1
|
LaPotin S, Swartz ME, Luecke DM, Constantinou SJ, Gallant JR, Eberhart JK, Zakon HH. Divergent cis-regulatory evolution underlies the convergent loss of sodium channel expression in electric fish. SCIENCE ADVANCES 2022; 8:eabm2970. [PMID: 35648851 PMCID: PMC9159570 DOI: 10.1126/sciadv.abm2970] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
South American and African weakly electric fish independently evolved electric organs from muscle. In both groups, a voltage-gated sodium channel gene independently lost expression from muscle and gained it in the electric organ, allowing the channel to become specialized for generating electric signals. It is unknown how this voltage-gated sodium channel gene is targeted to muscle in any vertebrate. We describe an enhancer that selectively targets sodium channel expression to muscle. Next, we demonstrate how the loss of this enhancer, but not trans-activating factors, drove the loss of sodium channel gene expression from muscle in South American electric fish. While this enhancer is also altered in African electric fish, key transcription factor binding sites and enhancer activity are retained, suggesting that the convergent loss of sodium channel expression from muscle in these two electric fish lineages occurred via different processes.
Collapse
Affiliation(s)
- Sarah LaPotin
- Department of Neuroscience, The University of Texas, Austin, TX 78712, USA
| | - Mary E. Swartz
- Department of Molecular Biosciences, The University of Texas, Austin, TX 78712, USA
| | - David M. Luecke
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Savvas J. Constantinou
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
- Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI 48824, USA
| | - Jason R. Gallant
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
- Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI 48824, USA
| | - Johann K. Eberhart
- Department of Molecular Biosciences, The University of Texas, Austin, TX 78712, USA
| | - Harold H. Zakon
- Department of Neuroscience, The University of Texas, Austin, TX 78712, USA
- Department of Integrative Biology, The University of Texas, Austin, TX 78712, USA
- Corresponding author.
| |
Collapse
|
2
|
Nicole S, Lory P. New Challenges Resulting From the Loss of Function of Na v1.4 in Neuromuscular Diseases. Front Pharmacol 2021; 12:751095. [PMID: 34671263 PMCID: PMC8521073 DOI: 10.3389/fphar.2021.751095] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
The voltage-gated sodium channel Nav1.4 is a major actor in the excitability of skeletal myofibers, driving the muscle force in response to nerve stimulation. Supporting further this key role, mutations in SCN4A, the gene encoding the pore-forming α subunit of Nav1.4, are responsible for a clinical spectrum of human diseases ranging from muscle stiffness (sodium channel myotonia, SCM) to muscle weakness. For years, only dominantly-inherited diseases resulting from Nav1.4 gain of function (GoF) were known, i.e., non-dystrophic myotonia (delayed muscle relaxation due to myofiber hyperexcitability), paramyotonia congenita and hyperkalemic or hypokalemic periodic paralyses (episodic flaccid muscle weakness due to transient myofiber hypoexcitability). These last 5 years, SCN4A mutations inducing Nav1.4 loss of function (LoF) were identified as the cause of dominantly and recessively-inherited disorders with muscle weakness: periodic paralyses with hypokalemic attacks, congenital myasthenic syndromes and congenital myopathies. We propose to name this clinical spectrum sodium channel weakness (SCW) as the mirror of SCM. Nav1.4 LoF as a cause of permanent muscle weakness was quite unexpected as the Na+ current density in the sarcolemma is large, securing the ability to generate and propagate muscle action potentials. The properties of SCN4A LoF mutations are well documented at the channel level in cellular electrophysiological studies However, much less is known about the functional consequences of Nav1.4 LoF in skeletal myofibers with no available pertinent cell or animal models. Regarding the therapeutic issues for Nav1.4 channelopathies, former efforts were aimed at developing subtype-selective Nav channel antagonists to block myofiber hyperexcitability. Non-selective, Nav channel blockers are clinically efficient in SCM and paramyotonia congenita, whereas patient education and carbonic anhydrase inhibitors are helpful to prevent attacks in periodic paralyses. Developing therapeutic tools able to counteract Nav1.4 LoF in skeletal muscles is then a new challenge in the field of Nav channelopathies. Here, we review the current knowledge regarding Nav1.4 LoF and discuss the possible therapeutic strategies to be developed in order to improve muscle force in SCW.
Collapse
Affiliation(s)
- Sophie Nicole
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx 'Ion Channel Science and Therapeutics (ICST), Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx 'Ion Channel Science and Therapeutics (ICST), Montpellier, France
| |
Collapse
|
3
|
Loussouarn G, Sternberg D, Nicole S, Marionneau C, Le Bouffant F, Toumaniantz G, Barc J, Malak OA, Fressart V, Péréon Y, Baró I, Charpentier F. Physiological and Pathophysiological Insights of Nav1.4 and Nav1.5 Comparison. Front Pharmacol 2016; 6:314. [PMID: 26834636 PMCID: PMC4712308 DOI: 10.3389/fphar.2015.00314] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 12/21/2015] [Indexed: 12/19/2022] Open
Abstract
Mutations in Nav1.4 and Nav1.5 α-subunits have been associated with muscular and cardiac channelopathies, respectively. Despite intense research on the structure and function of these channels, a lot of information is still missing to delineate the various physiological and pathophysiological processes underlying their activity at the molecular level. Nav1.4 and Nav1.5 sequences are similar, suggesting structural and functional homologies between the two orthologous channels. This also suggests that any characteristics described for one channel subunit may shed light on the properties of the counterpart channel subunit. In this review article, after a brief clinical description of the muscular and cardiac channelopathies related to Nav1.4 and Nav1.5 mutations, respectively, we compare the knowledge accumulated in different aspects of the expression and function of Nav1.4 and Nav1.5 α-subunits: the regulation of the two encoding genes (SCN4A and SCN5A), the associated/regulatory proteins and at last, the functional effect of the same missense mutations detected in Nav1.4 and Nav1.5. First, it appears that more is known on Nav1.5 expression and accessory proteins. Because of the high homologies of Nav1.5 binding sites and equivalent Nav1.4 sites, Nav1.5-related results may guide future investigations on Nav1.4. Second, the analysis of the same missense mutations in Nav1.4 and Nav1.5 revealed intriguing similarities regarding their effects on membrane excitability and alteration in channel biophysics. We believe that such comparison may bring new cues to the physiopathology of cardiac and muscular diseases.
Collapse
Affiliation(s)
- Gildas Loussouarn
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Damien Sternberg
- Institut National de la Santé et de la Recherche Médicale, U1127Paris, France; Sorbonne Universités, Université Pierre-et-Marie-Curie, UMR S1127Paris, France; Centre National de la Recherche Scientifique, UMR 7225Paris, France; Institut du Cerveau et de la Moelle Épinière, ICMParis, France; Assistance Publique - Hôpitaux de Paris (AP-HP), Centres de Référence des Canalopathies Musculaires et des Maladies Neuro-musculaires Paris-EstParis, France; Assistance Publique - Hôpitaux de Paris (AP-HP), Hôpital de la Pitié Salpêtrière, Service de Biochimie Métabolique, Unité de Cardiogénétique et MyogénétiqueParis, France
| | - Sophie Nicole
- Institut National de la Santé et de la Recherche Médicale, U1127Paris, France; Sorbonne Universités, Université Pierre-et-Marie-Curie, UMR S1127Paris, France; Centre National de la Recherche Scientifique, UMR 7225Paris, France; Institut du Cerveau et de la Moelle Épinière, ICMParis, France
| | - Céline Marionneau
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Francoise Le Bouffant
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Gilles Toumaniantz
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Julien Barc
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Olfat A Malak
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Véronique Fressart
- Assistance Publique - Hôpitaux de Paris (AP-HP), Hôpital de la Pitié Salpêtrière, Service de Biochimie Métabolique, Unité de Cardiogénétique et Myogénétique Paris, France
| | - Yann Péréon
- Centre Hospitalier Universitaire de Nantes, Centre de Référence Maladies Neuromusculaires Nantes-AngersNantes, France; Atlantic Gene Therapies - Biotherapy Institute for Rare DiseasesNantes, France
| | - Isabelle Baró
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France
| | - Flavien Charpentier
- Institut National de la Santé et de la Recherche Médicale, UMR 1087, l'Institut du ThoraxNantes, France; Centre National de la Recherche Scientifique, UMR 6291Nantes, France; Université de NantesNantes, France; Centre Hospitalier Universitaire de Nantes, l'Institut du ThoraxNantes, France
| |
Collapse
|
4
|
García-Villegas R, López-Alvarez LE, Arni S, Rosenbaum T, Morales MA. Identification and functional characterization of the promoter of the mouse sodium-activated sodium channel Na(x) gene (Scn7a). J Neurosci Res 2009; 87:2509-19. [PMID: 19326446 DOI: 10.1002/jnr.22069] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Na(x) is a sodium channel, thought to be a descendant of the voltage-gated sodium channel family. Nevertheless, Na(x) is not activated by voltage but rather by augmentation of extracellular sodium over 150 mM. In the brain, it is localized to the circumventricular organs, important regions for salt and water homeostasis in mammals, where it operates as a sodium-level sensor of body fluid. Na(x) channel is expressed in lung, uterus, and heart, and it is also found in trigeminal and dorsal root ganglia and in nonmyelinating Schwann cells, where its physiological role remains unclarified. Here we identified the promoter and transcription start sites of Na(x) sodium channel in dorsal root ganglia neurons from mouse. We report a characterization of the basal TATA-less promoter and the sequence requirements for promoter activity in Neuro 2A neuroblastoma cells and in dorsal root ganglia neurons, where basal promoter activity seems to require NGFI-C and Ebox DNA elements. Finally, we provide evidence that a repression mechanism that inhibits Na(x) expression may be present in certain tissues. These findings provide the basis with which to understand tissue-specific regulation of Na(x) sodium channel gene (Scn7a) expression.
Collapse
Affiliation(s)
- Refugio García-Villegas
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, D.F., México.
| | | | | | | | | |
Collapse
|
5
|
Hirn C, Shapovalov G, Petermann O, Roulet E, Ruegg UT. Nav1.4 deregulation in dystrophic skeletal muscle leads to Na+ overload and enhanced cell death. ACTA ACUST UNITED AC 2008; 132:199-208. [PMID: 18625851 PMCID: PMC2483333 DOI: 10.1085/jgp.200810024] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Duchenne muscular dystrophy (DMD) is a hereditary degenerative disease manifested by the absence of dystrophin, a structural, cytoskeletal protein, leading to muscle degeneration and early death through respiratory and cardiac muscle failure. Whereas the rise of cytosolic Ca2+ concentrations in muscles of mdx mouse, an animal model of DMD, has been extensively documented, little is known about the mechanisms causing alterations in Na+ concentrations. Here we show that the skeletal muscle isoform of the voltage-gated sodium channel, Nav1.4, which represents over 90% of voltage-gated sodium channels in muscle, plays an important role in development of abnormally high Na+ concentrations found in muscle from mdx mice. The absence of dystrophin modifies the expression level and gating properties of Nav1.4, leading to an increased Na+ concentration under the sarcolemma. Moreover, the distribution of Nav1.4 is altered in mdx muscle while maintaining the colocalization with one of the dystrophin-associated proteins, syntrophin α-1, thus suggesting that syntrophin is an important linker between dystrophin and Nav1.4. Additionally, we show that these modifications of Nav1.4 gating properties and increased Na+ concentrations are strongly correlated with increased cell death in mdx fibers and that both cell death and Na+ overload can be reversed by 3 nM tetrodotoxin, a specific Nav1.4 blocker.
Collapse
Affiliation(s)
- Carole Hirn
- Laboratory of Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, CH 1211 Geneva 4, Switzerland
| | | | | | | | | |
Collapse
|
6
|
Puhl HL, Ikeda SR. Identification of the sensory neuron specific regulatory region for the mouse gene encoding the voltage-gated sodium channel NaV1.8. J Neurochem 2008; 106:1209-24. [PMID: 18466327 DOI: 10.1111/j.1471-4159.2008.05466.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Voltage-gated sodium channels (VGSC) are critical membrane components that participate in the electrical activity of excitable cells. The type one VGSC family includes the tetrodotoxin insensitive sodium channel, Na(V)1.8, encoded by the Scn10a gene. Na(V)1.8 expression is restricted to small and medium diameter nociceptive sensory neurons of the dorsal root ganglia and cranial sensory ganglia. To understand the stringent transcriptional regulation of the Scn10a gene, the sensory neuron specific promoter was functionally identified. While identifying the mRNA 5'-end, alternative splicing within the 5'-UTR was observed to create heterogeneity in the RNA transcript. Four kilobases of upstream genomic DNA was cloned and the presence of tissue specific promoter activity was tested by microinjection and adenoviral infection of fluorescent protein reporter constructs into primary mouse and rat neurons, and cell lines. The region contained many putative transcription factor-binding sites and strong homology with the predicted rat ortholog. Homology to the predicted human ortholog was limited to the proximal end and several conserved cis elements were noted. Two regulatory modules were identified by microinjection of reporter constructs into dorsal root ganglia and superior cervical ganglia neurons: a neuron specific proximal promoter region between -1.6 and -0.2 kb of the transcription start site cluster, and a distal sensory neuron switch region beyond -1.6 kb that restricted fluorescent protein expression to a subset of primary sensory neurons.
Collapse
Affiliation(s)
- Henry L Puhl
- Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-9411, USA.
| | | |
Collapse
|
7
|
Hebert SL, Simmons C, Thompson AL, Zorc CS, Blalock EM, Kraner SD. Basic helix-loop-helix factors recruit nuclear factor I to enhance expression of the NaV 1.4 Na+ channel gene. ACTA ACUST UNITED AC 2007; 1769:649-58. [PMID: 17936922 DOI: 10.1016/j.bbaexp.2007.08.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Revised: 08/18/2007] [Accepted: 08/20/2007] [Indexed: 11/29/2022]
Abstract
We have previously shown that the basic helix-loop-helix (bHLH) transcription factors coordinate Na(V) 1.4 Na(+) channel gene expression in skeletal muscle, but the identity of the co-factors they direct is unknown. Using C2C12 muscle cells as a model system, we test the hypothesis that the bHLH factors counteract negative regulation exerted through a repressor E box (-90/-85) by recruiting positive-acting transcription factors to the nucleotides (-135/-57) surrounding the repressor E box. We used electrophoretic mobility shift assays to identify candidate factors that bound the repressor E box or these adjacent regions. Repressor E box-binding factors included the known transcription factor, ZEB/AREB6, and a novel repressor E box-binding factor designated REB. Mutations of the repressor E box that interfere with the binding of these factors prevented repression. The transcription factor, nuclear factor I (NFI), bound immediately upstream and downstream of the repressor E box. Mutation of the NFI-binding sites diminished the ability of myogenin and MRF4 to counteract repression. Based on these observations we suggest that bHLH factors recruit NFI to enhance skeletal muscle Na(+) channel expression.
Collapse
Affiliation(s)
- Sadie L Hebert
- Department of Molecular and Biomedical Pharmacology, University of Kentucky Medical Center, Lexington, KY 40536, USA.
| | | | | | | | | | | |
Collapse
|
8
|
Diss JKJ, Faulkes DJ, Walker MM, Patel A, Foster CS, Budhram-Mahadeo V, Djamgoz MBA, Latchman DS. Brn-3a neuronal transcription factor functional expression in human prostate cancer. Prostate Cancer Prostatic Dis 2006; 9:83-91. [PMID: 16276351 DOI: 10.1038/sj.pcan.4500837] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Neuroendocrine differentiation has been associated with prostate cancer (CaP). Brn-3a (short isoform) and Brn-3c, transcriptional controllers of neuronal differentiation, were readily detectable in human CaP both in vitro and in vivo. Brn-3a expression, but not Brn-3c, was significantly upregulated in >50% of tumours. Furthermore, overexpression of this transcription factor in vitro (i) potentiated CaP cell growth and (ii) regulated the expression of a neuronal gene, the Nav1.7 sodium channel, concomitantly upregulated in human CaP, in an isoform-specific manner. It is concluded that targeting Brn-3a could be a useful strategy for controlling the expression of multiple genes that promote CaP.
Collapse
Affiliation(s)
- J K J Diss
- Medical Molecular Biology Unit, Institute of Child Health, University College London, London, UK.
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Thompson AL, Filatov G, Chen C, Porter I, Li Y, Rich MM, Kraner SD. A selective role for MRF4 in innervated adult skeletal muscle: Na(V) 1.4 Na+ channel expression is reduced in MRF4-null mice. Gene Expr 2005; 12:289-303. [PMID: 16358417 PMCID: PMC6009121 DOI: 10.3727/000000005783992034] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The factors that regulate transcription and spatial expression of the adult skeletal muscle Na+ channel, Na(V) 1.4, are poorly understood. Here we tested the role of the transcription factor MRF4, one of four basic helix-loop-helix (bHLH) factors expressed in skeletal muscle, in regulation of the Na(V) 1.4 Na+ channel. Overexpression of MRF4 in C2C12 muscle cells dramatically elevated Na(V) 1.4 reporter gene expression, indicating that MRF4 is more efficacious than the other bHLH factors expressed at high levels endogenously in these cells. In vivo, MRF4 protein was found both in extrajunctional and subsynaptic muscle nuclei. To test the importance of MRF4 in Na(V) 1.4 gene regulation in vivo, we examined Na+ channel expression in MRF4-null mice using several techniques, including Western blotting, immunocytochemistry, and electrophysiological recording. By all methods, we found that expression of the Na(V) 1.4 Na+ channel was substantially reduced in MRF4-null mice, both in the surface membrane and at neuromuscular junctions. In contrast, expression of the acetylcholine receptor, and in particular its alpha subunit, was unchanged, indicating that MRF4 regulation of Na+ channel expression was selective. Expression of the bHLH factors myf-5, MyoD, and myogenin was increased in MRF4-null mice, but these factors were not able to fully maintain Na(V) 1.4 Na+ channel expression either in the extrajunctional membrane or at the synapse. Thus, MRF4 appears to play a novel and selective role in adult muscle.
Collapse
Affiliation(s)
- Amy L Thompson
- Department of Molecular and Biomedical Pharmacology, University of Kentucky Medical Center, Lexington, KY 40536, USA.
| | | | | | | | | | | | | |
Collapse
|
10
|
Yue L, Navarro B, Ren D, Ramos A, Clapham DE. The cation selectivity filter of the bacterial sodium channel, NaChBac. J Gen Physiol 2002; 120:845-53. [PMID: 12451053 PMCID: PMC2229573 DOI: 10.1085/jgp.20028699] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Bacillus halodurans voltage-gated sodium-selective channel (NaChBac) (Ren, D., B. Navarro, H. Xu, L. Yue, Q. Shi, and D.E. Clapham. 2001b. SCIENCE: 294:2372-2375), is an ideal candidate for high resolution structural studies because it can be expressed in mammalian cells and its functional properties studied in detail. It has the added advantage of being a single six transmembrane (6TM) orthologue of a single repeat of mammalian voltage-gated Ca(2+) (Ca(V)) and Na(+) (Na(V)) channels. Here we report that six amino acids in the pore domain (LESWAS) participate in the selectivity filter. Replacing the amino acid residues adjacent to glutamatic acid (E) by a negatively charged aspartate (D; LEDWAS) converted the Na(+)-selective NaChBac to a Ca(2+)- and Na(+)-permeant channel. When additional aspartates were incorporated (LDDWAD), the mutant channel resulted in a highly expressing voltage-gated Ca(2+)-selective conductance.
Collapse
Affiliation(s)
- Lixia Yue
- Howard Hughes Medical Institute, Children's Hospital, Boston, MA 02115, USA
| | | | | | | | | |
Collapse
|
11
|
Abstract
The E-Box is a widely used DNA control element. Despite its brevity and broad distribution the E-Box is a remarkably versatile sequence that affects many different genetic programs, including proliferation, differentiation, tissue-specific responses, and cell death. The circadian clock is one of the latest pathways shown to employ this element. In this context, E-Boxes are likely to play a key role in establishing the robust waves of gene expression characteristic of circadian transcription. The regulatory flexibility of the E-Box hinges on the sequence ambiguity allowed at its core, the strong influence of the surrounding sequences, and the recruitment of spatially and temporally regulated E-Box-binding factors. Therefore, understanding how a particular E-Box can accomplish a specific task entails the identification and systematic analysis of these cis- and trans-acting E-Box modifiers. In the present study we compared the E-Box-containing minimal promoters of vasopressin and cyclin B1, two genes that can respond to the transcriptional oscillators driving the circadian clock and cell cycle, respectively. Results of this comparison will help elucidate the manner in which discreet DNA modules associate to either augment or restrain the activation of potential circadian E-Boxes in response to competing regulatory signals.
Collapse
Affiliation(s)
- Estela Muñoz
- Unit on Temporal Gene Expression, Laboratory of Cellular and Molecular Regulation, National Institute of Mental Health, Bethesda, Maryland 20892, USA
| | | | | |
Collapse
|
12
|
Sodium channel mRNAs at the neuromuscular junction: distinct patterns of accumulation and effects of muscle activity. J Neurosci 2001. [PMID: 11606634 DOI: 10.1523/jneurosci.21-21-08456.2001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are highly concentrated at the neuromuscular junction (NMJ) in mammalian skeletal muscle. Here we test the hypothesis that local upregulation of mRNA contributes to this accumulation. We designed radiolabeled antisense RNA probes, specific for the "adult" Na(V)1.4 and "fetal" Na(V)1.5 isoforms of VGSC in mammalian skeletal muscle, and used them in in situ hybridization studies of rat soleus muscles. Na(V)1.4 mRNA is present throughout normal adult muscles but is highly concentrated at the NMJ, in which the amount per myonucleus is more than eightfold greater than away from the NMJ. Na(V)1.5 mRNA is undetectable in innervated muscles but is dramatically upregulated by denervation. In muscles denervated for 1 week, both Na(V)1.4 and Na(V)1.5 mRNAs are present throughout the muscle, and both are concentrated at the NMJ. No Na(V)1.5 mRNA was detectable in denervated muscles stimulated electrically for 1 week in vivo. Neither denervation nor stimulation had any significant effect on the level or distribution of Na(V)1.4 mRNA. We conclude that factors, probably derived from the nerve, lead to the increased concentration of VGSC mRNAs at the NMJ. In addition, the expression of Na(V)1.5 mRNA is downregulated by muscle activity, both at the NMJ and away from it.
Collapse
|
13
|
Tsai CW, Tseng JJ, Lin SC, Chang CY, Wu JL, Horng JF, Tsay HJ. Primary structure and developmental expression of zebrafish sodium channel Na(v)1.6 during neurogenesis. DNA Cell Biol 2001; 20:249-55. [PMID: 11410161 DOI: 10.1089/104454901750232445] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A zebrafish sodium channel cDNA encoding a 1949-amino acid polypeptide, Na(v)1.6, was isolated. Two transcripts were detected in zebrafish adult brain but not in cardiac or skeletal muscle. The RNase protection analysis confirmed the neural specificity of zebrafish Na(v)1.6 24 hours postfertilization (hpf) Na(v)1.6 was expressed in the trigeminal ganglion, anterior and posterior lateral line ganglia, rhombomeres, and Rohon-Beard neurons. This preferential localization suggests that Na(v)1.6 plays an important role in tactile sensitivity. The abundance of zebrafish Na(v) 1.6 mRNA in the central and peripheral nervous systems increased markedly between 48 and 72 hpf, during the maturation of the nervous system.
Collapse
Affiliation(s)
- C W Tsai
- Institute of Neuroscience, School of Life Science, National Yang-Ming University, Taipei, Taiwan, ROC
| | | | | | | | | | | | | |
Collapse
|
14
|
Kemp TJ, Sadusky TJ, Saltisi F, Carey N, Moss J, Yang SY, Sassoon DA, Goldspink G, Coulton GR. Identification of Ankrd2, a novel skeletal muscle gene coding for a stretch-responsive ankyrin-repeat protein. Genomics 2000; 66:229-41. [PMID: 10873377 DOI: 10.1006/geno.2000.6213] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mechanically induced hypertrophy of skeletal muscles involves shifts in gene expression leading to increases in the synthesis of specific proteins. Full characterization of the regulation of muscle hypertrophy is a prerequisite for the development of novel therapies aimed at treating muscle wasting (atrophy) in human aging and disease. Using suppression subtractive hybridization, cDNAs corresponding to mRNAs that increase in relative abundance in response to mechanical stretch of mouse skeletal muscles in vivo were identified. A novel 1100-bp transcript was detected exclusively in skeletal muscle. This exhibited a fourfold increase in expression after 7 days of stretch. The transcript had an open reading frame of 328 amino acids encoding an ATP/GTP binding domain, a nuclear localization signal, two PEST protein-destabilization motifs, and a 132-amino-acid ankyrin-repeat region. We have named this gene ankyrin-repeat domain 2 (stretch-responsive muscle) (Ankrd2). We hypothesize that Ankrd2 plays an important role in skeletal muscle hypertrophy.
Collapse
MESH Headings
- Amino Acid Motifs
- Animals
- Ankyrin Repeat/genetics
- Base Sequence
- Cell Differentiation
- Cells, Cultured
- Cloning, Molecular
- DNA, Complementary/genetics
- Exons
- Gene Expression
- Genomic Library
- Humans
- Mice
- Mice, Inbred C57BL
- Molecular Sequence Data
- Muscle Proteins/biosynthesis
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Muscle, Skeletal/cytology
- Muscle, Skeletal/embryology
- Muscle, Skeletal/metabolism
- Nuclear Proteins
- Organ Specificity/genetics
- Promoter Regions, Genetic
- RNA, Messenger/biosynthesis
- Repressor Proteins
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Stress, Mechanical
Collapse
Affiliation(s)
- T J Kemp
- Division of Biomedical Sciences, Imperial College of Science, Technology and Medicine, London, SW7 2AZ, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Gramolini AO, Wu J, Jasmin BJ. Regulation and functional significance of utrophin expression at the mammalian neuromuscular synapse. Microsc Res Tech 2000; 49:90-100. [PMID: 10757882 DOI: 10.1002/(sici)1097-0029(20000401)49:1<90::aid-jemt10>3.0.co;2-l] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Duchenne muscular dystrophy (DMD) is caused by the absence of full-length dystrophin molecules in skeletal muscle fibers. In normal muscle, dystrophin is found along the length of the sarcolemma where it links the intracellular actin cytoskeleton to the extracellular matrix, via the dystrophin-associated protein (DAP) complex. Several years ago, an autosomal homologue to dystrophin, termed utrophin, was identified and shown to be expressed in a variety of tissues, including skeletal muscle. However, in contrast to the localization of dystrophin in extrajunctional regions of muscle fibers, utrophin preferentially accumulates at the postsynaptic membrane of the neuromuscular junction in both normal and DMD adult muscle fibers. Since it has recently been suggested that the upregulation of utrophin might functionally compensate for the lack of dystrophin in DMD, considerable interest is now directed toward the elucidation of the various regulatory mechanisms presiding over expression of utrophin in normal and dystrophic skeletal muscle fibers. In this review, we discuss some of the most recent data relevant to our understanding of the impact of myogenic differentiation and innervation on the expression and localization of utrophin in skeletal muscle fibers.
Collapse
Affiliation(s)
- A O Gramolini
- Department of Cellular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Canada K1H 8M5
| | | | | |
Collapse
|
16
|
Gramolini AO, Jasmin BJ. Expression of the utrophin gene during myogenic differentiation. Nucleic Acids Res 1999; 27:3603-9. [PMID: 10446253 PMCID: PMC148607 DOI: 10.1093/nar/27.17.3603] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The process of myogenic differentiation is known to be accompanied by large increases ( approximately 10-fold) in the expression of genes encoding cytoskeletal and membrane proteins including dystrophin and the acetylcholine receptor (AChR) subunits, via the effects of transcription factors belonging to the MyoD family. Since in skeletal muscle (i) utrophin is a synaptic homolog to dystrophin, and (ii) the utrophin promoter contains an E-box, we examined, in the present study, expression of the utrophin gene during myogenic differentiation using the mouse C2 muscle cell line. We observed that in comparison to myoblasts, the levels of utrophin and its transcript were approximately 2-fold higher in differentiated myotubes. In order to address whether a greater rate of transcription contributed to the elevated levels of utrophin transcripts, we performed nuclear run-on assays. In these studies we determined that the rate of transcription of the utrophin gene was approximately 2-fold greater in myotubes as compared to myoblasts. Finally, we examined the stability of utrophin mRNAs in muscle cultures by two separate methods: following transcription blockade with actinomycin D and by pulse-chase experiments. Under these conditions, we determined that the half-life of utrophin mRNAs in myoblasts was approximately 20 h and that it remained largely unaffected during myogenic differentiation. Altogether, these results show that in comparison to other synaptic proteins and to dystrophin, expression of the utrophin gene is only moderately increased during myogenic differentiation.
Collapse
Affiliation(s)
- A O Gramolini
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
| | | |
Collapse
|
17
|
Kraner SD, Rich MM, Sholl MA, Zhou H, Zorc CS, Kallen RG, Barchi RL. Interaction between the skeletal muscle type 1 Na+ channel promoter E-box and an upstream repressor element. Release of repression by myogenin. J Biol Chem 1999; 274:8129-36. [PMID: 10075715 DOI: 10.1074/jbc.274.12.8129] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have defined how four elements that regulate expression of the rat skeletal muscle type 1 sodium channel (SkM1) gene cooperate to yield specific expression in differentiated muscle. A basal promoter region containing within it a promoter E-box (-31/-26) is broadly expressed in many cells, including myoblasts and myotubes; mutations within the promoter E-box that disrupt binding of the myogenic basic helix-loop-helix (bHLH) factors reduce expression in all cell types only slightly. Sequential addition of upstream elements to the wild-type promoter confer increasing specificity of expression in differentiated cells, even though all three upstream elements, including a positive element (-85/-57), a repressor E-box (-90/-85), and upstream repressor sequences (-135/-95), bind ubiquitously expressed transcription factors. Mutations in the promoter E-box that disrupt the binding of the bHLH factors counteract the specificity conferred by addition of the upstream elements, with the greatest interaction observed between the upstream repressor sequences and the promoter E-box. Forced expression of myogenin in myoblasts releases repression exerted by the upstream repressor sequences in conjunction with the wild-type, but not mutant, promoter E-box, and also initiates expression of the endogenous SkM1 protein. Our data suggest that particular myogenic bHLH proteins bound at the promoter E-box control expression of SkM1 by releasing repression exerted by upstream repressor sequences in differentiated muscle cells.
Collapse
Affiliation(s)
- S D Kraner
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | | | | | | | |
Collapse
|