Mitochondrial dysfunction in adult midbrain dopamine neurons triggers an early immune response

Dopamine (DA) neurons of the midbrain are at risk to become affected by mitochondrial damage over time and mitochondrial defects have been frequently reported in Parkinson\u27s disease (PD) patients. However, the causal contribution of adult-onset mitochondrial dysfunction to PD remains uncertain. Here, we developed a mouse model lacking Mitofusin 2 (MFN2), a key regulator of mitochondrial network homeostasis, in adult midbrain DA neurons. The knockout mice develop severe and progressive DA neuron-specific mitochondrial dysfunction resulting in neurodegeneration and parkinsonism. To gain further insights into pathophysiological events, we performed transcriptomic analyses of isolated DA neurons and found that mitochondrial dysfunction triggers an early onset immune response, which precedes mitochondrial swelling, mtDNA depletion, respiratory chain deficiency and cell death. Our experiments show that the immune response is an early pathological event when mitochondrial dysfunction is induced in adult midbrain DA neurons and that neuronal death may be promoted non-cell autonomously by the cross-talk and activation of surrounding glial cells

Targeting OGG1 arrests cancer cell proliferation by inducing replication stress

Altered oncogene expression in cancer cells causes loss of redox homeostasis resulting in oxidative DNA damage, e.g. 8-oxoguanine (8-oxoG), repaired by base excision repair (BER). PARP1 coordinates BER and relies on the upstream 8-oxoguanine-DNA glycosylase (OGG1) to recognise and excise 8-oxoG. Here we hypothesize that OGG1 may represent an attractive target to exploit reactive oxygen species (ROS) elevation in cancer. Although OGG1 depletion is well tolerated in non-transformed cells, we report here that OGG1 depletion obstructs A3 T-cell lymphoblastic acute leukemia growth in vitro and in vivo, validating OGG1 as a potential anti-cancer target. In line with this hypothesis, we show that OGG1 inhibitors (OGG1i) target a wide range of cancer cells, with a favourable therapeutic index compared to non-transformed cells. Mechanistically, OGG1i and shRNA depletion cause S-phase DNA damage, replication stress and proliferation arrest or cell death, representing a novel mechanistic approach to target cancer. This study adds OGG1 to the list of BER factors, e.g. PARP1, as potential targets for cancer treatment

Intern marknadsföring leder till servicekvalitet : En fallstudie av Jerns

Den svenska detaljhandelns försäljning har stadigt ökat under de senaste åren. En av de starkaste tillväxterna under år 2006 står skobranschen för. Svenskar i gemen konsumera mer och intresset för skor har aldrig varit större. Störst på den svenska skomarknaden idag är Nilson Group som har 25 procent av den totala marknaden, det vill säga att vart fjärde par skor som säljs i Sverige kommer från någon av deras butiker. En modeorienterad bransch som skor konkurrerar naturligtvis med design. Dock hävdar ledande befattningshavare inom branschen att de ska särskilja sig ”genom att kunna erbjuda service och medarbetare som kan skor”, det vill säga servicekvalitet och kunskap är viktiga konkurrensfördelar i försäljningsledet. I och med att nya konkurrenter dyker upp på skomarknaden krävs det sannolikt att företagen särskiljer sig och har en fungerande organisation som motiverar, attraherar och bibehåller både sina medarbetare och kunder. Syftet med denna uppsats är att genom en fallstudie undersöka om Nilson Group och deras affärskoncept Jerns har samma syn och uppfattning som sina medarbetare angående den interna marknadsföringen. Vi har studerat hur de implementerar sin affärsidé och hur de bedriver sin interna marknadsföring för att motivera butikspersonalen och hur den påverkar samt ökar servicekvaliteten hos Jerns anställda. Vi har valt att utgå ifrån olika teorier för att undersöka syftet. Affärsidén har vi definierat utifrån Normanns syn där han betonar vikten av att affärsidén och visionen ska vara invävda i organisationsstrukturen och hos företagets anställda. Sedan har vi använt oss av Grönroos riktlinjer för intern marknadsföring, där han bland annat förespråkar ett fungerande informationsflöde, utbildningar och ett dagligt servicemedvetande. Sedan har vi valt att utgå ifrån Zeithamls kundvärdesmodell där vi använt oss av hans tio dimensioner för att definiera servicekvalitet. Utifrån dessa teorier har variabler tagits fram för att formulera frågor till ledningen och butikspersonalen för att fastställa deras syn på företagets affärsidé, interna marknadsföring och service. Utifrån den data som erhölls genom en enkätundersökning bland butikspersonalen och en intervju med ledningen har skillnader och likheter mellan de och butikspersonalen jämförts för att upptäcka eventuella gap som finns. Som slutsats så ser vi att den interna marknadsföringen som helhet är fungerande trots vissa gap. Servicemedvetenheten är god bland butikspersonalen vilket ledningen arbetar för, detta tack vare att den interna marknadsföringen fungerar. Beträffande företagets affärsidé så har företaget lyckats sprida den på ett bra sätt. Vi upptäckte dock att den inte fullt ut överensstämmer med Jerns arbetssätt

A role for BCL2L13 and autophagy in germline purifying selection of mtDNA.

Acknowledgements: We would like to thank Leila Izadi for the support in genotyping of the mice.Mammalian mitochondrial DNA (mtDNA) is inherited uniparentally through the female germline without undergoing recombination. This poses a major problem as deleterious mtDNA mutations must be eliminated to avoid a mutational meltdown over generations. At least two mechanisms that can decrease the mutation load during maternal transmission are operational: a stochastic bottleneck for mtDNA transmission from mother to child, and a directed purifying selection against transmission of deleterious mtDNA mutations. However, the molecular mechanisms controlling these processes remain unknown. In this study, we systematically tested whether decreased autophagy contributes to purifying selection by crossing the C5024T mouse model harbouring a single pathogenic heteroplasmic mutation in the tRNAAla gene of the mtDNA with different autophagy-deficient mouse models, including knockouts of Parkin, Bcl2l13, Ulk1, and Ulk2. Our study reveals a statistically robust effect of knockout of Bcl2l13 on the selection process, and weaker evidence for the effect of Ulk1 and potentially Ulk2, while no statistically significant impact is seen for knockout of Parkin. This points at distinctive roles of these players in germline purifying selection. Overall, our approach provides a framework for investigating the roles of other important factors involved in the enigmatic process of purifying selection and guides further investigations for the role of BCL2L13 in the elimination of non-synonymous mutations in protein-coding genes

High levels of TFAM repress mammalian mitochondrial DNA transcription in vivo

Mitochondrial transcription factor A (TFAM) is compacting mitochondrial DNA (dmtDNA) into nucleoids and directly controls mtDNA copy number. Here, we show that the TFAM-to-mtDNA ratio is critical for maintaining normal mtDNA expression in different mouse tissues. Moderately increased TFAM protein levels increase mtDNA copy number but a normal TFAM-to-mtDNA ratio is maintained resulting in unaltered mtDNA expression and normal whole animal metabolism. Mice ubiquitously expressing very high TFAM levels develop pathology leading to deficient oxidative phosphorylation (OXPHOS) and early postnatal lethality. The TFAM-to-mtDNA ratio varies widely between tissues in these mice and is very high in skeletal muscle leading to strong repression of mtDNA expression and OXPHOS deficiency. In the heart, increased mtDNA copy number results in a near normal TFAM-to-mtDNA ratio and maintained OXPHOS capacity. In liver, induction of LONP1 protease and mitochondrial RNA polymerase expression counteracts the silencing effect of high TFAM levels. TFAM thus acts as a general repressor of mtDNA expression and this effect can be counterbalanced by tissue-specific expression of regulatory factors

The amino terminal extension of mammalian mitochondrial RNA polymerase ensures promoter specific transcription initiation

Mammalian mitochondrial transcription is executed by a single subunit mitochondrial RNA polymerase (Polrmt) and its two accessory factors, mitochondrial transcription factors A and B2 (Tfam and Tfb2m). Polrmt is structurally related to singlesubunit phage RNA polymerases, but it also contains a unique N-terminal extension (NTE) of unknown function. We here demonstrate that the NTE functions together with Tfam to ensure promoter-specific transcription. When the NTE is deleted, Polrmt can initiate transcription in the absence of Tfam, both from promoters and nonspecific DNA sequences. Additionally, when in presence of Tfam and a mitochondrial promoter, the NTE-deleted mutant has an even higher transcription activity than wild-type polymerase, indicating that the NTE functions as an inhibitory domain. Our studies lead to a model according to which Tfam specifically recruits wild-type Polrmt to promoter sequences, relieving the inhibitory effect of the NTE, as a first step in transcription initiation. In the second step, Tfb2m is recruited into the complex and transcription is initiated.\ua9 The Author(s) 2014. Published by Oxford University Press

FBXL4 deficiency increases mitochondrial removal by autophagy

Abstract Pathogenic variants in FBXL4 cause a severe encephalopathic syndrome associated with mtDNA depletion and deficient oxidative phosphorylation. To gain further insight into the enigmatic pathophysiology caused by FBXL4 deficiency, we generated homozygous Fbxl4 knockout mice and found that they display a predominant perinatal lethality. Surprisingly, the few surviving animals are apparently normal until the age of 8–12 months when they gradually develop signs of mitochondrial dysfunction and weight loss. One‐year‐old Fbxl4 knockouts show a global reduction in a variety of mitochondrial proteins and mtDNA depletion, whereas lysosomal proteins are upregulated. Fibroblasts from patients with FBXL4 deficiency and human FBXL4 knockout cells also have reduced steady‐state levels of mitochondrial proteins that can be attributed to increased mitochondrial turnover. Inhibition of lysosomal function in these cells reverses the mitochondrial phenotype, whereas proteasomal inhibition has no effect. Taken together, the results we present here show that FBXL4 prevents mitochondrial removal via autophagy and that loss of FBXL4 leads to decreased mitochondrial content and mitochondrial disease

Fig 1 -

(A) Overview of the experimental setup. Female mice transmitting the pathogenic C5024T mutation in combination with Parkin-/-, Bcl2l13-/-, Ulk1-/-, or Ulk2-/-alleles were crossed to C57BL6/N males with wild-type (wt) mtDNA and the mutation load was measured in the resulting offspring. (B) Western blots analysis of BCL2L13 protein levels in mouse liver (n = 3; * = unspecific bands), levels of GAPDH shown as loading control.</p

The numerical data underyling the results of this study.

(XLSX)</p