Maternal imprinting at the H19-Igf2 locus maintains adult haematopoietic stem cell quiescence.

The epigenetic regulation of imprinted genes by monoallelic DNA methylation of either maternal or paternal alleles is critical for embryonic growth and development. Imprinted genes were recently shown to be expressed in mammalian adult stem cells to support self-renewal of neural and lung stem cells; however, a role for imprinting per se in adult stem cells remains elusive. Here we show upregulation of growth-restricting imprinted genes, including in the H19-Igf2 locus, in long-term haematopoietic stem cells and their downregulation upon haematopoietic stem cell activation and proliferation. A differentially methylated region upstream of H19 (H19-DMR), serving as the imprinting control region, determines the reciprocal expression of H19 from the maternal allele and Igf2 from the paternal allele. In addition, H19 serves as a source of miR-675, which restricts Igf1r expression. We demonstrate that conditional deletion of the maternal but not the paternal H19-DMR reduces adult haematopoietic stem cell quiescence, a state required for long-term maintenance of haematopoietic stem cells, and compromises haematopoietic stem cell function. Maternal-specific H19-DMR deletion results in activation of the Igf2-Igfr1 pathway, as shown by the translocation of phosphorylated FoxO3 (an inactive form) from nucleus to cytoplasm and the release of FoxO3-mediated cell cycle arrest, thus leading to increased activation, proliferation and eventual exhaustion of haematopoietic stem cells. Mechanistically, maternal-specific H19-DMR deletion leads to Igf2 upregulation and increased translation of Igf1r, which is normally suppressed by H19-derived miR-675. Similarly, genetic inactivation of Igf1r partly rescues the H19-DMR deletion phenotype. Our work establishes a new role for this unique form of epigenetic control at the H19-Igf2 locus in maintaining adult stem cells.

ESTIMATING BACTERIAL DIVERSITY IN SCIRTOTHRIPS DORSALIS (THYSANOPTERA: THRIPIDAE) VIA NEXT GENERATION SEQUENCING.

The last 2 decades have produced a better understanding of insect-microbial associations and yielded some important opportunities for insect control. However, most of our knowledge comes from model systems. Thrips (Thysanoptera: Thripidae) have been understudied despite their global importance as invasive species, plant pests and disease vectors. Using a culture and primer independent next-generation sequencing and metagenomics pipeline, we surveyed the bacteria of the globally important pest, Scirtothrips dorsalis Hood. The most abundant bacterial phyla identified were Actinobacteria and Proteobacteria and the most abundant genera were Propionibacterium, Stenotrophomonas, and Pseudomonas. A total of 189 genera of bacteria were identified. The absence of any vertically transferred symbiont taxa commonly found in insects is consistent with other studies suggesting that thrips primarilly acquire resident microbes from their environment. This does not preclude a possible beneficial/intimate association between S. dorsalis and the dominant taxa identified and future work should determine the nature of these associations.

De novo Assembly and Analysis of the Northern Leopard Frog Rana pipiens Transcriptome.

The northern leopard frog Rana (Lithobates) pipiens is an important animal model, being used extensively in cancer, neurology, physiology, and biomechanical studies. R. pipiens is a native North American frog whose range extends from northern Canada to southwest United States, but over the past few decades its populations have declined significantly and is now considered uncommon in large portions of the United States and Canada. To aid in the study and conservation of R. pipiens, this paper describes the first R. pipiens transcriptome. The R. pipiens transcriptome was annotated using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Eukaryotic Orthologous Groups (KOG). Differential expression analysis revealed universal and tissue specific genes, and endocrine-related genes were identified. Transcriptome assemblies and other sequence data are available for download.

Characterization of the Asian Citrus Psyllid Transcriptome.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a vector for the causative agents of Huanglongbing, which threatens citrus production worldwide. This study reports and discusses the first D. citri transcriptomes, encompassing the three main life stages of D. citri, egg, nymph and adult. The transcriptomes were annotated using Gene Ontology (GO) and insecticide-related genes within each life stage were identified to aid the development of future D. citri insecticides. Transcriptome assemblies and other sequence data are available for download at the International Asian Citrus Psyllid Genome Consortium website [http://psyllid.org/download] and at NCBI [http://www.ncbi.nlm.nih.gov/bioproject/29447].

The spring runoff in Nebraska's (USA) Elkhorn River watershed and its impact on two sentinel organisms.

The objectives of the present study were to determine 1) if temporal variability influenced the toxicity of Elkhorn River, Nebraska, USA, water, and 2) if the toxic effect was consistent between 2 sentinel organisms, the fathead minnow (Pimephales promelas) and the northern leopard frog (Rana pipiens). During spring 2012, atrazine indicator strips were used to document the occurrence of agrichemical pulses in the Elkhorn River. Polar organic chemical integrative samplers (POCIS) were deployed for 14 d during both a pulse and a postpulse period as indicated by the atrazine strips. Pesticide concentrations detected in the POCIS extracts ranged from 1.6-fold to 281-fold higher during the pulse period compared to the postpulse period. Fish and frog bioassays were conducted for 7 d, and hepatic mRNA expression of vitellogenin (VTG) and estrogen receptor alpha (ERα) was determined by quantitative real-time polymerase chain reaction. Compared with lab water controls, fish exposed to water collected during an agrichemical pulse experienced significant reductions in VTG and ERα, whereas exposed female frogs did not. Male leopard frogs, in contrast, experienced significant increases in the expression of ERα, whereas pulse-exposed male minnows did not. The significant effects observed following agrichemical pulse exposure demonstrate that episodic agrichemical runoff adversely impacts sentinel organisms, and that the adverse impacts observed depend on the sex and species of the sentinel organism.