Genome-Wide Analysis Reveals a Major Role in Cell Fate Maintenance and an Unexpected Role in Endoreduplication for the Drosophila FoxA Gene Fork Head

Transcription factors drive organogenesis, from the initiation of cell fate decisions to the maintenance and implementation of these decisions. The Drosophila embryonic salivary gland provides an excellent platform for unraveling the underlying transcriptional networks of organ development because Drosophila is relatively unencumbered by significant genetic redundancy. The highly conserved FoxA family transcription factors are essential for various aspects of organogenesis in all animals that have been studied. Here, we explore the role of the single Drosophila FoxA protein Fork head (Fkh) in salivary gland organogenesis using two genome-wide strategies. A large-scale in situ hybridization analysis reveals a major role for Fkh in maintaining the salivary gland fate decision and controlling salivary gland physiological activity, in addition to its previously known roles in morphogenesis and survival. The majority of salivary gland genes (59%) are affected by fkh loss, mainly at later stages of salivary gland development. We show that global expression of Fkh cannot drive ectopic salivary gland formation. Thus, unlike the worm FoxA protein PHA-4, Fkh does not function to specify cell fate. In addition, Fkh only indirectly regulates many salivary gland genes, which is also distinct from the role of PHA-4 in organogenesis. Our microarray analyses reveal unexpected roles for Fkh in blocking terminal differentiation and in endoreduplication in the salivary gland and in other Fkh-expressing embryonic tissues. Overall, this study demonstrates an important role for Fkh in determining how an organ preserves its identity throughout development and provides an alternative paradigm for how FoxA proteins function in organogenesis

Rotifer communities under variable predation-turbulence combinations

The effects of water turbulence on rotifer communities were experimentally studied under different predation pressures. When the larvae of the phantom midge (Chaoborus flavicans) were present in turbulent water, the abundance of most rotifer taxa was enhanced. Especially the genera Chromogaster, Keratella, Polyarthra, and Trichocerca, increased in abundance. In calm water, chaoborids did not affect the rotifer community. In turbulent water predation by chaoborids was targeted more towards cladocerans (Bosmina sp.) and predation pressure on rotifers was relaxed. Additionally, reduced competition with cladocerans probably contributed to the increase of rotifer abundance. Turbulence alone had no significant effect on rotifer abundance because their individual size was small compared with the diameter of the turbulent eddies. The study suggested that the effects of turbulence on rotifers is not direct but takes place through changed predator-prey relations, i.e., the effect depends on the abundance of invertebrate predators. In aquatic ecosystems with a high density of chaoborids, increasing turbulence can considerably increase the abundance of rotifers.Peer reviewe

Oncostatin M drives intestinal inflammation and predicts response to tumor necrosis factor-neutralizing therapy in patients with inflammatory bowel disease

Inflammatory bowel diseases (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), are complex chronic inflammatory conditions of the gastrointestinal tract that are driven by perturbed cytokine pathways. Anti-tumour necrosis factor-α (TNF) antibodies are a mainstay therapeutic approach for IBD. However, up to 40% of patients are non-responsive to anti-TNF agents, and identifying alternative therapeutic targets is a priority. Here we show that expression of the cytokine Oncostatin M (OSM) and its receptor (OSMR) is increased in the inflamed intestine of IBD patients compared to healthy controls, and correlates closely with histopathological disease severity. OSMR is expressed in non-hematopoietic, non-epithelial intestinal stromal cells, which respond to OSM by producing various pro-inflammatory factors including interleukin-6 (IL-6), the leukocyte adhesion factor ICAM-1, and chemokines that attract neutrophils, monocytes, and T cells. In an animal model of anti-TNF refractory intestinal inflammation, genetic deletion or pharmacological blockade of OSM significantly attenuates colitis. Furthermore, high pre-treatment OSM expression is strongly associated with failure of anti-TNF therapy based on analysis of over 200 IBD patients, including two cohorts from phase 3 clinical trials of infliximab and golimumab. OSM is thus a potential biomarker and therapeutic target for IBD, with particular relevance for anti-TNF refractory patients

Zooplankton grazing on Phaeocystis: A quantitative review and future challenges

The worldwide colony-forming haptophyte phytoplankton Phaeocystis spp. are key organisms in trophic and biogeochemical processes in the ocean. Many organisms from protists to fish ingest cells and/or colonies of Phaeocystis. Reports on specific mortality of Phaeocystis in natural plankton or mixed prey due to grazing by zooplankton, especially protozooplankton, are still limited. Reported feeding rates vary widely for both crustaceans and protists feeding on even the same Phaeocystis types and sizes. Quantitative analysis of available data showed that: (1) laboratory-derived crustacean grazing rates on monocultures of Phaeocystis may have been overestimated compared to feeding in natural plankton communities, and should be treated with caution; (2) formation of colonies by P. globosa appeared to reduce predation by small copepods (e.g., Acartia, Pseudocalanus, Temora and Centropages), whereas large copepods (e.g., Calanus spp.) were able to feed on colonies of Phaeocystis pouchetii; (3) physiological differences between different growth states, species, strains, cell types, and laboratory culture versus natural assemblages may explain most of the variations in reported feeding rates; (4) chemical signaling between predator and prey may be a major factor controlling grazing on Phaeocystis; (5) it is unclear to what extent different zooplankton, especially protozooplankton, feed on the different life forms of Phaeocystis in situ. To better understand the mechanisms controlling zooplankton grazing in situ, future studies should aim at quantifying specific feeding rates on different Phaeocystis species, strains, cell types, prey sizes and growth states, and account for chemical signaling between the predator and prey. Recently developed molecular tools are promising approaches to achieve this goal in the future. © 2007 Springer Science+Business Media B.V