Ecdysone promotes growth of imaginal discs through the regulation of Thor in D. melanogaster

Animals have a determined species-specific body size that results from the combined action of hormones and signaling pathways regulating growth rate and duration. In Drosophila, the steroid hormone ecdysone controls developmental transitions, thereby regulating the duration of the growth period. Here we show that ecdysone promotes the growth of imaginal discs in mid-third instar larvae, since imaginal discs from larvae with reduced or no ecdysone synthesis are smaller than wild type due to smaller and fewer cells. We show that insulin-like peptides are produced and secreted normally in larvae with reduced ecdysone synthesis, and upstream components of insulin/insulin-like signaling are activated in their discs. Instead, ecdysone appears to regulate the growth of imaginal discs via Thor/4E-BP, a negative growth regulator downstream of the insulin/insulin-like growth factor/Tor pathways. Discs from larvae with reduced ecdysone synthesis have elevated levels of Thor, while mutations in Thor partially rescue their growth. The regulation of organ growth by ecdysone is evolutionarily conserved in hemimetabolous insects, as shown by our results obtained using Blattella germanica. In summary, our data provide new insights into the relationship between components of the insulin/insulin-like/Tor and ecdysone pathways in the control of organ growth.Spanish Ministry of Science and Consolider program grants: (BFU-2008-01884, BFU2011-25986, CSD2007-008-25120, BFU2009-10571 and BES-2009-016077); Departments of Education and Industry of the Basque Government grant: (PI2012/42); Bizkaia County; Instituto Gulbenkian de Ciência/Fundação Calouste Gulbenkian; Fundação Para a Ciência e a Tecnologia fellowship: (SFRH/BD/51181/2010)

Estudio comparativo de los usos del condicional en español e inglés a través de la traducción de la novela "Dime quién soy"

33 p. -- Bibliogr.: p. 32-33El presente Trabajo de Fin de Grado tiene como objetivo exponer de manera concisa y clara los diferentes usos del condicional en castellano y las diferencias que podemos encontrar en cuanto a sus usos en inglés. Concretamente, analizaré los diferentes valores, tanto modales como temporales, que se han identificado para el condicional en español. Asimismo, el trabajo recoge un ejemplo de cada tipo de condicional descrito en la primera parte, extraído de una novela escrita en castellano que he escogido con este objetivo, Díme quién soy, de Julia Navarro. Para llevar a cabo un análisis comparativo completo, he hecho uso de la traducción de esta novela al inglés para observar el grado de equivalencia a nivel morfológico y semántico que pudiera haber entre el uso del condicional en las dos lenguas. Por otra parte, dado que en español el uso del condicional va muchas veces unido al uso del subjuntivo en la prótasis, y puesto que en inglés el subjuntivo no se expresa morfológicamente, me parecía interesante ver cómo se comportaba. Además, cabe destacar que sus usos en inglés, como se puede esperar, son bastante más limitados. Sin embargo, con el objetivo de profundizar en los usos del condicional en ambas lenguas, el trabajo incluye un apartado en el que he tratado recoger los usos del would condicional en inglés que no utilizamos en la lengua castellana

SUMOylation in the control of cholesterol homeostasis

SUMOylation-protein modification by the small ubiquitin-related modifier (SUMO)-affects several cellular processes by modulating the activity, stability, interactions or subcellular localization of a variety of substrates. SUMO modification is involved in most cellular processes required for the maintenance of metabolic homeostasis. Cholesterol is one of the main lipids required to preserve the correct cellular function, contributing to the composition of the plasma membrane and participating in transmembrane receptor signalling. Besides these functions, cholesterol is required for the synthesis of steroid hormones, bile acids, oxysterols and vitamin D. Cholesterol levels need to be tightly regulated: in excess, it is toxic to the cell, and the disruption of its homeostasis is associated with various disorders like atherosclerosis and cardiovascular diseases. This review focuses on the role of SUMO in the regulation of proteins involved in the metabolism of cholesterol.We apologize to those whose related publications could not be cited due to space limitations. We are grateful to all members of Barrio's Lab for comments and suggestions. R.B. acknowledges grant nos. BFU2017-84653-P (MINECO/AEI/FEDER/EU), SEV-2016-0644 (Severo Ochoa Excellence Program, MINECO/AEI), 765445-EU (UbiCODE Program, EU) and SAF2017-90900-REDT (UBIRed Program, MINECO/AEI)

The role of SUMOylation during development

During the development of multicellular organisms, transcriptional regulation plays an important role in the control of cell growth, differentiation and morphogenesis. SUMOylation is a reversible post-translational process involved in transcriptional regulation through the modification of transcription factors and through chromatin remodelling (either modifying chromatin remodelers or acting as a `molecular glue' by promoting recruitment of chromatin regulators). SUMO modification results in changes in the activity, stability, interactions or localization of its substrates, which affects cellular processes such as cell cycle progression, DNA maintenance and repair or nucleocytoplasmic transport. This review focuses on the role of SUMO machinery and the modification of target proteins during embryonic development and organogenesis of animals, from invertebrates to mammals.We apologize to those whose related publication could not be cited due to space limitations. We are grateful to all members of Barrio's Lab for comments and suggestions. R.B. acknowledges grants BFU2017-84653-P (MINECO/AEI/FEDER/EU), SEV-2016-0644 (Severo Ochoa Excellence Program, MINECO/AEI), 765445-EU (UbiCODE Program, EU), SAF2017-90900-REDT (UBIRed Program, MINECO/AEI)

Sumoylation of Drosophila SU(VAR)3-7 is required for its heterochromatic function

In Drosophila, SU(VAR)3-7 is an essential heterochromatin component. It is required for proper chromatin condensation, and changing its dose modifies position-effect variegation. Sumoylation is a post-translational modification shown to play a role in diverse biological processes. Here, we demonstrate that sumoylation is essential for proper heterochromatin function in Drosophila through modification of SU(VAR)3-7. Indeed, SU(VAR)3-7 is sumoylated at lysine K839; this modification is required for localization of SU(VAR)3-7 at pericentric heterochromatin, chromosome 4, and telomeres. In addition, sumoylation of SU(VAR)3-7 is a prerequisite for its ability to enhance position-effect variegation. Thus, these results show that the heterochromatic function of SU(VAR)3-7 depends on its own sumoylation, and unveil a role for sumoylation in Drosophila heterochromatin

Identification of multiple transcription initiation, polyadenylation, and splice sites in the Drosophila melanogaster TART family of telomeric retrotransposons

The Drosophila non-long terminal repeat (non-LTR) retrotransposons TART and HeT-A specifically retrotranspose to chromosome ends to maintain Drosophila telomeric DNA. Relatively little is known, though, about the regulation of their expression and their retrotransposition to telomeres. We have used rapid amplification of cDNA ends (RACE) to identify multiple transcription initiation and polyadenylation sites for sense and antisense transcripts of three subfamilies of TART elements in Drosophila melanogaster. These results are consistent with the production of an array of TART transcripts. In contrast to other Drosophila non-LTR elements, a major initiation site for sense transcripts was mapped near the 3′ end of the TART 5′-untranslated region (5′-UTR), rather than at the start of the 5′-UTR. A sequence overlapping this sense start site contains a good match to an initiator consensus for the transcription start sites of Drosophila LTR retrotransposons. Interestingly, analysis of 5′ RACE products for antisense transcripts and the GenBank EST database revealed that TART antisense transcripts contain multiple introns. Our results highlight differences between transcription of TART and of other Drosophila non-LTR elements and they provide a foundation for testing the relationship between exceptional aspects of TART transcription and TART's specialized role at telomeres

Novel lines of Pax6-/- embryonic stem cells exhibit reduced neurogenic capacity without loss of viability

<p>Abstract</p> <p>Background</p> <p>Embryonic stem (ES) cells can differentiate into all cell types and have been used extensively to study factors affecting neuronal differentiation. ES cells containing mutations in known genes have the potential to provide useful in vitro models for the study of gene function during neuronal differentiation. Recently, mouse ES cell lines lacking the neurogenic transcription factor Pax6 were reported; neurons derived from these <it>Pax6</it>^-/-ES cells died rapidly after neuronal differentiation in vitro.</p> <p>Results</p> <p>Here we report the derivation of new lines of <it>Pax6</it>^-/-ES cells and the assessment of their ability to survive and differentiate both in vitro and in vivo. Neurons derived from our new <it>Pax6</it>^-/-lines were viable and continued to elaborate processes in culture under conditions that resulted in the death of neurons derived from previously reported <it>Pax6</it>^-/-ES cell lines. The new lines of <it>Pax6</it>^-/-ES cells showed reduced neurogenic potential, mimicking the effects of loss of Pax6 in vivo. We used our new lines to generate <it>Pax6</it>^-/-↔ <it>Pax6</it>^+/+chimeras in which the mutant cells survived and displayed the same phenotypes as <it>Pax6</it>^-/-cells in <it>Pax6</it>^-/-↔ <it>Pax6</it>^+/+chimeras made by embryo aggregation.</p> <p>Conclusions</p> <p>We suggest that loss of Pax6 from ES cells reduces their neurogenic capacity but does not necessarily result in the death of derived neurons. We offer these new lines as additional tools for those interested in the generation of chimeras and the analysis of in vitro ES cell models of Pax6 function during neuronal differentiation, embryonic and postnatal development.</p

Dual-functioning transcription factors in the developmental gene network of Drosophila melanogaster

Quantitative models for transcriptional regulation have shown great promise for advancing our understanding of the biological mechanisms underlying gene regulation. However, all of the models to date assume a transcription factor (TF) to have either activating or repressing function towards all the genes it is regulating.In this paper we demonstrate, on the example of the developmental gene network in D. melanogaster, that the data-fit can be improved by up to 40% if the model is allowing certain TFs to have dual function, that is, acting as activator for some genes and as repressor for others. We demonstrate that the improvement is not due to additional flexibility in the model but rather derived from the data itself. We also found no evidence for the involvement of other known site-specific TFs in regulating this network. Finally, we propose SUMOylation as a candidate biological mechanism allowing TFs to switch their role when a small ubiquitin-like modifier (SUMO) is covalently attached to the TF. We strengthen this hypothesis by demonstrating that the TFs predicted to have dual function also contain the known SUMO consensus motif, while TFs predicted to have only one role lack this motif.We argue that a SUMOylation-dependent mechanism allowing TFs to have dual function represents a promising area for further research and might be another step towards uncovering the biological mechanisms underlying transcriptional regulation

Genetic manipulation of LKB1 elicits lethal metastatic prostate cancer

Gene dosage is a key defining factor to understand cancer pathogenesis and progression, which requires the development of experimental models that aid better deconstruction of the disease. Here, we model an aggressive form of prostate cancer and show the unconventional association of LKB1 dosage to prostate tumorigenesis. Whereas loss of Lkbl alone in the murine prostate epithelium was inconsequential for tumorigenesis, its combination with an oncogenic insult, illustrated by Pten heterozygosity, elicited lethal metastatic prostate cancer. Despite the low frequency of LKB1 deletion in patients, this event was significantly enriched in lung metastasis. Modeling the role of LKB1 in cellular systems revealed that the residual activity retained in a reported kinase-dead form, LKB1(K781), was sufficient to hamper tumor aggressiveness and metastatic dissemination. Our data suggest that prostate cells can function normally with low activity of LKB1, whereas its complete absence influences prostate cancer pathogenesis and dissemination

Transcriptional Control of Steroid Biosynthesis Genes in the Drosophila Prothoracic Gland by Ventral Veins Lacking and Knirps.

Specialized endocrine cells produce and release steroid hormones that govern development, metabolism and reproduction. In order to synthesize steroids, all the genes in the biosynthetic pathway must be coordinately turned on in steroidogenic cells. In Drosophila, the steroid producing endocrine cells are located in the prothoracic gland (PG) that releases the steroid hormone ecdysone. The transcriptional regulatory network that specifies the unique PG specific expression pattern of the ecdysone biosynthetic genes remains unknown. Here, we show that two transcription factors, the POU-domain Ventral veins lacking (Vvl) and the nuclear receptor Knirps (Kni), have essential roles in the PG during larval development. Vvl is highly expressed in the PG during embryogenesis and is enriched in the gland during larval development, suggesting that Vvl might function as a master transcriptional regulator in this tissue. Vvl and Kni bind to PG specific cis-regulatory elements that are required for expression of the ecdysone biosynthetic genes. Knock down of either vvl or kni in the PG results in a larval developmental arrest due to failure in ecdysone production. Furthermore, Vvl and Kni are also required for maintenance of TOR/S6K and prothoracicotropic hormone (PTTH) signaling in the PG, two major pathways that control ecdysone biosynthesis and PG cell growth. We also show that the transcriptional regulator, Molting defective (Mld), controls early biosynthetic pathway steps. Our data show that Vvl and Kni directly regulate ecdysone biosynthesis by transcriptional control of biosynthetic gene expression and indirectly by affecting PTTH and TOR/S6K signaling. This provides new insight into the regulatory network of transcription factors involved in the coordinated regulation of steroidogenic cell specific transcription, and identifies a new function of Vvl and Knirps in endocrine cells during post-embryonic development