NEK10 kinase ablation affects mitochondrial morphology, function and protein phosphorylation status.

Background: NEK10, a serine/threonine/tyrosine kinase belonging to the NEK (NIMA-related kinases) family, has been associated with diverse cellular processes. However, no specific target pathways have been identified. Our previous work knocking down NEK10 in HeLa cells suggested a functional association with mitochondria, as we observed altered mitochondrial morphology, mitochondrial oxygen consumption, mtDNA integrity, and reactive oxygen species levels.

Restoration of defective oxidative phosphorylation to a subset of neurons prevents mitochondrial encephalopathy.

Oxidative Phosphorylation (OXPHOS) defects can cause severe encephalopathies and no effective treatment exists for these disorders. To assess the ability of gene replacement to prevent disease progression, we subjected two different CNS-deficient mouse models (Ndufs3/complex I or Cox10/complex IV conditional knockouts) to gene therapy. We used retro-orbitally injected AAV-PHP.

Tools for editing the mammalian mitochondrial genome.

The manipulation of animal mitochondrial genomes has long been a challenge due to the lack of an effective transformation method. With the discovery of specific gene editing enzymes, designed to target pathogenic mitochondrial DNA mutations (often heteroplasmic), the selective removal or modification of mutant variants has become a reality. Because mitochondria cannot efficiently import RNAs, CRISPR has not been the first choice for editing mitochondrial genes.

Absence of both MGME1 and POLG EXO abolishes mtDNA whereas absence of either creates unique mtDNA duplications.

Both POLG and MGME1 are needed for mitochondrial DNA (mtDNA) maintenance in animal cells. POLG, the primary replicative polymerase of the mitochondria, has an exonuclease activity (3'→5') that corrects for the misincorporation of bases. MGME1 serves as an exonuclease (5'→3'), producing ligatable DNA ends.

mitoTALEN reduces the mutant mtDNA load in neurons.

Mutations within mtDNA frequently give rise to severe encephalopathies. Given that a majority of these mtDNA defects exist in a heteroplasmic state, we harnessed the precision of mitochondrial-targeted TALEN (mitoTALEN) to selectively eliminate mutant mtDNA within the CNS of a murine model harboring a heteroplasmic mutation in the mitochondrial tRNA alanine gene (m.5024C>T).

PI3K signaling promotes formation of lipid-laden foamy macrophages at the spinal cord injury site.

After spinal cord injury (SCI), infiltrating macrophages undergo excessive phagocytosis of myelin and cellular debris, forming lipid-laden foamy macrophages. To understand their role in the cellular pathology of SCI, investigation of the foamy macrophage phenotype in vitro revealed a pro-inflammatory profile, increased reactive oxygen species (ROS) production, and mitochondrial dysfunction. Bioinformatic analysis identified PI3K as a regulator of inflammation in foamy macrophages, and inhibition of this pathway decreased their lipid content, inflammatory cytokines, and ROS production.

Efficient elimination of MELAS-associated m.3243G mutant mitochondrial DNA by an engineered mitoARCUS nuclease.

Nuclease-mediated editing of heteroplasmic mitochondrial DNA (mtDNA) seeks to preferentially cleave and eliminate mutant mtDNA, leaving wild-type genomes to repopulate the cell and shift mtDNA heteroplasmy. Various technologies are available, but many suffer from limitations based on size and/or specificity. The use of ARCUS nucleases, derived from naturally occurring I-CreI, avoids these pitfalls due to their small size, single-component protein structure and high specificity resulting from a robust protein-engineering process.

Mitochondrial dysfunction characterized in human induced pluripotent stem cell disease models in MELAS syndrome: A brief summary.

Human induced pluripotent stem cells (hiPSCs) for MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes) may allow deeper understanding of how tissue-specific mitochondrial dysfunction result in multi-systemic disease. Here, we summarize how the m.3243G mtDNA mutation affects mitochondrial function in different tissues using iPSC and iPSC-differentiated cell type disease models and what significant findings have been replicated in the independent studies.

A Defect in Mitochondrial Complex III but Not in Complexes I or IV Causes Early β-Cell Dysfunction and Hyperglycemia in Mice.

Unlabelled: Mitochondrial metabolism and oxidative respiration are crucial for pancreatic β-cell function and stimulus secretion coupling. Oxidative phosphorylation (OxPhos) produces ATP and other metabolites that potentiate insulin secretion. However, the contribution of individual OxPhos complexes to β-cell function is unknown.

Precise and simultaneous quantification of mitochondrial DNA heteroplasmy and copy number by digital PCR.

Mitochondrial DNA (mtDNA) is present in multiple copies and phenotypic consequences of mtDNA mutations depend on the mutant load surpassing a specific threshold. Additionally, changes in mtDNA copy number can impact mitochondrial ATP production, resulting in disease. Therefore, the precise determination of mtDNA heteroplasmy and copy number is crucial to the study of mitochondrial diseases.

Adult-Onset Deficiency of Mitochondrial Complex III in a Mouse Model of Alzheimer's Disease Decreases Amyloid Beta Plaque Formation.

For decades, mitochondrial dysfunctions and the generation of reactive oxygen species have been proposed to promote the development and progression of the amyloid pathology in Alzheimer's disease, but this association is still debated. It is unclear whether different mitochondrial dysfunctions, such as oxidative phosphorylation deficiency and oxidative stress, are triggers or rather consequences of the formation of amyloid aggregates. Likewise, the role of the different mitochondrial oxidative phosphorylation complexes in Alzheimer's patients' brain remains poorly understood.

Nuclear-Mitochondrial Interactions.

Mitochondria, the cell's major energy producers, also act as signaling hubs, interacting with other organelles both directly and indirectly. Despite having its own circular genome, the majority of mitochondrial proteins are encoded by nuclear DNA. To respond to changes in cell physiology, the mitochondria must send signals to the nucleus, which can, in turn, upregulate gene expression to alter metabolism or initiate a stress response.

ATAD3A has a scaffolding role regulating mitochondria inner membrane structure and protein assembly.

The ATPase Family AAA Domain Containing 3A (ATAD3A), is a mitochondrial inner membrane protein conserved in metazoans. ATAD3A has been associated with several mitochondrial functions, including nucleoid organization, cholesterol metabolism, and mitochondrial translation. To address its primary role, we generated a neuronal-specific conditional knockout (Atad3 nKO) mouse model, which developed a severe encephalopathy by 5 months of age.

Enhanced glycolysis and GSK3 inactivation promote brain metabolic adaptations following neuronal mitochondrial stress.

We analyzed early brain metabolic adaptations in response to mitochondrial dysfunction in a mouse model of mitochondrial encephalopathy with complex IV deficiency [neuron-specific COX10 knockout (KO)]. In this mouse model, the onset of the mitochondrial defect did not coincide with immediate cell death, suggesting early adaptive metabolic responses to compensate for the energetic deficit. Metabolomic analysis in the KO mice revealed increased levels of glycolytic and pentose phosphate pathway intermediates, amino acids and lysolipids.

Treatment with ROS detoxifying gold quantum clusters alleviates the functional decline in a mouse model of Friedreich ataxia.

Friedreich ataxia (FRDA) is caused by the reduced expression of the mitochondrial protein frataxin (FXN) due to an intronic GAA trinucleotide repeat expansion in the gene. Although FRDA has no cure and few treatment options, there is research dedicated to finding an agent that can curb disease progression and address symptoms as neurobehavioral deficits, muscle endurance, and heart contractile dysfunctions. Because oxidative stress and mitochondrial dysfunctions are implicated in FRDA, we demonstrated the systemic delivery of catalysts activity of gold cluster superstructures (Au-pXs) to improve cell response to mitochondrial reactive oxygen species and thereby alleviate FRDA-related pathology in mesenchymal stem cells from patients with FRDA.

Mitochondrial targeted meganuclease as a platform to eliminate mutant mtDNA in vivo.

Diseases caused by heteroplasmic mitochondrial DNA mutations have no effective treatment or cure. In recent years, DNA editing enzymes were tested as tools to eliminate mutant mtDNA in heteroplasmic cells and tissues. Mitochondrial-targeted restriction endonucleases, ZFNs, and TALENs have been successful in shifting mtDNA heteroplasmy, but they all have drawbacks as gene therapy reagents, including: large size, heterodimeric nature, inability to distinguish single base changes, or low flexibility and effectiveness.

Biallelic loss-of-function variations in PRDX3 cause cerebellar ataxia.

Peroxiredoxin 3 (PRDX3) belongs to a superfamily of peroxidases that function as protective antioxidant enzymes. Among the six isoforms (PRDX1-PRDX6), PRDX3 is the only protein exclusively localized to the mitochondria, which are the main source of reactive oxygen species. Excessive levels of reactive oxygen species are harmful to cells, inducing mitochondrial dysfunction, DNA damage, lipid and protein oxidation and ultimately apoptosis.

Metformin delays neurological symptom onset in a mouse model of neuronal complex I deficiency.

Complex I (also known as NADH-ubiquinone oxidoreductase) deficiency is the most frequent mitochondrial disorder present in childhood. NADH-ubiquinone oxidoreductase iron-sulfur protein 3 (NDUFS3) is a catalytic subunit of the mitochondrial complex I; NDUFS3 is conserved from bacteria and essential for complex I function. Mutations affecting complex I, including in the Ndufs3 gene, cause fatal neurodegenerative diseases, such as Leigh syndrome.

Author Correction: Impaired mitophagy links mitochondrial disease to epithelial stress in methylmalonyl-CoA mutase deficiency.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Manipulation of mitochondrial genes and mtDNA heteroplasmy.

Most patients with mitochondrial DNA (mtDNA) mutations have a mixture of mutant and wild-type mtDNA in their cells. This phenomenon, known as mtDNA heteroplasmy, provides an opportunity to develop therapies by selectively eliminating the mutant fraction. In the last decade, several enzyme-based gene editing platforms were developed to cleave specific DNA sequences.