Hepatitis C virus alters the morphology and function of peroxisomes.

Despite the introduction of effective treatments for hepatitis C in clinics, issues remain regarding the liver disease induced by chronic hepatitis C virus (HCV) infection. HCV is known to disturb the metabolism of infected cells, especially lipid metabolism and redox balance, but the mechanisms leading to HCV-induced pathogenesis are still poorly understood. In an APEX2-based proximity biotinylation screen, we identified ACBD5, a peroxisome membrane protein, as located in the vicinity of HCV replication complexes. Confocal microscopy confirmed the relocation of peroxisomes near HCV replication complexes and indicated that their morphology and number are altered in approximately 30% of infected Huh-7 cells. Peroxisomes are small versatile organelles involved among other functions in lipid metabolism and ROS regulation. To determine their importance in the HCV life cycle, we generated Huh-7 cells devoid of peroxisomes by inactivating the PEX5 and PEX3 genes using CRISPR/Cas9 and found that the absence of peroxisomes had no impact on replication kinetics or infectious titers of HCV strains JFH1 and DBN3a. The impact of HCV on peroxisomal functions was assessed using sub-genomic replicons. An increase of ROS was measured in peroxisomes of replicon-containing cells, correlated with a significant decrease of catalase activity with the DBN3a strain. In contrast, HCV replication had little to no impact on cytoplasmic and mitochondrial ROS, suggesting that the redox balance of peroxisomes is specifically impaired in cells replicating HCV. Our study provides evidence that peroxisome function and morphology are altered in HCV-infected cells.

An extended transcription factor regulatory network controls hepatocyte identity.

Cell identity is specified by a core transcriptional regulatory circuitry (CoRC), typically limited to a small set of interconnected cell-specific transcription factors (TFs). By mining global hepatic TF regulons, we reveal a more complex organization of the transcriptional regulatory network controlling hepatocyte identity. We show that tight functional interconnections controlling hepatocyte identity extend to non-cell-specific TFs beyond the CoRC, which we call hepatocyte identity (Hep-ID)CONNECT TFs. Besides controlling identity effector genes, Hep-IDCONNECT TFs also engage in reciprocal transcriptional regulation with TFs of the CoRC. In homeostatic basal conditions, this translates into Hep-IDCONNECT TFs being involved in fine tuning CoRC TF expression including their rhythmic expression patterns. Moreover, a role for Hep-IDCONNECT TFs in the control of hepatocyte identity is revealed in dedifferentiated hepatocytes where Hep-IDCONNECT TFs are able to reset CoRC TF expression. This is observed upon activation of NR1H3 or THRB in hepatocarcinoma or in hepatocytes subjected to inflammation-induced loss of identity. Our study establishes that hepatocyte identity is controlled by an extended array of TFs beyond the CoRC.

[The keys to success in French Medical National Ranking Examination: Integrated training activities in teaching hospital and medical school]. / Les clefs de la réussite à Grenoble aux Épreuves classantes nationales : les formations intégrées hospitalo-universitaire.

INTRODUCTION: The National Ranking Examination (NRE) is the key to the choice of career and specialty for future physicians; it lets them choose their place of employment in a specialty and an hospital for their internship. It seems interesting to model the success factors to this exam for the medical students from Grenoble University. METHODS: For each of the medical students at Grenoble University who did apply to the NRE in 2012, data have been collected about their academic background and personal details from the administration of the University. A simple logistic regression with success set as being ranked in the first 2000 students, then a polytomous logistic regression, have been performed. RESULTS: The 191 students in the models are 59% female, 25 years old in average (SD 1.8). The factors associated to a ranking in the first 2000 are: not repeating the PCEM1 class (odds ratio [OR] 2.63, CI95: [1.26; 5.56]), performing nurse practice during internships (OR=1.27 [1.00; 1.62]), being ranked in the first half of the class for S3 pole (OR=6.04 [1.21; 30.20] for the first quarter, OR=5.65 [1.15; 27.74] for the second quarter) and being in the first quarter at T5 pole (OR=3.42 [1.08; 10.82]). CONCLUSION: Our study finds four factors independently contributing to the success at NRE: not repeating PCEM1, performing nurse practice and being ranked in the top of the class at certain academic fields. The AUC is 0.76 and student accuracy is more than 80%. However, some items, for example repeating DCEM4 or participating in NRE mock exams, have no influence on success. A different motivation should be a part of the explanation… As these analysed data are mainly institutional, they are accurate and reliable. The polytomic logistic model, sharing 3 factors with the simple logistic model, replace a performing nurse practice factor's by a grant recipient factor.