Sex-biased egg cannibalism in spawning walleye pollock: the role of reproductive behavior

We studied inadvertent egg cannibalism in spawning stocks of walleye pollock, Theragra chalcogramma, in the Gulf of Alaska and the Bering Sea between 1986 and 1996. Male pollock had on average 3 times more eggs in their stomachs than females. For both sexes adult fish of average body length had more eggs in their stomach than did smaller or larger fish. When maturity of fish was taken into account, actively spawning males had the highest numbers of eggs in their stomachs. We found weak evidence for a diel variation; the number of eggs per stomach was high in both sexes during the day and lower during the night. We suggest two possible explanations for this phenomenon. Sex-biased egg cannibalism may reflect the differential time spent in layers of high egg densities. Hydroacoustic and trawl catch data from both areas suggest that males aggregate deeper than females. Spawning takes place in the deeper layers of the fish aggregation, so males spend more time in high egg densities. Alternatively, males may be more active than females and increased gill ventilation and/or drinking rates may be responsible for the differences in egg cannibalism.     

A cryptic frizzled module in cell surface collagen 18 inhibits Wnt/beta-catenin signaling

Collagens contain cryptic polypeptide modules that regulate major cell functions, such as cell proliferation or death. Collagen XVIII (C18) exists as three amino terminal end variants with specific amino terminal polypeptide modules. We investigated the function of the variant 3 of C18 (V3C18) containing a frizzled module (FZC18), which carries structural identity with the extracellular cysteine-rich domain of the frizzled receptors. We show that V3C18 is a cell surface heparan sulfate proteoglycan, its topology being mediated by the FZC18 module. V3C18 mRNA was expressed at low levels in 21 normal adult human tissues. Its expression was up-regulated in fibrogenesis and in small well-differentiated liver tumors, but decreased in advanced human liver cancers. Low FZC18 immunostaining in liver cancer nodules correlated with markers of high Wnt/beta-catenin activity. V3C18 (M(r) = 170 kD) was proteolytically processed into a cell surface FZC18-containing 50 kD glycoprotein precursor that bound Wnt3a in vitro through FZC18 and suppressed Wnt3a-induced stabilization of beta-catenin. Ectopic expression of either FZC18 (35 kD) or its 50 kD precursor inhibited Wnt/beta-catenin signaling in colorectal and liver cancer cell lines, thus downregulating major cell cycle checkpoint gatekeepers cyclin D1 and c-myc and reducing tumor cell growth. By contrast, full-length V3C18 was unable to inhibit Wnt signaling. In summary, we identified a cell-surface signaling pathway whereby FZC18 inhibits Wnt/beta-catenin signaling. The signal, encrypted within cell-surface C18, is released by enzymatic processing as an active frizzled cysteine-rich domain (CRD) that reduces cancer cell growth. Thus, extracellular matrix controls Wnt signaling through a collagen-embedded CRD behaving as a cell-surface sensor of proteolysis, conveying feedback cues to control cancer cell fate.     

Skeletal muscle collagen content in humans after high-force eccentric contractions.

The purpose of this study was to investigate the effects of high-force eccentric muscle contractions on collagen remodeling and on circulating levels of matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) in humans. Nine volunteers [5 men and 4 women, mean age 23 (SD 4) yr] each performed a bout of 100 maximum voluntary eccentric contractions of the knee extensors. Muscle biopsies were taken before exercise and on days 4 and 22 afterward. Image analysis of stained tissue sections was used to quantify endomysial collagen staining intensity. Maximum voluntary contractile isometric force was recorded preexercise and on days 1, 2, 3, 4, 8, 11, and 14 postexercise. Venipuncture blood samples were also drawn on these days for measurement of serum creatine kinase activity and concentrations of MMP-9, TIMP-1, TIMP-2, and the MMP-2/TIMP-2 complex. Maximum voluntary contractile force declined by 39 +/- 23% (mean +/- SD) on day 2 postexercise and recovered thereafter. Serum creatine kinase activity peaked on day 4 postexercise (P < 0.01). Collagen type IV staining intensity increased significantly on day 22 postexercise to 126 +/- 29% (mean +/- SD) of preexercise values (P < 0.05). Serum MMP-9 levels increased on day 8 postexercise (P < 0.01), and serum TIMP-1 was also significantly elevated on days 1, 2, 3, 4, and 14 postexercise (P < 0.05). These results suggest that a single bout of eccentric muscle contractions results in remodeling of endomysial type IV collagen, possibly via the MMP pathway.     

Production of a recombinant full-length collagen type I α-1 and of a 45-kDa collagen type I α-1 fragment in barley seeds

Recombinant DNA technology can be used to design and express collagen and gelatin-related proteins with predetermined composition and structure. Barley seed was chosen as a production host for a recombinant full-length collagen type I α1 (rCIa1) and a related 45-kDa rCIa1 fragment. The transgenic barley seeds were shown to accumulate both the rCIa1 and the 45-kDa rCIa1 fragment. Even when the amount of the rCIa1 was just above the detection threshold, this work using rCIa1 as a model demonstrated for the first time that barley seed can be used as a production system for collagen-related structural proteins. The 45-kDa rCI1a fragment expression, targeted to the endoplasmic reticulum, was controlled by three different promoters (a constitutive maize ubiquitin , seed endosperm-specific rice glutelin and germination-specific barley α - amylase fusion) to compare their effects on rCIa1 accumulation. Highest accumulation of the 45-kDa rCIa1 was obtained with the glutelin promoter (140 mg/kg seed), whereas the lowest accumulation was obtained with the α - amylase promoter. To induce homozygosity for stable 45-kDa rCIa1 production in the transgenic lines, doubled haploid (DH) progeny was generated through microspore culture. The 45-kDa rCIa1 expression levels achieved from the best DH lines were 13 mg/kg dry seeds under the ubiquitin promoter and 45 mg/kg dry seeds under the glutelin promoter. Mass spectroscopy and amino acid composition analysis of the purified 45-kDa rCIa1 fragment revealed that a small percent of prolines were hydroxylated with no additional detectable post-translational modifications.     

Co-expression of two mammalian glycosyltransferases in the yeast cell wall allows synthesis of sLex

Interactions between selectins and their oligosaccharide-decorated counter-receptors play an important role in the initiation of leukocyte extravasation in inflammation. L-selectin ligands are O-glycosylated with sulphated sialyl Lewis X epitopes (sulpho-sLex). Synthetic sLex oligosaccharides have been shown to inhibit adhesion of lymphocytes to endothelium at sites of inflammation. Thus, they could be used to prevent undesirable inflammatory reactions such as rejection of organ transplants. In vitro synthesis of sLex glycans is dependent on the availability of recombinant glycosyltransferases. Here we expressed the catalytic domain of human alpha-1,3-fucosyltransferase VII in the yeasts Saccharomyces cerevisiae and Pichia pastoris. To promote proper folding and secretion competence of this catalytic domain in yeast, it was fused to the Hsp150 delta carrier, which is an N-terminal fragment of a secretory glycoprotein of S. cerevisiae. In both yeasts, the catalytic domain acquired an active conformation and the fusion protein was externalised, but remained mostly attached to the cell wall in a non-covalent fashion. Incubation of intact S. cerevisiae or P. pastoris cells with GDP-[14C]fucose and sialyl-alpha-2,3-N-acetyllactosamine resulted in synthesis of radioactive sLex, which diffused to the medium. Finally, we constructed an S. cerevisiae strain co-expressing the catalytic domains of alpha-2,3-sialyltransferase and alpha-1,3-fucosyltransferase VII, which were targeted to the cell wall. When these cells were provided with N-acetyllactosamine, CMP-sialic acid and GDP-[14C]fucose, radioactive sLex was produced to the medium. These data imply that yeast cells can provide a self-perpetuating source of fucosyltransferase activity immobilized in the cell wall, useful for the in vitro synthesis of sLex.     

Polymorphisms of the ITGAM gene confer higher risk of discoid cutaneous than of systemic lupus erythematosus

Background

Lupus erythematosus (LE) is a heterogeneous disease ranging from mainly skin-restricted manifestations (discoid LE [DLE] and subacute cutaneous LE) to a progressive multisystem disease (systemic LE [SLE]). Genetic association studies have recently identified several strong susceptibility genes for SLE, including integrin alpha M (ITGAM), also known as CD11b, whereas the genetic background of DLE is less clear.

Principal Findings

To specifically investigate whether ITGAM is a susceptibility gene not only for SLE, but also for cutaneous DLE, we genotyped 177 patients with DLE, 85 patients with sporadic SLE, 190 index cases from SLE families and 395 population control individuals from Finland for nine genetic markers at the ITGAM locus. SLE patients were further subdivided by the presence or absence of discoid rash and renal involvement. In addition, 235 Finnish and Swedish patients positive for Ro/SSA-autoantibodies were included in a subphenotype analysis. Analysis of the ITGAM coding variant rs1143679 showed highly significant association to DLE in patients without signs of systemic disease (P-value  = 4.73×10⁻¹¹, OR  = 3.20, 95% CI  = 2.23–4.57). Significant association was also detected to SLE patients (P-value  = 8.29×10⁻⁶, OR  = 2.14, 95% CI  = 1.52–3.00), and even stronger association was found when stratifying SLE patients by presence of discoid rash (P-value  = 3.59×10⁻⁸, OR  = 3.76, 95% CI  = 2.29–6.18).

Significance

We propose ITGAM as a novel susceptibility gene for cutaneous DLE. The risk effect is independent of systemic involvement and has an even stronger genetic influence on the risk of DLE than of SLE.     

Belowground interspecific competition in mixed boreal forests: fine root and ectomycorrhiza characteristics along stand developmental stage and soil fertility gradients

We studied fine roots and ectomycorrhizas in relation to aboveground tree and stand characteristics in five mixed Betula pendula Roth, Picea abies (L.) H. Karst., and Pinus sylvestris L. stands in Southern Finland. The stands formed gradients of developmental stage (15-, 30-, and 50-year-old stands) in the stands of medium fertility, and of site fertility in the young stands (30-year-old fertile, medium fertile, and least fertile stands). The biomass of the external hyphae of ectomycorrhizas (ECM) was the highest, and the diversity of the fungal community the lowest, in the most fertile stand. The vertical distributions of fine roots of the three tree species were mostly overlapping, indicating high inter-specific belowground competition in the stands. We did not find any clear trends in the fine root biomass (FRB) or length across the stand developmental stages. The FRB of the conifers varied with site fertility, whereas in B. pendula it was almost constant. In contrast to the conifers, the specific root length (SRL) of B. pendula clearly increased from the most fertile to the least fertile stand. This indicates differences in the primary nutrient acquisition strategy between conifers and B. pendula.