Increased levels of mitochondrial import factor Mia40 prevent the aggregation of polyQ proteins in the cytosol.

The formation of protein aggregates is a hallmark of neurodegenerative diseases. Observations on patient samples and model systems demonstrated links between aggregate formation and declining mitochondrial functionality, but causalities remain unclear. We used Saccharomyces cerevisiae to analyze how mitochondrial processes regulate the behavior of aggregation-prone polyQ protein derived from human huntingtin. Expression of Q97-GFP rapidly led to insoluble cytosolic aggregates and cell death. Although aggregation impaired mitochondrial respiration only slightly, it considerably interfered with the import of mitochondrial precursor proteins. Mutants in the import component Mia40 were hypersensitive to Q97-GFP, whereas Mia40 overexpression strongly suppressed the formation of toxic Q97-GFP aggregates both in yeast and in human cells. Based on these observations, we propose that the post-translational import of mitochondrial precursor proteins into mitochondria competes with aggregation-prone cytosolic proteins for chaperones and proteasome capacity. Mia40 regulates this competition as it has a rate-limiting role in mitochondrial protein import. Therefore, Mia40 is a dynamic regulator in mitochondrial biogenesis that can be exploited to stabilize cytosolic proteostasis.

LIVECell-A large-scale dataset for label-free live cell segmentation.

Light microscopy combined with well-established protocols of two-dimensional cell culture facilitates high-throughput quantitative imaging to study biological phenomena. Accurate segmentation of individual cells in images enables exploration of complex biological questions, but can require sophisticated imaging processing pipelines in cases of low contrast and high object density. Deep learning-based methods are considered state-of-the-art for image segmentation but typically require vast amounts of annotated data, for which there is no suitable resource available in the field of label-free cellular imaging. Here, we present LIVECell, a large, high-quality, manually annotated and expert-validated dataset of phase-contrast images, consisting of over 1.6 million cells from a diverse set of cell morphologies and culture densities. To further demonstrate its use, we train convolutional neural network-based models using LIVECell and evaluate model segmentation accuracy with a proposed a suite of benchmarks.

Pre-existing chronic kidney disease and acute kidney injury among critically ill patients.

BACKGROUND: The impact of pre-existing chronic kidney disease (CKD) and acute kidney injury (AKI) on health outcomes in critically ill patients is unclear. Yet, CKD complicated by AKI in critically ill patients is common. OBJECTIVES: To compare risk of death within one-month of admission in critically ill patients with and without pre-existing CKD who developed AKI. METHODS: A multicenter retrospective comparative study using medical records review was conducted. Study participants consisted of 826 adult patients who received mechanical ventilation for at least 6 h in the critical care units from January 2012 to December 2017. Assessment of kidney function was established by serum creatinine. Severity and staging of AKI were defined using RIFLE criteria: Risk, Injury, Failure, Loss and End stage of renal disease. Chronic kidney disease was defined as eGFR > 60 ml/mg/1.73 m2 on admission. RESULTS: Pre-existing CKD was present in 55% of patients and 7% had AKI within 7 days of admission. The overall mortality rate among these patients was 87.3%. The mortality rate was highest in patients with CKD (70.1%) followed by that of patients without pre-existing CKD but with AKI (20.7%) and that of patients with pre-existing CKD (7.1%) and AKI. Risks associated with mortality were APACHE II score (1.03; 95% CI 1.02-1.05;(P<0.001) and AKI (1.68; 95% CI 1.12-2.5;P<0.01) in patients with pre-existing CKD. Only APACHI-II (1.03; 95% CI 1.0-1.1; p < 0.001) was predictive of death in patients without pre-existing CKD. CONCLUSION: Pre-existing comorbid CKD increases risks of death among critically ill patients compared to patients without CKD and regardless of whether they develop AKI or not. Early identification of CKD and recognition of the risk for mortality among these patients may result in earlier intervention that could reduce mortality.