E-Cadherin Is Transcriptionally Activated via Suppression of ZEB1 Transcriptional Repressor by Small RNA-Mediated Gene Silencing

RNA activation has been reported to be induced by small interfering RNAs (siRNAs) that act on the promoters of several genes containing E-cadherin. In this study, we present an alternative mechanism of E-cadherin activation in human PC-3 cells by siRNAs previously reported to possess perfect-complementary sequences to E-cadherin promoter. We found that activation of E-cadherin can be also induced via suppression of ZEB1, which is a transcriptional repressor of E-cadherin, by seed-dependent silencing mechanism of these siRNAs. The functional seed-complementary sites of the siRNAs were found in the coding region in addition to the 3′ untranslated region of ZEB1 mRNA. Promoter analyses indicated that E-boxes, which are ZEB1-binding sites, in the upstream promoter region are indispensable for E-cadherin transcription by the siRNAs. Thus, the results caution against ignoring siRNA seed-dependent silencing effects in genome-wide transcriptional regulation. In addition, members of miR-302/372/373/520 family, which have the same seed sequences with one of the siRNAs containing perfect-complementarity to E-cadherin promoter, are also found to activate E-cadherin transcription. Thus, E-cadherin could be upregulated by the suppression of ZEB1 transcriptional repressor by miRNAs in vivo

Three Drosophila Hox Complex microRNAs Do Not Have Major Effects on Expression of Evolutionarily Conserved Hox Gene Targets during Embryogenesis

The discovery of microRNAs has resulted in a major expansion of the number of molecules known to be involved in gene regulation. Elucidating the functions of animal microRNAs has posed a significant challenge as their target interactions with messenger RNAs do not adhere to simple rules. Of the thousands of known animal microRNAs, relatively few microRNA:messenger RNA regulatory interactions have been biologically validated in an normal organismal context. Here we present evidence that three microRNAs from the Hox complex in Drosophila (miR-10-5p, miR-10-3p, miR-iab-4-5p) do not have significant effects during embryogenesis on the expression of Hox genes that contain high confidence microRNAs target sites in the 3′ untranslated regions of their messenger RNAs. This is significant, in that it suggests that many predicted microRNA-target interactions may not be biologically relevant, or that the outcomes of these interactions may be so subtle that mutants may only show phenotypes in specific contexts, such as in environmental stress conditions, or in combinations with other microRNA mutations

SMG-1 and mTORC1 Act Antagonistically to Regulate Response to Injury and Growth in Planarians

Planarian flatworms are able to both regenerate their whole bodies and continuously adapt their size to nutrient status. Tight control of stem cell proliferation and differentiation during these processes is the key feature of planarian biology. Here we show that the planarian homolog of the phosphoinositide 3-kinase-related kinase (PIKK) family member SMG-1 and mTOR complex 1 components are required for this tight control. Loss of smg-1 results in a hyper-responsiveness to injury and growth and the formation of regenerative blastemas that remain undifferentiated and that lead to lethal ectopic outgrowths. Invasive stem cell hyper-proliferation, hyperplasia, hypertrophy, and differentiation defects are hallmarks of this uncontrolled growth. These data imply a previously unappreciated and novel physiological function for this PIKK family member. In contrast we found that planarian members of the mTOR complex 1, tor and raptor, are required for the initial response to injury and blastema formation. Double smg-1 RNAi experiments with tor or raptor show that abnormal growth requires mTOR signalling. We also found that the macrolide rapamycin, a natural compound inhibitor of mTORC1, is able to increase the survival rate of smg-1 RNAi animals by decreasing cell proliferation. Our findings support a model where Smg-1 acts as a novel regulator of both the response to injury and growth control mechanisms. Our data suggest the possibility that this may be by suppressing mTOR signalling. Characterisation of both the planarian mTORC1 signalling components and another PIKK family member as key regulators of regeneration and growth will influence future work on regeneration, growth control, and the development of anti-cancer therapies that target mTOR signalling

Comparative Analysis of mRNA Targets for Human PUF-Family Proteins Suggests Extensive Interaction with the miRNA Regulatory System

Genome-wide identification of mRNAs regulated by RNA-binding proteins is crucial to uncover post-transcriptional gene regulatory systems. The conserved PUF family RNA-binding proteins repress gene expression post-transcriptionally by binding to sequence elements in 3′-UTRs of mRNAs. Despite their well-studied implications for development and neurogenesis in metazoa, the mammalian PUF family members are only poorly characterized and mRNA targets are largely unknown. We have systematically identified the mRNAs associated with the two human PUF proteins, PUM1 and PUM2, by the recovery of endogenously formed ribonucleoprotein complexes and the analysis of associated RNAs with DNA microarrays. A largely overlapping set comprised of hundreds of mRNAs were reproducibly associated with the paralogous PUM proteins, many of them encoding functionally related proteins. A characteristic PUF-binding motif was highly enriched among PUM bound messages and validated with RNA pull-down experiments. Moreover, PUF motifs as well as surrounding sequences exhibit higher conservation in PUM bound messages as opposed to transcripts that were not found to be associated, suggesting that PUM function may be modulated by other factors that bind conserved elements. Strikingly, we found that PUF motifs are enriched around predicted miRNA binding sites and that high-confidence miRNA binding sites are significantly enriched in the 3′-UTRs of experimentally determined PUM1 and PUM2 targets, strongly suggesting an interaction of human PUM proteins with the miRNA regulatory system. Our work suggests extensive connections between the RBP and miRNA post-transcriptional regulatory systems and provides a framework for deciphering the molecular mechanism by which PUF proteins regulate their target mRNAs

A Cross-Species Analysis of MicroRNAs in the Developing Avian Face

Higher vertebrates use similar genetic tools to derive very different facial features. This diversity is believed to occur through temporal, spatial and species-specific changes in gene expression within cranial neural crest (NC) cells. These contribute to the facial skeleton and contain species-specific information that drives morphological variation. A few signaling molecules and transcription factors are known to play important roles in these processes, but little is known regarding the role of micro-RNAs (miRNAs). We have identified and compared all miRNAs expressed in cranial NC cells from three avian species (chicken, duck, and quail) before and after species-specific facial distinctions occur. We identified 170 differentially expressed miRNAs. These include thirty-five novel chicken orthologs of previously described miRNAs, and six avian-specific miRNAs. Five of these avian-specific miRNAs are conserved over 120 million years of avian evolution, from ratites to galliforms, and their predicted target mRNAs include many components of Wnt signaling. Previous work indicates that mRNA gene expression in NC cells is relatively static during stages when the beak acquires species-specific morphologies. However, miRNA expression is remarkably dynamic within this timeframe, suggesting that the timing of specific developmental transitions is altered in birds with different beak shapes. We evaluated one miRNA:mRNA target pair and found that the cell cycle regulator p27KIP1 is a likely target of miR-222 in frontonasal NC cells, and that the timing of this interaction correlates with the onset of phenotypic variation. Our comparative genomic approach is the first comprehensive analysis of miRNAs in the developing facial primordial, and in species-specific facial development

Cefaléia cervicogênica relato de um caso

A produção de cefaléias a partir de anormalidades no pescoço nunca foi sistematizada a ponto de permitir o estudo de sua patogenia, embora fosse fato conhecido há muitos anos. Sjaastad et al. descreveram, em 1983, grupo de pacientes com uma cefaléia uniforme e estereotipada. Os ataques se caracterizavam por dor moderada, unilateral sem mudança de lado, de longa duração, recorrendo em poucas semanas. A cefaléia podia ser provocada por certos movimentos do pescoço ou por compressão de pontos desencadeadores ali localizados. A dor se iniciava rua região cervical, irradiando-se para as áreas órbito-fronto-temporal e/ou facial. A denominação «cefaléia cervicogênica» (CC) foi proposta para esta entidade. Sua fisiopatogenia não é completamente conhecida. Bloqueios da raiz C2 e do nervo grande occipital eliminam a dor. Apresentamos um caso de CC, fazendo alguns comentários acerca do seu quadro clínico, fisiopatologia e tratamento