Modification of BRCA1-associated breast cancer risk by the polymorphic androgen-receptor CAG repeat

Compared with the general population, women who have inherited a germline mutation in the BRCA1 gene have a greatly increased risk of developing breast cancer. However, there is also substantial interindividual variability in the occurrence of breast cancer among BRCA1 mutation carriers. We hypothesize that other genes, particularly those involved in endocrine signaling, may modify the BRCA1-associated age-specific breast cancer risk. We studied the effect of the CAG repeat-length polymorphism found in exon 1 of the androgen-receptor (AR) gene (AR-CAG). AR alleles containing longer CAG repeat lengths are associated with a decreased ability to activate androgen-responsive genes. Using a sample of women who inherited germline BRCA1 mutations, we compared AR-CAG repeat length in 165 women with and 139 women without breast cancer. We found that women were at significantly increased risk of breast cancer if they carried at least one AR allele with >/=28 CAG repeats. Women who carried an AR-CAG allele of >/=28, >/=29, or >/=30 repeats were given a diagnosis 0.8, 1.8, or 6.3 years earlier than women who did not carry at least one such allele. All 11 women in our sample who carried at least one AR-CAG allele with >/=29 repeats had breast cancer. Our results support the hypothesis that age at breast cancer diagnosis is earlier among BRCA1 mutation carriers who carry very long AR-CAG repeats. These results suggest that pathways involving androgen signaling may affect the risk of BRCA1-associated breast cancer.     

Photolytic Generation of Nitric Oxide through a Porous Glass Partitioning Membrane

We report a new method of generating nitric oxide that possesses several potential advantages for experimental use. This method consists of a microphotolysis chamber where NO is released by illuminating photolabile NO donors with light from a xenon lamp. NO then diffuses through a porous glass membrane to the experimental preparation. We observed that the rate of NO generation is a linear function of light intensity. Due to a dynamic equilibrium between the mechanisms of NO generation and dissipation (by diffusion or oxidation) the NO concentration in the experimental cuvette can be reversibly and reproducibly controlled. The major potential advantages of this device include its use as a NO point source, and the ability to partition the NO donor compound from the experimental preparation by a porous glass membrane. The diffusion of the caging moiety through the membrane is insignificant as seen by absorption spectroscopy due to its large relative size to NO. In this way, the porous glass membrane protects the preparation from the potential bioactive effects of the caging moiety, which is an important consideration for biological experiments.     

Cytotoxicity mediated by tumor necrosis factor in variant subclones of the ME-180 cervical carcinoma line: modulation by specific inhibitors of DNA topoisomerase II

The mechanism of tumor necrosis factor (TNF)-induced cytotoxicity has been investigated using two clonal variants of the ME-180 human cervical carcinoma cell line. The clonal lines were characterized with respect to their expression of TNF receptors, kinetics of cell death, and their ability to communicate intercellularly through gap junctions. The ME-180.4 and ME-180.8 clones were identified by their relative sensitivity to TNF induced lysis in a 24-h assay. The dose of TNF required to kill 50% of the target cells was 60 pM for the sensitive ME-180.4 and 2.5 nM for the ME-180.8. However, when assay times were extended, the dose response for both clones was the same, indicating that a difference in the kinetics of cell death and not absolute TNF sensitivity existed between the ME-180.4 and ME-180.8 clones. Both clones were gap junction deficient as judged by their inability to transfer Lucifer yellow or 6-carboxyfluorescein, a characteristic phenotype of cells sensitive to cytotoxicity by TNF. The level of surface receptor expressed on these clones was nearly identical with a Kd = 0.3 nM and 5,000 binding sites per cell. Measurement of the kinetics of cell death revealed that the time between the addition of TNF and the onset of observed cell death (induction phase) was much shorter for the ME-180.4 (32-55 h) than for the resistant ME-180.8 (55-80 h). Mitomycin C, a DNA alkylating agent, significantly reduced the length of the induction phase for both clones, although the kinetic difference between the clones remained unchanged. Two epipodophyllotoxins, VP-16 and VM-26, which specifically inhibit the rejoining activity of DNA topoisomerase II, showed a 10-100-fold synergistic effect when combined with TNF as shown by isobologram analysis. VM-26 when added to the resistant ME-180.8 clones decreased the length of induction phase and abolished the kinetic difference observed with the ME-180.4 clone. These results indicate that the variance in the TNF response of these two clones was closely associated with DNA topoisomerase II, and suggest that this enzyme may play an important role in TNF mediated cytotoxicity.     

An assessment of shallow and mesophotic reef brachyuran crab assemblages on the south shore of O‘ahu,Hawai‘i

Shallow coral reefs are extensively studied but, although scleractinian corals have been recorded to 165 m, little is known about other mesophotic coral reef ecosystem (MCE) inhabitants. Brachyuran crabs fill many ecological and trophic niches on reefs, making them ideal candidates for evaluating species composition among depths to ask whether MCEs host the same communities as shallower reef communities that have been well studied. Here we deployed autonomous reef monitoring structures for 2 yr on the south shore of O‘ahu along a depth gradient (12, 30, 60, and 90 m) to sample and assess brachyuran crab communities. A total of 663 brachyuran crabs representing 69 morphospecies (16 families) were found. Community composition was not significantly different within depths, but was highly stratified by depth. Each depth was distinct, but the 30 and 60 m depths were least dissimilar from one another. We show that deeper reefs host significantly different brachyuran communities, and at much lower total abundance, than shallow reefs in Hawai‘i, with 4–27 unique morphospecies per depth and only 3 of 69 morphospecies (~4 %) occurring across the entire depth range sampled.     

Applications and potential of genome editing in crop improvement

Genome-editing tools provide advanced biotechnological techniques that enable the precise and efficient targeted modification of an organism’s genome. Genome-editing systems have been utilized in a wide variety of plant species to characterize gene functions and improve agricultural traits. We describe the current applications of genome editing in plants, focusing on its potential for crop improvement in terms of adaptation, resilience, and end-use. In addition, we review novel breakthroughs that are extending the potential of genome-edited crops and the possibilities of their commercialization. Future prospects for integrating this revolutionary technology with conventional and new-age crop breeding strategies are also discussed.     

Genome-wide association study of stem rust resistance in a world collection of cultivated barley

Key message

QTL conferring a 14–40% reduction in adult plant stem rust severity to multiple races of Pgt were found on chromosome 5H and will be useful in barley breeding.

Abstract

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt) is an important disease of barley. The resistance gene Rpg1 has protected the crop against stem rust losses for over 70 years in North America, but is not effective against the African Pgt race TTKSK (and its variants) nor the domestic race QCCJB. To identify resistance to these Rpg1-virulent races, the Barley iCore Collection, held by the United States Department of Agriculture-Agricultural Research Service National Small Grains Collection was evaluated for adult plant resistance (APR) and seedling resistance to race TTKSK and APR to race QCCJB and the Pgt TTKSK composite of races TTKSK, TTKST, TTKTK, and TTKTT. Using a genome-wide association study approach based on 6224 single nucleotide polymorphic markers, seven significant loci for stem rust resistance were identified on chromosomes 1H, 2H, 3H, and 5H. The most significant markers detected were 11_11355 and SCRI_RS_177017 at 71–75 cM on chromosome 5H, conferring APR to QCCJB and TTKSK composite. Significant markers were also detected for TTKSK seedling resistance on chromosome 5H. All markers detected on 5H were independent of the rpg4/Rpg5 complex at 152–168 cM. This study verified the importance of the 11_11355 locus in conferring APR to races QCCJB and TTKSK and suggests that it may be effective against other races in the Ug99 lineage.