Loss of FBXO7 results in a Parkinson’s-like dopaminergic degeneration via an RPL23-MDM2-TP53 pathway

The field of Parkinson’s disease research has been impeded by the absence of animal models that clearly phenocopy the features of this neurodegenerative condition. Mutations in FBXO7/PARK15 are associated with both sporadic Parkinson’s disease and a severe form of autosomal recessive early-onset Parkinsonism. Here we report that conditional deletion of Fbxo7 in the midbrain dopamine neurons results in an early reduction in striatal dopamine levels, together with a slow, progressive loss of midbrain dopamine neurons and onset of locomotor defects. Unexpectedly, a later compensatory response led to a near-full restoration of dopaminergic fibre innervation in the striatum, but nigral cell loss was irreversible. Mechanistically, there was increased expression in the dopamine neurons of FBXO7-interacting protein, RPL23, which is a sensor of ribosomal stress that inhibits MDM2, the negative regulator of p53. A corresponding activated p53 transcriptional signature biased towards pro-apoptotic genes was also observed. These data suggest the neuroprotective role of FBXO7 involves its suppression of the RPL23-MDM2-p53 axis that promotes cell death in dopaminergic midbrain neurons.Biotechnology and Biological Sciences Research Council (BB/J007846/1), DDPDgenes, Parkinson's UK and the CurePD Trust, and Wellcome Trust-MRC funded Cambridge Stem Cell Institute and an NIHR award of a Biomedical Research Centre for Addenbrooke’s Hospital/University of Cambridge

A Conserved Requirement for fbxo7 during Male Germ Cell Cytoplasmic Remodelling

Fbxo7 is the substrate-recognition subunit of an SCF-type ubiquitin E3 ligase complex. It has physiologically important functions in regulating mitophagy, proteasome activity and the cell cycle in multiple cell types, like neurons, lymphocytes and erythrocytes. Here, we show that in addition to the previously known Parkinsonian and hematopoietic phenotypes, male mice with reduced Fbxo7 expression are sterile. In these males, despite successful meiosis, nuclear elongation and eviction of histones from chromatin, the developing spermatids are phagocytosed by Sertoli cells during late spermiogenesis, as the spermatids undergo cytoplasmic remodeling. Surprisingly, despite the loss of all germ cells, there was no evidence of the symplast formation and cell sloughing that is typically associated with spermatid death in other mouse sterility models, suggesting that novel cell death and/or cell disposal mechanisms may be engaged in Fbxo7 mutant males. Mutation of the Drosophila Fbxo7 ortholog, nutcracker (ntc) also leads to sterility with germ cell death during cytoplasmic remodeling, indicating that the requirement for Fbxo7 at this stage is conserved. The ntc phenotype was attributed to decreased levels of the proteasome regulator, DmPI31 and reduced proteasome activity. Consistent with the fly model, we observe a reduction in PI31 levels in mutant mice; however, there is no alteration in proteasome activity in whole mouse testes. Our results are consistent with findings that Fbxo7 regulates PI31 protein levels, and indicates that a defect at the late stages of spermiogenesis, possibly due to faulty spatial dynamics of proteasomes during cytoplasmic remodeling, may underlie the fertility phenotype in mice

Identification of the mechanism of paternal mitochondria targeting prior to fertilization in the early embryo of C. elegans

Chez la majorité des espèces, les mitochondries et leur ADN sont hérités de manière uniparentale maternelle. Au moment de la fécondation, le spermatozoïde entre dans l'ovocyte avec ses mitochondries et leur ADN menant à se demander pourquoi et comment les mitochondries paternelles ne sont plus détectées chez le nouvel individu. Chez le ver C. elegans, les mitochondries d’origine spermatique sont activement dégradées par autophagie dans l’embryon une cellule. Les marqueurs de l’autophagie chez le ver, les protéines LGG-1 et LGG-2, sont observés autour des organites d’origine spermatique après la fécondation et l’interférence avec l’autophagie bloque l’élimination de ces organites. Néanmoins, il n’est toujours pas clair comment ce ciblage s’effectue ni le rôle des différentes protéines de l’autophagies impliquées dans le processus. La première partie des résultats montre que LGG-2 permet le transport des autophagosomes et de leur contenu vers la zone pericentrosomale afin de faciliter leur fusion avec les lysosomes qui se concentrent dans cette zone. En parallèle, j’ai testé plusieurs hypothèses afin d’identifier les mécanismes de ciblage des mitochondries d’origine spermatique. J’ai montré que l’ubiquitine joue un rôle dans le recrutement de la protéine LGG-1 autour des organites spermatiques. J’ai également décrit plusieurs propriétés des mitochondries spermatiques et ovocytaires qui semblent jouer un rôle dans le recrutement de la machinerie de l’autophagie. Ainsi, la dégradation des mitochondries d’origine spermatique représente une forme originale et physiologique de mitophagie.In most animal species, mitochondria and their DNA are maternally inherited. Upon fertilization, the spermatozoid and its mitochondria enter into the oocyte leading to the questions why and how are those mitochondria not detected in the new born. The sperm derived mitochondria are selectively degraded by autophagy in C. elegans. The autophagy proteins, LGG-1 and LGG-2, are recruited around sperm-derived organelles upon fertilization in the early embryo of C. elegans and the interference with the autophagy blocks the degradation of those organelles. The mechanism permitting this specific targeting of the paternal mitochondria and the role of the different autophagy proteins are still unclear. First, we showed that LGG-2 plays an important role in the clearance of sperm-derived organelles by targeting them to the pericentrosomal area to facilitate their fusion with lysosomes. In parallel, I tested several hypotheses to identify the mechanism permitting the specific targeting of sperm-derived mitochondria. I showed that the ubiquitin plays a role in the recruitment of LGG-1 around sperm-derived organelles and described several properties of the sperm and oocyte-derived mitochondria that are likely to play an important role for the recruitment of the autophagy machinery. This led us to conclude that sperm derived mitochondria degradation represent an original physiologic mitophagy

Allophagy, or how the embryo eliminates mitochondria and other paternal organelles

International audienceno abstrac

Mitophagy of polarized sperm-derived mitochondria after fertilization

International audienceLoss of membrane potential of sperm mitochondria has been regarded as the first step preceding mitophagy degradation after their entry into the C. elegans oocyte at fertilization. This is in line with the classical view of mitophagy of defective or abnormal mitochondria and could serve as a recognition signal for their specific and quick autophagy degradation. Here, using TMRE (tetramethylrhodamine ethyl ester) and live imaging we show that this is not the case. Instead, sperm inherited mitochondria show a stable labeling with TMRE before and at the time of autophagosomes formation. Interestingly, this labeling remains in late-stage-embryos of autophagy-defective-mutants suggesting that the loss of membrane potential occurs upon the entry of the mitochondria into the autophagy pathway. These stabilized and still polarized sperm mitochondria remain distinct but associated with the maternal-derived mitochondrial network suggesting a mechanism that prevents their fusion and represents an efficient additional protective system against fertilization-induced heteroplasmy

Concerns and considerations among caregivers of a child with autism in Qatar

Abstract Background Autism impacts the lives of the family looking after a child with the condition in different ways, and forces family members to modify their daily lives to suit their reality. To our knowledge, no previous research investigated concern and considerations of parents/caregivers of children with autism in Qatar or the Arabic speaking Middle Eastern region. Methods Caregivers of a child who was between the age of 3 to17 years old at the time of the study and who was diagnosed with ASD (Autistic Group or AG) were recruited from the two main developmental pediatric and children rehabilitation clinics in Qatar. The control group (non-autism group, or NAG) was represented by caregivers of a non-autistic child between the age of 3 to 17 years old at the time of the study and who were visiting a family clinic of a primary health care facility for routine medical check-up. Data collected from both groups included related to the child (e.g. the child’s date of birth, his/her relation to the caregiver, number of siblings, number of hours of sleep in a day, number of hours spent watching television or videos prior to age 3, time spent indoors prior to age 3, absenteeism from school, and use of a nanny to care for the child) and to the caregiver (education level, profession, level of consanguinity using the phylogram method). In addition to these questions, caregivers in the AG were asked specific questions around maternal concern and considerations in respect to the future of their children and the specialized services they receive. Results Children in the autism group spent more time indoors, watching television, or sleeping than children in the non-autism group. Only around 40% of caregivers in the autism group said they would encourage their child to get married and become a parent when s/he grows up. A number of caregivers of children with autism frequently utilize specialized rehabilitation services; others did express their needs for these services and made comments about having to wait a long time before they were provided with some of the services. Religious faith helped caregivers in accepting having a child with autism. General health-related quality of life did not differ significantly between the caregivers of the two groups, although mental health was consistently poorer in the autism group of caregivers. Conclusions The study draws attention to the concerns of the families of children with autism and their expectations about the future of their children. The findings can be used by policy makers in planning services to support these families in Qatar.</p

Dense urbanism and economic multi-centrism at third-millennium BC Lagash

Studies of ancient Mesopotamian cities have long focused on their institutions. Here, instead, the authors draw on recent investigations at the third-millennium BC site of Lagash (modern Tell al-Hiba, Iraq) to explore urban density, economy and sustainability at one of the largest ancient urban centres of the region. Drawing on excavation, environmental and remote-sensing data, the authors adopt a multi-scalar approach, revealing dense urban occupation, with subdivision into distinct walled quarters, as well as evidence for multiple foci of intensive industrial production and the exploitation of a rich mosaic of surrounding micro-environments. The study emphasises how a combination of new field data and alternative research directions offers novel insights into early urbanism

Sperm-inherited organelle clearance in C-elegans relies on LC3-dependent autophagosome targeting to the pericentrosomal area

International audienceMacroautophagic degradation of sperm-inherited organelles prevents paternal mitochondrial DNA transmission in C. elegans. The recruitment of autophagy markers around sperm mitochondria has also been observed in mouse and fly embryos but their role in degradation is debated. Both worm Atg8 ubiquitin-like proteins, LGG1/GABARAP and LGG-2/LC3, are recruited around sperm organelles after fertilization. Whereas LGG-1 depletion affects autophagosome function, stabilizes the substrates and is lethal, we demonstrate that LGG-2 is dispensable for autophagosome formation but participates in their microtubule-dependent transport toward the pericentrosomal area prior to acidification. In the absence of LGG-2, autophagosomes and their substrates remain clustered at the cell cortex, away from the centrosomes and their associated lysosomes. Thus, the clearance of sperm organelles is delayed and their segregation between blastomeres prevented. This allowed us to reveal a role of the RAB5/RAB-7 GTPases in autophagosome formation. In conclusion, the major contribution of LGG-2 in sperm-inherited organelle clearance resides in its capacity to mediate the retrograde transport of autophagosomes rather than their fusion with acidic compartments: a potential key function of LC3 in controlling the fate of sperm mitochondria in other species

Allophagy

PMID: 22361582International audienceIn most animals, during oocyte fertilization the spermatozoon provides DNA and centrioles together with some cytoplasm and organelles, but paternal mitochondria are generally eliminated in the embryo. Using the model animal C. elegans we have shown that paternal organelle degradation is dependent on the formation of autophagosomes a few minutes after fertilization. This macroautophagic process is preceded by an active ubiquitination of some spermatozoon-inherited organelles. Analysis of fertilized mouse embryos suggests that this autophagy event is evolutionarily conserved

Study of an FBXO7 patient mutation reveals Fbxo7 and PI31 co-regulate proteasomes and mitochondria.

Mutations in FBXO7 have been discovered to be associated with an atypical parkinsonism. We report here a new homozygous missense mutation in a paediatric patient that causes an L250P substitution in the dimerisation domain of Fbxo7. This alteration selectively ablates the Fbxo7-PI31 interaction and causes a significant reduction in Fbxo7 and PI31 levels in patient cells. Consistent with their association with proteasomes, patient fibroblasts have reduced proteasome activity and proteasome subunits. We also show PI31 interacts with the MiD49/51 fission adaptor proteins, and unexpectedly, PI31 acts to facilitate SCFFbxo7 -mediated ubiquitination of MiD49. The L250P mutation reduces the SCFFbxo7 ligase-mediated ubiquitination of a subset of its known substrates. Although MiD49/51 expression was reduced in patient cells, there was no effect on the mitochondrial network. However, patient cells show reduced levels of mitochondrial function and mitophagy, higher levels of ROS and are less viable under stress. Our study demonstrates that Fbxo7 and PI31 regulate proteasomes and mitochondria and reveals a new function for PI31 in enhancing the SCFFbxo7 E3 ubiquitin ligase activity.This work is supported by funding from the BBSRC DTP to LS and HL, a Parkinson’s UK grant (G-1701) to RAB, MZ and HL, and a Rosetrees Trust Project Grant (PGL22/100035) to SAR, RAB, and HL. This research is also supported by the NIHR Cambridge Biomedical Research Centre (BRC-1215-20014, including the Cell Phenotyping Hub. The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care. This research was funded in whole, or in part, by the Wellcome Trust 203151/Z/16/Z. NQM is supported by the Francis Crick Institute, which receives its core funding (FC001115) from Cancer Research UK, the UK Medical Research Council and the Wellcome Trust