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BACKGROUND: The most-common strategy for zebrafish Cre/lox-mediated lineage labeling experiments combines ubiquitously expressed, lox-based Switch reporter transgenes with tissue-specific Cre or 4-OH-Tamoxifen-inducible CreERT2 driver lines. Although numerous Cre driver lines have been produced, only a few broadly expressed Switch reporters exist in zebrafish and their generation by random transgene integration has been challenging due to position-effect sensitivity of the lox-flanked recombination cassettes. Here, we compare commonly used Switch reporter lines for their recombination efficiency and reporter expression pattern during zebrafish development. RESULTS: Using different experimental setups, we show that ubi:Switch and hsp70l:Switch outperform current generations of the two additional Switch reporters actb2:BFP-DsRed and actb2:Stop-DsRed. Our comparisons also document preferential Cre-dependent recombination of ubi:Switch and hsp70l:Switch in distinct zebrafish tissues at early developmental stages. To investigate what genomic features may influence Cre accessibility and lox recombination efficiency in highly functional Switch lines, we mapped these transgenes and charted chromatin dynamics at their integration sites. CONCLUSIONS: Our data documents the heterogeneity among lox-based Switch transgenes towards informing suitable transgene selection for lineage labeling experiments. Our work further proposes that ubi:Switch and hsp70l:Switch define genomic integration sites suitable for universal transgene or switch reporter knock-in in zebrafish.

We previously observed increased levels of adenosine-deaminase-acting-on-dsRNA (Adar)-dependent RNA editing during mesothelioma development in mice exposed to asbestos. The aim of this study was to characterize and assess the role of ADAR-dependent RNA editing in mesothelioma. Tumors and mesothelioma primary cultures have higher ADAR-mediated RNA editing compared to mesothelial cells. Unsupervised clustering of editing in different genomic regions revealed heterogeneity between tumor samples as well as mesothelioma primary cultures. ADAR2 expression levels are higher in BRCA1-associated protein 1 wild-type tumors, with corresponding changes in RNA editing in transcripts and 3’UTR. ADAR2 knockdown and rescue models indicated a role in cell proliferation, altered cell cycle, increased sensitivity to antifolate treatment and type-1 interferon signaling upregulation, leading to changes in the microenvironment in vivo. Our data indicate that RNA editing contributes to mesothelioma heterogeneity and highlights an important role of ADAR2 not only in growth regulation in mesothelioma but also chemotherapy response, in addition to regulating inflammatory response downstream of sensing nucleic acid structures.

The most-common strategy for zebrafish Cre/lox-mediated lineage labeling experiments combines ubiquitously expressed, lox-based Switch reporter transgenes with tissue-specific Cre or 4-OH-Tamoxifen-inducible CreERT2 driver lines. Although numerous Cre driver lines have been produced, only a few broadly expressed Switch reporters exist in zebrafish and their generation by random transgene integration has been challenging due to position-effect sensitivity of the lox-flanked recombination cassettes. Here, we compare commonly used Switch reporter lines for their recombination efficiency and reporter expression pattern during zebrafish development. Using different experimental setups, we show that ubi:Switch and hsp70l:Switch outperform current generations of two additional Switch reporters due to favorable transgene integration sites. Our comparisons also document preferential Cre-dependent recombination of ubi:Switch and hsp70l:Switch in distinct zebrafish tissues at early developmental stages. To investigate what genomic features may influence Cre accessibility and lox recombination efficiency in highly functional Switch lines, we mapped these transgenes and charted chromatin dynamics at their integration sites. Our data documents the heterogeneity among lox-based Switch transgenes towards informing suitable transgene selection for lineage labeling experiments. Our work further proposes that ubi:Switch and hsp70l:Switch define genomic integration sites suitable for universal transgene or switch reporter knock-in in zebrafish.

The nucleolus is the largest substructure in the nucleus and forms around the nucleolar organizer regions (NORs) that comprise hundreds of ribosomal RNA (rRNA) genes. Recent evidence highlights further functions of the nucleolus that go beyond ribosome biogenesis. Data indicate that the nucleolus acts as a compartment for the location and regulation of repressive genomic domains and, together with the nuclear lamina, represents the hub for the organization of the inactive heterochromatin. In this review, we discuss recent findings that have revealed how nucleolar structure and rRNA gene chromatin states are regulated during early mammalian development and their contribution in the higher-order spatial organization of the genome.

Combining neo-adjuvant chemotherapy and surgery is part of multimodality treatment of malignant pleural mesothelioma (MPM), but not all patients benefit from this approach. In this exploratory analysis, we investigated the prognostic value of circulating miR-625-3p and lncRNA GAS5 after neo-adjuvant chemotherapy. 36 MPM patients from the SAKK 17/04 trial (NCT00334594), whose blood was available before and after chemotherapy were investigated. RNA was isolated from plasma and reverse transcribed into cDNA. miR-16-5p and &beta, actin were used as a reference gene for miR-625-3p and GAS5, respectively. After exclusion of samples due to hemolysis or RNA degradation, paired plasma samples from 32 patients before and after chemotherapy were further analyzed. Quantification of miR-625-3p levels in all 64 samples revealed a bimodal distribution and cloning and sequencing of miR-625-3p qPCR product revealed the presence of miR-625-3p isomiRs. Relative change of the circulating miR-625-3p and GAS5 levels after chemotherapy showed that increased circulating miR-625-3p and decreased GAS5 was significantly associated with disease progression (Fisher&rsquo, s test, p = 0.0393). In addition, decreased levels of circulating GAS5 were significantly associated with shorter overall and progression-free survival. Our exploratory analysis revealed a potential value of circulating non-coding RNA for selection of patients likely to benefit from surgery after platinum-based adjuvant chemotherapy.

The in vitro RNA-pulldown is still largely used in the first steps of protocols aimed at identifying RNA-binding proteins that recognize specific RNA structures and motifs. In this RNA-pulldown protocol, commercially synthesized RNA probes are labeled with a modified form of biotin, desthiobiotin, at the 3' terminus of the RNA strand, which reversibly binds to streptavidin and thus allows elution of proteins under more physiological conditions. The RNA-desthiobiotin is immobilized through interaction with streptavidin on magnetic beads, which are used to pull down proteins that specifically interact with the RNA of interest. Non-denatured and active proteins from the cytosolic fraction of mesothelioma cells are used as the source of proteins. The method described here can be applied to detect the interaction between known RNA binding proteins and a 25-nucleotide (nt) long RNA probe containing a sequence of interest. This is useful to complete the functional characterization of stabilizing or destabilizing elements present in RNA molecules achieved using a reporter vector assay.

Experimental models closely representing in vivo conditions allow investigating mechanisms of resistance. Our aims were to establish a live-cell biobank of malignant pleural mesothelioma (MPM) samples, and to obtain proof of principle that primary culture chemoresistant models, mimicking tumor progression observed in patients, can be obtained in vitro, providing a useful tool to investigate underlying mechanisms. Primary mesothelioma cultures were established from 235 samples between 2007 and 2014. Of two MPM patients, primary cultures obtained at different time points: at initial diagnosis, after neoadjuvant treatment at surgery and/or after tumor recurrence, were deeply investigated. Cells and corresponding tumor tissue were characterized by mesothelial protein and gene expression analysis. In addition, primary cultures from chemo naive patients were exposed to increasing doses of cisplatin/pemetrexed during three months and compared with non-treated cells in a cytotoxicity assay, and by selected profiling of senescence markers. In vitro chemoresistance in the primary mesothelioma cell cultures was associated with increased Thy1 (CD90) expression. Thy1 expression in MPM samples was significantly associated with poor overall survival in the TCGA MPM cohort. Our results illustrate that the establishment of a large live-cell MPM biobank contributes to a better understanding of therapy resistance observed in vivo, which eventually may lead to a more logical approach for developing new treatment strategies.