Étude du protéome alternatif d'origine mitochondriale chez l'humain

Les mitochondries, organelles d’origine bactérienne, sont trouvées dans les cellules de presque tous les organismes eucaryotes. Elles exercent des rôles centraux dans les fonctions cellulaires tels que la production d’énergie, la signalisation cellulaire et l’apoptose et ont aussi un impact sur le vieillissement ainsi que certains cancers et maladies neurodégénératives. Chez l’humain et les mammifères en général, le génome mitochondrial est une molécule d’ADN double brin circulaire composée de 37 gènes. Seulement 13 de ces gènes codent des protéines mitochondriales et les 24 autres produisent 22 ARNt (ARN de transfert) et 2 ARNr (ARN ribosomal) qui sont nécessaires à la traduction des 13 protéines mitochondriales. L’ADNmt (ADN mitochondrial) étant très compact, ceci suggère qu’il y a peu de possibilités pour des nouveautés évolutives. Cependant, de récentes recherches ont permis de révéler la présence de près d’une dizaine de petits ORF (cadres de lecture ouverts) fonctionnels à l’intérieur des gènes mitochondriaux 12S ARNr et 16S ARNr. Ceci remet en question la complexité du génome mitochondrial et montre que son potentiel codant a été sous-estimé. Une analyse approfondie du génome mitochondrial humain a révélé la présence de 227 séquences potentiellement traduites en protéines mitochondriales à travers l’ensemble du génome. Dans cette étude, nous avons sélectionné 9 de ces 227 séquences afin de déterminer si effectivement, elles produisent un peptide identifiable. Pour ce faire, des expériences d’immunobuvardage, d’immunofluorescence et d’immunoprécipitation ont été réalisées sur des cellules HeLa et des cellules HEK293T. Ces expériences ont permis d’identifier une protéine mitochondriale alternative nommée MTALTND4 dont la séquence codante est trouvée à l’intérieur du gène nd4, dans un cadre de lecture alternatif. MTALTND4 est traduite dans la mitochondrie et peut être exportée dans le cytoplasme ainsi qu’à l’extérieur de la cellule puisqu’elle a été retrouvée dans le plasma humain. Bien que la fonction de cette protéine n’ait pas encore été confirmée, des résultats préliminaires indiquent qu’elle a un impact sur la respiration cellulaire. MTALTND4 diminue la respiration mitochondriale et nos résultats suggèrent que son action serait induite par l’hypoxie. La découverte de ce nouveau gène mitochondrial humain confirme que le potentiel codant du génome mitochondrial est beaucoup plus vaste que ce que nous croyions. Il existe fort probablement encore plusieurs autres protéines mitochondriales dont les effets pourraient se révéler d’une grande importance. En effet, plusieurs des protéines dérivées du génome mitochondrial découvertes à ce jour ont des impacts majeurs au niveau du métabolisme et pourraient agir en tant que molécules thérapeutiques importantes. Nos résultats amènent à repenser l’évolution et les pressions de sélection exercées sur le génome mitochondrial et ouvrent la porte à de nombreuses recherches futures qui permettront de re-caractériser le génome mitochondrial et d’avoir une compréhension encore plus approfondie du rôle des mitochondries dans les fonctions cellulaires.Mitochondria, organelles of bacterial origin, are found in almost every eukaryotic organism and play a central role in cellular functions such as energy production, cellular signaling and apoptosis and are also known to have an impact on aging, certain cancers and neurodegenerative diseases. In humans and mammals in general, the mitochondrial DNA is a small double-stranded circular molecule coding for only 37 genes. Only 13 of them code for mitochondrial proteins and the other 24 genes produce 22 tRNAs (transfer RNA) and 2 rRNAs (ribosomal RNA) necessary for the translation of the 13 protein coding genes. The extremely compact nature of mtDNA (mitochondrial DNA) suggests that there is little room for evolutionary novelties. However, recent research revealed the presence of about ten small functional ORFs inside the mitochondrial genes 12S rRNA and 16S rRNA. This calls into question the complexity of the mitochondrial genome and shows that its coding potential has been greatly underestimated. A thorough examination of the human mitochondrial genome revealed the presence of 227 sequences potentially translated into mitochondrial alternative proteins across the entire genome. In this study, we selected 9 of the 227 sequences to determine if they indeed produce identifiable peptides. This was done by immunoblotting, immunofluorescence and immunoprecipitation experiments on HeLa and HEK293T cells. These experiments allowed us to identify one alternative protein named MTALTND4 whose coding sequence is found inside the nd4 gene, in an alternative sequence. MTALTND4 is translated inside the mitochondria and can be exported in the cytoplasm as well as outside the cell since it has been found in human plasma. Although the function of this protein has not yet been confirmed preliminary results indicate its impact on cellular respiration. MTALTND4 decreases mitochondrial respiration and our results suggest that its action could be induced by hypoxia. The discovery of this new human mitochondrial gene confirms that the coding potential of the mitochondrial genome is much larger than we thought. There are most likely still many other mitochondrial proteins whose effects could prove to be of great importance. Indeed, several of the mitochondrial derived proteins discovered to date have major impacts on metabolism and could act as important therapeutic molecules. Our results lead to rethink the evolution and the selection pressures exerted on the mitochondrial genome and open the door to many future researches which will allow to re-characterize the mitochondrial genome and to have an even deeper understanding of the role of mitochondria in cellular functions

Centralising the Admission Process in a German Hospital

The admission process is the first part of a hospital stay for all in- and outpatients. For the hospital, it is a critical part as all the necessary data must be stored in the hospital information system and all legal documents have to be signed in order to guarantee the best possible treatment and efficient logistics. In this paper, we focus on the admission process in a German hospital. As the admission of a patient, especially informing and advising him, is very time consuming, the hospital aims at installing a digital admission process. The first important step towards this goal is pooling the current decentralised patient admission in one new building. Using a simulation, we determine efficient staffing levels and rosters for the centralised admission and analyse the expected waiting times for the patients. In addition, we outline potential steps towards a digital patient admission process

A small protein coded within the mitochondrial canonical gene nd4 regulates mitochondrial bioenergetics

BACKGROUND: Mitochondria have a central role in cellular functions, aging, and in certain diseases. They possess their own genome, a vestige of their bacterial ancestor. Over the course of evolution, most of the genes of the ancestor have been lost or transferred to the nucleus. In humans, the mtDNA is a very small circular molecule with a functional repertoire limited to only 37 genes. Its extremely compact nature with genes arranged one after the other and separated by short non-coding regions suggests that there is little room for evolutionary novelties. This is radically different from bacterial genomes, which are also circular but much larger, and in which we can find genes inside other genes. These sequences, different from the reference coding sequences, are called alternatives open reading frames or altORFs, and they are involved in key biological functions. However, whether altORFs exist in mitochondrial protein-coding genes or elsewhere in the human mitogenome has not been fully addressed. RESULTS: We found a downstream alternative ATG initiation codon in the + 3 reading frame of the human mitochondrial nd4 gene. This newly characterized altORF encodes a 99-amino-acid-long polypeptide, MTALTND4, which is conserved in primates. Our custom antibody, but not the pre-immune serum, was able to immunoprecipitate MTALTND4 from HeLa cell lysates, confirming the existence of an endogenous MTALTND4 peptide. The protein is localized in mitochondria and cytoplasm and is also found in the plasma, and it impacts cell and mitochondrial physiology. CONCLUSIONS: Many human mitochondrial translated ORFs might have so far gone unnoticed. By ignoring mtaltORFs, we have underestimated the coding potential of the mitogenome. Alternative mitochondrial peptides such as MTALTND4 may offer a new framework for the investigation of mitochondrial functions and diseases

Opening Pandora’s Box? Guiding Organizations Through Selective Open Data Revealing

Concealing knowledge is critical for companies to maintain their competitive advantage in the long-term. Globalization and digitalization, however, force companies to rethink their approach to knowledge sharing to combat increasing competition. In recent years, private sector organizations have started to engage in open data initiatives, thereby allowing the in- and outflow of knowledge. While open data may foster innovation and increase transparency, it does not come without risk. Incautiously revealing data to the public may harm the data provider itself, calling for guidance on the decision-making process. Based on a design science research (DSR) approach, we address this research problem and thereby make the following contributions: First, we derive universal design requirements for artifacts on selective knowledge revealing. Second, we design and evaluate a method for the application case of open data revealing. For practitioners, we provide concrete guidance for the decision-making process in form of a workshop concep

A small protein coded within the mitochondrial canonical gene nd4 regulates mitochondrial bioenergetics

Abstract Background Mitochondria have a central role in cellular functions, aging, and in certain diseases. They possess their own genome, a vestige of their bacterial ancestor. Over the course of evolution, most of the genes of the ancestor have been lost or transferred to the nucleus. In humans, the mtDNA is a very small circular molecule with a functional repertoire limited to only 37 genes. Its extremely compact nature with genes arranged one after the other and separated by short non-coding regions suggests that there is little room for evolutionary novelties. This is radically different from bacterial genomes, which are also circular but much larger, and in which we can find genes inside other genes. These sequences, different from the reference coding sequences, are called alternatives open reading frames or altORFs, and they are involved in key biological functions. However, whether altORFs exist in mitochondrial protein-coding genes or elsewhere in the human mitogenome has not been fully addressed. Results We found a downstream alternative ATG initiation codon in the + 3 reading frame of the human mitochondrial nd4 gene. This newly characterized altORF encodes a 99-amino-acid-long polypeptide, MTALTND4, which is conserved in primates. Our custom antibody, but not the pre-immune serum, was able to immunoprecipitate MTALTND4 from HeLa cell lysates, confirming the existence of an endogenous MTALTND4 peptide. The protein is localized in mitochondria and cytoplasm and is also found in the plasma, and it impacts cell and mitochondrial physiology. Conclusions Many human mitochondrial translated ORFs might have so far gone unnoticed. By ignoring mtaltORFs, we have underestimated the coding potential of the mitogenome. Alternative mitochondrial peptides such as MTALTND4 may offer a new framework for the investigation of mitochondrial functions and diseases

Fundamentals and Applications of Chitosan

International audienceChitosan is a biopolymer obtained from chitin, one of the most abundant and renewable material on Earth. Chitin is a primary component of cell walls in fungi, the exoskeletons of arthropods, such as crustaceans, e.g. crabs, lobsters and shrimps, and insects, the radulae of molluscs, cephalopod beaks, and the scales of fish and lissamphibians. The discovery of chitin in 1811 is attributed to Henri Braconnot while the history of chitosan dates back to 1859 with the work of Charles Rouget. The name of chitosan was, however, introduced in 1894 by Felix Hoppe-Seyler. Because of its particular macromolecular structure, biocompatibility, biode-gradability and other intrinsic functional properties, chitosan has attracted major scientific and industrial interests from the late 1970s. Chitosan and its derivatives have practical applications in food industry, agriculture, pharmacy, medicine, cos-metology, textile and paper industries, and chemistry. In the last two decades, chito-san has also received much attention in numerous other fields such as dentistry, ophthalmology, biomedicine and bio-imaging, hygiene and personal care, veterinary medicine, packaging industry, agrochemistry, aquaculture, functional textiles and cosmetotextiles, catalysis, chromatography, beverage industry, photography, wastewater treatment and sludge dewatering, and biotechnology. Nutraceuticals and cosmeceuticals are actually growing markets, and therapeutic and biomedical products should be the next markets in the development of chitosan. Chitosan is also the N. Morin-Crini (*) · Laboratoire Chrono-environnement, UMR 6249, UFR Sciences et Techniques