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Inv(16)(p13q22)/t(16;16)(p13.1;q22) is one of the most common chromosomal mutations found in human acute myeloid leukemia (AML). This inversion on chromosome 16 creates a fusion gene CBFb-MYH11 and leads to the expression of a fusion protein CBFβ-SMMHC. Expression of Cbfβ-SMMHC (CM) in a conditional Cbfb-MYH11 knock-in mouse model (Cbfb+/56M/Mx1-Cre) leads to development of spontaneous AML with the acquisition of additional genetic and epigenetic alterations. In order to further understand the underlying mechanism(s) driving leukemogenesis and identify predictive biomarkers during disease progression, we performed RNA-seq to track changes of transcriptiome in time series peripheral blood samples using illumina HiSeq sequencer. A cohort of 16 mice were included in the experiment, 9 out of which are CM conditional knock-in mice and the remaining 7 are controls. Peripheral blood samples were collected before the induction of CM expression as the "0" time point samples. After induction, peripheral blood samples were collected at 1, 2, 3.5, 4.5, 5.5 and 6.5 month (experimental end point) after induction, and leukemic samples were collected when mice were moribund as the "end" time point samples. Between 3.5 and 6.5 months, 6 out of 9 CM knock-in mice in this cohort had succumbed to lethal leukemia. Total RNA was isolated for mRNA and microRNA (miR) sequencing library preparation. The mapped sequencing read counts were annotated to genes and differential expression was compared using edgeR. False discovery rate (FDR) were used to adjust for multiple comparisons. Genes with adjusted P value (FDR) 2 were considered differentially expressed genes. Unsupervised clustering analysis revealed that all diseased mice showed unique disease-related mRNA and miRNA signatures at the end point. The disease-related signatures were absent in all control mice and the three CM conditional knock-in mice that did not develop leukemia. We found that 2,032 mRNA genes and 106 miRs were significantly up-regulated whereas 2,926 mRNA genes and 121 miRs were significantly down-regulated at the leukemia end point. Principal component analysis revealed that the disease-related changes occur quite early, at 1-2 month after induction. Among the earliest changes, miR-126-3p and miR-126-5p, previously reported to be associated with human inv(16) AML, were significantly up-regulated (log fold change =2.09 and 2.36 respectively; p< 0.0001) at 1 month and increased progressively throughout leukemia progression (log fold change = 4.11 and 4.45; p< 0.0001). DAVID gene ontology (GO) analysis of genes negatively correlated with miR-126 expression showed significant enrichment for mitotic cell cycle and cell division GO pathways. In addition, dynamic changes in a number of predicted miR-126 targets were seen during disease progression. We reasoned that high miR-126 expression might contribute to AML progression. Lentiviral miR-126 knock-down in AML LSK (Lin-/Sca1+/cKit+) cells from CM induced mice led to increased apoptosis and reduced quiescence in vitro. To assess the role of miR-126 in leukemia progression in vivo, we then designed a novel CpG-miR-126 inhibitor (Zhang et al, submitted). Mice transplanted with CM+ AML and treated with with anti-miR126 (5 mg/kg, daily, 30 days) had a significant delay in leukemia progression and enhanced survival (control 42% survival v.s. anti-miR-126 80% survival at 70 days; n=7-10), supporting the notion that high miR-126 contributes to disease growth. Further mechanistic investigation of miR-126 function during inv(16) AML progression are ongoing. In conclusion, transcriptome analysis of time series samples during spontaneous leukemia progression allows identification of disease-related changes and early increase of miR-126 as a potential biomarker. Further functional validation is expected to provide mechanistic insights and rational for targeting miR-126 in inv(16) AML. Disclosures Stein: Seattle Genetics: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau; Stemline Therapeutics: Consultancy, Research Funding; Argios: Research Funding; Celgene: Research Funding.

The secondary structure of the 5S ribosomal RNA (5S rRNA) molecule shows a high degree of symmetry. In order to explain the origin of this symmetry, it has been conjectured that one half of the 5S rRNA molecule was its precursor and that an indirect duplication of this precursor created the other half and thus the current symmetry of the molecule. Here, we have subjected to an empirical test both the indirect duplication model, analysing a total of 684 5S rRNA sequences for complementarity between the two halves of the 5S rRNA, and the direct duplication model analysing in this case the similarity between the two halves of this molecule. In intra- and inter-molecule and intra- and inter-domain comparisons, we find a high statistical support to the hypothesis of a complementarity relationship between the two halves of the 5S rRNA molecule, denying vice versa the hypothesis of similarity between these halves. Therefore, these observations corroborate the indirect duplication model at the expense of the direct duplication model, as reason of the origin of the 5S rRNA molecule. More generally, we discuss and favour the hypothesis that all RNAs and proteins, which present symmetry, did so through gene duplication and not by gradualistic accumulation of few monomers or segments of molecule into a gradualistic growth process. This would be the consequence of the very high propensity that nucleic acids have to be subjected to duplications.

In this paper we report about the BIOKIS payload: a multidisciplinary set of experiments and measurements in the fields of Biology (4) and Dosimetry (3) performed in microgravity. BIOKIS took advantage of the last STS-134 Endeavour mission and engineering state of the art in Space Life Science. The BIOKIS payload is compact, efficient, and capable to host experiments with different samples and science disciplines. Moreover, the time overlap of biological experiments and dosimetry measurements will produce more insightful information.

Molecules which store genetic information, DNA and RNA, are central to all life forms on Earth. The building of these complex molecules, and ultimately life, required specific conditions, including the synthesis and concentration of precursors (nucleotides), the joining of these monomers into larger molecules (polynucleotides), their protection in critical environmental conditions, like those probably existing in ancestral habitats, and the expression of the biological potential of the molecules, i.e., their capacity to self-replicate and evolve.

The discovery of ribozymes, RNAs with catalytic activity, revealed the extraordinary characteristic of this molecule, and corroborated the idea that RNA was the first informative polymer. The "RNA world" hypothesis asserts that the DNA/RNA/PROTEIN world arose from an earlier RNA world in which were present only RNA molecules able to perform both of the two functions performed separately by DNA and proteins in the present-day cells: the ability to transfer genetic information and to carry out catalytic activity. The catalytic properties of ribozymes are exclusively due to the capacity of RNA molecules to assume particular structures. Moreover, the structural versatility of RNA can allow to a single RNA sequence to fold in more than one structure, able to perform more than one function. In the first part of this work we will discuss the RNA plasticity, focusing on "bifunctional" ribozymes isolated by in vitro selection experiments, and on the consequences of this plasticity in the prospective of the emergence of new specific functions. The possibility that one sequence could have more than one structure/function, greatly increase the evolutionary potential of RNA, and the capacity of RNA to switch from a structure/function to another is probably one of the reasons of the evolutionary success also in modern-day cells. Naturally occurring ribozymes discovered in contemporary cells, demonstrate the crucial role that ribozymes still have in the modern protein world. In the second part of this paper we will discuss the capacity of natural ribozymes to modulate gene expression making use of their exclusive catalytic properties. Moreover, we will consider the possibility of their ancient origin.

For the RNA-world hypothesis to be ecologically feasible, selection mechanisms acting on replicator communities need to be invoked and the corresponding scenarios of molecular evolution specified. Complementing our previous models of chemical evolution on mineral surfaces, in which selection was the consequence of the limited mobility of macromolecules attached to the surface, here we offer an alternative realization of prebiotic group-level selection: the physical encapsulation of local replicator communities into the pores of the mineral substrate. Based on cellular automaton simulations we argue that the effect of group selection in a mineral honeycomb could have been efficient enough to keep prebiotic ribozymes of different specificities and replication rates coexistent, and their metabolic cooperation protected from extensive molecular parasitism. We suggest that mutants of the mild parasites persistent in the metabolic system can acquire useful functions such as replicase activity or the production of membrane components, thus opening the way for the evolution of the first autonomous protocells on Earth.

The combined action of a wide substrate range toluene o-xylene monooxygenase from Pseudomonas sp. OX1, able to convert many aromatic compounds into mono- and di-hydroxylated derivatives, and fungal laccases from Pleurotus ostreatus which oxidize these hydroxylated products yielding polymers with reduced toxicity is described. This strategy permits to overcome many of the substrate specificity problems and dead end toxic products formation generally encountered in complex bacterial biodegradation pathways. Toluene and naphthalene degradations were tested as representative of mono- and poly-aromatic pollutants. The combined biological action was optimized in micellar and microemulsion systems able to increase the bioavailability of the hydrophobic aromatic pollutants. This approach allows efficient hydroxylations of hydrophobic substrates thus favoring the further action of fungal oxidases.

Background The hypothesis of an RNA-based origin of life, known as the "RNA world", is strongly affected by the hostile environmental conditions probably present in the early Earth. In particular, strong UV and X-ray radiations could have been a major obstacle to the formation and evolution of the first biomolecules. In 1951, J. D. Bernal first proposed that clay minerals could have served as the sites of accumulation and protection from degradation of the first biopolymers, providing the right physical setting for the evolution of more complex systems. Numerous subsequent experimental studies have reinforced this hypothesis. Results The ability of the possibly widespread prebiotic, clay mineral montmorillonite to protect the catalytic RNA molecule ADHR1 (Adenine Dependent Hairpin Ribozyme 1) from UV-induced damages was experimentally checked. In particular, the self-cleavage reaction of the ribozyme was evaluated after UV-irradiation of the molecule in the absence or presence of clay particles. Results obtained showed a three-fold retention of the self-cleavage activity of the montmorillonite-protected molecule, with respect to the same reaction performed by the ribozyme irradiated in the absence of the clay. Conclusion These results provide a suggestion with which RNA, or RNA-like molecules, could have overcame the problem of protection from UV irradiation in the RNA world era, and suggest that a clay-rich environment could have favoured not only the formation of first genetic molecules, but also their evolution towards increasingly complex molecular organization.