Search

We combined county-based data for tularemia incidence from 1990 to 2003 for a nine-state region (Arkansas, Illinois, Indiana, Kansas, Kentucky, Missouri, Nebraska, Oklahoma, and Tennessee) in the southcentral United States with Geographic Information System (GIS)-based environmental data to determine associations between coverage by different habitats (especially dry forest representing suitable tick habitat) and tularemia incidence. High-risk counties (> 1 case per 100,000 person-years) clustered in Arkansas-Missouri and far eastern Oklahoma and Kansas. County tularemia incidence was positively associated with coverage by dry forested habitat suitable for vector ticks for Oklahoma-Kansas-Nebraska and Arkansas-Missouri but not for Illinois-Indiana-Kentucky-Tennessee. A multivariate logistic regression model predicting presence of areas with risk of tularemia based on GIS-derived environmental data was developed for the Arkansas-Missouri tularemia focus. The study shows the potential for research on tularemia ecoepidemiology and highlights the need for further modeling efforts based on acarologic data and more fine-scale point or zip code/census tract epidemiologic data.

Aquatic ecosystems are connected to their surrounding watersheds through inputs of terrestrial-derived dissolved organic matter (DOM). The assimilation of this allochthonous resource by recipient bacterioplankton has consequences for food webs and the biogeochemistry of aquatic ecosystems. We used laboratory batch experiments to examine how variation in the source and supply (i.e. concentration) of DOM affects the productivity, respiration and growth efficiency of heterotrophic lake bacterioplankton. We created 6 different DOM sources from soils beneath near- monotypic tree stands in a temperate deciduous-coniferous forest. We then exposed freshwater microcosms containing a natural microbial community to a 1100 µM supply gradient of each DOM source. Bacterial productivity (BP) and bacterial respiration (BR) increased linearly over the broad gradient, on average consuming 7% of the standing pool of dissolved organic carbon (DOC). Bacter- ial metabolism was also influenced by the chemical composition of the DOM source. Carbon-specific productivity declined exponentially with an increase in the carbon:phosphorus (C:P) ratio of the dif- ferent DOM sources, consistent with the predictions of ecological stoichiometry. Together, our short- term laboratory experiments quantitatively describe the metabolic responses of freshwater bacterio- plankton to variation in the supply of terrestrial-derived DOM. Furthermore, our results suggest that dissolved organic phosphorus (DOP) content, which may be linked to the identity of terrestrial vege- tation, is indicative of DOM quality and influences the productivity of freshwater bacterioplankton.

We combined county-based data for tularemia incidence from 1990 to 2003 for a nine-state region (Arkansas, Illinois, Indiana, Kansas, Kentucky, Missouri, Nebraska, Oklahoma, and Tennessee) in the southcentral United States with Geographic Information System (GIS)-based environmental data to determine associations between coverage by different habitats (especially dry forest representing suitable tick habitat) and tularemia incidence. High-risk counties (1 case per 100,000 person-years) clustered in Arkansas-Missouri and far eastern Oklahoma and Kansas. County tularemia incidence was positively associated with coverage by dry forested habitat suitable for vector ticks for Oklahoma-Kansas-Nebraska and Arkansas-Missouri but not for Illinois-Indiana-Kentucky-Tennessee. A multivariate logistic regression model predicting presence of areas with risk of tularemia based on GIS-derived environmental data was developed for the Arkansas-Missouri tularemia focus. The study shows the potential for research on tularemia ecoepidemiology and highlights the need for further modeling efforts based on acarologic data and more fine-scale point or zip code/census tract epidemiologic data.

Ovarian estrogen exerts both positive and negative feedback control over luteinizing hormone (LH) secretion during the ovulatory cycle. Estrogen receptor (ER) α but not ERβ knockout mice lack estrogen feedback. Thus, estrogen feedback appears to be primarily mediated by ERα. However, it is now recognized that, in addition to binding to estrogen response elements (EREs) in DNA to alter target gene transcription, ERα signals through ERE-independent or nonclassical pathways, and the relative contributions of these pathways in conveying estrogen feedback remain unknown. Previously we created a knockin mouse model expressing a mutant form of ERα (AA) with ablated ERE-dependent but intact ERE-independent activity. Breeding this allele onto the ERα-null (−/−) background, we examine the ability of ERE-independent ERα signaling pathways to convey estrogen feedback regulation of the female hypothalamic–pituitary axis in vivo . ERα −/AA exhibited 69.9% lower serum LH levels compared with ERα −/− mice. Additionally, like wild type, ERα −/AA mice exhibited elevated LH after ovariectomy (OVX). Furthermore, the post-OVX rise in serum LH was significantly suppressed by estrogen treatment in OVX ERα −/AA mice. However, unlike wild type, both ERα −/AA and ERα −/− mice failed to exhibit estrous cyclicity, spontaneous ovulation, or an afternoon LH surge response to estrogen. These results indicate that ERE-independent ERα signaling is sufficient to convey a major portion of estrogen's negative feedback actions, whereas positive feedback and spontaneous ovulatory cyclicity require ERE-dependent ERα signaling.

Transcription factors, such as PDX-1, that normally mediate pancreatic development are capable of inducing hepatic progenitor cells to differentiate into cells with pancreatic islet characteristics. We hypothesized that simultaneous expression of multiple transcription factors involved in islet development might enhance the differentiation of hepatic progenitor cells. Bi- or tri-cistronic constructs were generated in hybrid adenovirus/adeno-associated virus (Ad/AAV) vectors containing neurogenin 3 (NGN3), BETA2 (NeuroD), and RIPE3b1 (MafA), each of which plays a role in islet cell differentiation. These vectors efficiently express multiple transcription factors and stimulate insulin promoter activity in a combinatorial manner. When these multi-cistronic constructs were administered in vivo, they induce hepatic expression of islet-specific markers, including PDX-1, insulin, glucagon, somatostatin, and islet-amyloid peptide. Administration of the Ad/AAV hybrid vectors to streptozotocin-induced diabetic mice reversed hyperglycemia, consistent the differentiation of functional hepatic insulin-secreting cells. These results indicate that Ad/AAV hybrid vectors can be used to administer combinations of factors that induce islet cell differentiation in hepatic progenitor cells.

Acting via the estrogen receptor (ER), estradiol exerts pleomorphic effects on the uterus, producing cyclical waves of cellular proliferation and differentiation in preparation for embryo implantation. In the classical pathway, the ER binds directly to an estrogen response element to activate or repress gene expression. However, emerging evidence supports the existence of nonclassical pathways in which the activated ER alters gene expression through protein-protein tethering with transcription factors such as c-Fos/c-Jun B (AP-1) and Sp1. In this report, we examined the relative roles of classical and nonclassical ER signaling in vivo by comparing the estrogen-dependent uterine response in mice that express wild-type ERalpha, a mutant ERalpha (E207A/G208A) that selectively lacks ERE binding, or ERalpha null. In the compound heterozygote (AA/-) female, the nonclassical allele (AA) was insufficient to mediate an acute uterotrophic response to 17beta-estradiol (E2). The uterine epithelial proliferative response to E2 and 4-hydroxytamoxifen was retained in the AA/-females, and uterine luminal epithelial height increased commensurate with the extent of ERalpha signaling. This proliferative response was confirmed by 5-bromo-2'-deoxyuridine incorporation. Microarray experiments identified cyclin-dependent kinase inhibitor 1A as a nonclassical pathway-responsive gene, and transient expression experiments using the cyclin-dependent kinase inhibitor 1A promoter confirmed transcriptional responses to the ERalpha (E207A/G208A) mutant. These results indicate that nonclassical ERalpha signaling is sufficient to restore luminal epithelial proliferation but not other estrogen-responsive events, such as fluid accumulation and hyperemia. We conclude that nonclassical pathway signaling via ERalpha plays a critical physiologic role in the uterine response to estrogen.

Osteosarcoma (OSA) is the most common bone tumor in children. Dose intensive therapies have resulted in survival rates of 75%, however for patients with metastasis at diagnosis, the survival rate is only 20%, indicating the need for improved therapeutic strategies for metastatic osteosarcoma. Unfortunately, the availability of human OSA samples for study is extremely limited; however, over 10,000 canine patients spontaneously develop OSA annually and canine tumors share common histological features, genetic mutations and gene expression profiles with human OSA. To identify factors that contribute to metastasis and chemotherapeutic resistance of OSA, we assessed the gene expression signatures of normal bone and groups of primary canine OSA tumors surgically resected from dogs with short (300 day) disease free intervals (DFI) following standard treatment. Insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) was identified as a negative prognostic indicator in this canine OSA study. IGF2BP1 is an oncofetal protein that binds multiple RNA targets to regulate their nuclear transport, stability, translation and subcellular localization. We have further investigated the role of IGF2BP1 in the development and metastatic progression of both human and canine osteosarcoma. IGF2BP1 transcripts were virtually undetectable on microarray analysis of normal bone and up-regulated greater-than 65-fold in both canine tumor groups relative to normal bone. RT-qPCR analysis validated these findings demonstrating a stair-step pattern of expression in which normal bone had virtually no IGF2BP1 expression, and IGF2BP1 expression was elevated 132-fold and 915-fold compared to normal bone in the long and short DFI tumor groups, respectively. Array CGH analysis revealed no genomic amplification of the IGF2BP1 locus, but 3′ UTR truncation may contribute to increased IGF2BP1 mRNA half-life. Similarly, human osteosarcoma cell lines, on average, expressed 14-fold higher levels of IGF2BP1 transcripts compared to human osteoblasts. Further, in the MG63.2 cell line, a metastatic variant of the MG63 human OSA cell line, we measured elevated mRNA transcripts (five-fold, p=0.0368) and protein levels (seven-fold), implicating IGF2BP1 in metastasis of osteosarcoma. IGF2BP1 knockdown in shRNA-expressing MG63.2 clones resulted in a three-fold (p Citation Format: Liza E. Pfaff, Brian T. Kalet, Deanna D. Dailey, Dawn L. Duval. Insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) drives growth, metastasis and chemoresistance in human and canine osteosarcoma. [abstract]. In: Proceedings of the AACR Special Conference: The Translational Impact of Model Organisms in Cancer; Nov 5-8, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(11 Suppl):Abstract nr A23.

Mutations of orphan nuclear receptors SF1 and DAX1 each cause adrenal insufficiency and gonadal dysgenesis in humans, although the pathological features are distinct. Because Dax1 antagonizes Sf1-mediated transcription in vitro, we hypothesized that Dax1 deficiency would compensate for allelic loss of Sf1. In studies of the developing testis, expression of the fetal Leydig cell markers Cyp17 and Cyp11a1 was reduced in heterozygous Sf1-deficient mice at E13.5, consistent with dose-dependent effects of Sf1. In Sf1/Dax1 (Sf1 heterozygous and Dax1-deleted) double mutant gonads, the expression of these genes was unexpectedly reduced further,indicating that loss of Dax1 did not compensate for reduced Sf1 activity. The Sertoli cell product Dhh was reduced in Sf1 heterozygotes at E11.5, and it was undetectable in Sf1/Dax1 double mutants, indicating that Sf1 and Dax1 function cooperatively to induce Dhh expression. Similarly, Amh expression was reduced in both Sf1 and Dax1 single mutants at E11.5, and it was not rescued by the Sf1/Dax1 double mutant. By contrast, Sox9 was expressed in single and in double mutants, suggesting that various Sertoli cell genes are differentially sensitive to Sf1 and Dax1 function. Reduced expression of Dhh and Amh was transient, and was largely restored by E12.5. Similarly, there was recovery of fetal Leydig cell markers by E14.5, indicating that loss of Sf1/Dax1 delays but does not preclude fetal Leydig cell development. Thus, although Sf1 and Dax1 function as transcriptional antagonists for many target genes in vitro, they act independently or cooperatively in vivo during male gonadal development.

Background Hairy and enhancer of split 1 (HES1), a basic helix-loop-helix transcriptional repressor, is a downstream target of Notch signaling. Notch signaling and HES1 expression have been linked to growth and survival in a variety of human cancer types and have been associated with increased metastasis and invasiveness in human osteosarcoma cell lines. Osteosarcoma (OSA) is an aggressive cancer demonstrating both high metastatic rate and chemotherapeutic resistance. The current study examined expression of Notch signaling mediators in primary canine OSA tumors and canine and human osteosarcoma cell lines to assess their role in OSA development and progression. Results Reverse transcriptase - quantitative PCR (RT-qPCR) was utilized to quantify HES1, HEY1, NOTCH1 and NOTCH2 gene expression in matched tumor and normal metaphyseal bone samples taken from dogs treated for appendicular OSA at the Colorado State University Veterinary Teaching Hospital. Gene expression was also assessed in tumors from dogs with a disease free interval (DFI) of 300 days following treatment with surgical amputation followed by standard chemotherapy. Immunohistochemistry was performed to confirm expression of HES1. Data from RT-qPCR and immunohistochemical (IHC) experiments were analyzed using REST2009 software and survival analysis based on IHC expression employed the Kaplan-Meier method and log rank analysis. Unbiased clustered images were generated from gene array analysis data for Notch/HES1 associated genes. Gene array analysis of Notch/HES1 associated genes suggested alterations in the Notch signaling pathway may contribute to the development of canine OSA. HES1 mRNA expression was elevated in tumor samples relative to normal bone, but decreased in tumor samples from dogs with a DFI 300 days. NOTCH2 and HEY1 mRNA expression was also elevated in tumors relative to normal bone, but was not differentially expressed between the DFI tumor groups. Survival analysis confirmed an association between decreased HES1 immunosignal and shorter DFI. Conclusions Our findings suggest that activation of Notch signaling occurs and may contribute to the development of canine OSA. However, association of low HES1 expression and shorter DFI suggests that mechanisms that do not alter HES1 expression may drive the most aggressive tumors.