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Bogolyubov DS, Chistyakova LV, Goodkov AV. Glomerulosomes: morphologically distinct nuclear organelles of unknown nature. PROTOPLASMA 2022; 259:1409-1415. [PMID: 35103866 DOI: 10.1007/s00709-022-01742-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
The nucleus of some representatives of the genus Pelomyxa (Amoebozoa, Archamoebae, Pelobiontida) contains specific bodies (membrane-less organelles). They may be either embedded in the nucleolar mass or detached from the nucleolus. We termed these nuclear bodies the glomerulosomes for their characteristic ultrastructural appearance. The glomerulosomes are distinct nuclear bodies, about 1 μm in diameter. The morphological and diagnostic unit of a glomerulosome is an electron-dense thread/string, about 30-40 nm in thickness. These threads are not direct continuation of the nucleolar material. The threads create the unique geometric appearance of the glomerulosome by being organized into precisely parallel rows/cords. Each cord of the threads can curve at different angles within the glomerulosome body, but the threads themselves are not coiled. Nowadays, the glomerulosomes have been discovered in P. palustris, P. stagnalis, P. paradoxa, and Pelomyxa sp. Despite the unique appearance of glomerulosomes, their existence may be a more common phenomenon in eukaryotic cells than just a specific feature of the nucleus of elected pelomyxes.
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Affiliation(s)
- Dmitry S Bogolyubov
- Laboratory of Cell Morphology, Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, 194064, Russia.
| | | | - Andrew V Goodkov
- Laboratory of Cytology of Unicellular Organisms, Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, 194064, Russia
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Malatesta M, Costanzo M, Cisterna B, Zancanaro C. Satellite Cells in Skeletal Muscle of the Hibernating Dormouse, a Natural Model of Quiescence and Re-Activation: Focus on the Cell Nucleus. Cells 2020; 9:cells9041050. [PMID: 32340154 PMCID: PMC7226265 DOI: 10.3390/cells9041050] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/15/2020] [Accepted: 04/21/2020] [Indexed: 02/06/2023] Open
Abstract
Satellite cells (SCs) participate in skeletal muscle plasticity/regeneration. Activation of SCs implies that nuclear changes underpin a new functional status. In hibernating mammals, periods of reduced metabolic activity alternate with arousals and resumption of bodily functions, thereby leading to repeated cell deactivation and reactivation. In hibernation, muscle fibers are preserved despite long periods of immobilization. The structural and functional characteristics of SC nuclei during hibernation have not been investigated yet. Using ultrastructural and immunocytochemical analysis, we found that the SCs of the hibernating edible dormouse, Glis glis, did not show apoptosis or necrosis. Moreover, their nuclei were typical of quiescent cells, showing similar amounts and distributions of heterochromatin, pre-mRNA transcription and processing factors, as well as paired box protein 7 (Pax7) and the myogenic differentiation transcription factor D (MyoD), as in euthermia. However, the finding of accumulated perichromatin granules (i.e., sites of storage/transport of spliced pre-mRNA) in SC nuclei of hibernating dormice suggested slowing down of the nucleus-to-cytoplasm transport. We conclude that during hibernation, SC nuclei maintain similar transcription and splicing activity as in euthermia, indicating an unmodified status during immobilization and hypometabolism. Skeletal muscle preservation during hibernation is presumably not due to SC activation, but rather to the maintenance of some functional activity in myofibers that is able to counteract muscle wasting.
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Affiliation(s)
- Manuela Malatesta
- Anatomy and Histology Section, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie, 8 I-37134 Verona, Italy; (M.M.); (M.C.); (C.Z.)
| | - Manuela Costanzo
- Anatomy and Histology Section, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie, 8 I-37134 Verona, Italy; (M.M.); (M.C.); (C.Z.)
| | - Barbara Cisterna
- Anatomy and Histology Section, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie, 8 I-37134 Verona, Italy; (M.M.); (M.C.); (C.Z.)
- Correspondence:
| | - Carlo Zancanaro
- Anatomy and Histology Section, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie, 8 I-37134 Verona, Italy; (M.M.); (M.C.); (C.Z.)
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Gattoni G, Bernocchi G. Calcium-Binding Proteins in the Nervous System during Hibernation: Neuroprotective Strategies in Hypometabolic Conditions? Int J Mol Sci 2019; 20:ijms20092364. [PMID: 31086053 PMCID: PMC6540041 DOI: 10.3390/ijms20092364] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 05/06/2019] [Accepted: 05/11/2019] [Indexed: 02/07/2023] Open
Abstract
Calcium-binding proteins (CBPs) can influence and react to Ca2+ transients and modulate the activity of proteins involved in both maintaining homeostatic conditions and protecting cells in harsh environmental conditions. Hibernation is a strategy that evolved in vertebrate and invertebrate species to survive in cold environments; it relies on molecular, cellular, and behavioral adaptations guided by the neuroendocrine system that together ensure unmatched tolerance to hypothermia, hypometabolism, and hypoxia. Therefore, hibernation is a useful model to study molecular neuroprotective adaptations to extreme conditions, and can reveal useful applications to human pathological conditions. In this review, we describe the known changes in Ca2+-signaling and the detection and activity of CBPs in the nervous system of vertebrate and invertebrate models during hibernation, focusing on cytosolic Ca2+ buffers and calmodulin. Then, we discuss these findings in the context of the neuroprotective and neural plasticity mechanisms in the central nervous system: in particular, those associated with cytoskeletal proteins. Finally, we compare the expression of CBPs in the hibernating nervous system with two different conditions of neurodegeneration, i.e., platinum-induced neurotoxicity and Alzheimer's disease, to highlight the similarities and differences and demonstrate the potential of hibernation to shed light into part of the molecular mechanisms behind neurodegenerative diseases.
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Affiliation(s)
- Giacomo Gattoni
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
| | - Graziella Bernocchi
- Former Full Professor of Zoology, Neurogenesis and Comparative Neuromorphology, (Residence address) Viale Matteotti 73, I-27100 Pavia, Italy.
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4
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Rouble AN, Storey KB. Characterization of the SIRT family of NAD+-dependent protein deacetylases in the context of a mammalian model of hibernation, the thirteen-lined ground squirrel. Cryobiology 2015; 71:334-43. [DOI: 10.1016/j.cryobiol.2015.08.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/06/2015] [Accepted: 08/11/2015] [Indexed: 12/23/2022]
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Grabek KR, Diniz Behn C, Barsh GS, Hesselberth JR, Martin SL. Enhanced stability and polyadenylation of select mRNAs support rapid thermogenesis in the brown fat of a hibernator. eLife 2015; 4. [PMID: 25626169 PMCID: PMC4383249 DOI: 10.7554/elife.04517] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 12/23/2014] [Indexed: 12/21/2022] Open
Abstract
During hibernation, animals cycle between torpor and arousal. These cycles involve
dramatic but poorly understood mechanisms of dynamic physiological regulation at the
level of gene expression. Each cycle, Brown Adipose Tissue (BAT) drives periodic
arousal from torpor by generating essential heat. We applied digital transcriptome
analysis to precisely timed samples to identify molecular pathways that underlie the
intense activity cycles of hibernator BAT. A cohort of transcripts increased during
torpor, paradoxical because transcription effectively ceases at these low
temperatures. We show that this increase occurs not by elevated transcription but
rather by enhanced stabilization associated with maintenance and/or extension of long
poly(A) tails. Mathematical modeling further supports a temperature-sensitive
mechanism to protect a subset of transcripts from ongoing bulk degradation instead of
increased transcription. This subset was enriched in a C-rich motif and genes
required for BAT activation, suggesting a model and mechanism to prioritize
translation of key proteins for thermogenesis. DOI:http://dx.doi.org/10.7554/eLife.04517.001 Many mammals hibernate to avoid food scarcity and harsh conditions during winter.
Hibernation involves entering a state called torpor, which drastically reduces the
amount of energy used by the body. During torpor, body temperature also decreases.
This is particularly exemplified in ground squirrels, whose body temperature can
hover at just above or even below the point of freezing. However, hibernating mammals
cannot remain in this state continuously over the months of hibernation but instead
cycle between bouts of torpor lasting for 1–3 weeks and brief periods of
‘arousal’ lasting between 12–24 hr, during which their body
rapidly warms up. The heat required to start warming up the hibernator is generated from a specialized
form of fat called brown adipose tissue. Normally, the bursts of metabolic activity
that are required to create this heat depend on certain proteins being produced.
Making a protein involves ‘translating’ its sequence from template
molecules called messenger RNA (mRNA), which are ‘transcribed’ from the
gene that encodes the protein. During the low body temperatures experienced during
torpor, both of these processes stop. So how is the hibernator able to quickly and
efficiently heat itself up during the arousal periods of hibernation? Grabek et al. investigated this by analyzing the relative levels of mRNA in the brown
adipose tissue of hibernating 13-lined ground squirrels. Using a special technique to
sample and sequence small fragments of mRNA taken from brown adipose tissue, Grabek
et al. compiled a profile of the mRNA molecules present at different points in the
torpor–arousal cycle and compared this with a similar profile taken from
squirrels that were not hibernating. From this analysis, Grabek et al. detected that a particular group of mRNA molecules
that are required for producing heat increase in abundance during torpor, even though
body temperature is low enough to stop gene transcription. This increased abundance
does not occur because more of the mRNA molecules are made; instead, the mRNA
molecules are modified to become more stable and long lasting. Once the animal warms
up during arousal, gene transcription is reactivated and more new mRNA molecules are
made. Grabek et al. suggest that the key mRNAs required for brown adipose tissue function
are selectively stabilized during torpor through a temperature-dependent protective
mechanism. These mRNAs are then preferentially translated into proteins during
arousal to rapidly and efficiently heat the hibernator. Most other mRNA molecules
degrade throughout torpor, and so their numbers decline as replacements are not
transcribed until body temperature briefly recovers during arousal. Whether this
protective mechanism is also used in other tissues during torpor remains a question
for future work. DOI:http://dx.doi.org/10.7554/eLife.04517.002
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Affiliation(s)
- Katharine R Grabek
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States
| | - Cecilia Diniz Behn
- Department of Applied Math and Statistics, Colorado School of Mines, Golden, United States
| | - Gregory S Barsh
- Department of Research, HudsonAlpha Institute for Biotechnology, Huntsville, United States
| | - Jay R Hesselberth
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States
| | - Sandra L Martin
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States
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Abstract
For many animals, survival of severe environmental stress (e.g. to extremes of heat or cold, drought, oxygen limitation, food deprivation) is aided by entry into a hypometabolic state. Strong depression of metabolic rate, often to only 1–20% of normal resting rate, is a core survival strategy of multiple forms of hypometabolism across the animal kingdom, including hibernation, anaerobiosis, aestivation and freeze tolerance. Global biochemical controls are needed to suppress and reprioritize energy use; one such well-studied control is reversible protein phosphorylation. Recently, we turned our attention to the idea that mechanisms previously associated mainly with epigenetic regulation can also contribute to reversible suppression of gene expression in hypometabolic states. Indeed, situations as diverse as mammalian hibernation and turtle anoxia tolerance show coordinated changes in histone post-translational modifications (acetylation, phosphorylation) and activities of histone deacetylases, consistent with their use as mechanisms for suppressing gene expression during hypometabolism. Other potential mechanisms of gene silencing in hypometabolic states include altered expression of miRNAs that can provide post-transcriptional suppression of mRNA translation and the formation of ribonuclear protein bodies in the nucleus and cytoplasm to allow storage of mRNA transcripts until animals rouse themselves again. Furthermore, mechanisms first identified in epigenetic regulation (e.g. protein acetylation) are now proving to apply to many central metabolic enzymes (e.g. lactate dehydrogenase), suggesting a new layer of regulatory control that can contribute to coordinating the depression of metabolic rate.
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Affiliation(s)
- Kenneth B. Storey
- Institute of Biochemistry and Departments of Biology and Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
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Tessier SN, Storey KB. To be or not to be: the regulation of mRNA fate as a survival strategy during mammalian hibernation. Cell Stress Chaperones 2014; 19:763-76. [PMID: 24789358 PMCID: PMC4389848 DOI: 10.1007/s12192-014-0512-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 04/13/2014] [Indexed: 12/20/2022] Open
Abstract
Mammalian hibernators undergo profound behavioral, physiological, and biochemical changes in order to cope with hypothermia, ischemia-reperfusion, and finite fuel reserves over days or weeks of continuous torpor. Against a backdrop of global reductions in energy-expensive processes such as transcription and translation, a subset of genes/proteins are strategically upregulated in order to meet challenges associated with hibernation. Consequently, hibernation involves substantial transcriptional and posttranscriptional regulatory mechanisms and provides a phenomenon with which to understand how a set of common genes/proteins can be differentially regulated in order to enhance stress tolerance beyond that which is possible for nonhibernators. The present review focuses on the involvement of messenger RNA (mRNA) interacting factors that play a role in the regulation of gene/protein expression programs that define the hibernating phenotype. These include proteins involved in mRNA processing (i.e., capping, splicing, and polyadenylation) and the possible role of alternative splicing as a means of enhancing protein diversity. Since the total pool of mRNA remains constant throughout torpor, mechanisms which enhance mRNA stability are discussed in the context of RNA binding proteins and mRNA decay pathways. Furthermore, mechanisms which control the global reduction of cap-dependent translation and the involvement of internal ribosome entry sites in mRNAs encoding stress response proteins are also discussed. Finally, the concept of regulating each of these factors in discrete subcellular compartments for enhanced efficiency is addressed. The analysis draws on recent research from several well-studied mammalian hibernators including ground squirrels, bats, and bears.
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Affiliation(s)
- Shannon N. Tessier
- Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
| | - Kenneth B. Storey
- Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
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Tessier SN, Audas TE, Wu CW, Lee S, Storey KB. The involvement of mRNA processing factors TIA-1, TIAR, and PABP-1 during mammalian hibernation. Cell Stress Chaperones 2014; 19:813-25. [PMID: 24590458 PMCID: PMC4389841 DOI: 10.1007/s12192-014-0505-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/11/2014] [Accepted: 02/12/2014] [Indexed: 01/10/2023] Open
Abstract
Mammalian hibernators survive low body temperatures, ischemia-reperfusion, and restricted nutritional resources via global reductions in energy-expensive cellular processes and selective increases in stress pathways. Consequently, studies that analyze hibernation uncover mechanisms which balance metabolism and support survival by enhancing stress tolerance. We hypothesized processing factors that influence messenger ribonucleic acid (mRNA) maturation and translation may play significant roles in hibernation. We characterized the amino acid sequences of three RNA processing proteins (T cell intracellular antigen 1 (TIA-1), TIA1-related (TIAR), and poly(A)-binding proteins (PABP-1)) from thirteen-lined ground squirrels (Ictidomys tridecemlineatus), which all displayed a high degree of sequence identity with other mammals. Alternate Tia-1 and TiaR gene variants were found in the liver with higher expression of isoform b versus a in both cases. The localization of RNA-binding proteins to subnuclear structures was assessed by immunohistochemistry and confirmed by subcellular fractionation; TIA-1 was identified as a major component of subnuclear structures with up to a sevenfold increase in relative protein levels in the nucleus during hibernation. By contrast, there was no significant difference in the relative protein levels of TIARa/TIARb in the nucleus, and a decrease was observed for TIAR isoforms in cytoplasmic fractions of torpid animals. Finally, we used solubility tests to analyze the formation of reversible aggregates that are associated with TIA-1/R function during stress; a shift towards the soluble fraction (TIA-1a, TIA-1b) was observed during hibernation suggesting enhanced protein aggregation was not present during torpor. The present study identifies novel posttranscriptional regulatory mechanisms that may play a role in reducing translational rates and/or mRNA processing under unfavorable environmental conditions.
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Affiliation(s)
- Shannon N. Tessier
- />Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
| | - Timothy E. Audas
- />Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5 Canada
| | - Cheng-Wei Wu
- />Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
| | - Stephen Lee
- />Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5 Canada
| | - Kenneth B. Storey
- />Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
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Effect of Opioids on Tissue Metabolism in Aestivating and Active Green-Striped Burrowing Frogs,Cyclorana alboguttata. J HERPETOL 2013. [DOI: 10.1670/12-039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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10
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Malatesta M, Giagnacovo M, Costanzo M, Cisterna B, Cardani R, Meola G. Muscleblind-like1 undergoes ectopic relocation in the nuclei of skeletal muscles in myotonic dystrophy and sarcopenia. Eur J Histochem 2013; 57:e15. [PMID: 23807294 PMCID: PMC3794341 DOI: 10.4081/ejh.2013.e15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 02/13/2013] [Accepted: 02/14/2013] [Indexed: 01/24/2023] Open
Abstract
Muscleblind-like 1 (MBNL1) is an alternative splicing factor involved in postnatal development of skeletal muscles and heart in humans and mice, and its deregulation is known to be pivotal in the onset and development of myotonic dystrophy (DM). In fact, in DM patients this protein is ectopically sequestered into intranuclear foci, thus compromising the regulation of the alternative splicing of several genes. However, despite the numerous biochemical and molecular studies, scarce attention has been paid to the intranuclear location of MBNL1 outside the foci, although previous data demonstrated that in DM patients various splicing and cleavage factors undergo an abnormal intranuclear distribution suggestive of impaired RNA processing. Interestingly, these nuclear alterations strongly remind those observed in sarcopenia i.e., the loss of muscle mass and function which physiologically occurs during ageing. On this basis, in the present investigation the ultrastructural localization of MBNL1 was analyzed in the myonuclei of skeletal muscles from healthy and DM patients as well as from adult and old (sarcopenic) mice, in the attempt to elucidate possible changes in its distribution and amount. Our data demonstrate that in both dystrophic and sarcopenic muscles MBNL1 undergoes intranuclear relocation, accumulating in its usual functional sites but also ectopically moving to domains which are usually devoid of this protein in healthy adults. This accumulation/delocalization could contribute to hamper the functionality of the whole splicing machinery, leading to a lower nuclear metabolic activity and, consequently, to a less efficient protein synthesis. Moreover, the similar nuclear alterations found in DM and sarcopenia may account for the similar muscle tissue features (myofibre atrophy, fibre size variability and centrally located nuclei), and, in general, for the aging-reminiscent phenotype observed in DM patients.
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Affiliation(s)
- M Malatesta
- Dipartimento di Scienze Neurologiche, Neuropsicologiche, Morfologiche e Motorie, Sezione di Anatomia e Istologia, Università di Verona, 37134 Verona, Italy.
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11
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Malatesta M, Fattoretti P, Giagnacovo M, Pellicciari C, Zancanaro C. Physical training modulates structural and functional features of cell nuclei in type II myofibers of old mice. Rejuvenation Res 2011; 14:543-52. [PMID: 21978085 DOI: 10.1089/rej.2011.1175] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Aging is associated with a progressive loss of muscle mass, strength, and function, a condition known as sarcopenia, which represents an important risk factor for physical disability in elderly. The mechanisms leading to sarcopenia are still largely unknown, and no specific therapy is presently available to counteract its onset or progress. Many studies have stressed the importance of physical exercise as an effective approach to prevent/limit the age-related muscle mass loss. This study investigated the effects of physical training on pre-mRNA pathways in quadriceps and gastrocnemius muscles of old mice by ultrastructural cytochemistry: Structural and in situ molecular features of myonuclei and satellite cell nuclei of type II fibers were compared in exercised versus sedentary old mice, using adult individuals as control. Our results demonstrated that in myonuclei of old mice physical exercise stimulates pre-mRNA transcription, splicing, and export to the cytoplasm, likely increasing muscle protein turnover. In satellite cells, the effect of physical exercise seems to be limited to the reactivation of some factors involved in the transcriptional and splicing apparatus without increasing RNA production, probably making these quiescent cells more responsive to activating stimuli.
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Affiliation(s)
- Manuela Malatesta
- Department of Neurological, Neuropsychological, Morphological and Motor Sciences, Anatomy and Histology Section, University of Verona, Verona, Italy.
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12
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Malatesta M, Giagnacovo M, Renna LV, Cardani R, Meola G, Pellicciari C. Cultured myoblasts from patients affected by myotonic dystrophy type 2 exhibit senescence-related features: ultrastructural evidence. Eur J Histochem 2011; 55:e26. [PMID: 22073373 PMCID: PMC3203470 DOI: 10.4081/ejh.2011.e26] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 09/05/2011] [Indexed: 01/19/2023] Open
Abstract
Myotonic dystrophy type 2 (DM2) is an autosomal dominant disorder caused by the expansion of the tetranucleotidic repeat (CCTG)n in the first intron of the Zinc Finger Protein-9 gene. In DM2 tissues, the expanded mutant transcripts accumulate in nuclear focal aggregates where splicing factors are sequestered, thus affecting mRNA processing. Interestingly, the ultrastructural alterations in the splicing machinery observed in the myonuclei of DM2 skeletal muscles are reminiscent of the nuclear changes occurring in age-related muscle atrophy. Here, we investigated in vitro structural and functional features of satellite cell-derived myoblasts from biceps brachii, in the attempt to investigate cell senescence indices in DM2 patients by ultrastructural cytochemistry. We observed that in satellite cell-derived DM2 myoblasts, cell-senescence alterations such as cytoplasmic vacuolization, reduction of the proteosynthetic apparatus, accumulation of heterochromatin and impairment of the pre-mRNA maturation pathways occur earlier than in myoblasts from healthy patients. These results, together with preliminary in vitro observations on the early onset of defective structural features in DM2 myoblast derived-myotubes, suggest that the regeneration capability of DM2 satellite cells may be impaired, thus contributing to the muscular dystrophy in DM2 patients.
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Affiliation(s)
- M Malatesta
- Dipartimento di Scienze Neurologiche, Neuropsicologiche, Morfologiche e Motorie, Sezione di Anatomia e Istologia, University of Verona, Italy.
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13
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Malatesta M, Zancanaro C, Biggiogera M. Immunoelectron microscopic characterization of nucleolus-associated domains during hibernation. Microsc Res Tech 2010; 74:47-53. [DOI: 10.1002/jemt.20872] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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15
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Malatesta M, Meola G. Structural and functional alterations of the cell nucleus in skeletal muscle wasting: the evidence in situ. Eur J Histochem 2010; 54:e44. [PMID: 21263743 PMCID: PMC3167325 DOI: 10.4081/ejh.2010.e44] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 09/09/2010] [Indexed: 11/22/2022] Open
Abstract
The histochemical and ultrastructural analysis of the nuclear components involved in RNA transcription and splicing can reveal the occurrence of cellular dysfunctions eventually related to the onset of a pathological phenotype. In recent years, nuclear histochemistry at light and electron microscopy has increasingly been used to investigate the basic mechanisms of skeletal muscle diseases; the in situ study of nuclei of myofibres and satellite cells proved to be crucial for understanding the pathogenesis of skeletal muscle wasting in sarcopenia, myotonic dystrophy and laminopathies.
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Affiliation(s)
- M Malatesta
- Dipartimento di Scienze Neurologiche, Neuropsicologiche, Morfologiche e Motorie, Sezione di Anatomia e Istologia, Università di Verona, Italy.
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16
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Sakashita E, Endo H. SR and SR-related proteins redistribute to segregated fibrillar components of nucleoli in a response to DNA damage. Nucleus 2010; 1:367-80. [PMID: 21327085 DOI: 10.4161/nucl.1.4.12683] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Revised: 06/15/2010] [Accepted: 06/16/2010] [Indexed: 11/19/2022] Open
Abstract
Pre-mRNA splicing factors are often redistributed to nucleoli in response to physiological conditions and cell stimuli. In telophase nuclei, serine-arginine rich (SR) proteins, which usually reside in nuclear speckles, localize transiently to active ribosomal DNA (rDNA) transcription sites called nucleolar organizing region-associated patches (NAPs). Here, we show that ultraviolet light and DNA damaging chemicals induce the redistribution of SR and SR-related proteins to areas around nucleolar fibrillar components in interphase nuclei that are similar to, but distinct from, NAPs, and these areas have been termed DNA damage-induced NAPs (d-NAPs). In vivo labeling of nascent RNA distinguished d-NAPs from NAPs in that d-NAPs were observed even after full rDNA transcriptional arrest as a result of DNA damage. Studies under a variety of conditions revealed that d-NAP formation requires both RNA polymerase II-dependent transcriptional arrest and nucleolar segregation, in particular, the disorganization of the granular nucleolar components. Despite the redistribution of SR proteins, splicing factor-enriched nuclear speckles were not disrupted because other nuclear speckle components, such as nuclear poly(A) RNA and the U5-116K protein, remained in DNA-damaged cells. These data suggest that the selective redistribution of splicing factors contributes to the regulation of specific genes via RNA metabolism. Finally, we demonstrate that a change in alternative splicing of apoptosis-related genes is coordinated with the occurrence of d-NAPs. Our results reveal a novel response to DNA damage that involves the dynamic redistribution of splicing factors to nucleoli.
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Affiliation(s)
- Eiji Sakashita
- Department of Biochemistry, Jichi Medical University School of Medicine, Tochigi, Japan.
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Suozzi A, Malatesta M, Zancanaro C. Subcellular distribution of key enzymes of lipid metabolism during the euthermia-hibernation-arousal cycle. J Anat 2010; 214:956-62. [PMID: 19538638 DOI: 10.1111/j.1469-7580.2009.01086.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Mammalian hibernation is a natural, fully reversible hypometabolic state characterized by a drastic reduction of body temperature and metabolic activity, which ensures survival to many species under adverse environmental conditions. During hibernation, many hibernators rely for energy supply almost exclusively on lipid reserves; the shift from carbohydrate to lipid metabolism implies profound rearrangement of the anabolic and catabolic pathways of energetic substrates. However, the structural counterpart of such adaptation is not known. In this study we investigated, by using immunoelectron microscopy, the fine intracellular distribution of two key enzymes involved in lipid metabolism, namely, the fatty acid synthase (FAS) and the long-chain fatty acyl-CoA synthetase (ACSL), in hepatocytes of euthermic, hibernating and arousing hazel dormice. Our results show that the two enzymes are differentially distributed in cellular compartments (cytoplasm, mitochondria and cell nuclei) of hepatocytes during euthermia. Quantitative redistribution of both enzymes among cellular compartments takes place during hibernation and arousal, in accordance with the physiological changes. Interestingly, this redistribution follows different seasonal patterns in cytoplasm, mitochondria and nuclei. In conclusion, our data represent the first quantitative morphological evidence of lipid enzyme distribution in a true hibernator throughout the year cycle, thus providing a structural framework to biochemical changes associated with the hypometabolism of hibernation.
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Affiliation(s)
- Anna Suozzi
- Dipartimento di Scienze Morfologico-Biomediche, University of Verona, Italy
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Malatesta M, Biggiogera M, Cisterna B, Balietti M, Bertoni-Freddari C, Fattoretti P. Perichromatin fibrils accumulation in hepatocyte nuclei reveals alterations of pre-mRNA processing during aging. DNA Cell Biol 2010; 29:49-57. [PMID: 20025533 DOI: 10.1089/dna.2009.0880] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We previously described an unusual accumulation of perichromatin fibrils (PF)-the in situ form of pre-mRNA transcription and early splicing-in hepatocyte nuclei of old rats. Here we have investigated, by immunoelectron microscopy, the nature of such PF, analyzing the presence of transcription, splicing and cleavage factors, polyadenylated RNA, and the incorporation of bromouridine in adult and old rats. Our observations revealed alterations in amount and/or distribution of pre-mRNA transcription, splicing and cleavage factors, as well as of polyadenylated RNA, together with lower bromouridine incorporation in newly transcribed RNA in the hepatocyte nucleoplasm of old rats. Therefore, our data indicate both a decrease in pre-mRNA transcription and a slow down of PF processing and transport during aging.
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Affiliation(s)
- Manuela Malatesta
- 1 Department of Morphological and Biomedical Sciences, Anatomy and Histology Section, University of Verona, Verona, Italy
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Malatesta M, Perdoni F, Battistelli S, Muller S, Zancanaro C. The cell nuclei of skeletal muscle cells are transcriptionally active in hibernating edible dormice. BMC Cell Biol 2009; 10:19. [PMID: 19284674 PMCID: PMC2663540 DOI: 10.1186/1471-2121-10-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 03/14/2009] [Indexed: 12/18/2022] Open
Abstract
Background Skeletal muscle is able to react in a rapid, dynamic way to metabolic and mechanical stimuli. In particular, exposure to either prolonged starvation or disuse results in muscle atrophy. At variance, in hibernating animals muscle atrophy may be scarce or absent after bouts of hibernation i.e., periods of prolonged (months) inactivity and food deprivation, and muscle function is fully preserved at arousal. In this study, myocytes from the quadriceps muscle of euthermic and hibernating edible dormice were investigated by a combination of morphological, morphometrical and immunocytochemical analyses at the light and electron microscopy level. The focus was on cell nuclei and mitochondria, which are highly sensitive markers of changing metabolic rate. Results Findings presented herein demonstrate that: 1) the general histology of the muscle, inclusive of muscle fibre shape and size, and the ratio of fast and slow fibre types are not affected by hibernation; 2) the fine structure of cytoplasmic and nuclear constituents is similar in euthermia and hibernation but for lipid droplets, which accumulate during lethargy; 3) during hibernation, mitochondria are larger in size with longer cristae, and 4) myonuclei maintain the same amount and distribution of transcripts and transcription factors as in euthermia. Conclusion In this study we demonstrate that skeletal muscle cells of the hibernating edible dormouse maintain their structural and functional integrity in full, even after months in the nest. A twofold explanation for that is envisaged: 1) the maintenance, during hibernation, of low-rate nuclear and mitochondrial activity counterbalancing myofibre wasting, 2) the intensive muscle stimulation (shivering) during periodic arousals in the nest, which would mimic physical exercise. These two factors would prevent muscle atrophy usually occurring in mammals after prolonged starvation and/or inactivity as a consequence of prevailing catabolism. Understanding the mechanisms responsible for skeletal muscle preservation in hibernators could pave the way to prevention and treatment of muscle wasting associated with pathological conditions or ageing as well as life in extreme environments, such as ocean deeps or spaceflights.
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Affiliation(s)
- Manuela Malatesta
- Dipartimento di Scienze Morfologico-Biomediche, Sezione di Anatomia e Istologia, University of Verona, Italy.
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