scholarly journals Nuclear lipid droplets and nuclear damage in Caenorhabditis elegans

PLoS Genetics ◽  
2021 ◽  
Vol 17 (6) ◽  
pp. e1009602
Author(s):  
Jose Verdezoto Mosquera ◽  
Meghan C. Bacher ◽  
James R. Priess
Keyword(s):  
Germ Cells ◽  
Lipid Droplets ◽  
Low Frequency ◽  
Intestinal Cells ◽  
Wild Type ◽  
Forward Genetic Screen ◽  
Damage Repair ◽  
Inner Nuclear Membrane Protein ◽  
Multiple Cells ◽  
Nuclear Damage

Fat stored in the form of lipid droplets has long been considered a defining characteristic of cytoplasm. However, recent studies have shown that nuclear lipid droplets occur in multiple cells and tissues, including in human patients with fatty liver disease. The function(s) of stored fat in the nucleus has not been determined, and it is possible that nuclear fat is beneficial in some situations. Conversely, nuclear lipid droplets might instead be deleterious by disrupting nuclear organization or triggering aggregation of hydrophobic proteins. We show here that nuclear lipid droplets occur normally in C. elegans intestinal cells and germ cells, but appear to be associated with damage only in the intestine. Lipid droplets in intestinal nuclei can be associated with novel bundles of microfilaments (nuclear actin) and membrane tubules that might have roles in damage repair. To increase the normal, low frequency of nuclear lipid droplets in wild-type animals, we used a forward genetic screen to isolate mutants with abnormally large or abundant nuclear lipid droplets. Genetic analysis and cloning of three such mutants showed that the genes encode the lipid regulator SEIP-1/seipin, the inner nuclear membrane protein NEMP-1/Nemp1/TMEM194A, and a component of COPI vesicles called COPA-1/α-COP. We present several lines of evidence that the nuclear lipid droplet phenotype of copa-1 mutants results from a defect in retrieving mislocalized membrane proteins that normally reside in the endoplasmic reticulum. The seip-1 mutant causes most germ cells to have nuclear lipid droplets, the largest of which occupy more than a third of the nuclear volume. Nevertheless, the nuclear lipid droplets do not trigger apoptosis, and the germ cells differentiate into gametes that produce viable, healthy progeny. Thus, our results suggest that nuclear lipid droplets are detrimental to intestinal nuclei, but have no obvious deleterious effect on germ nuclei.

scholarly journals SUN-564 ATG7 Overexpression Results in Reduction of Hepatocellular Lipid Content in Vitro

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Federica Tavaglione ◽  
Guido Baselli ◽  
Ester Ciociola ◽  
Umberto Vespasiani Gentilucci ◽  
Luca Valenti ◽  
...  
Keyword(s):  
Liver Disease ◽  
Lipid Content ◽  
Lipid Droplets ◽  
Low Frequency ◽  
Underlying Mechanism ◽  
Loss Of Function ◽  
Wild Type ◽  
Intracellular Lipid ◽  
Heparg Cells

Abstract Abstract: Non-alcoholic fatty liver disease (NAFLD) is currently the most common liver disease worldwide, paralleling the epidemic of obesity and type 2 diabetes. Despite the high prevalence of NAFLD, only a minority of patients progress to NASH and advanced fibrosis. The reasons for this inter-individual variability are not completely understood but can be partially accounted for by genetic risk factors (1). Although several common genetic variants associated with liver disease have been identified, there is still a proportion of NAFLD heritability that remains unknown. The rare rs143545741 C>T variant in the autophagy related 7 (ATG7) gene (P426L) has been associated with a higher risk of progressive NAFLD (2). Interestingly, ATG7 encodes a E1-like ubiquitin activating enzyme which is involved in hepatic lipophagy (3). We hypothesized that the unknown heritability of NAFLD might be partially explained by rare genetic variants, therefore not identified in the GWAS studies. Moreover, we assumed that loss-of-function variants in ATG7 might confer an increased susceptibility to NAFLD by reducing autophagic catabolism of lipid droplets in the liver. To examine the underlying mechanism of the low-frequency V471A variant and the rare T86I, L127I, Q170E, and P426L variants in ATG7, we performed in vitro experiments of HepaRG cells overexpressing the human V5-tagged ATG7. We observed a reduction in intracellular lipid content in HepaRG cells overexpressing the ATG7 wild type and the 86I mutant protein (p=0.029, n=4) but not the 127I, 170E, 426L, and 471A mutant proteins. Cells with the ATG7 127I, 170E, 426L, and 471A mutants had higher intracellular lipid content compared to cells overexpressing the wild type protein (p=0.029, n=4). Our data suggested that the low-frequency V471A variant and the rare L127I, Q170E, and P426L variants in ATG7 are loss-of-function, resulting in defective lipophagy, reduced hepatocellular lipid droplets turnover, and excessive lipid accumulation. More experiments are needed to clarify the underlying mechanism of the T86I variant. In conclusion, we highlighted a role for ATG7 in reducing hepatocellular lipid content. Furthermore, we provided evidence showing non-synonymous variants in ATG7 increase the risk of NAFLD and that these variants are loss-of-function. We speculate that ATG7 might be a new susceptibility risk genetic locus for liver disease development and progression. References: (1) Eslam et al. J Hepatol. 2018;68(2):268–279. (2) Baselli et al. The Liver Meeting 2018 - AASLD. Hepatology. October 2018. Volume 68, Issue S1. (3) Martinez-Lopez and Singh. Annu Rev Nutr. 2015;35:215–37.

scholarly journals RUNX1 and REXO2 are associated with the heterogeneity and prognosis of IDH wild type lower grade glioma

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Haiwei Wang ◽  
Xinrui Wang ◽  
Liangpu Xu ◽  
Ji Zhang ◽  
Hua Cao
Keyword(s):  
Transcription Factor ◽  
Low Frequency ◽  
Tumor Grade ◽  
The Cancer Genome Atlas ◽  
Lower Grade ◽  
Wild Type ◽  
Lower Grade Glioma ◽  
Cancer Genome Atlas ◽  
Worse Prognosis ◽  
Genome Atlas

AbstractBased on isocitrate dehydrogenase (IDH) alterations, lower grade glioma (LGG) is divided into IDH mutant and wild type subgroups. However, the further classification of IDH wild type LGG was unclear. Here, IDH wild type LGG patients in The Cancer Genome Atlas and Chinese Glioma Genome Atlas were divided into two sub-clusters using non-negative matrix factorization. IDH wild type LGG patients in sub-cluster2 had prolonged overall survival and low frequency of CDKN2A alterations and low immune infiltrations. Differentially expressed genes in sub-cluster1 were positively correlated with RUNX1 transcription factor. Moreover, IDH wild type LGG patients with higher stromal score or immune score were positively correlated with RUNX1 transcription factor. RUNX1 and its target gene REXO2 were up-regulated in sub-cluster1 and associated with the worse prognosis of IDH wild type LGG. RUNX1 and REXO2 were associated with the higher immune infiltrations. Furthermore, RUNX1 and REXO2 were correlated with the worse prognosis of LGG or glioma. IDH wild type LGG in sub-cluster2 was hyper-methylated. REXO2 hyper-methylation was associated with the favorable prognosis of LGG or glioma. At last, we showed that, age, tumor grade and REXO2 expression were independent prognostic factors in IDH wild type LGG.

scholarly journals Phosphoglycolate has profound metabolic effects but most likely no role in a metabolic DNA response in cancer cell lines

2019 ◽  
Vol 476 (4) ◽  
pp. 629-643 ◽  
Author(s):  
Isabelle Gerin ◽  
Marina Bury ◽  
Francesca Baldin ◽  
Julie Graff ◽  
Emile Van Schaftingen ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Lines ◽  
Oxidative Dna Damage ◽  
Fold Increase ◽  
Metabolic Effects ◽  
Phosphoglycerate Mutase ◽  
Wild Type ◽  
Metabolic Disturbances ◽  
Phosphoglycolate Phosphatase ◽  
Damage Repair

Abstract Repair of a certain type of oxidative DNA damage leads to the release of phosphoglycolate, which is an inhibitor of triose phosphate isomerase and is predicted to indirectly inhibit phosphoglycerate mutase activity. Thus, we hypothesized that phosphoglycolate might play a role in a metabolic DNA damage response. Here, we determined how phosphoglycolate is formed in cells, elucidated its effects on cellular metabolism and tested whether DNA damage repair might release sufficient phosphoglycolate to provoke metabolic effects. Phosphoglycolate concentrations were below 5 µM in wild-type U2OS and HCT116 cells and remained unchanged when we inactivated phosphoglycolate phosphatase (PGP), the enzyme that is believed to dephosphorylate phosphoglycolate. Treatment of PGP knockout cell lines with glycolate caused an up to 500-fold increase in phosphoglycolate concentrations, which resulted largely from a side activity of pyruvate kinase. This increase was much higher than in glycolate-treated wild-type cells and was accompanied by metabolite changes consistent with an inhibition of phosphoglycerate mutase, most likely due to the removal of the priming phosphorylation of this enzyme. Surprisingly, we found that phosphoglycolate also inhibits succinate dehydrogenase with a Ki value of <10 µM. Thus, phosphoglycolate can lead to profound metabolic disturbances. In contrast, phosphoglycolate concentrations were not significantly changed when we treated PGP knockout cells with Bleomycin or ionizing radiation, which are known to lead to the release of phosphoglycolate by causing DNA damage. Thus, phosphoglycolate concentrations due to DNA damage are too low to cause major metabolic changes in HCT116 and U2OS cells.

PATH-40. SPORADIC NF2 WILD-TYPE MULTIPLE MENINGIOMAS HARBOR DISTINCT DRIVER MUTATIONS

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi124-vi124
Author(s):  
Insa Prilop ◽  
Thomas Pinzer ◽  
Daniel Cahill ◽  
Priscilla Brastianos ◽  
Gabriele Schackert ◽  
...  
Keyword(s):  
Hot Spot ◽  
Low Frequency ◽  
Neurofibromatosis Type ◽  
Driver Mutations ◽  
Wild Type ◽  
Driver Genes ◽  
Who Grade ◽  
Genetic Changes ◽  
Histologic Subtype ◽  
Multiple Meningiomas

Abstract OBJECTIVE Multiple meningiomas (MM) are rare and present a unique management challenge. While the mutational landscape of single meningiomas has been extensively studied, understanding the molecular pathogenesis of sporadic MM remains incomplete. The objective of this study is to elucidate the genetic features of sporadic MM. METHODS We identified nine patients with MM (n=19) defined as ≥2 spatially separated synchronous or metachronous meningiomas. We profiled genetic changes in these tumors using next-generation sequencing (NGS) assay that covers a large number of targetable and frequently mutated genes in meningiomas including AKT1, KLF4, NF2, PIK3CA/PIK3R1, POLR2A, SMARCB1, SMO, SUFU, TRAF7, and the TERT promoter. RESULTS Most of MM were WHO grade 1 (n= 16, 84.2%). Within individual patients, no driver mutation was shared between separate tumors. All but two cases harbored different hot spot mutations in known meningioma-driver genes like TRAF7 (n= 5), PIK3CA (n= 4), AKT1 (n= 3), POLR2A (n=1) and SMO (n= 1). Moreover, individual tumors differed in histologic subtype in 8/9 patients. The low frequency of NF2 mutations in our series stands in contrast to previous studies that included hereditary cases arising in the setting of neurofibromatosis type 2 (NF2). CONCLUSIONS Our findings provide evidence for genomic inter-tumor heterogeneity and an independent molecular origin of sporadic NF2 wild-type MM. Furthermore, these findings suggest that genetic characterization of each lesion is warranted in sporadic MM.

Mutation at autosomal loci of Chinese hamster ovary cells: involvement of a high-frequency event silencing two linked alleles

1983 ◽  
Vol 3 (7) ◽  
pp. 1172-1181
Author(s):  
W E Bradley
Keyword(s):  
Cell Lines ◽  
Chinese Hamster Ovary ◽  
High Frequency ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Low Frequency ◽  
Class Ii ◽  
Class I ◽  
Wild Type ◽  
Ovary Cells

Two classes of cell lines heterozygous at the galactokinase (glk) locus have been isolated from Chinese hamster ovary cells. Class I, selected by plating nonmutagenized wild-type cells at low density in medium containing 2-deoxygalactose at a partially selective concentration, underwent subsequent mutation to the glk-/- genotype at a low frequency (approximately 10(-6) per cell), which was increased by mutagenesis. Class II heterozygotes, isolated by sib selection from mutagenized wild-type cells, had a higher spontaneous frequency of mutation to the homozygous state (approximately 10(-4) per cell), which was not affected by mutagenesis. About half of the glk-/- mutants derived from a class II heterozygote, but not the heterozygote itself, were functionally hemizygous at the syntenic thymidine kinase (tk) locus. Similarly, a tk+/- heterozygote with characteristics analogous to the class II glk+/- cell lines underwent high-frequency mutation to tk-/-, and most of these mutants, but not the tk+/- heterozygote, were functionally hemizygous at the glk locus. A model is proposed, similar to that for the mutational events at the adenine phosphoribosyl transferase locus (W. E. C. Bradley and D. Letovanec, Somatic Cell Genet. 8:51-66, 1982), of two different events, high and low frequency, being responsible for mutation at either of the linked loci tk and glk. The low-frequency event may be a point mutation, but the high-frequency event, in many instances, involves coordinated inactivation of a portion of a chromosome carrying the two linked alleles. Class II heterozygotes would be generated as a result of a low-frequency event at one allele, and class I heterozygotes would be generated by a high-frequency event. Supporting this model was the demonstration that all class I glk+/- lines examined were functionally hemizygous at tk.

scholarly journals Active elimination of intestinal cells drives oncogenic growth in organoids

2020 ◽  
Author(s):  
Ana Krotenberg Garcia ◽  
Arianna Fumagalli ◽  
Huy Quang Le ◽  
Owen J. Sansom ◽  
Jacco van Rheenen ◽  
...  
Keyword(s):  
Quality Control ◽  
Cell Death ◽  
Cancer Cells ◽  
Cell Fate ◽  
Crucial Role ◽  
Intestinal Cells ◽  
Dependent Manner ◽  
Wild Type ◽  
Cell Competition ◽  
Type Population

AbstractCompetitive cell-interactions play a crucial role in quality control during development and homeostasis. Here we show that cancer cells use such interactions to actively eliminate wild-type intestine cells in enteroid monolayers and organoids. This apoptosis-dependent process boosts proliferation of intestinal cancer cells. The remaining wild-type population activates markers of primitive epithelia and transits to a fetal-like state. Prevention of this cell fate transition avoids elimination of wild-type cells and, importantly, limits the proliferation of cancer cells. JNK signalling is activated in competing cells and is required for cell fate change and elimination of wild-type cells. Thus, cell competition drives growth of cancer cells by active out-competition of wild-type cells through forced cell death and cell fate change in a JNK dependent manner.

scholarly journals Conserved induction of distinct antiviral signalling kinetics by primate interferon lambda 4 proteins

2021 ◽  
Author(s):  
Cuncai Guo ◽  
Dorothee Reuss ◽  
Jonathon Dean Coey ◽  
Swathi Sukumar ◽  
Benjamin Lang ◽  
...  
Keyword(s):  
Hepatitis C ◽  
Gastrointestinal Tract ◽  
Cell Types ◽  
Intestinal Cells ◽  
Wild Type ◽  
Sequence Identity ◽  
Functional Differences ◽  
Naturally Occurring ◽  
Barrier Tissues ◽  
Human Primate

Interferon lambdas (IFNλ) (also known as type III IFNs) are critical cytokines that combat infection predominantly at barrier tissues, such as the lung, liver and gastrointestinal tract. Humans have four IFNλs (1-4) where IFNλ1-3 show ~80-95% homology and IFNλ4 is the most divergent displaying only ~30% sequence identity. Variants in IFNλ4 in humans are associated with the outcome of infection, such as with hepatitis C virus. However, how IFNλ4 variants impact cytokine signalling in other tissues and how well this is conserved is largely unknown. In this study we address whether differences in antiviral signalling exist between IFNλ4 variants in human hepatocyte and intestinal cells, comparing them to IFNλ3. We demonstrate that compared to IFNλ3, wild-type human IFNλ4 induces a signalling response with distinct magnitudes and kinetics, which is modified by naturally-occurring variants P70S and K154E in both cell types. IFNλ4s distinct antiviral response was more rapid yet transient compared to IFNλ1 and 3. Additionally, divergent antiviral kinetics were also observed using non-human primate IFNλs and cell lines. Furthermore, an IFNλ4-like receptor-interacting interface failed to alter IFNλ1s kinetics. Together our data provide further evidence that major functional differences exist within the IFNλ gene family. These results highlight the possible tissue specialisation of IFNλs and encourage further investigation of the divergent, non-redundant activities of IFNλ4 and other IFNλs.

scholarly journals The mitochondrial AAA protease FTSH3 regulates Complex I abundance by promoting its disassembly

2021 ◽  
Author(s):  
Aneta Ivanova ◽  
Abi S Ghifari ◽  
Oliver Berkowitz ◽  
James Whelan ◽  
Monika W Murcha
Keyword(s):  
Complex I ◽  
Nadh Dehydrogenase ◽  
Slow Growth ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Forward Genetic Screen ◽  
Slow Growth Rate ◽  
Partial Restoration ◽  
Screen Approach

Abstract ATP is generated in mitochondria by oxidative phosphorylation. Complex I (NADH:ubiquinone oxidoreductase or NADH dehydrogenase) is the first multisubunit protein complex of this pathway, oxidising NADH and transferring electrons to the ubiquinone pool. Typically Complex I mutants display a slow growth rate compared to wild-type plants. Here, using a forward genetic screen approach for restored growth of a Complex I mutant, we have identified the mitochondrial ATP dependent metalloprotease, Filamentous Temperature Sensitive H 3 (FTSH3), as a factor that is required for the disassembly of Complex I. An ethyl methanesulfonate-induced mutation in FTSH3, named rmb1 (restoration of mitochondrial biogenesis 1), restored Complex I abundance and plant growth. Complementation could be achieved with FTSH3 lacking proteolytic activity, suggesting the unfoldase function of FTSH3 has a role in Complex I disassembly. The introduction of the rmb1 to an additional, independent, and extensively characterised Complex I mutant, ndufs4, resulted in similar increases to Complex I abundance and a partial restoration of growth. These results show that disassembly or degradation of Complex I plays a role in determining its steady-state abundance and thus turnover may vary under different conditions.

INHERITANCE OF RADIATION-INDUCED SPINAL CURVATURES IN THE GUPPY LEBISTES RETICULATUS

1969 ◽  
Vol 11 (4) ◽  
pp. 937-947 ◽  
Author(s):  
Johannes Horst Schröder
Keyword(s):  
Germ Cells ◽  
Vertebral Column ◽  
Segregation Ratio ◽  
X Rays ◽  
Wild Type ◽  
Spinal Curvatures ◽  
Recessive Mutations ◽  
Quantitative Characters ◽  
Radiation Induced ◽  
Lebistes Reticulatus

Hereditary changes in the shape of the vertebral column in Lebistes reticulatus appeared after ancestral irradiation of immature germ cells with 500 or 1000 R of X-rays. Although the mutant to wild-type ratios in the F2 generation after outcrossing fitted a digenic and a trigenic segregation ratio, respectively, the quantitative characters in question are assumed to be caused by recessive mutations of polygenes which are highly mutable.

scholarly journals Phosphatidylcholine transfer protein/StarD2 promotes microvesicular steatosis and liver injury in murine experimental steatohepatitis

2017 ◽  
Vol 313 (1) ◽  
pp. G50-G61 ◽  
Author(s):  
Hayley T. Nicholls ◽  
Jason L. Hornick ◽  
David E. Cohen
Keyword(s):  
Liver Injury ◽  
Lipid Droplets ◽  
Plasma Concentrations ◽  
Fibroblast Growth Factor 21 ◽  
Wild Type ◽  
Hepatocellular Injury ◽  
Pathogenic Role ◽  
Deficient Diet ◽  
Transfer Protein ◽  
Phosphatidylcholine Transfer Protein

Mice fed a methionine- and choline-deficient (MCD) diet develop steatohepatitis that recapitulates key features of nonalcoholic steatohepatitis (NASH) in humans. Phosphatidylcholine is the most abundant phospholipid in the surfactant monolayer that coats and stabilizes lipid droplets within cells, and choline is required for its major biosynthetic pathway. Phosphatidylcholine-transfer protein (PC-TP), which exchanges phosphatidylcholines among membranes, is enriched in hepatocytes. PC-TP also regulates fatty acid metabolism through interactions with thioesterase superfamily member 2. We investigated the contribution of PC-TP to steatohepatitis induced by the MCD diet. Pctp−/− and wild-type control mice were fed the MCD diet for 5 wk and were then euthanized for histopathologic and biochemical analyses, as well as determinations of mRNA and protein expression. Whereas all mice developed steatohepatitis, plasma alanine aminotransferase and aspartate aminotransferase activities were only elevated in wild-type mice, indicating that Pctp−/− mice were protected from MCD diet-induced hepatocellular injury. Reduced hepatotoxicity due to the MCD diet in the absence of PC-TP expression was further evidenced by decreased activation of c-Jun and reduced plasma concentrations of fibroblast growth factor 21. Despite similar total hepatic concentrations of phosphatidylcholines and other lipids, the relative abundance of microvesicular lipid droplets within hepatocytes was reduced in Pctp−/− mice. Considering that the formation of larger lipid droplets may serve to protect against lipotoxicity in NASH, our findings suggest a pathogenic role for PC-TP that could be targeted in the management of this condition. NEW & NOTEWORTHY Phosphatidylcholine-transfer protein (PC-TP) is a highly specific phosphatidylcholine-binding protein that we previously showed to regulate hepatocellular nutrient metabolism through its interacting partner thioesterase superfamily member 2 (Them2). This study identifies a pathogenic role for PC-TP, independent of Them2, in the methionine- and choline-deficient diet model of experimental steatohepatitis. Our current observations suggest that PC-TP promotes liver injury by mediating the intermembrane transfer of phosphatidylcholines, thus stabilizing more pathogenic microvesicular lipid droplets.

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