Mitonuclear interactions influence multiple sclerosis risk

The Protective Mechanism of TFAM on Mitochondrial DNA and its Role in Neurodegenerative Diseases

Mitochondrial transcription factor A (TFAM) is a mitochondrial protein encoded by nuclear genes and transported from the cytoplasm to the mitochondria. TFAM is essential for the maintenance, expression, and delivery of mitochondrial DNA (mtDNA) and can regulate the replication and transcription of mtDNA. TFAM is associated with the formation of mtDNA nucleomimetic structures, mtDNA repair, and mtDNA stability. However, the mechanism by which TFAM protects mtDNA is still being studied. This review provides a summary of the protective mechanism of TFAM on mtDNA including the discrete regulatory effects of TFAM acetylation and phosphorylation on mtDNA, the regulation of Ca2+ levels by TFAM to activate transcription in mitochondria, and the increased binding of TFAM to mtDNA damage hot spots. This review also discusses the association between TFAM and some neurodegenerative diseases.

Mapping mitonuclear epistasis using a novel recombinant yeast population

Genetic variation in mitochondrial and nuclear genomes can perturb mitonuclear interactions and lead to phenotypic differences between individuals and populations. Despite their importance to most complex traits, it has been difficult to identify the interacting mitonuclear loci. Here, we present a novel advanced intercrossed population of Saccharomyces cerevisiae yeasts, called the Mitonuclear Recombinant Collection (MNRC), designed explicitly for detecting mitonuclear loci contributing to complex traits. For validation, we focused on mapping genes that contribute to the spontaneous loss of mitochondrial DNA (mtDNA) that leads to the petite phenotype in yeast. We found that rates of petite formation in natural populations are variable and influenced by genetic variation in nuclear DNA, mtDNA and mitonuclear interactions. We mapped nuclear and mitonuclear alleles contributing to mtDNA stability using the MNRC by integrating a term for mitonuclear epistasis into a genome-wide association model. We found that the associated mitonuclear loci play roles in mitotic growth most likely responding to retrograde signals from mitochondria, while the associated nuclear loci with main effects are involved in genome replication. We observed a positive correlation between growth rates and petite frequencies, suggesting a fitness tradeoff between mitotic growth and mtDNA stability. We also found that mtDNA stability was correlated with a mobile mitochondrial GC-cluster that is present in certain populations of yeast and that selection for nuclear alleles that stabilize mtDNA may be rapidly occurring. The MNRC provides a powerful tool for identifying mitonuclear interacting loci that will help us to better understand genotype-phenotype relationships and coevolutionary trajectories.

Mitochondrial Impairment: A Common Motif in Neuropsychiatric Presentation? The Link to the Tryptophan-Kynurenine Metabolic System

Nearly half a century has passed since the discovery of cytoplasmic inheritance of human chloramphenicol resistance. The inheritance was then revealed to take place maternally by mitochondrial DNA (mtDNA). Later, a number of mutations in mtDNA were identified as a cause of severe inheritable metabolic diseases with neurological manifestation, and the impairment of mitochondrial functions has been probed in the pathogenesis of a wide range of illnesses including neurodegenerative diseases. Recently, a growing number of preclinical studies have revealed that animal behaviors are influenced by the impairment of mitochondrial functions and possibly by the loss of mitochondrial stress resilience. Indeed, as high as 54% of patients with one of the most common primary mitochondrial diseases, mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome, present psychiatric symptoms including cognitive impairment, mood disorder, anxiety, and psychosis. Mitochondria are multifunctional organelles which produce cellular energy and play a major role in other cellular functions including homeostasis, cellular signaling, and gene expression, among others. Mitochondrial functions are observed to be compromised and to become less resilient under continuous stress. Meanwhile, stress and inflammation have been linked to the activation of the tryptophan (Trp)-kynurenine (KYN) metabolic system, which observably contributes to the development of pathological conditions including neurological and psychiatric disorders. This review discusses the functions of mitochondria and the Trp-KYN system, the interaction of the Trp-KYN system with mitochondria, and the current understanding of the involvement of mitochondria and the Trp-KYN system in preclinical and clinical studies of major neurological and psychiatric diseases.

Long Non-Coding RNAs, Novel Offenders or Guardians in Multiple Sclerosis: A Scoping Review

Multiple sclerosis (MS), a chronic inflammatory demyelinating disease of the central nervous system, is one of the most common neurodegenerative diseases worldwide. MS results in serious neurological dysfunctions and disability. Disturbances in coding and non-coding genes are key components leading to neurodegeneration along with environmental factors. Long non-coding RNAs (lncRNAs) are long molecules in cells that take part in the regulation of gene expression. Several studies have confirmed the role of lncRNAs in neurodegenerative diseases such as MS. In the current study, we performed a systematic analysis of the role of lncRNAs in this disorder. In total, 53 studies were recognized as eligible for this systematic review. Of the listed lncRNAs, 52 lncRNAs were upregulated, 37 lncRNAs were downregulated, and 11 lncRNAs had no significant expression difference in MS patients compared with controls. We also summarized some of the mechanisms of lncRNA functions in MS. The emerging role of lncRNAs in neurodegenerative diseases suggests that their dysregulation could trigger neuronal death via still unexplored RNA-based regulatory mechanisms. Evaluation of their diagnostic significance and therapeutic potential could help in the design of novel treatments for MS.

Mitochondrial DNA genetic variants are associated with systemic lupus erythematosus susceptibility, glucocorticoids efficacy, and prognosis

OBJECTIVE

To investigate the associations of mitochondrial DNA (mtDNA) genetic variants with systemic lupus erythematosus (SLE) susceptibility, glucocorticoids (GCs) efficacy, and prognosis.

METHODS

Our study was done in two stages. First, we performed the whole mitochondrial genome sequencing in 100 patients and 100 controls to initially screen potential mtDNA variants associated with disease and glucocorticoids efficacy. Then, we validated the results in an independent set of samples. In total, 605 SLE patients and 604 normal controls were included in our two-stage study. A two-stage efficacy study was conducted in 512 patients treated with GCs for 12 weeks. We also explored the association between mtDNA variants and SLE prognosis.

RESULTS

In the combined sample, four mtDNA variants (A4833G, T5108C, G14569A, CA514-515-) were associated with SLE susceptibility (all P  BH<0.05). We confirmed that T16362C was related to GCs efficacy (P  BH=0.014). Significant associations were detected between T16362C and T16519C and the efficacy of GCs in females with SLE (P  BH<0.05). In the prognosis study, variants A4833G (P  BH=0.003) and G14569A (P  BH=9.744 × 1 0 -4) substantially increased SLE relapse risk. Female patients harbouring variants T5108C and T16362C were more prone to relapse (P  BH<0.05). Haplotype analysis showed that haplogroup G was linked with SLE susceptibility (P  BH=0.001) and prognosis (P  BH=0.013). Moreover, mtDNA variants-environment interactions were observed.

CONCLUSION

We identified novel mtDNA genetic variants that were associated with SLE susceptibility, GCs efficacy, and prognosis. Interactions between mtDNA variants and environmental factors were related to SLE risk and GCs efficacy. Our findings provide important information for future understanding the occurrence and development of SLE.

[The possibility of using multiple sclerosis-associated variants of the mitochondrial genome to predict the development of multiple sclerosis]

Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by autoimmune inflammation, demyelination, and neurodegeneration. MS is a complex disease that develops under the influence of environmental factors in genetically predisposed individuals. Currently, more than 200 genetic loci associated with MS have been identified by various methods. Some of them are located in the mitochondrial DNA. This paper collects data on mtDNA variants associated with MS in the Russian ethnic group, and shows the possibility of using this information to construct and refine models for predicting the development of MS.

Contribution of lncRNA CASC8, CASC11, and PVT1 Genetic Variants to the Susceptibility of Coronary Heart Disease

ABSTRACT

The purpose of this study was to explore the relationship between lncRNA CASC8, CASC11, and plasmacytoma variant translocation 1 (PVT1). genetic variants and coronary heart disease (CHD) susceptibility among a Chinese Han population. Five single nucleotide polymorphisms were genotyped by Agena MassARRAY platform among 464 CHD patients and 510 healthy controls. Binary logistic regression models by calculating odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association between selected single nucleotide polymorphisms and CHD risk. Multifactor dimensionality reduction analysis was performed to analyze gene-gene interaction. PVT1 rs4410871 (OR = 0.77, P = 0.040) was associated with a reduced risk of CHD occurrence in the Chinese population. CASC11 rs9642880 (OR = 1.49, P = 0.021) was a risk factor for increased CHD susceptibility in subjects over 60 years old, and PVT1 rs4410871 was a protective factor for CHD susceptibility in males (OR = 0.67, P = 0.015) and smokers (OR = 0.62, P = 0.047). Complications (hypertension or diabetes) of CHD influenced the association between CASC8, CASC11, and PVT1 genetic polymorphisms and CHD predisposition. Moreover, CASC8, CASC11, and PVT1 polymorphisms were related to the number of pathological branches and Gensini score in CHD patients. The study displayed the contribution of CASC8, CASC11, and PVT1 genetic polymorphisms to CHD predisposition, and these variants could serve as potential biomarkers of CHD susceptibility. These findings contribute to enhancing the understanding of the role of lncRNA polymorphisms in CHD risk.