Periodic Reporting for period 1 - MitoFeron (Mitochondrial integrity and autoinflammation)
Okres sprawozdawczy: 2020-07-01 do 2022-06-30
Autoinflammatory diseases, such as lupus, are caused by overactivation or failure to regulate the immune system. Their origin is often poorly understood, and pathogens, environment and genetics can contribute to their onset. Type I interferonopathies are rare genetic diseases associated with an inappropriate upregulation of type I interferon (IFN) signalling. IFNs represent the first line of defence against viruses, and are induced by sensing of viral nucleic acids. Importantly, definition of the genetic basis of the type I interferonopathies has led to a coherent understanding of underlying pathology, involving previously unappreciated pathways of nucleic acid metabolism, and enabled the introduction of rational therapy targeted at blocking IFN signalling, relevant to more common autoinflammatory diseases. Thus, it is important to identify new type I interferonopathies and determine their molecular and cellular basis.
Beyond their role in energy metabolism, mitochondria are also recognised to play a role in the immune response to infection. Interestingly, both mitochondrial DNA and RNA have the potential to trigger IFN in cells. Indeed, loss of mitochondrial integrity promoting pathogenic IFN induction, through mitochondrial nucleic acids released into the cytosol, is a novel topic of high clinical and scientific interest, namely in autoinflammatory diseases. We have identified patients with mutations in a gene encoding a mitochondrial protein, ATAD3A, in which we consider the observed enhanced IFN signalling directly relevant to the associated neuropathology. Our project aims to better understand the link between mitochondrial homeostasis and IFN induction, thereby defining novel pathways relating to mitochondrial integrity, mitochondrial nucleic acids and innate immune surveillance. Specifically, we will study these relationships in the context of human disease, and we will search for further novel determinants of mitochondrial function linked to innate immune homeostasis using a unique clinical screening protocol. This will help us define new therapeutic approaches applicable to other autoinflammatory diseases.
Conclusion of the action :
We have confirmed and elucidated some aspects of the links between ATAD3A dysfunction and enhanced IFN signalling, the results of which have been published in the Journal of Experimental Medicine in 2021 and disseminated in complementary ways to the scientific community and the general public. Moreover, by identifying more mitochondrial diseases associated with upregulated IFN, we have derived new leads to further study the relationship between mitochondrial dysfunction and the IFN pathway, solidifying the basis for mitochondria-related and/or IFN-targeting therapeutic strategies. Finally, this action has allowed me to obtained a permanent research position at Inserm medical research institute in France in 2021.
Beyond their role in energy metabolism, mitochondria are also recognised to play a role in the immune response to infection. Interestingly, both mitochondrial DNA and RNA have the potential to trigger IFN in cells. Indeed, loss of mitochondrial integrity promoting pathogenic IFN induction, through mitochondrial nucleic acids released into the cytosol, is a novel topic of high clinical and scientific interest, namely in autoinflammatory diseases. We have identified patients with mutations in a gene encoding a mitochondrial protein, ATAD3A, in which we consider the observed enhanced IFN signalling directly relevant to the associated neuropathology. Our project aims to better understand the link between mitochondrial homeostasis and IFN induction, thereby defining novel pathways relating to mitochondrial integrity, mitochondrial nucleic acids and innate immune surveillance. Specifically, we will study these relationships in the context of human disease, and we will search for further novel determinants of mitochondrial function linked to innate immune homeostasis using a unique clinical screening protocol. This will help us define new therapeutic approaches applicable to other autoinflammatory diseases.
Conclusion of the action :
We have confirmed and elucidated some aspects of the links between ATAD3A dysfunction and enhanced IFN signalling, the results of which have been published in the Journal of Experimental Medicine in 2021 and disseminated in complementary ways to the scientific community and the general public. Moreover, by identifying more mitochondrial diseases associated with upregulated IFN, we have derived new leads to further study the relationship between mitochondrial dysfunction and the IFN pathway, solidifying the basis for mitochondria-related and/or IFN-targeting therapeutic strategies. Finally, this action has allowed me to obtained a permanent research position at Inserm medical research institute in France in 2021.
Through our network of clinicians, we were able to assess further patients carrying mutations affecting ATAD3A function and confirmed the presence of signs of enhanced IFN signalling in vivo. We obtained primary fibroblasts from three of these patients, where we detected signs of enhanced IFN signalling at steady state, compared to control fibroblasts, suggesting a cell-intrinsic process linking mutations in ATAD3A and IFN induction. Interestingly, using knockdown approaches and mitochondrial DNA depletion, we observed that cytosolic sensing of mitochondrial DNA, leading to IFN induction, was implicated. Moreover, imaging studies confirmed this result by showing that upon loss of ATAD3A function, mitochondrial DNA escapes mitochondria and accumulates in the cytosol. Remarkably, incubation with rapamycin, an anti-inflammatory drug used to treat inflammatory symptoms in two patients, abrogated IFN signalling in patient fibroblasts, providing a further lead for investigation. Mutations in ATAD3A have previously been reported to act in a dominant-negative manner. For IFN signalling too, mutated ATAD3A impaired ATAD3A function, as revealed by enhanced IFN-stimulated gene expression upon mutated ATAD3A overexpression in cell lines. Consistently, knockdown of ATAD3A was sufficient to trigger IFN signalling in a mtDNA- and cytosolic DNA sensing pathway-dependent manner. We are currently investigating the mechanisms of mtDNA release into the cytosol upon ATAD3A dysfunction.
The above results have been published in a peer-reviewed article for which I am first author (Lepelley et al. JEM 2021). Moreover, insight from this work and a thorough knowledge of the literature has led me to write and publish a review on genetic diseases implicating mitochondrial nucleic acid in their pathogenesis (Lepelley et al. Front Immunol 2021).
This work has also been selected for awards and presentations through short talks at national (1) and international (5) conferences and I have been invited to present at a symposium at the University of Edinburgh.
Moreover, the dissemination of results from this project has sparked collaborations with mitochondrial disease clinicians on campus at Hopital Necker (Paris) and in the UK (Newcastle) to screen mitochondrial disease patients for interferon signalling, with a view to identify more genes associated with pathogenic interferon signalling related to mitochondrial dysfunction.
The above results have been published in a peer-reviewed article for which I am first author (Lepelley et al. JEM 2021). Moreover, insight from this work and a thorough knowledge of the literature has led me to write and publish a review on genetic diseases implicating mitochondrial nucleic acid in their pathogenesis (Lepelley et al. Front Immunol 2021).
This work has also been selected for awards and presentations through short talks at national (1) and international (5) conferences and I have been invited to present at a symposium at the University of Edinburgh.
Moreover, the dissemination of results from this project has sparked collaborations with mitochondrial disease clinicians on campus at Hopital Necker (Paris) and in the UK (Newcastle) to screen mitochondrial disease patients for interferon signalling, with a view to identify more genes associated with pathogenic interferon signalling related to mitochondrial dysfunction.
Through this project investigating IFN signalling in disease due to ATAD3A mutations, we have demonstrated for the first time in a mitochondrial disease the implication of mitochondrial DNA mislocalization, potentially leading to pathogenic interferon signalling. Mitochondrial disease suffers from complex diagnosis and few therapeutic options. Thus, our work opens three main perspectives:
-Mitochondrial nucleic acid sensing and IFN induction may be more broadly associated with mitochondrial disease, deserving more thorough evaluation with biomarker potential.
-The observation of IFN signalling with pathogenic potential in such disease offers a new therapeutic strategy by targeting the interferon pathway.
-The involvement of mitochondrial nucleic acids in disease is broader than genetic disease, so that our results bring insight and therapeutic leads for more common disease such as lupus and neurodegeneration.
Importantly, during this work, I have consolidated collaborations with mitochondrial biologists (Institut Pasteur, Paris) and mitochondrial disease specialists (Newcastle UK, Necker Hospital, Paris), which will be instrumental for the continuation of my research derived from this project. Indeed, I have applied to the very selective competition for French permanent public research position and was selected in 2021 with my position starting in January 2022. The MSCA program has provided me the opportunity to become an independent researcher building a solid basis for my own research themes.
-Mitochondrial nucleic acid sensing and IFN induction may be more broadly associated with mitochondrial disease, deserving more thorough evaluation with biomarker potential.
-The observation of IFN signalling with pathogenic potential in such disease offers a new therapeutic strategy by targeting the interferon pathway.
-The involvement of mitochondrial nucleic acids in disease is broader than genetic disease, so that our results bring insight and therapeutic leads for more common disease such as lupus and neurodegeneration.
Importantly, during this work, I have consolidated collaborations with mitochondrial biologists (Institut Pasteur, Paris) and mitochondrial disease specialists (Newcastle UK, Necker Hospital, Paris), which will be instrumental for the continuation of my research derived from this project. Indeed, I have applied to the very selective competition for French permanent public research position and was selected in 2021 with my position starting in January 2022. The MSCA program has provided me the opportunity to become an independent researcher building a solid basis for my own research themes.