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© 2015 Elsevier Inc. dKDM5/LID regulates transcription of essential developmental genes and, thus, is required for different developmental processes. Here, we report the essential contribution of dKDM5/LID to hematopoiesis in Drosophila. Our results show that dKDM5/LID is abundant in hemocytes and that its depletion induces over-proliferation and differentiation defects of larval hemocytes and disrupts organization of the actin cytoskeleton. We also show that dKDM5/LID regulates expression of key factors of hematopoietic development. In particular, dKDM5/LID depletion up-regulates expression of several transcription factors involved in hemocytes proliferation and differentiation as well as of several small-GTPases that link signaling effectors to actin cytoskeleton formation and dynamics., This work was supported by grants from MICINN (BFU2012-30724) and the Generalitat de Catalunya (SGR2009-1023 and SGR2014-204). This work was carried out within the framework of the “Centre de Referència en Biotecnologia” of the “Generalitat de Catalunya”

Histone H1 is an essential chromatin component. Metazoans usually contain multiple stage-specific H1s. In particular, specific variants replace somatic H1s during early embryogenesis. In this regard, Drosophila was an exception because a single dH1 was identified that, starting at cellularization, is detected throughout development in somatic cells. Here, we identify the embryonic H1 of Drosophila, dBigH1. dBigH1 is abundant before cellularization occurs, when somatic dH1 is absent and the zygotic genome is inactive. Upon cellularization, when the zygotic genome is progressively activated, dH1 replaces dBigH1 in the soma, but not in the primordial germ cells (PGCs) that have delayed zygotic genome activation (ZGA). In addition, a loss-of-function mutant shows premature ZGA in both the soma andPGCs. Mutant embryos die at cellularization, showing increased levels of active RNApol II and zygotic transcripts, along with DNA damage and mitotic defects. These results show an essential function of dBigH1 in ZGA regulation. © 2013 Elsevier Inc., This work was supported by grants from the Ministerio de Ciencia e Innovación (MICINN) (CSD2006-49, BFU2009-07111, and BFU2012-30724) and the Generalitat de Catalunya (SGR2009-1023). This work was carried out within the framework of the Centre de Referència en Biotecnologia of the Generalitat de Catalunya. S.P.-M. received an FPI fellowship from the MICINN.

The hydei subgroup (Drosophila repleta group) consists of seven species divided into two complexes: bifurca and hydei, whose phylogenetic relationships are not well understood. To evaluate the molecular phylogeny of this subgroup, we analyzed 2085 bp of coding sequence of the Xanthine dehydrogenase gene in six available species of the hydei subgroup, with Drosophila buzzatii and Drosophila mulleri as an outgroup. For phylogenetic reconstruction we adopted a maximum-likelihood framework, based on the adjustment of descriptive models of nucleotide substitution to real data. We employed distance-based and weighted parsimony methods to construct candidate phylogenies. In all cases, we obtained only one completely resolved tree with strong statistical support for each node, that shows a phylogeny that is partially discordant with the proposed systematics of the subgroup. This tree suggests that the two species complexes are paraphyletic, as opposed to classic phylogenies using morphologic and cytologic traits. This discordance is discussed in relation to its implication for the evolutionary history of the hydei subgroup.

To date, different studies about the genetic basis of hybrid male sterility (HMS), a postzygotic reproductive barrier thoroughly investigated using Drosophila species, have demonstrated that no single major gene can produce hybrid sterility without the cooperation of several genetic factors. Early work using hybrids between Drosophila koepferae (Dk) and Drosophila buzzatii (Db) was consistent with the idea that HMS requires the cooperation of several genetic factors, supporting a polygenic threshold (PT) model. Here we present a genome-wide mapping strategy to test the PT model, analyzing serially backcrossed fertile and sterile males in which the Dk genome was introgressed into the Db background. We identified 32 Dk-specific markers sig nificantly associated with hybrid sterility. Our results demonstrate 1) a strong correlation between the number of segregated sterility markers and males’ degree of sterility, 2) the exchangeability among markers, 3) their tendency to cluster into lowrecombining chromosomal regions, and 4) the requirement for a minimum number (threshold) of markers to elicit sterility. Although our findings do not contradict a role for occasional major hybrid-sterility genes, they conform more to the view that HMS primarily evolves by the cumulative action of many interacting genes of minor effect in a complex PT architecture.

This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- et al., Protein components of the spliceosome are highly conserved in eukaryotes and can influence several steps of the gene expression process. RSR-2, the Caenorhabditis elegans ortholog of the human spliceosomal protein SRm300/SRRM2, is essential for viability, in contrast to the yeast ortholog Cwc21p. We took advantage of mutants and RNA interference (RNAi) to study rsr-2 functions in C. elegans, and through genetic epistasis analysis found that rsr-2 is within the germline sex determination pathway. Intriguingly, transcriptome analyses of rsr-2(RNAi) animals did not reveal appreciable splicing defects but instead a slight global decrease in transcript levels. We further investigated this effect in transcription and observed that RSR-2 colocalizes with DNA in germline nuclei and coprecipitates with chromatin, displaying a ChIP-Seq profile similar to that obtained for the RNA Polymerase II (RNAPII). Consistent with a novel transcription function we demonstrate that the recruitment of RSR-2 to chromatin is splicing-independent and that RSR-2 interacts with RNAPII and affects RNAPII phosphorylation states. Proteomic analyses identified proteins associated with RSR-2 that are involved in different gene expression steps, including RNA metabolism and transcription with PRP-8 and PRP-19 being the strongest interacting partners. PRP-8 is a core component of the spliceosome and PRP-19 is the core component of the PRP19 complex, which interacts with RNAPII and is necessary for full transcriptional activity. Taken together, our study proposes that RSR-2 is a multifunctional protein whose role in transcription influences C. elegans development. © 2013 Fontrodona et al., This work was funded by the European Commision (Marie Curie International Reintegration Grant: MIRG-CT-2007-206584), the Carlos III Institute (FIS: PS09/02145, PI12/01554), and the Marató of TV3 (Ref. 100910). Laura Fontrodona was supported by an AGAUR predoctoral fellowship. Julián Cerón is a Miguel Servet Junior Investigator.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License., H3K4me3 is a histone modification that accumulates at the transcription-start site (TSS) of active genes and is known to be important for transcription activation. The way in which H3K4me3 is regulated at TSS and the actual molecular basis of its contribution to transcription remain largely unanswered. To address these questions, we have analyzed the contribution of dKDM5/LID, the main H3K4me3 demethylase in Drosophila, to the regulation of the pattern of H3K4me3. ChIP-seq results show that, at developmental genes, dKDM5/LID localizes at TSS and regulates H3K4me3. dKDM5/LID target genes are highly transcribed and enriched in active RNApol II and H3K36me3, suggesting a positive contribution to transcription. Expression-profiling show that, though weakly, dKDM5/LID target genes are significantly downregulated upon dKDM5/LID depletion. Furthermore, dKDM5/LID depletion results in decreased RNApol II occupancy, particularly by the promoter-proximal Pol llo ser5 form. Our results also show that ASH2, an evolutionarily conserved factor that locates at TSS and is required for H3K4me3, binds and positively regulates dKDM5/LID target genes. However, dKDM5/LID and ASH2 do not bind simultaneously and recognize different chromatin states, enriched in H3K4me3 and not, respectively. These results indicate that, at developmental genes, dKDM5/LID and ASH2 coordinately regulate H3K4me3 at TSS and that this dynamic regulation contributes to transcription. © 2012 The Author(s)., Seed Funding for Applied Research (Project No. 201007160001 to M.S.Y.H.); URC-PDF Scheme, Centre for Cancer Research HKU [to S.M.H.S. and S.S.D. (in part)]; Faculty Development Fund. Funding for open access charge: Seed Funding for Applied Research, University of Hong Kong (Project No. 201007160001 to M.S.Y.H.).