Expression of Transposable Elements in Neural Tissues during Xenopus Development

Transposable elements comprise a large proportion of animal genomes. Transposons can have detrimental effects on genome stability but also offer positive roles for genome evolution and gene expression regulation. Proper balance of the positive and deleterious effects of transposons is crucial for cell homeostasis and requires a mechanism that tightly regulates their expression. Herein we describe the expression of DNA transposons of the Tc1/mariner superfamily during Xenopus development. Sense and antisense transcripts containing complete Tc1-2_Xt were detected in Xenopus embryos. Both transcripts were found in zygotic stages and were mainly localized in Spemann's organizer and neural tissues. In addition, the Tc1-like elements Eagle, Froggy, Jumpy, Maya, Xeminos and TXr were also expressed in zygotic stages but not oocytes in X. tropicalis. Interestingly, although Tc1-2_Xt transcripts were not detected in Xenopus laevis embryos, transcripts from other two Tc1-like elements (TXr and TXz) presented a similar temporal and spatial pattern during X. laevis development. Deep sequencing analysis of Xenopus tropicalis gastrulae showed that PIWI-interacting RNAs (piRNAs) are specifically derived from several Tc1-like elements. The localized expression of Tc1-like elements in neural tissues suggests that they could play a role during the development of the Xenopus nervous system

Different reprogramming propensities in plants and mammals: Are small variations in the core network wirings responsible?

Although the plant and animal kingdoms were separated more than 1,6 billion years ago, multicellular development is for both guided by similar transcriptional, epigenetic and posttranscriptional machinery. One may ask to what extent there are similarities and differences in the gene regulation circuits and their dynamics when it comes to important processes like stem cell regulation. The key players in mouse embryonic stem cells governing pluripotency versus differentiation are Oct4, Sox2 and Nanog. Correspondingly, the WUSCHEL and CLAVATA3 genes represent a core in the Shoot Apical Meristem regulation for plants. In addition, both systems have designated genes that turn on differentiation. There is very little molecular homology between mammals and plants for these core regulators. Here, we focus on functional homologies by performing a comparison between the circuitry connecting these players in plants and animals and find striking similarities, suggesting that comparable regulatory logics have been evolved for stem cell regulation in both kingdoms. From in silico simulations we find similar differentiation dynamics. Further when in the differentiated state, the cells are capable of regaining the stem cell state. We find that the propensity for this is higher for plants as compared to mammalians. Our investigation suggests that, despite similarity in core regulatory networks, the dynamics of these can contribute to plant cells being more plastic than mammalian cells, i.e. capable to reorganize from single differentiated cells to whole plants-reprogramming. The presence of an incoherent feed-forward loop in the mammalian core circuitry could be the origin of the different reprogramming behaviour.This work was supported Swedish Research Council, grant VR 621-2013-4547 to CP; the Swedish Foundation for Strategic Research, grant A3 04 159p to CP; the Gatsby Charitable Foundation (GB), grant GAT3395-PR4 to HJ and the Swedish Research Council, grant VR 621- 2013-4632 to HJ

U-Pb Zircon Geochronology of Granitic Rocks from the Chuquicamata-El Abra Porphyry Copper Belt of Northern Chile: Excimer Laser Ablation ICP-MS Analysis

This study reports the results of a comprehensive geochronological study of Tertiary plutonic rocks in the Chuquicamata-El Abra porphyry copper belt of northern Chile. Zircon U-Pb isotope ages of 22 intrusions from the composite Los Picos-Fortuna-Pajonal-El Abra igneous complex, Radomiro Tomic mine, and Opache prospect were determined by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS). The dated samples from the Pajonal-El Abra complex show a continuous age range from 42.7 to 37.2 Ma, indicating that the intrusions were emplaced over a period of at least 5.5 m.y. Only the youngest of these, the El Abra mine porphyry, is ore bearing. The five units that were dated from the Los Picos-Fortuna complex range in age from 42.3 to 38.0 Ma and none host significant economic mineralization. An increase in the abundance of inherited zircons with decreasing age in the intrusive rocks is interpreted to indicate that magmatic activity in the source region of the Los Picos-Fortuna-Pajonal-El Abra igneous complex increased steadily from about 55 Ma. The five dated units from the Los Picos-Fortuna igneous complex have the same age, within analytical uncertainty, as petrologically equivalent units in the Pajonal-El Abra complex to the north, supporting the correlation suggested by previous workers. Because these complexes are now on opposite sides of the West fissure and separated by 35 km, the correlation constrains the net sinistral displacement on the fault subsequent to ca. 33 Ma. Ore-bearing porphyries at Chuquicamata, E1 Abr a, Radomiro Tomic, and Opache span an age range of almost 5 m.y. from 37.9 to 33.3 Ma. The ore-bearing intrusions of the Chuquicamata Igneous Complex are 3.5 m.y. younger than the youngest intrusions of the Los Picos-Fortuna-Pajonal-El Abra igneous complex, which makes it unlikely that they are genetically related. The Opache porphyry, on the other hand, which is on the same side of the West fissure as the Los Picos-Fortuna complex and has the same age as the El Abra mine porphyry, could have formed during the final stages of crystallization of that complex

Automating the Formalization of Product Comparison Matrices

International audienceProduct Comparison Matrices (PCMs) form a rich source of data for comparing a set of related and competing products over numerous features. Despite their apparent simplicity, PCMs contain heterogeneous, ambiguous, uncontrolled and partial information that hinders their efficient exploitations. In this paper, we formalize PCMs through model-based automated techniques and develop additional tooling to support the edition and re-engineering of PCMs. 20 participants used our editor to evaluate the PCM metamodel and automated transformations. The results over 75 PCMs from Wikipedia show that (1) a significant proportion of the formalization of PCMs can be automated - 93.11% of the 30061 cells are correctly formalized; (2) the rest of the formalization can be realized by using the editor and mapping cells to existing concepts of the metamodel. The automated approach opens avenues for engaging a community in the mining, re-engineering, edition, and exploitation of PCMs that now abound on the Internet

Structural correlates of heterogeneous in vivo activity of midbrain dopaminergic neurons

Dopaminergic neurons of the substantia nigra pars compacta (SNc) exhibit functional heterogeneity that likely underpins their diverse roles in behavior. We examined how the functional diversity of identified dopaminergic neurons in vivo correlates with differences in somato-dendritic architecture and afferent synaptic organization. Stereological analysis of individually recorded and labeled dopaminergic neurons of rat SNc revealed that they received approximately 8,000 synaptic inputs, at least 30% of which were glutamatergic and 40-70% were GABAergic. The latter synapses were proportionally greater in number and denser on dendrites located in the substantia nigra pars reticulata (SNr) than on those located in SNc, revealing the existence of two synaptically distinct and region-specific subcellular domains. We also found that the relative extension of SNc neuron dendrites into the SNr dictated overall GABAergic innervation and predicted inhibition responses to aversive stimuli. We conclude that diverse wiring patterns determine the heterogeneous activities of midbrain dopaminergic neurons in vivo. © 2012 Nature America, Inc. All rights reserved