Project description:Mesocosms (600 L) were deployed at the Southern Ocean Time Series (SOTS) in Austral late summer during a high nutrient, low chlorophyll period. One mesocosm represented control, present-day conditions (high nutrients/low temperature/low pCO2/low Fe/low irradiance), while the other was amended to represent a projected 2100 scenario (low nutrients/high temperature/high pCO2/high Fe/high irradiance). Approximately 2 L were filtered from the mesocosms onto 5 µm filters at Days 0, 2, 4, and 7 of the incubation.
Project description:Polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs) are mega enzymes responsible for the biosynthesis of a large fraction of natural products (NPs). Molecular markers for biosynthetic genes, such as the ketosynthase (KS) domain of PKSs, have been used to assess the diversity and distribution of biosynthetic genes in complex microbial communities. More recently, metagenomic studies have complemented and enhanced this approach by allowing the recovery of complete biosynthetic gene clusters (BGCs) from environmental DNA. In this study, the distribution and diversity of biosynthetic genes and clusters from Arctic Ocean samples (NICE-2015 expedition), was assessed using PCR-based strategies coupled with high-throughput sequencing and metagenomic analysis. In total, 149 KS domain OTU sequences were recovered, 36 % of which could not be assigned to any known BGC. In addition, 74 bacterial metagenome-assembled genomes were recovered, from which 179 BGCs were extracted. A network analysis identified potential new NP families, including non-ribosomal peptides and polyketides. Complete or near-complete BGCs were recovered, which will enable future heterologous expression efforts to uncover the respective NPs. Our study represents the first report of biosynthetic diversity assessed for Arctic Ocean metagenomes and highlights the potential of Arctic Ocean planktonic microbiomes for the discovery of novel secondary metabolites. The strategy employed in this study will enable future bioprospection, by identifying promising samples for bacterial isolation efforts, while providing also full-length BGCs for heterologous expression.
Project description:Serum-dependent transcriptional networks identify distinct functional roles for H-ras and N-ras during initial stages of the cell cycle Using oligonucleotide microarrays, we compared gene expression transcriptional profiles corresponding to the initial cell cycle stages of mouse fibroblasts lacking H-Ras and/or NRas with those of matching, WT controls. The similarity of transcription profiles among serum-starved fibroblasts of all different WT and ras knockout genotypes tested, indicated that H-Ras and N-Ras do not play significant roles in control of transcriptional responses to serum deprivation stress. In contrast, genomic disruption of H-ras or N-ras, individually or in combination, determined highly specific, differential gene expression profiles in response to post-starvation stimulation with serum for 1 hour (G0/G1 transition) or for 8 hours (mid-G1 progression). The absence of N-Ras caused significantly higher changes than the absence of H-Ras on the wave of transcriptional activation linked to G0/G1 transition. In contrast, the absence of H-Ras affected more potently the profile of the transcriptional wave detected during mid-G1 progression. Functional analysis demonstrated a predominant functional association of H-Ras with growth and proliferation, whereas N-Ras exhibited a closer functional link to development or cell cycle regulation as well as immunomodulation and apoptosis. Mechanistic analysis indicated that ERK-dependent activation of Stat1 mediates the regulatory effect of N-Ras on defense and immunity, whereas the pro-apoptotic effects of N-Ras are mediated through ERK and p38 signaling. Our observations support previous reports of an absolute requirement for different peaks of Ras activity during the initial stages of the cell cycle and confirm the notion of functional specificity for the H-Ras and N-Ras isoforms. Keywords: different gene KO mice and time course
Project description:Ephexin1 was initially identified as a neuronal guanine nucleotide exchange factor involved in the control of neuronal development and synaptic homeostasis. Here, we demonstrate that the induction of Ephexin1 expression by an oncogenic K-Ras mutation amplifies the MAPK signaling via direct interaction with oncogenic Ras and contributes to colon and lung tumorigenesis. Ephexin1 cooperates with mutant Ras to accelerate skin tumorigenesis in vivo. In addition, we have demonstrated that the functionally relevant interaction between oncogenic K-Ras and Ephexin1. Together, these findings suggest that Ephexin1 serves as a positive regulator of Ras-driven oncogenesis and potentially represents a novel target for therapeutic intervention.
Project description:Comparison of gene expression in Ha-RAS transformed cells versus untransformed Caco-2. Comparison of gene expression in Ki-RAS transformed cells versus untransformed Caco-2.