MOLECULAR PHYLOGENY OF THE UPRIGHT ERYTHROPELTIDALES (COMPSOPOGONOPHYCEAE,RHODOPHYTA): MULTIPLE CRYPTIC LINEAGES OF ERYTHROTRICHIA CARNEA1

The phylogeny of morphologically simple algae is problematic due to insufficient morphological characters to aid in distinguishing species and relationships. The problem is further compounded because multiple evolutionary lineages of morphologically similar species occur in most well‐sampled biogeographic locations; therefore, location cannot be used as a proxy for species. The phylogeny of the upright members of the Erythropeltidales is partially clarified by combining molecular data, unialgal culture observations, and worldwide sampling. Our results show that there are several well‐supported lineages within the Erythropeltidales with only two morphologically recognizable taxa at present. The first is the genus Porphyrostromium, with a well‐developed basal crust, which includes two Erythrotrichia species (Porphyrostromium ligulatum comb. nov. and Porphyrostromium pulvinatum comb. nov.). The second is the branched species Erythrotrichia welwitschii (Rupr.) Batters. There are also six strongly supported Erythrotrichia carnea–like lineages. While not completely satisfactory, we propose that one lineage (lineage 2) with samples close to the type locality be designated as E. carnea with a specific isolate as an epitype. The lack of morphology to differentiate the other lineages leads to a taxonomy based solely on gene sequencing and molecular phylogeny, with rbcL sequences differentiating the lineages proposed. We hold off on proposing more species and genera until more data and samples can be gathered.     

Prevalence of Clonorchis sinensis metacercariae in freshwater fish from three latitudinal regions of the Korean Peninsula

A large-scale survey was conducted to investigate the infection status of fresh water fishes with Clonorchis sinensis metacercariae (CsMc) in 3 wide regions, which were tentatively divided by latitudinal levels of the Korean peninsula. A total of 4,071 freshwater fishes were collected from 3 regions, i.e., northern (Gangwon-do: 1,543 fish), middle (Chungcheongbuk-do and Gyeongsangbuk-do: 1,167 fish), and southern areas (Jeollanam-do, Ulsan-si, and Gyeongsangnam-do: 1,361 fish). Each fish was examined by the artificial digestion method from 2003 to 2010. In northern areas, only 11 (0.7%) fish of 2 species, Pungtungia herzi and Squalidus japonicus coreanus from Hantan-gang, Cheolwon-gun, Gangwon-do were infected with av. 2.6 CsMc. In middle areas, 149 (12.8%) fish were infected with av. 164 CsMc. In southern areas, 538 (39.5%) fish were infected with av. 159 CsMc. In the analysis of endemicity in 3 regions with an index fish, P. herzi, 9 (6.2%) of 146 P. herzi from northern areas were infected with av. 2.8 CsMc. In middle areas, 34 (31.8%) of 107 P. herzi were infected with av. 215 CsMc, and in southern areas, 158 (92.9%) of 170 P. herzi were infected with av. 409 CsMc. From these results, it has been confirmed that the infection status of fish with CsMc is obviously different among the 3 latitudinal regions of the Korean peninsula with higher prevalence and burden in southern regions.     

Raptor and Rheb negatively regulate skeletal myogenesis through suppression of insulin receptor substrate 1 (IRS1)

The mammalian target of rapamycin (mTOR) is essential for skeletal myogenesis through controlling distinct cellular pathways. The importance of the canonical mTOR complex 1 signaling components, including raptor, S6K1, and Rheb, had been suggested in muscle maintenance, growth, and metabolism. However, the role of those components in myogenic differentiation is not entirely clear. In this study we have investigated the functions of raptor, S6K1, and Rheb in the differentiation of C2C12 mouse myoblasts. We find that although mTOR knockdown severely impairs myogenic differentiation as expected, the knockdown of raptor, as well as Rheb, enhances differentiation. Consistent with a negative role for these proteins in myogenesis, overexpression of raptor or Rheb inhibits C2C12 differentiation. On the other hand, neither knockdown nor overexpression of S6K1 has any effect. Moreover, the enhanced differentiation elicited by raptor or Rheb knockdown is accompanied by increased Akt activation, elevated IRS1 protein levels, and decreased Ser-307 (human Ser-312) phosphorylation on IRS1. Finally, IRS1 knockdown eliminated the enhancement in differentiation elicited by raptor or Rheb knockdown, suggesting that IRS1 is a critical mediator of the myogenic functions of raptor and Rheb. In conclusion, the Rheb-mTOR/raptor pathway negatively regulates myogenic differentiation by suppressing IRS1-PI3K-Akt signaling. These findings underscore the versatility of mTOR signaling in biological regulations and implicate the existence of novel mTOR complexes and/or signaling mechanism in skeletal myogenesis.     

Crystal structure of class I acetohydroxy acid isomeroreductase from Pseudomonas aeruginosa

Acetohydroxy acid isomeroreductase (AHIR) is a key enzyme in the biosynthesis of branched-chain amino acids. We have determined the first crystal structure of a class I AHIR from Pseudomonas aeruginosa at 2.0 A resolution. Its dodecameric architecture of 23 point group symmetry is assembled of six dimeric units and dimerization is essential for the formation of the active site. The dimeric unit of P.aeruginosa AHIR partially superimposes with a three-domain monomer of spinach AHIR, a class II enzyme. This demonstrates that the so-called plant-specific insert in the middle of spinach AHIR is structurally and functionally equivalent to the C-terminal alpha-helical domain of P.aeruginosa AHIR, and the C-terminal alpha-helical domain was duplicated during evolution from the shorter, class I AHIRs to the longer, class II AHIRs. The dimeric unit of P.aeruginosa AHIR possesses a deep figure-of-eight knot, essentially identical with that in the spinach AHIR monomer. Thus, our work lowers the likelihood of the previous proposal that "domain duplication followed by exchange of a secondary structure element can be a source of such a knot in the protein structure" being correct.     

4-1BB-like molecule is expressed in islet-infiltrating mononuclear cells and in the gray matter of the brain

4-1BB is an inducible costimulatory molecule that can exert regulatory effects on T cells. Polyclonal antibodies against oligopeptides representing an evolutionarily-conserved region of murine 4-1BB, were prepared and used to stain tissues in normal and inflammatory conditions. The 4-1BB mRNA was detected in the PMA-treated spleen and heart, and constitutively in the brain, kidneys and lungs. The 4-1BB-like protein (BBLP) was expressed on mononuclear cells infiltrating islet cells in the pancreata of NOD mice. Expression was prominent in the early phase of insulitis and the level of expression diminished or disappeared in the later phase. BBLP was identified in the gray matter of brain where neuronal cell bodies, dendrites, and fiber terminals reside but was almost entirely absent in the white matter where axonal fibers dwell. A peculiar rosette pattern was observed in a granular layer of cerebellum and scattered in the stria terminalis. The staining pattern strongly resembled the receptor/nerve terminals in the brain and in the peripheral nervous system. Taken together, BBLP may be associated with the early phase of inflammation and with brain function.     

TopBP1 deficiency impairs V(D)J recombination during lymphocyte development

TopBP1 was initially identified as a topoisomerase II‐β‐binding protein and it plays roles in DNA replication and repair. We found that TopBP1 is expressed at high levels in lymphoid tissues and is essential for early lymphocyte development. Specific abrogation of TopBP1 expression resulted in transitional blocks during early lymphocyte development. These defects were, in major part, due to aberrant V(D)J rearrangements in pro‐B cells, double‐negative and double‐positive thymocytes. We also show that TopBP1 was located at sites of V(D)J rearrangement. In TopBP1‐deficient cells, γ‐H2AX foci were found to be increased. In addition, greater amount of γ‐H2AX product was precipitated from the regions where TopBP1 was localized than from controls, indicating that TopBP1 deficiency results in inefficient DNA double‐strand break repair. The developmental defects were rescued by introducing functional TCR αβ transgenes. Our data demonstrate a novel role for TopBP1 as a crucial factor in V(D)J rearrangement during the development of B, T and iNKT cells.