scholarly journals A new automated tool to quantify nucleoid distribution within mitochondrial networks

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hema Saranya Ilamathi ◽  
Mathieu Ouellet ◽  
Rasha Sabouny ◽  
Justine Desrochers-Goyette ◽  
Matthew A. Lines ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Mitochondrial Fission ◽  
Healthy Population ◽  
Primary Cells ◽  
Mitochondrial Homeostasis ◽  
Mtdna Replication ◽  
Mitochondrial Networks ◽  
Automated Tool ◽  
Regular Spacing

AbstractMitochondrial DNA (mtDNA) maintenance is essential to sustain a functionally healthy population of mitochondria within cells. Proper mtDNA replication and distribution within mitochondrial networks are essential to maintain mitochondrial homeostasis. However, the fundamental basis of mtDNA segregation and distribution within mitochondrial networks is still unclear. To address these questions, we developed an algorithm, Mitomate tracker to unravel the global distribution of nucleoids within mitochondria. Using this tool, we decipher the semi-regular spacing of nucleoids across mitochondrial networks. Furthermore, we show that mitochondrial fission actively regulates mtDNA distribution by controlling the distribution of nucleoids within mitochondrial networks. Specifically, we found that primary cells bearing disease-associated mutations in the fission proteins DRP1 and MYH14 show altered nucleoid distribution, and acute enrichment of enlarged nucleoids near the nucleus. Further analysis suggests that the altered nucleoid distribution observed in the fission mutants is the result of both changes in network structure and nucleoid density. Thus, our study provides novel insights into the role of mitochondria fission in nucleoid distribution and the understanding of diseases caused by fission defects.

scholarly journals Mitochondrial fission is required for proper nucleoid distribution within mitochondrial networks

2021 ◽  
Author(s):  
Hema Saranya Ilamathi ◽  
Mathieu Ouellet ◽  
Rasha Sabouny ◽  
Justine Desrochers-Goyette ◽  
Matthew A Lines ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Network Structure ◽  
Mitochondrial Fission ◽  
Healthy Population ◽  
Primary Cells ◽  
Mitochondrial Homeostasis ◽  
Mtdna Replication ◽  
Mitochondrial Networks ◽  
Regular Spacing

Mitochondrial DNA (mtDNA) maintenance is essential to sustain a functionally healthy population of mitochondria within cells. Proper mtDNA replication and distribution within mitochondrial networks are essential to maintain mitochondrial homeostasis. However, the fundamental basis of mtDNA segregation and distribution within mitochondrial networks is still unclear. To address these questions, we developed an algorithm, Mitomate tracker to unravel the global distribution of nucleoids within mitochondria. Using this tool, we decipher the semi-regular spacing of nucleoids across mitochondrial networks. Furthermore, we show that mitochondrial fission actively regulates mtDNA distribution by controlling the distribution of nucleoids within mitochondrial networks. Specifically, we found that primary cells bearing disease-associated mutations in the fission proteins DRP1 and MYH14 show altered nucleoid distribution, and acute enrichment of enlarged nucleoids near the nucleus. Further analysis suggests that the altered nucleoid distribution observed in the fission mutants is the result of both changes in network structure and nucleoid density. Thus, our study provides novel insights into the role of mitochondria fission in nucleoid distribution and the understanding of diseases caused by fission defects.

scholarly journals DRP1 regulates endoplasmic reticulum sheets to control mitochondrial DNA replication and segregation

2021 ◽  
Author(s):  
Hema Saranya Ilamathi ◽  
Sara Benhammouda ◽  
Justine Desrochers-Goyette ◽  
Matthew A Lines ◽  
Marc Germain
Keyword(s):  
Endoplasmic Reticulum ◽  
Mitochondrial Dna ◽  
Protein Complexes ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Mitochondrial Diseases ◽  
Contact Sites ◽  
Transport Chain ◽  
Essential Components ◽  
Mtdna Replication

Mitochondria are multi-faceted organelles crucial for cellular homeostasis that contain their own genome. Mitochondrial DNA (mtDNA) codes for several essential components of the electron transport chain, and mtDNA maintenance defects lead to mitochondrial diseases. mtDNA replication occurs at endoplasmic reticulum (ER)-mitochondria contact sites and is regulated by mitochondrial dynamics. Specifically, mitochondrial fusion is essential for mtDNA maintenance. In contrast, while loss of mitochondrial fission causes the aggregation of nucleoids (mtDNA-protein complexes), its role in nucleoid distribution remains unclear. Here, we show that the mitochondrial fission protein DRP1 regulates nucleoid segregation by altering ER sheets, the ER structure associated with protein synthesis. Specifically, DRP1 loss or mutation leads to altered ER sheets that physically interact with mitobulbs, mitochondrial structures containing aggregated nucleoids. Importantly, nucleoid distribution and mtDNA replication were rescued by expressing the ER sheet protein CLIMP63. Thus, our work identifies a novel mechanism by which DRP1 regulates mtDNA replication and distribution.

scholarly journals Mechanisms of Human Mitochondrial DNA Maintenance: The Determining Role of Primary Sequence and Length over Function

1999 ◽  
Vol 10 (10) ◽  
pp. 3345-3356 ◽  
Author(s):  
Carlos T. Moraes ◽  
Lesley Kenyon ◽  
Huiling Hao
Keyword(s):  
Mitochondrial Dna ◽  
Oxidative Phosphorylation ◽  
Copy Number ◽  
Human Cells ◽  
Mtdna Copy Number ◽  
Molecular Features ◽  
Mtdna Replication ◽  
Selection For ◽  
Dna Maintenance

Although the regulation of mitochondrial DNA (mtDNA) copy number is performed by nuclear-coded factors, very little is known about the mechanisms controlling this process. We attempted to introduce nonhuman ape mtDNA into human cells harboring either no mtDNA or mutated mtDNAs (partial deletion and tRNA gene point mutation). Unexpectedly, only cells containing no mtDNA could be repopulated with nonhuman ape mtDNA. Cells containing a defective human mtDNA did not incorporate or maintain ape mtDNA and therefore died under selection for oxidative phosphorylation function. On the other hand, foreign human mtDNA was readily incorporated and maintained in these cells. The suicidal preference for self-mtDNA showed that functional parameters associated with oxidative phosphorylation are less relevant to mtDNA maintenance and copy number control than recognition of mtDNA self-determinants. Non–self-mtDNA could not be maintained into cells with mtDNA even if no selection for oxidative phosphorylation was applied. The repopulation kinetics of several mtDNA forms after severe depletion by ethidium bromide treatment showed that replication and maintenance of mtDNA in human cells are highly dependent on molecular features, because partially deleted mtDNA molecules repopulated cells significantly faster than full-length mtDNA. Taken together, our results suggest that mtDNA copy number may be controlled by competition for limiting levels of trans-acting factors that recognize primarily mtDNA molecular features. In agreement with this hypothesis, marked variations in mtDNA levels did not affect the transcription of nuclear-coded factors involved in mtDNA replication.

scholarly journals Dynamics of Mitochondrial DNA Nucleoids Regulated by Mitochondrial Fission Is Essential for Maintenance of Homogeneously Active Mitochondria during Neonatal Heart Development

2014 ◽  
Vol 35 (1) ◽  
pp. 211-223 ◽  
Author(s):  
Takaya Ishihara ◽  
Reiko Ban-Ishihara ◽  
Maki Maeda ◽  
Yui Matsunaga ◽  
Ayaka Ichimura ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Heart Development ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Cardiomyocyte Hypertrophy ◽  
Homogeneous Distribution ◽  
Mitochondrial Homeostasis ◽  
Neonatal Heart ◽  
Neonatal Lethality

Mitochondria are dynamic organelles, and their fusion and fission regulate cellular signaling, development, and mitochondrial homeostasis, including mitochondrial DNA (mtDNA) distribution. Cardiac myocytes have a specialized cytoplasmic structure where large mitochondria are aligned into tightly packed myofibril bundles; however, recent studies have revealed that mitochondrial dynamics also plays an important role in the formation and maintenance of cardiomyocytes. Here, we precisely analyzed the role of mitochondrial fissionin vivo. The mitochondrial fission GTPase, Drp1, is highly expressed in the developing neonatal heart, and muscle-specific Drp1 knockout (Drp1-KO) mice showed neonatal lethality due to dilated cardiomyopathy. The Drp1 ablation in heart and primary cultured cardiomyocytes resulted in severe mtDNA nucleoid clustering and led to mosaic deficiency of mitochondrial respiration. The functional and structural alteration of mitochondria also led to immature myofibril assembly and defective cardiomyocyte hypertrophy. Thus, the dynamics of mtDNA nucleoids regulated by mitochondrial fission is required for neonatal cardiomyocyte development by promoting homogeneous distribution of active mitochondria throughout the cardiomyocytes.

scholarly journals Mitochondrial fission facilitates the selective mitophagy of protein aggregates

2017 ◽  
Vol 216 (10) ◽  
pp. 3231-3247 ◽  
Author(s):  
Jonathon L. Burman ◽  
Sarah Pickles ◽  
Chunxin Wang ◽  
Shiori Sekine ◽  
Jose Norberto S. Vargas ◽  
...  
Keyword(s):  
Protein Aggregation ◽  
Matrix Protein ◽  
Mitochondrial Fission ◽  
Protein Aggregates ◽  
Mitochondrial Matrix ◽  
Unfolded Protein ◽  
Protein Response ◽  
Mitochondrial Networks ◽  
Mitochondrial Unfolded Protein Response

Within the mitochondrial matrix, protein aggregation activates the mitochondrial unfolded protein response and PINK1–Parkin-mediated mitophagy to mitigate proteotoxicity. We explore how autophagy eliminates protein aggregates from within mitochondria and the role of mitochondrial fission in mitophagy. We show that PINK1 recruits Parkin onto mitochondrial subdomains after actinonin-induced mitochondrial proteotoxicity and that PINK1 recruits Parkin proximal to focal misfolded aggregates of the mitochondrial-localized mutant ornithine transcarbamylase (ΔOTC). Parkin colocalizes on polarized mitochondria harboring misfolded proteins in foci with ubiquitin, optineurin, and LC3. Although inhibiting Drp1-mediated mitochondrial fission suppresses the segregation of mitochondrial subdomains containing ΔOTC, it does not decrease the rate of ΔOTC clearance. Instead, loss of Drp1 enhances the recruitment of Parkin to fused mitochondrial networks and the rate of mitophagy as well as decreases the selectivity for ΔOTC during mitophagy. These results are consistent with a new model that, instead of promoting mitophagy, fission protects healthy mitochondrial domains from elimination by unchecked PINK1–Parkin activity.

scholarly journals Mitochondrial DNA as DAMP in critical conditions

2019 ◽  
Vol 18 (3) ◽  
pp. 134-143
Author(s):  
E. V. Grigoriev ◽  
R. R. Salakhov ◽  
M. V. Golubenko ◽  
A. V. Ponasenko ◽  
D. L. Shukevich ◽  
...  
Keyword(s):  
Immune Response ◽  
Mitochondrial Dna ◽  
Inflammatory Response ◽  
Systemic Inflammatory Response ◽  
Critical Conditions ◽  
Inflammatory Reactions ◽  
Surgical Interventions ◽  
Mitochondrial Homeostasis ◽  
Pathological Conditions

The focus of the researchers’ attention today includes the recently discovered role of mitochondria in the immune response. Increasing evidence shows that mitochondrial DNA, in retaining some of their characteristics of the ancient α-proteobacteria’s genome, is a potent immune stimulus for inflammatory reactions. Systemic inflammatory response is a frequent complication in surgical interventions and various traumas, and its development cannot be explained using common conceptions. This review provides information on the current understanding of the development of inflammation mediated by mtDNA, including systemic inflammatory response, and on the mechanisms regulating mitochondrial homeostasis and mtDNA release in various pathological conditions.

scholarly journals A mitochondrial delicacy: dynamin-related protein 1 and mitochondrial dynamics

2018 ◽  
Vol 315 (1) ◽  
pp. C80-C90 ◽  
Author(s):  
Mason T. Breitzig ◽  
Matthew D. Alleyn ◽  
Richard F. Lockey ◽  
Narasaiah Kolliputi
Keyword(s):  
Signaling Pathways ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Pulmonary Diseases ◽  
Related Protein ◽  
Limited Knowledge ◽  
Cellular Bioenergetics ◽  
Complex Signaling ◽  
Mitochondrial Networks

The constant physiological flux of mitochondrial fission and fusion is inextricably tied to the maintenance of cellular bioenergetics and the fluidity of mitochondrial networks. Yet, the intricacies of this dynamic duo remain unclear in diseases that encompass mitochondrial dysregulation. Particularly, the role of the GTPase fission protein dynamin-related protein 1 (Drp1) is of profound interest. Studies have identified that Drp1 participates in complex signaling pathways, suggesting that the function of mitochondria in pathophysiology may extend far beyond energetics alone. Research indicates that, in stressed conditions, Drp1 translocation to the mitochondria leads to elevated fragmentation and mitophagy; however, despite this, there is limited knowledge about the mechanistic regulation of Drp1 in disease conditions. This review highlights literature about fission, fusion, and, more importantly, discusses Drp1 in cardiac, neural, carcinogenic, renal, and pulmonary diseases. The therapeutic desirability for further research into its contribution to diseases that involve mitochondrial dysregulation is also discussed.

Mitochondria Metabolomics Reveals a Role of β-Nicotinamide Mononucleotide Metabolism in Mitochondrial DNA Replication

2021 ◽  
Author(s):  
Tomoko Nomiyama ◽  
Daiki Setoyama ◽  
Takehiro Yasukawa ◽  
Dongchon Kang
Keyword(s):  
Mitochondrial Dna ◽  
Degradation Products ◽  
Mitochondrial Metabolism ◽  
Hek293 Cells ◽  
Nicotinamide Mononucleotide ◽  
Streptolysin O ◽  
Mtdna Replication ◽  
Glycolytic Inhibitor ◽  
Hemolytic Toxin

Summary Mitochondrial DNA (mtDNA) replication is tightly regulated and necessary for cellular homeostasis; however, its relationship with mitochondrial metabolism remains unclear. Advances in metabolomics integrated with the rapid isolation of mitochondria will allow for remarkable progress in analyzing mitochondrial metabolism. Here, we propose a novel methodology for mitochondria-targeted metabolomics, which employs a quick isolation procedure using a hemolytic toxin from Streptococcus pyogenes streptolysin O (SLO). SLO-isolation of mitochondria from cultured HEK293 cells is time- and labor-saving for simultaneous multi-sample processing and has been applied to various other cell lines in this study. Furthermore, our method can detect the time-dependent reduction in mitochondrial ATP in response to a glycolytic inhibitor 2-deoxyglucose, indicating the suitability to prepare metabolite analysis-competent mitochondria. Using this methodology, we searched for specific mitochondrial metabolites associated with mtDNA replication activation, and nucleotides and NAD+ were identified to be prominently altered. Most notably, treatment of β-Nicotinamide Mononucleotide (β-NMN), a precursor of NAD+, to HEK293 cells activated and improved the rate of mtDNA replication by increasing nucleotides in mitochondria and decreasing their degradation products: nucleosides. Our results suggest that β-NMN metabolism play a role in supporting mtDNA replication by maintaining the nucleotide pool balance in the mitochondria.

Impaired dynamics and function of mitochondria caused by mtDNA toxicity leads to heart failure

2015 ◽  
Vol 309 (3) ◽  
pp. H434-H449 ◽  
Author(s):  
Knut H. Lauritzen ◽  
Liv Kleppa ◽  
Jan Magnus Aronsen ◽  
Lars Eide ◽  
Harald Carlsen ◽  
...  
Keyword(s):  
Heart Failure ◽  
Mitochondrial Fission ◽  
Clinical Manifestations ◽  
Premature Death ◽  
Specific Expression ◽  
Mitochondrial Homeostasis ◽  
Transport Chain ◽  
Mtdna Replication ◽  
Dynamics And Function ◽  
And Function

Cardiac mitochondrial dysfunction has been implicated in heart failure of diverse etiologies. Generalized mitochondrial disease also leads to cardiomyopathy with various clinical manifestations. Impaired mitochondrial homeostasis may over time, such as in the aging heart, lead to cardiac dysfunction. Mitochondrial DNA (mtDNA), close to the electron transport chain and unprotected by histones, may be a primary pathogenetic site, but this is not known. Here, we test the hypothesis that cumulative damage of cardiomyocyte mtDNA leads to cardiomyopathy and heart failure. Transgenic mice with Tet-on inducible, cardiomyocyte-specific expression of a mutant uracil-DNA glycosylase 1 (mutUNG1) were generated. The mutUNG1 is known to remove thymine in addition to uracil from the mitochondrial genome, generating apyrimidinic sites, which obstruct mtDNA function. Following induction of mutUNG1 in cardiac myocytes by administering doxycycline, the mice developed hypertrophic cardiomyopathy, leading to congestive heart failure and premature death after ∼2 mo. The heart showed reduced mtDNA replication, severely diminished mtDNA transcription, and suppressed mitochondrial respiration with increased Pgc-1α, mitochondrial mass, and antioxidative defense enzymes, and finally failing mitochondrial fission/fusion dynamics and deteriorating myocardial contractility as the mechanism of heart failure. The approach provides a model with induced cardiac-restricted mtDNA damage for investigation of mtDNA-based heart disease.

The role of mitochondrial DNA in the cancerogenesis of cervix HPV positive women

2008 ◽  
Vol 21 (2) ◽  
pp. 85-89
Author(s):  
Alicja Warowicka ◽  
Joanna Pacholska-Bogalska ◽  
Anna Kwaśniewska ◽  
Anna Goździcka-Józefiak
Keyword(s):  
Mitochondrial Dna
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