Unlike pluripotent cells, which generate only embryonic tissues, totipotent cells can generate a full organism, including extra-embryonic tissues. A rare population of cells resembling 2-cell-stage ...embryos arises in pluripotent embryonic stem (ES) cell cultures. These 2-cell-like cells display molecular features of totipotency and broader developmental plasticity. However, their specific nature and the process through which they arise remain outstanding questions. Here we identified intermediate cellular states and molecular determinants during the emergence of 2-cell-like cells. By deploying a quantitative single-cell expression approach, we identified an intermediate population characterized by expression of the transcription factor ZSCAN4 as a precursor of 2-cell-like cells. By using a small interfering RNA (siRNA) screen, we identified epigenetic regulators of 2-cell-like cell emergence, including the non-canonical PRC1 complex PRC1.6 and the EP400-TIP60 complex. Our data shed light on the mechanisms that underlie exit from the ES cell state toward the formation of early-embryonic-like cells in culture and identify key epigenetic pathways that promote this transition.
Due to compromised homologous recombination (HR) repair, BRCA1‐ and BRCA2‐mutated tumours accumulate DNA damage and genomic rearrangements conducive of tumour progression. To identify drugs that ...target specifically BRCA2‐deficient cells, we screened a chemical library containing compounds in clinical use. The top hit was chlorambucil, a bifunctional alkylating agent used for the treatment of chronic lymphocytic leukaemia (CLL). We establish that chlorambucil is specifically toxic to BRCA1/2‐deficient cells, including olaparib‐resistant and cisplatin‐resistant ones, suggesting the potential clinical use of chlorambucil against disease which has become resistant to these drugs. Additionally, chlorambucil eradicates BRCA2‐deficient xenografts and inhibits growth of olaparib‐resistant patient‐derived tumour xenografts (PDTXs). We demonstrate that chlorambucil inflicts replication‐associated DNA double‐strand breaks (DSBs), similarly to cisplatin, and we identify ATR, FANCD2 and the SNM1A nuclease as determinants of sensitivity to both drugs. Importantly, chlorambucil is substantially less toxic to normal cells and tissues in vitro and in vivo relative to cisplatin. Because chlorambucil and cisplatin are equally effective inhibitors of BRCA2‐compromised tumours, our results indicate that chlorambucil has a higher therapeutic index than cisplatin in targeting BRCA‐deficient tumours.
Synopsis
BRCA1/2‐deficient tumours accumulate DNA damage and genomic rearrangements conducive for tumour progression, which is exploited in the clinic by targeted therapies against the BRCA1/2‐mutated tumour subset. Chlorambucil is identified as the most effective drug in eliminating BRCA2‐deficient cells.
The bi‐functional alkylator chlorambucil was specifically toxic to BRCA1/2‐deficient cells and tumours, but not to wild type controls.
Chlorambucil effectively eliminated cisplatin‐resistant and olaparib‐resistant BRCA1/2‐deficient cells and tumours.
Mechanistically, chlorambucil toxicity is mediated by accumulation of replication‐associated DNA damage, similarly to cisplatin.
ATR, FANCD2 and SNM1A nuclease are determinants of cellular sensitivity to both drugs.
Chlorambucil is substantially less toxic to normal cells and tissues than cisplatin.
BRCA1/2‐deficient tumours accumulate DNA damage and genomic rearrangements conducive for tumour progression, which is exploited in the clinic by targeted therapies against the BRCA1/2‐mutated tumour subset. Chlorambucil is identified as the most effective drug in eliminating BRCA2‐deficient cells.
Cellular translation is down-regulated by host antiviral responses. Picornaviridae and Flaviviridae including hepatitis C virus (HCV) evade this process using internal ribosomal entry sequences ...(IRESs). Although HCV IRES translation is a prerequisite for HCV replication, only few host factors critical for IRES activity are known and the global regulator network remains largely unknown. Since signal transduction is an import regulator of viral infections and the host antiviral response we combined a functional RNAi screen targeting the human signaling network with a HCV IRES-specific reporter mRNA assay. We demonstrate that the HCV host cell cofactors PI4K and MKNK1 are positive regulators of HCV IRES translation representing a novel pathway with a functional relevance for the HCV life cycle and IRES-mediated translation of viral RNA.
ObjectiveHepatitis D virus (HDV) is a circular RNA virus coinfecting hepatocytes with hepatitis B virus. Chronic hepatitis D results in severe liver disease and an increased risk of liver cancer. ...Efficient therapeutic approaches against HDV are absent.DesignHere, we combined an RNAi loss-of-function and small molecule screen to uncover host-dependency factors for HDV infection.ResultsFunctional screening unravelled the hypoxia-inducible factor (HIF)-signalling and insulin-resistance pathways, RNA polymerase II, glycosaminoglycan biosynthesis and the pyrimidine metabolism as virus-hepatocyte dependency networks. Validation studies in primary human hepatocytes identified the carbamoyl-phosphatesynthetase 2, aspartate transcarbamylase and dihydroorotase (CAD) enzyme and estrogen receptor alpha (encoded by ESR1) as key host factors for HDV life cycle. Mechanistic studies revealed that the two host factors are required for viral replication. Inhibition studies using N-(phosphonoacetyl)-L-aspartic acid and fulvestrant, specific CAD and ESR1 inhibitors, respectively, uncovered their impact as antiviral targets.ConclusionThe discovery of HDV host-dependency factors elucidates the pathogenesis of viral disease biology and opens therapeutic strategies for HDV cure.
MicroRNAs (miRNAs) are small regulatory RNAs which act by modulating the expression of target genes. In addition to their role in maintaining essential physiological functions in the cell, miRNAs can ...also regulate viral infections. They can do so directly by targeting RNAs of viral origin or indirectly by targeting host mRNAs, and this can result in a positive or negative outcome for the virus. Here, we performed a fluorescence-based miRNA genome-wide screen in order to identify cellular miRNAs involved in the regulation of arbovirus infection in human cells. We identified 16 miRNAs showing a positive effect on Sindbis virus (SINV) expressing green fluorescent protein (GFP), among which were a number of neuron-specific ones such as miR-124. We confirmed that overexpression of miR-124 increases both SINV structural protein translation and viral production and that this effect is mediated by its seed sequence. We further demonstrated that the SINV genome possesses a binding site for miR-124. Both inhibition of miR-124 and silent mutations to disrupt this binding site in the viral RNA abolished positive regulation. We also proved that miR-124 inhibition reduces SINV infection in human differentiated neuronal cells. Finally, we showed that the proviral effect of miR-124 is conserved in other alphaviruses, as its inhibition reduces chikungunya virus (CHIKV) production in human cells. Altogether, our work expands the panel of positive regulation of the viral cycle by direct binding of host miRNAs to the viral RNA and provides new insights into the role of cellular miRNAs as regulators of alphavirus infection.
Arthropod-borne (arbo) viruses are part of a class of pathogens that are transmitted to their final hosts by insects. Because of climate change, the habitat of some of these insects, such as mosquitoes, is shifting, thereby facilitating the emergence of viral epidemics. Among the pathologies associated with arbovirus infection, neurological diseases such as meningitis and encephalitis represent a significant health burden. Using a genome-wide miRNA screen, we identified neuronal miR-124 as a positive regulator of the Sindbis and chikungunya alphaviruses. We also showed that this effect was in part direct, thereby opening novel avenues to treat alphavirus infections.
Due to compromised homologous recombination (HR) repair, BRCA1‐ and BRCA2‐mutated tumours accumulate DNA damage and genomic rearrangements conducive of tumour progression. To identify drugs that ...target specifically BRCA2‐deficient cells, we screened a chemical library containing compounds in clinical use. The top hit was chlorambucil, a bifunctional alkylating agent used for the treatment of chronic lymphocytic leukaemia (CLL). We establish that chlorambucil is specifically toxic to BRCA1/2‐deficient cells, including olaparib‐resistant and cisplatin‐resistant ones, suggesting the potential clinical use of chlorambucil against disease which has become resistant to these drugs. Additionally, chlorambucil eradicates BRCA2‐deficient xenografts and inhibits growth of olaparib‐resistant patient‐derived tumour xenografts (PDTXs). We demonstrate that chlorambucil inflicts replication‐associated DNA double‐strand breaks (DSBs), similarly to cisplatin, and we identify ATR, FANCD2 and the SNM1A nuclease as determinants of sensitivity to both drugs. Importantly, chlorambucil is substantially less toxic to normal cells and tissues in vitro and in vivo relative to cisplatin. Because chlorambucil and cisplatin are equally effective inhibitors of BRCA2‐compromised tumours, our results indicate that chlorambucil has a higher therapeutic index than cisplatin in targeting BRCA‐deficient tumours.
Due to compromised homologous recombination (HR) repair,
and
mutated tumours accumulate DNA damage and genomic rearrangements conducive of tumour progression. To identify drugs that target ...specifically BRCA2-deficient cells, we screened a chemical library containing compounds in clinical use. The top hit was chlorambucil, a bifunctional alkylating agent used for the treatment of chronic lymphocytic leukaemia (CLL). We establish that chlorambucil is specifically toxic to BRCA1/2-deficient cells, including olaparib-resistant and cisplatin-resistant ones, suggesting the potential clinical use of chlorambucil against disease which has become resistant to these drugs. Additionally, chlorambucil eradicates BRCA2-deficient xenografts and inhibits growth of olaparib-resistant patient-derived tumour xenografts (PDTXs). We demonstrate that chlorambucil inflicts replication-associated DNA double-strand breaks (DSBs), similarly to cisplatin, and we identify ATR, FANCD2 and the SNM1A nuclease as determinants of sensitivity to both drugs. Importantly, chlorambucil is substantially less toxic to normal cells and tissues
and
relative to cisplatin. Because chlorambucil and cisplatin are equally effective inhibitors of BRCA2-compromised tumours, our results indicate that chlorambucil has a higher therapeutic index than cisplatin in targeting BRCA-deficient tumours.
Background
The natural history of multiple endocrine neoplasia type 1 (MEN1) is known through single-institution or single-family studies. We aimed to analyze the risk factors and causes of death in ...a large cohort of MEN1 patients.
Methods
Overall, 758 symptomatic MEN1 patients were identified through the GTE network (Groupe d’étude des Tumeurs Endocrines), which involves French and Belgian genetics laboratories responsible for MEN1 diagnosis and 80 clinical reference centers. The causes of death were analyzed. A frailty model, including time-dependent variables, was used to assess the impact of each clinical lesion, except for hyperparathyroidism, on survival.
Results
The median follow-up was 6.3 years. Female gender, family history of MEN1, and recent diagnosis were associated with a lower risk of death. Compared with nonaffected patients, those with thymic tumors (hazard ratio HR = 4.64, 95% CI = 1.73-12.41), glucagonomas–vipomas–somatostatinomas (HR = 4.29, 95% CI = 1.54-11.93), nonfunctioning pancreatic tumors (HR = 3.43, 95% CI = 1.71-6.88), and gastrinoma (HR = 1.89, 95% CI = 1.09-3.25) had a higher risk of death after adjustment for age, gender, and diagnosis period. The increased risk of death among patients with adrenal tumors was not significant, but three patients died from aggressive adrenal tumors. Pituitary tumors, insulinomas, and bronchial tumors did not increase the risk of death. The proportion of MEN1-related deaths decreased from 76.8 to 71.4% after 1990.
Conclusions
The prognosis of MEN1 disease has improved since 1980. Thymic tumors and duodenopancreatic tumors, including nonsecreting pancreatic tumors, increased the risk of death. Rare but aggressive adrenal tumors may also cause death. Most deaths were related to MEN1. New recommendations on abdominal and thoracic imaging are required.
Both trophic structure and biomass flow within marine food webs are influenced by the abiotic environment and anthropogenic stressors such as fishing. The abiotic environment has a large effect on ...species spatial distribution patterns and productivity and, consequently, spatial co-occurrence between predators and prey, while fishing alters species abundances and food-web structure. In order to disentangle the impacts of the abiotic environment and fishing in the Celtic Sea ecosystem, we developed a spatio-temporal trophic model, specifically an Ecopath with Ecosim with Ecospace model, for the period 1985–2016. In this model, particular attention was paid to the parameterization of the responses of all trophic levels to abiotic environmental changes. Satellite remote sensing data were employed to determine the spatial distribution and annual fluctuations of primary production (PP). Spatial and temporal changes in the habitat favorable for zooplankton were predicted with a novel ecological-niche approach using daily detection of productivity fronts from satellite ocean color. Finally, functional responses characterizing the effect of several abiotic environmental variables (including, among others, temperature, salinity and dissolved oxygen concentration, both at the surface and at the bottom) on fish species groups’ habitat suitability were produced from the predictions of statistical habitat models fitted to presence-absence data collected by multiple fisheries-independent surveys. The dynamic component of our model (Ecosim) was driven by time-series of fishing effort, PP, zooplankton habitat suitability and abiotic environmental variables, and was fitted to abundance and fisheries catch data. The spatial component of our model (Ecospace) was constructed, for specific years of the period 1985–2016 with contrasted abiotic environmental conditions, to predict the variable distribution of the biomass of all functional groups. We found that fishing was the main driver of observed ecosystem changes in the Celtic Sea over the period 1985–2016. However, the integration of the environmental variability into the model and the subsequent improvement of the fit of the dynamic Ecosim component highlighted (i) the control of the overall pelagic production by PP and (ii) the influence of temperature on the productivity of several trophic levels in the Celtic Sea, especially on trophic groups with warm and cold water affinities. In addition, Ecospace predictions indicated that the spatial distributions of commercial fish species may have substantially changed over the studied period. These spatial changes mainly appeared to be driven by temperature and may, therefore, largely impact future fisheries given the continuity of climatic changes.
PDF
