Fibroblast growth factor (FGF) signaling during gastrulation negatively modulates the abundance of microRNAs that regulate proteins required for cell migration and embryo patterning.

FGF signaling plays a pivotal role in regulating cell movements and lineage induction during gastrulation. Here we identify 44 microRNAs that are expressed in the primitive streak region of gastrula stage chicken embryos. We show that the primary effect of FGF signaling on microRNA abundance is to negatively regulate the levels of miR-let-7b, -9, -19b, -107, -130b, and -218. LIN28B inhibits microRNA processing and is positively regulated by FGF signaling. Gain- and loss-of-function experiments show that LIN28B negatively regulates the expression of miR-19b, -130b, and let-7b, whereas negative modulation of miR-9, -107, and -218 appears to be independent of LIN28B function. Predicted mRNA targets of the FGF-regulated microRNAs are over-represented in serine/threonine and tyrosine kinase receptors, including ACVR1, ACVR2B, PDGFRA, TGFBR1, and TGFBR3. Luciferase assays show that these and other candidates are targeted by FGF-regulated microRNAs. PDGFRA, a receptor whose activity is required for cell migration through the primitive streak, is a target of miR-130b and -218 in vivo. These results identify a novel mechanism by which FGF signaling regulates gene expression by negatively modulating microRNA abundance through both LIN28B-dependent and LIN28B-independent pathways.

FGF signalling through RAS/MAPK and PI3K pathways regulates cell movement and gene expression in the chicken primitive streak without affecting E-cadherin expression.

BACKGROUND: FGF signalling regulates numerous aspects of early embryo development. During gastrulation in amniotes, epiblast cells undergo an epithelial to mesenchymal transition (EMT) in the primitive streak to form the mesoderm and endoderm. In mice lacking FGFR1, epiblast cells in the primitive streak fail to downregulate E-cadherin and undergo EMT, and cell migration is inhibited. This study investigated how FGF signalling regulates cell movement and gene expression in the primitive streak of chicken embryos. RESULTS: We find that pharmacological inhibition of FGFR activity blocks migration of cells through the primitive streak of chicken embryos without apparent alterations in the level or intracellular localization of E-cadherin. E-cadherin protein is localized to the periphery of epiblast, primitive streak and some mesodermal cells. FGFR inhibition leads to downregulation of a large number of regulatory genes in the preingression epiblast adjacent to the primitive streak, the primitive streak and the newly formed mesoderm. This includes members of the FGF, NOTCH, EPH, PDGF, and canonical and non-canonical WNT pathways, negative modulators of these pathways, and a large number of transcriptional regulatory genes. SNAI2 expression in the primitive streak and mesoderm is not altered by FGFR inhibition, but is downregulated only in the preingression epiblast region with no significant effect on E-cadherin. Furthermore, over expression of SNAIL has no discernable effect on E-cadherin protein levels or localization in epiblast, primitive streak or mesodermal cells. FGFR activity modulates distinct downstream pathways including RAS/MAPK and PI3K/AKT. Pharmacological inhibition of MEK or AKT indicate that these downstream effectors control discrete and overlapping groups of genes during gastrulation. FGFR activity regulates components of several pathways known to be required for cell migration through the streak or in the mesoderm, including RHOA, the non-canonical WNT pathway, PDGF signalling and the cell adhesion protein N-cadherin. CONCLUSIONS: In chicken embryos, FGF signalling regulates cell movement through the primitive streak by mechanisms that appear to be independent of changes in E-cadherin expression or protein localization. The positive and negative effects on large groups of genes by pharmacological inhibition of FGF signalling, including major signalling pathways and transcription factor families, indicates that the FGF pathway is a focal point of regulation during gastrulation in chicken.

Emerging and Evolving Ovarian Cancer Animal Models.

Ovarian cancer (OC) is the leading cause of death from a gynecological malignancy in the United States. By the time a woman is diagnosed with OC, the tumor has usually metastasized. Mouse models that are used to recapitulate different aspects of human OC have been evolving for nearly 40 years. Xenograft studies in immunocompromised and immunocompetent mice have enhanced our knowledge of metastasis and immune cell involvement in cancer. Patient-derived xenografts (PDXs) can accurately reflect metastasis, response to therapy, and diverse genetics found in patients. Additionally, multiple genetically engineered mouse models have increased our understanding of possible tissues of origin for OC and what role individual mutations play in establishing ovarian tumors. Many of these models are used to test novel therapeutics. As no single model perfectly copies the human disease, we can use a variety of OC animal models in hypothesis testing that will lead to novel treatment options. The goal of this review is to provide an overview of the utility of different mouse models in the study of OC and their suitability for cancer research.

The mercury resistance (mer) operon in a marine gliding flavobacterium, Tenacibaculum discolor 9A5.

Genes conferring mercury resistance have been investigated in a variety of bacteria and archaea but not in bacteria of the phylum Bacteroidetes, despite their importance in many environments. We found, however, that a marine gliding Bacteroidetes species, Tenacibaculum discolor, was the predominant mercury-resistant bacterial taxon cultured from a salt marsh fertilized with mercury-contaminated sewage sludge. Here we report characterization of the mercuric reductase and the narrow-spectrum mercury resistance (mer) operon from one of these strains - T. discolor 9A5. This mer operon, which confers mercury resistance when cloned into Flavobacterium johnsoniae, encodes a novel mercury-responsive ArsR/SmtB family transcriptional regulator that appears to have evolved independently from other mercury-responsive regulators, a novel putative transport protein consisting of a fusion between the integral membrane Hg(II) transporter MerT and the periplasmic Hg(II)-binding protein MerP, an additional MerP protein, and a mercuric reductase that is phylogenetically distinct from other known mercuric reductases.

Associations of a polymorphism in the ornithine decarboxylase gene with colorectal cancer survival.

PURPOSE: Activity of ornithine decarboxylase (ODC), the first enzyme in polyamine synthesis, is required for normal growth and is elevated in many cancers, including colorectal cancer. We examined associations of the +316 ODC1 single nucleotide polymorphism (SNP) with colorectal cancer-specific survival among colorectal cancer cases, and then investigated its functional significance in colon cancer cells. EXPERIMENTAL DESIGN: The study included 400 incident stage I-III colorectal cancer cases from the population-based University of California Irvine Gene-Environment Study of Familial Colorectal Cancer (diagnosed from 1994 to 1996 with follow-up through March 2008). The primary outcome was colorectal cancer-specific survival dependent on ODC1 (rs2302615) genotype (GG versus GA/AA). In human colon cancer cell lines, ODC1 allele-specific binding of E-box transcription factors was determined via Western blotting and chromatin immunoprecipitation assays. ODC1 allele-specific promoter activity was determined using promoter constructs in combination with vectors expressing either the transcriptional activator c-MYC or the repressor MAD1. RESULTS: Genotype-specific survival differences were observed among colorectal cancer cases: compared with cases with the ODC1 GG genotype (hazards ratio, 1; reference) the adjusted colorectal cancer-specific survival hazards ratio was 2.02 (95% confidence interval, 1.17-3.50) for ODC1 GA/AA cases (P = 0.012). In colon cancer cells, the ODC1 SNP, flanked by two E-boxes, predicts ODC1 promoter activity. The E-box activator c-MYC and repressors MAD1 and MAD4 preferentially bind to ODC1 minor A-alleles, compared with major G-alleles, in cultured cells. CONCLUSIONS: These results have implications for conditional regulation of polyamine homeostasis and suggest a model in which the ODC1 SNP may be protective for colon adenoma recurrence and detrimental for survival after colon cancer diagnosis.