The diversity of the Sp185/333 protein repertoire in coelomocytes is far greater than the sequence diversity encoded in the genes, which may be the result of rapid gene recombination, RNA editing and/or low-fidelity transcription, plus post-translational modifications. This review concludes with preliminary results and speculations on protein function.11 page(s