Periodic Reporting for period 4 - Mitomorphosis (Metabolic regulation of mitochondrial morphology)
Reporting period: 2021-10-01 to 2022-11-30
The research goal of the Mitomorphosis project was to understand the complex interplay of mitochondrial dynamics and metabolism in health and disease. Mitochondria are a type of membrane-bound organelle found within all of our cells, responsible for the generation of cellular energy and the coordination of various processes that control the life and death of the cell. The need for mitochondria in the body is ubiquitous yet the shapes these organelles take vary widely across tissues and change rapidly in response to nutrient availability. How and why this occurs is not well understood. Therefore, in the Mitomorphosis project, we investigated the molecular basis and metabolic regulation of mitochondrial morphology. Mitochondrial morphology is defined by opposing events of fission and fusion, which must be tightly controlled. Balanced fusion and fission events shape mitochondria to meet metabolic demands and to ensure removal of damaged organelles. The morphology of mitochondria is inextricably linked to its many essential functions in the cell and we are interested in understanding the relationship between mitochondrial shape changes and metabolism in the context of acquired and inborn human diseases. Mitochondrial fragmentation occurs in response to nutrient excess and cellular dysfunction and has been observed in cardiovascular and neuromuscular disorders, cancer, and obesity, all of which heavily impact human mortality and morbidity. In addition, the disruption of mitochondrial shape also occurs in rare genetic diseases caused by mutations in the genes that control mitochondrial fusion and fission. Understanding how mitochondrial form and function are linked in healthy cells and tissues as well as in models of human diseases will help fill fundamental knowledge gaps we have in the basic processes of biology, while also paving the way to a better understanding and treatment of acquired and inherited human diseases associated with defects in the maintenance of mitochondrial morphology.
The objectives of the project were to identify and characterize molecules involved in the regulation of mitochondrial shape using targeted and non-targeted approaches in cell and animal models of mitochondrial disease. We aimed to develop first-in-kind tools and strategies applied to patient-derived cells and preclinical animal models of disease in order to advance our molecular and cellular understanding of mitochondrial dynamics, allowing us to advance the state of the art.
The objectives of the project were to identify and characterize molecules involved in the regulation of mitochondrial shape using targeted and non-targeted approaches in cell and animal models of mitochondrial disease. We aimed to develop first-in-kind tools and strategies applied to patient-derived cells and preclinical animal models of disease in order to advance our molecular and cellular understanding of mitochondrial dynamics, allowing us to advance the state of the art.
In the Mitomorphosis project, we developed new first-in-kind tools and strategies applied to patient-derived cells and preclinical animal models of disease in order to advance our molecular and cellular understanding of mitochondrial dynamics, allowing us to advance the state of the art.
To be able to measure mitochondrial morphology accurately, rapidly, and unbiasedly in cells, we generated an automated cellular imaging pipeline able that was able to quantify mitochondrial morphology using supervised machine learning, enabling us to define mitochondrial morphology at the single-cell level in a high throughput manner. We have applied this novel imaging pipeline to test all the known mitochondrial proteins (>1500) and identify the genes required for mitochondrial fission and fusion in human cells. By applying this technology to patient-derived cells that suffered from defects in mitochondrial morphology, we were able to identify 91 new targets able to restore normal mitochondrial shape. This work was shared as a pre-print and published in the journal EMBO Molecular Medicine (Cretin et al 2021). The work was presented in several international scientific meetings and invited presentations and the overall strategy was discussed on French radio and press releases.
The tools we established were used to screen patient-derived fibroblasts, allowing us to gain unexpected insights into the cellular and mitochondrial pathways caused by new disease-causing mutations in mitochondrial genes, which led to publications in the journals Molecular Genetics and Metabolism, Journal of Experimental Medicine, and Brain.
We also generated transgenic mouse models for a novel mitochondrial fission factor, allowing us to gain insights into its physiological relevance in various tissues that are commonly affected in mitochondrial genetic diseases. In the heart, we discovered that this protein plays important roles for mitochondrial healthy by maintaining the integrity of the inner membrane, specifically important for the resilience and bioenergetic efficiency of mitochondria. In its absence, mice succumbed to heart failure and middle-aged death, highlighting the importance of this gene. This work was published in the journal Nature Communications (Donnarumma et al. 2022), was shared as a referred pre-print and was presented in several international and national scientific meetings.
In the liver, we discovered this protein to be a key regulator of mitochondrial and metabolic activity. Its deletion in hepatocytes is physiologically benign in mice yet leads to the upregulation of oxidative phosphorylation complexes and mitochondrial respiration. Consequently, hepatocyte-specific knockout mice are protected against high fat diet-induced fatty liver disease, metabolic dysregulation, and liver cell death. This study uncovered novel functions of this protein in the liver, positioning it as an unexpected regulator of mitochondrial bioenergetics and therapeutic target for fatty liver disease, which is a disease caused by an imbalance between nutrient delivery and metabolism in the liver. This work is in preparation for publication and pre-print dissemination and has been presented at international scientific meetings and seminars.
To be able to measure mitochondrial morphology accurately, rapidly, and unbiasedly in cells, we generated an automated cellular imaging pipeline able that was able to quantify mitochondrial morphology using supervised machine learning, enabling us to define mitochondrial morphology at the single-cell level in a high throughput manner. We have applied this novel imaging pipeline to test all the known mitochondrial proteins (>1500) and identify the genes required for mitochondrial fission and fusion in human cells. By applying this technology to patient-derived cells that suffered from defects in mitochondrial morphology, we were able to identify 91 new targets able to restore normal mitochondrial shape. This work was shared as a pre-print and published in the journal EMBO Molecular Medicine (Cretin et al 2021). The work was presented in several international scientific meetings and invited presentations and the overall strategy was discussed on French radio and press releases.
The tools we established were used to screen patient-derived fibroblasts, allowing us to gain unexpected insights into the cellular and mitochondrial pathways caused by new disease-causing mutations in mitochondrial genes, which led to publications in the journals Molecular Genetics and Metabolism, Journal of Experimental Medicine, and Brain.
We also generated transgenic mouse models for a novel mitochondrial fission factor, allowing us to gain insights into its physiological relevance in various tissues that are commonly affected in mitochondrial genetic diseases. In the heart, we discovered that this protein plays important roles for mitochondrial healthy by maintaining the integrity of the inner membrane, specifically important for the resilience and bioenergetic efficiency of mitochondria. In its absence, mice succumbed to heart failure and middle-aged death, highlighting the importance of this gene. This work was published in the journal Nature Communications (Donnarumma et al. 2022), was shared as a referred pre-print and was presented in several international and national scientific meetings.
In the liver, we discovered this protein to be a key regulator of mitochondrial and metabolic activity. Its deletion in hepatocytes is physiologically benign in mice yet leads to the upregulation of oxidative phosphorylation complexes and mitochondrial respiration. Consequently, hepatocyte-specific knockout mice are protected against high fat diet-induced fatty liver disease, metabolic dysregulation, and liver cell death. This study uncovered novel functions of this protein in the liver, positioning it as an unexpected regulator of mitochondrial bioenergetics and therapeutic target for fatty liver disease, which is a disease caused by an imbalance between nutrient delivery and metabolism in the liver. This work is in preparation for publication and pre-print dissemination and has been presented at international scientific meetings and seminars.
We have devised novel methods to perform unbiased quantification of mitochondrial morphology, cell growth, cell death, and mitophagy in a high throughput fashion. We have combined this approach with siRNA screening and have been able to screen mutant cells and uncover novel regulators of mitochondrial morphology that are able to rebalance mitochondrial morphology in cells from patients with mitochondrial genetic disease. We expect to describe the molecular mechanisms associated with this phenotypic rescue and determine whether other mitochondrial functions besides mitochondrial morphology are also rescued and have thus determined which mitochondrial functions depend on mitochondrial morphology. In addition we have specifically probed the function of an inner membrane fission factor both in vitro and in vivo and have found that its removal both protects against liver disease but is also essential for cardiac function. Now, we understand that this factor physically interacts with and regulates core components of in the inner mitochondrial membrane that control mitochondrial permeability transition, cell death, and bioenergetics in tissue-specific manners, which can help explain the observed effects we see in the different knockout tissues under basal and stress conditions. Finally, we have generated novel animal models that will be useful for the study of heart failure, fatty liver disease, obesity, and cancer.