Author Correction: Longitudinal assessment of tumor development using cancer avatars derived from genetically engineered pluripotent stem cells.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Autophagy Induction Is a Tor- and Tp53-Independent Cell Survival Response in a Zebrafish Model of Disrupted Ribosome Biogenesis

Ribosome biogenesis underpins cell growth and division. Disruptions in ribosome biogenesis and translation initiation are deleterious to development and underlie a spectrum of diseases known collectively as ribosomopathies. Here, we describe a novel zebrafish mutant, titania (tti(s450)), which harbours a recessive lethal mutation in pwp2h, a gene encoding a protein component of the small subunit processome. The biochemical impacts of this lesion are decreased production of mature 18S rRNA molecules, activation of Tp53, and impaired ribosome biogenesis. In tti(s450), the growth of the endodermal organs, eyes, brain, and craniofacial structures is severely arrested and autophagy is up-regulated, allowing intestinal epithelial cells to evade cell death. Inhibiting autophagy in tti(s450) larvae markedly reduces their lifespan. Somewhat surprisingly, autophagy induction in tti(s450) larvae is independent of the state of the Tor pathway and proceeds unabated in Tp53-mutant larvae. These data demonstrate that autophagy is a survival mechanism invoked in response to ribosomal stress. This response may be of relevance to therapeutic strategies aimed at killing cancer cells by targeting ribosome biogenesis. In certain contexts, these treatments may promote autophagy and contribute to cancer cells evading cell death.This research was funded by the National Health and Medical Research Council of Australia through Project grant 433614 (JKH), Program grant 487922 (JKH), a Senior Research Fellowship (JKH), and a Howard Florey Centenary Fellowship (HV). Operational Infrastructure Support was provided by the Victorian Government, Australia. Additional support was from Australian Research Council grant DP0346823 (GJL); NIH grant DK060322 (DYRS); and CDMRP, Department of Defense, USA W81XWH-10-1-0854 (KCE)

The U12-dependent spliceosome is essential for regulating gene expression during zebrafish development

© 2010 Dr. Sebastian MarkmillerRemoval of introns from pre-mRNA is an essential step in generating mature mRNA. The majority of introns are removed by the major, or U2-type, spliceosome, while the minor, or U12-type, spliceosome catalyses the removal of a small set of introns with characteristic features that are highly conserved in metazoans and plants. A novel zebrafish mutant, caliban (cal), with specific U12-type splicing defects, was used to study the biochemistry of the U12-type spliceosome and the role of U12-type introns in the regulation of gene expression. Greater than 99% of vertebrate introns are U2-type introns. However, a second class of U12-type introns exists that is defined by highly conserved consensus splice sites. U12-type introns represent about 0.5% of all introns in vertebrate genomes and usually occur alone alongside U2-type introns in pre-mRNA. U12-type introns are removed by a separate spliceosome that shares many components with the U2-type spliceosome, but contains several unique small nuclear RNAs (snRNAs) and spliceosomal proteins. Several lines of evidence suggest a function for U12-type splicing in the regulation of gene expression. These include the high evolutionary conservation of U12-type introns, their enrichment in certain functional gene groups and the demonstration that their excision can be rate-limiting in the generation of mature mRNAs. Despite these observations, little is known about the role and possible regulatory function of U12-type splicing in vivo. cal is a zebrafish development mutant with abnormalities in the intestinal epithelium, which is poorly polarised and unfolded compared to wildtype (wt). Mutant embryos also show a reduction in size of the liver and the pancreas and display a morphologically abnormal lens in the context of a smaller eye. The genetic lesion in cal was mapped to rnpc3, encoding the zebrafish orthologue of the human U11/U12 snRNP 65KDa protein, a specific component of the U12-type spliceosome. It was shown that cal embryos specifically retain U12-type introns compared to wildtype. Biochemical analyses of U12-type spliceosomal small nuclear ribonucleoproteins (snRNPs) demonstrate abnormal formation of the U11/U12 di-snRNP, which represents the first step in U12-type spliceosome assembly. However, it was also demonstrated that larger spliceosomal particles form and accumulate in cal embryos in the absence of Rnpc3/65K, suggesting a potential novel role for Rnpc3/65K in U12-type spliceosome disassembly and recycling. Whole transcriptome analysis of cal and wt embryos by microarrays and RNA sequencing demonstrated retention of U12-type introns on a global scale as well as a set of about 700 differentially expressed genes between cal and wt at two different developmental time points. Further analysis of gene expression data has led to the emergence of a model in which cal embryos are sustained through the first 48-72hpf by maternally deposited rnpc3 mRNA and Rnpc3/65K protein. After this time, defective U12-type splicing induces a cell cycle arrest in the endoderm-derived tissues of the liver, pancreas and intestine, which are highly proliferative between 72 and 108hpf. These results are leading to further studies with a focus on the role of U12-type splicing in human cancer. It was found that several prominent human tumour suppressor genes such as PTEN, LKB1 and PROX1, contain U12-type introns, and we propose a model by which an intermediate reduction of U12-type splicing efficiency can be tumourigenic by reducing the activity of particular tumour suppressor genes in a dose-dependent fashion. To test this hypothesis, conditional Rnpc3 knockout mouse models are currently being generated on a range of different colorectal cancer-susceptible backgrounds

A Numerical Method for Blast Shock Wave Analysis of Missile Launch from Aircraft

An efficient empirical approach was developed to accurately represent the blast shock wave loading resulting from the launch of a missile from a military aircraft to be used in numerical analyses. Based on experimental test series of missile launches in laboratory environment and from a helicopter, equations were derived to predict the time- and position-dependent overpressure. The method was finally applied and validated in a structural analysis of a helicopter tail boom under missile launch shock wave loading

Active Protein Neddylation or Ubiquitylation Is Dispensable for Stress Granule Dynamics.

Stress granule (SG) formation is frequently accompanied by ubiquitin proteasome system (UPS) impairment and ubiquitylated protein accumulation. SGs, ubiquitin, and UPS components co-localize, but the relationship between the ubiquitin pathway and SGs has not been systematically characterized. We utilize pharmacological inhibition of either the ubiquitin- or NEDD8-activating enzyme (UAE or NAE) to probe whether active ubiquitylation or neddylation modulate SG dynamics. We show that UAE inhibition results in rapid loss of global protein ubiquitylation using ubiquitin-specific proteomics. Critically, inhibiting neither UAE nor NAE significantly affected SG formation or disassembly, indicating that active protein ubiquitylation or neddylation is dispensable for SG dynamics. Using antibodies with varying preference for free ubiquitin or polyubiquitin and fluorescently tagged ubiquitin variants in combination with UAE inhibition, we show that SGs co-localize primarily with unconjugated ubiquitin rather than polyubiquitylated proteins. These findings clarify the role of ubiquitin in SG biology and suggest that free ubiquitin may alter SG protein interactions

Svensk Botanisk Tidskrift : Volym 109: Häfte 6, 2015

INNEHÅLLSFÖRTECKNING. J. ELVELAND: Våtslåttermarker i Norrland - förr och nu. P. TORÄNG: Biffekter. M. LIDÉN: Hemligheten är att vara hemlig… G. MATTIASSON: Om fyra nya Skånearter. B. OLDHAMMER: Bomb i bageriet. Böcker: I. BACKÉUS: Ett etnobotaniskt livsverk; I. LARSSON: Norske klosterplanter; I. LARSSON: 1600-talets växtnamn. Föreningsnytt: Ledare: Satsningarna fortsätter; Kallelse till SBF:s årsmöte; Föreningskonferens 5-6 mars i Uppsala; Botanisk resa till Jämtland; Tidskriftsval; Ny webbutik