scholarly journals Mice harboring a SCA28 patient mutation in AFG3L2 develop late-onset ataxia associated with enhanced mitochondrial proteotoxicity.

2018 ◽  
Author(s):  
Cecilia Mancini ◽  
Eriola Hoxha ◽  
Luisa Iommarini ◽  
Alessandro Brussino ◽  
Uwe Richter ◽  
...  
Keyword(s):  
Network Formation ◽  
De Novo ◽  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Mitochondrial Protein ◽  
Atp Synthesis ◽  
Protein Translation ◽  
Mutant Mice ◽  
Mitochondrial Morphology ◽  
Missense Mutations

Spinocerebellar ataxia 28 is an autosomal dominant neurodegenerative disorder caused by missense mutations affecting the proteolytic domain of AFG3L2, a major component of the mitochondrial m-AAA protease. However, little is known of the underlying pathogenetic mechanisms or how to treat patients with SCA28. Currently available Afg3l2 mutant mice harbour deletions that lead to severe, early-onset neurological phenotypes that do not faithfully reproduce the late-onset and slowly progressing SCA28 phenotype. Here we describe production and detailed analysis of a new knock-in murine model harbouring an Afg3l2 allele carrying the p.Met665Arg patient-derived mutation. Heterozygous mutant mice developed normally but signs of ataxia were detectable by beam test at 18 months. Cerebellar pathology was negative; electrophysiological analysis showed increased spontaneous firing in Purkinje cells from heterozygous mutants with respect to wild-type controls, although not statistically significant. As homozygous mutants died perinatally with evidence of cardiac atrophy, for each genotype we generated mouse embryonic fibroblasts (MEFs) to investigate mitochondrial function. MEFs from mutant mice showed altered mitochondrial bioenergetics, with decreased basal oxygen consumption rate, ATP synthesis and mitochondrial membrane potential. Mitochondrial network formation and morphology was also altered, in line with greatly reduced expression of Opa1 fusogenic protein L-isoforms. The mitochondrial alterations observed in MEFs were also detected in cerebella of 18-month-old heterozygous mutants, suggesting they may be a hallmark of disease. Pharmacological inhibition of de novo mitochondrial protein translation with chloramphenicol caused reversal of mitochondrial morphology in homozygous mutant MEFs, supporting the relevance of mitochondrial proteotoxicity for SCA28 pathogenesis and therapy development.

scholarly journals Maintaining the balance of TDP-43, mitochondria, and autophagy: a promising therapeutic strategy for neurodegenerative diseases

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Chunhui Huang ◽  
Sen Yan ◽  
Zaijun Zhang
Keyword(s):  
Neurodegenerative Diseases ◽  
Current Knowledge ◽  
Mitochondrial Protein ◽  
Protein Translation ◽  
The Body ◽  
Acute Injury ◽  
Mitochondrial Morphology ◽  
Physiological Functions ◽  
Novel Approach ◽  
In Cells

Abstract Mitochondria are the energy center of cell operations and are involved in physiological functions and maintenance of metabolic balance and homeostasis in the body. Alterations of mitochondrial function are associated with a variety of degenerative and acute diseases. As mitochondria age in cells, they gradually become inefficient and potentially toxic. Acute injury can trigger the permeability of mitochondrial membranes, which can lead to apoptosis or necrosis. Transactive response DNA-binding protein 43 kDa (TDP-43) is a protein widely present in cells. It can bind to RNA, regulate a variety of RNA processes, and play a role in the formation of multi-protein/RNA complexes. Thus, the normal physiological functions of TDP-43 are particularly important for cell survival. Normal TDP-43 is located in various subcellular structures including mitochondria, mitochondrial-associated membrane, RNA particles and stress granules to regulate the endoplasmic reticulum–mitochondrial binding, mitochondrial protein translation, and mRNA transport and translation. Importantly, TDP-43 is associated with a variety of neurodegenerative diseases, including amyotrophic lateral sclerosis, frontotemporal dementia and Alzheimer's disease, which are characterized by abnormal phosphorylation, ubiquitination, lysis or nuclear depletion of TDP-43 in neurons and glial cells. Although the pathogenesis of TDP-43 proteinopathy remains unknown, the presence of pathological TDP-43 inside or outside of mitochondria and the functional involvement of TDP-43 in the regulation of mitochondrial morphology, transport, and function suggest that mitochondria are associated with TDP-43-related diseases. Autophagy is a basic physiological process that maintains the homeostasis of cells, including targeted clearance of abnormally aggregated proteins and damaged organelles in the cytoplasm; therefore, it is considered protective against neurodegenerative diseases. However, the combination of abnormal TDP-43 aggregation, mitochondrial dysfunction, and insufficient autophagy can lead to a variety of aging-related pathologies. In this review, we describe the current knowledge on the associations of mitochondria with TDP-43 and the role of autophagy in the clearance of abnormally aggregated TDP-43 and dysfunctional mitochondria. Finally, we discuss a novel approach for neurodegenerative treatment based on the knowledge.

scholarly journals Comprehensive Modeling of Spinal Muscular Atrophy in Drosophila melanogaster

2018 ◽  
Author(s):  
Ashlyn M. Spring ◽  
Amanda C. Raimer ◽  
Christine D. Hamilton ◽  
Michela J. Schillinger ◽  
A. Gregory Matera
Keyword(s):  
Spinal Muscular Atrophy ◽  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Muscular Atrophy ◽  
Full Range ◽  
Survival Motor Neuron ◽  
Model Systems ◽  
Null Alleles ◽  
Missense Mutations ◽  
Systematic Analysis

AbstractSpinal muscular atrophy (SMA) is a neurodegenerative disorder that affects motor neurons, primarily in young children. SMA is caused by mutations in the Survival Motor Neuron 1 (SMN1) gene. SMN functions in the assembly of spliceosomal RNPs and is well conserved in many model systems including mouse, zebrafish, fruit fly, nematode, and fission yeast. Work in Drosophila has primarily focused on loss of SMN function during larval stages, primarily using null alleles or strong hypomorphs. A systematic analysis of SMA-related phenotypes in the context of moderate alleles that more closely mimic the genetics of SMA has not been performed in the fly, leading to debate over the validity and translational value of this model. We therefore examined fourteen Drosophila lines expressing SMA patient-derived missense mutations in Smn, with a focus on neuromuscular phenotypes in the adult stage. Animals were evaluated on the basis of organismal viability and longevity, locomotor function, neuromuscular junction structure, and muscle health. In all cases, we observed phenotypes similar to those of SMA patients, including progressive loss of adult motor function. The severity of these defects is variable, and forms a broad spectrum across the fourteen lines examined, recapitulating the full range of phenotypic severity observed in human SMA. This includes late-onset models of SMA, which have been difficult to produce in other model systems. The results provide direct evidence that SMA-related locomotor decline can be reproduced in the fly and support the use of patient-derived SMN missense mutations as a comprehensive system for modeling SMA.

scholarly journals Impaired development of neocortical circuits contributes to the neurological alterations in DYRK1A haploinsufficiency syndrome

2018 ◽  
Author(s):  
Juan Arranz ◽  
Elisa Balducci ◽  
Krisztina Arató ◽  
Gentzane Sánchez-Elexpuru ◽  
Sònia Najas ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Catalytic Domain ◽  
De Novo ◽  
Epileptic Activity ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Mutant Mice ◽  
Chromosome 21 ◽  
Missense Mutations ◽  
Human Pathology

ABSTRACTAutism spectrum disorders are early onset neurodevelopmental disorders characterized by deficits in social communication and restricted repetitive behaviors, yet they are quite heterogeneous in terms of their genetic basis and phenotypic manifestations. Recently, de novo pathogenic mutations in DYRK1A, a chromosome 21 gene associated to neuropathological traits of Down syndrome, have been identified in patients presenting a recognizable syndrome included in the autism spectrum. These mutations produce DYRK1A kinases with partial or complete absence of the catalytic domain, or they represent missense mutations located within this domain. Here, we undertook an extensive biochemical characterization of the DYRK1A missense mutations reported to date and show that most of them, but not all, result in enzymatically dead DYRK1A proteins. We also show that haploinsufficient Dyrk1a+/- mutant mice mirror the neurological traits associated with the human pathology, such as defective social interactions, stereotypic behaviors and epileptic activity. These mutant mice present altered proportions of excitatory and inhibitory neocortical neurons and synapses. Moreover, we provide evidence that alterations in the production of cortical excitatory neurons are contributing to these defects. Indeed, by the end of the neurogenic period, the expression of developmental regulated genes involved in neuron differentiation and/or activity is altered. Therefore, our data indicate that altered neocortical neurogenesis could critically affect the formation of cortical circuits, thereby contributing to the neuropathological changes in DYRK1A haploinsufficiency syndrome.

scholarly journals Evidence of mitochondrial dysfunction in fragile X-associated tremor/ataxia syndrome

2010 ◽  
Vol 429 (3) ◽  
pp. 545-552 ◽  
Author(s):  
Catherine Ross-Inta ◽  
Alicja Omanska-Klusek ◽  
Sarah Wong ◽  
Cedrick Barrow ◽  
Dolores Garcia-Arocena ◽  
...  
Keyword(s):  
Mitochondrial Dysfunction ◽  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Fragile X ◽  
Mitochondrial Protein ◽  
Additional Treatment ◽  
Cgg Repeat ◽  
Cgg Repeats ◽  
Nitrative Stress ◽  
Ataxia Syndrome

FXTAS (fragile X-associated tremor/ataxia syndrome) is a late-onset neurodegenerative disorder that affects individuals who are carriers of premutation expansions (55–200 CGG repeats) in the 5′ untranslated region of the FMR1 (fragile X mental retardation 1) gene. The role of MD (mitochondrial dysfunction) in FXTAS was evaluated in fibroblasts and brain samples from premutation carriers with and without FXTAS symptoms, with a range of CGG repeats. This study resulted in several important conclusions: (i) decreased NAD- and FAD-linked oxygen uptake rates and uncoupling between electron transport and synthesis of ATP were observed in fibroblasts from premutation carriers; (ii) a lower expression of mitochondrial proteins preceded both in age and in CGG repeats the appearance of overt clinical involvement; (iii) the CGG repeat size required for altered mitochondrial protein expression was also smaller than that required to produce brain intranuclear inclusions from individuals with the premutation who died, suggesting that MD is an incipient pathological process occurring in individuals who do not display overt features of FXTAS; and (iv) on the basis of the CGG repeats, MD preceded the increase in oxidative/nitrative stress damage, indicating that the latter is a late event. MD in carriers of small CGG repeats, even when the allele size is not sufficient to produce FXTAS, may predispose them to other disorders (e.g. Parkinson's disease) that are likely to involve MD, and to environmental stressors, which may trigger the development of FXTAS symptoms. Detection of MD is of critical importance to the management of FXTAS, since it opens up additional treatment options for this disorder.

scholarly journals De novo disruption of promoter and exon 1 of STAR gene reveals essential role for gonadal development

2017 ◽  
Vol 2017 ◽  
Author(s):  
Anil Piya ◽  
Jasmeet Kaur ◽  
Alan M Rice ◽  
Himangshu S Bose
Keyword(s):  
Protein Import ◽  
De Novo ◽  
Regulatory Protein ◽  
Mitochondrial Protein ◽  
Protein Translation ◽  
Gonadal Development ◽  
Cholesterol Transport ◽  
List Type ◽  
Star Protein ◽  
Exon 1

Summary Cholesterol transport into the mitochondria is required for synthesis of the first steroid, pregnenolone. Cholesterol is transported by the steroidogenic acute regulatory protein (STAR), which acts at the outer mitochondrial membrane prior to its import. Mutations in the STAR protein result in lipoid congenital adrenal hyperplasia (CAH). Although the STAR protein consists of seven exons, biochemical analysis in nonsteroidogenic COS-1 cells showed that the first two were not essential for pregnenolone synthesis. Here, we present a patient with ambiguous genitalia, salt-lossing crisis within two weeks after birth and low cortisol levels. Sequence analysis of the STAR, including the exon–intron boundaries, showed the complete deletion of exon 1 as well as more than 50 nucleotides upstream of STAR promoter. Mitochondrial protein import with the translated protein through synthesis cassette of the mutant STAR lacking exon 1 showed protein translation, but it is less likely to have synthesized without a promoter in our patient. Thus, a full-length STAR gene is necessary for physiological mitochondrial cholesterol transport in vivo. Learning points: STAR exon 1 deletion caused lipoid CAH. Exon 1 substitution does not affect biochemical activity. StAR promoter is responsible for gonadal development.

scholarly journals DRP1-mediated mitochondrial fission is essential to maintain cristae morphology and bioenergetics

2022 ◽  
Author(s):  
Gabriella L. Robertson ◽  
Stellan Riffle ◽  
Mira Patel ◽  
Andrea Marshall ◽  
Heather Beasley ◽  
...  
Keyword(s):  
Cell Fate ◽  
De Novo ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Coupling Efficiency ◽  
Acid Oxidation ◽  
Mitochondrial Morphology ◽  
Missense Mutations ◽  
Neurodevelopmental Disease ◽  
Signaling Organelles

Mitochondria and peroxisomes are both dynamic signaling organelles that constantly undergo fission. While mitochondrial fission is known to coordinate cellular metabolism, proliferation, and apoptosis, the physiological relevance of peroxisome dynamics and the implications for cell fate are not fully understood. DRP1 (dynamin-related protein 1) is an essential GTPase that executes both mitochondrial and peroxisomal fission. Patients with de novo heterozygous missense mutations in the gene that encodes DRP1, DNM1L, present with encephalopathy due to defective mitochondrial and peroxisomal fission (EMPF1). EMPF1 is a devastating neurodevelopmental disease with no effective treatment. To interrogate the mechanisms by which DRP1 mutations cause cellular dysfunction, we utilized human-derived fibroblasts from patients with mutations in DRP1 who present with EMPF1. As expected, patient cells display elongated mitochondrial morphology and lack of fission. Patient cells display a lower coupling efficiency of the electron transport chain, increased proton leak, and upregulation of glycolysis. In addition to these metabolic abnormalities, mitochondrial hyperfusion results in aberrant cristae structure and hyperpolarized mitochondrial membrane potential, both of which are tightly linked to the changes in metabolism. Peroxisome structure is also severely elongated in patient cells and results in a potential functional compensation of fatty acid oxidation. Understanding the mechanism by which DRP1 mutations cause these metabolic changes will give insight into the role of mitochondrial dynamics in cristae maintenance and the metabolic capacity of the cell, as well as the disease mechanism underlying EMPF1.

scholarly journals 3548 De novo germline variants in Histone 3 Family 3A (H3F3A) and Histone 3 Family 3B (H3F3B) cause a severe neurodegenerative disorder and functional effects unique from their somatic mutations

2019 ◽  
Vol 3 (s1) ◽  
pp. 103-103 ◽  
Author(s):  
Divya R Nair ◽  
Elizabeth Bhoj
Keyword(s):  
Somatic Mutations ◽  
De Novo ◽  
Neurodegenerative Disorder ◽  
Germline Mutations ◽  
Dominant Negative ◽  
Missense Mutations ◽  
Repair Gene ◽  
Histone 3 ◽  
Expression Of Genes ◽  
Dna Repair Gene

OBJECTIVES/SPECIFIC AIMS: Histones are nuclear proteins that associate with DNA to facilitate packaging into condensed chromatin. Histones are dynamically decorated with post-translational modifications (PTMs), which regulate such processes as DNA repair, gene expression, mitosis, and meiosis. Histone 3 Family 3 (H3F3) histones (H3.3), encoded by H3F3A and H3F3B, mark active genes, maintain epigenetic memory, and maintain heterochromatin and telomeric integrity. Specific somatic mutations in H3F3A and H3F3B have been strongly associated with pediatric glia and other tumors, but no germline mutations have been reported. The goal of our study was to further understand the functional effects of germline mutations of H3F3A and H3F3B. METHODS/STUDY POPULATION: We analyzed 32 patients bearing de novo germline missense mutations in H3F3A or H3F3B with core phenotypes of progressive neurologic dysfunction and congenital anomalies, but no malignancies. Patient histones were analyzed by quantitative mass spectrometry (qMS). RESULTS/ANTICIPATED RESULTS: qMS results revealed that the mutant histone proteins are present at a concentration similar to that of wild-type H3.3. qMS analysis showed strikingly aberrant PTM patterns that suggested local dysregulation. These patterns are distinct from the dominant negative somatic mutations, which cause more global PTM dysregulation. Patient cells also demonstrated upregulation of the expression of genes related to mitosis and cell division, and had a greater proliferative capacity. DISCUSSION/SIGNIFICANCE OF IMPACT: Our data suggests that the pathogenic mechanism of germline histone mutations is distinct from that of the published cancer-associated somatic histone mutations, but may converge on control of cell proliferation. Further clarification of the pathophysiology in these patients can elucidate the roles of histones and histone PTMs in human development and non-syndromic neurodegeneration. In addition, it provides a framework for targeted therapy development for this and related progressive neurologic disorders.

scholarly journals On the Need to Tell Apart Fraternal Twins eEF1A1 and eEF1A2, and Their Respective Outfits

2021 ◽  
Vol 22 (13) ◽  
pp. 6973
Author(s):  
Alberto Mills ◽  
Federico Gago
Keyword(s):  
De Novo ◽  
Elongation Factor ◽  
Missense Mutations ◽  
Developmentally Regulated ◽  
High Sequence Identity ◽  
80S Ribosome ◽  
Cellular Effects ◽  
Cellular Processes ◽  
Eukaryotic Elongation Factor ◽  
A Site

eEF1A1 and eEF1A2 are paralogous proteins whose presence in most normal eukaryotic cells is mutually exclusive and developmentally regulated. Often described in the scientific literature under the collective name eEF1A, which stands for eukaryotic elongation factor 1A, their best known activity (in a monomeric, GTP-bound conformation) is to bind aminoacyl-tRNAs and deliver them to the A-site of the 80S ribosome. However, both eEF1A1 and eEF1A2 are endowed with multitasking abilities (sometimes performed by homo- and heterodimers) and can be located in different subcellular compartments, from the plasma membrane to the nucleus. Given the high sequence identity of these two sister proteins and the large number of post-translational modifications they can undergo, we are often confronted with the dilemma of discerning which is the particular proteoform that is actually responsible for the ascribed biochemical or cellular effects. We argue in this review that acquiring this knowledge is essential to help clarify, in molecular and structural terms, the mechanistic involvement of these two ancestral and abundant G proteins in a variety of fundamental cellular processes other than translation elongation. Of particular importance for this special issue is the fact that several de novo heterozygous missense mutations in the human EEF1A2 gene are associated with a subset of rare but severe neurological syndromes and cardiomyopathies.

scholarly journals Mitochondrial microRNAs: A Putative Role in Tissue Regeneration

Biology ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 486
Author(s):  
Sílvia C. Rodrigues ◽  
Renato M. S. Cardoso ◽  
Filipe V. Duarte
Keyword(s):  
Tissue Regeneration ◽  
Protein Complexes ◽  
Mitochondrial Protein ◽  
Noncoding Rnas ◽  
Atp Synthesis ◽  
Mitochondrial Proteins ◽  
Cellular Mechanisms ◽  
Small Noncoding Rnas ◽  
Mitochondrial Ribosome

The most famous role of mitochondria is to generate ATP through oxidative phosphorylation, a metabolic pathway that involves a chain of four protein complexes (the electron transport chain, ETC) that generates a proton-motive force that in turn drives the ATP synthesis by the Complex V (ATP synthase). An impressive number of more than 1000 mitochondrial proteins have been discovered. Since mitochondrial proteins have a dual genetic origin, it is predicted that ~99% of these proteins are nuclear-encoded and are synthesized in the cytoplasmatic compartment, being further imported through mitochondrial membrane transporters. The lasting 1% of mitochondrial proteins are encoded by the mitochondrial genome and synthesized by the mitochondrial ribosome (mitoribosome). As a result, an appropriate regulation of mitochondrial protein synthesis is absolutely required to achieve and maintain normal mitochondrial function. Regarding miRNAs in mitochondria, it is well-recognized nowadays that several cellular mechanisms involving mitochondria are regulated by many genetic players that originate from either nuclear- or mitochondrial-encoded small noncoding RNAs (sncRNAs). Growing evidence collected from whole genome and transcriptome sequencing highlight the role of distinct members of this class, from short interfering RNAs (siRNAs) to miRNAs and long noncoding RNAs (lncRNAs). Some of the mechanisms that have been shown to be modulated are the expression of mitochondrial proteins itself, as well as the more complex coordination of mitochondrial structure and dynamics with its function. We devote particular attention to the role of mitochondrial miRNAs and to their role in the modulation of several molecular processes that could ultimately contribute to tissue regeneration accomplishment.

scholarly journals Molecular Pathogenesis and Peripheral Monitoring of Adult Fragile X-Associated Syndromes

2021 ◽  
Vol 22 (16) ◽  
pp. 8368
Author(s):  
Luis M. Valor ◽  
Jorge C. Morales ◽  
Irati Hervás-Corpión ◽  
Rosario Marín
Keyword(s):  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Fragile X ◽  
Endocrine System ◽  
Molecular Pathogenesis ◽  
Adult Women ◽  
Adult Men ◽  
Cgg Repeats ◽  
Reproductive Impairment ◽  
Ataxia Syndrome

Abnormal trinucleotide expansions cause rare disorders that compromise quality of life and, in some cases, lifespan. In particular, the expansions of the CGG-repeats stretch at the 5’-UTR of the Fragile X Mental Retardation 1 (FMR1) gene have pleiotropic effects that lead to a variety of Fragile X-associated syndromes: the neurodevelopmental Fragile X syndrome (FXS) in children, the late-onset neurodegenerative disorder Fragile X-associated tremor-ataxia syndrome (FXTAS) that mainly affects adult men, the Fragile X-associated primary ovarian insufficiency (FXPOI) in adult women, and a variety of psychiatric and affective disorders that are under the term of Fragile X-associated neuropsychiatric disorders (FXAND). In this review, we will describe the pathological mechanisms of the adult “gain-of-function” syndromes that are mainly caused by the toxic actions of CGG RNA and FMRpolyG peptide. There have been intensive attempts to identify reliable peripheral biomarkers to assess disease progression and onset of specific pathological traits. Mitochondrial dysfunction, altered miRNA expression, endocrine system failure, and impairment of the GABAergic transmission are some of the affectations that are susceptible to be tracked using peripheral blood for monitoring of the motor, cognitive, psychiatric and reproductive impairment of the CGG-expansion carriers. We provided some illustrative examples from our own cohort. Understanding the association between molecular pathogenesis and biomarkers dynamics will improve effective prognosis and clinical management of CGG-expansion carriers.

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