The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Graciela A Unguez - One of the best experts on this subject based on the ideXlab platform.
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Reexpression of Myogenic Proteins in Mature Electric Organ after Removal of Neural Input
The Journal of Neuroscience, 2018Co-Authors: Graciela A Unguez, Harold H ZakonAbstract:The electric organ (EO) of the weakly electric fish Sternopygus Macrurus derives from striated myofibers that fuse and suppress many muscle properties. Mature electrocytes are larger than muscle fibers, do not contain sarcomeres, or express myosin heavy chain (MHC) or tropomyosin. Furthermore, electrocytes express keratin, a protein not expressed in muscle. In S. Macrurus the EO is driven continuously at frequencies higher than those of the intermittently active skeletal muscle. The extent to which differences in EO and muscle phenotype are accounted for by activity patterns, or innervation per se, was determined by assessing the expression of MHC, tropomyosin, and keratin 2 and 5 weeks after the elimination of (1) activity patterns by spinal transection or (2) all synaptic input by denervation. Immunohistochemical analyses showed no changes in muscle fiber phenotypes after either experimental treatment. In contrast, the keratin-positive electrocytes revealed an upregulation of MHC and tropomyosin. Nearly one-third of all electrocytes expressed MHC (35%) and tropomyosin (25%) 2 weeks after spinal transection, whereas approximately two-thirds (61%) expressed MHC 2 weeks after denervation. After 5 weeks of denervation or spinal transection, all electrocytes contained MHC and tropomyosin. Newly formed sarcomere clusters also were observed in denervated electrocytes. The MHC expressed in electrocytes corresponded to that present in a select population of muscle fibers, i.e., type II fibers. Thus, the elimination of electrical activity or all synaptic input resulted in a partial reversal of the electrocyte phenotype to an earlier developmental stage of its myogenic lineage.
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Properties of skeletal muscle in the teleost Sternopygus Macrurus are unaffected by short-term electrical inactivity
Physiological genomics, 2016Co-Authors: Robert Güth, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:Skeletal muscle is distinguished from other tissues on the basis of its shape, biochemistry, and physiological function. Based on mammalian studies, fiber size, fiber types, and gene expression profiles are regulated, in part, by the electrical activity exerted by the nervous system. To address whether similar adaptations to changes in electrical activity in skeletal muscle occur in teleosts, we studied these phenotypic properties of ventral muscle in the electric fish Sternopygus Macrurus following 2 and 5 days of electrical inactivation by spinal transection. Our data show that morphological and biochemical properties of skeletal muscle remained largely unchanged after these treatments. Specifically, the distribution of type I and type II muscle fibers and the cross-sectional areas of these fiber types observed in control fish remained unaltered after each spinal transection survival period. This response to electrical inactivation was generally reflected at the transcript level in real-time PCR and RNA-seq data by showing little effect on the transcript levels of genes associated with muscle fiber type differentiation and plasticity, the sarcomere complex, and pathways implicated in the regulation of muscle fiber size. Data from this first study characterizing the acute influence of neural activity on muscle mass and sarcomere gene expression in a teleost are discussed in the context of comparative studies in mammalian model systems and vertebrate species from different lineages.
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The myogenic electric organ of Sternopygus Macrurus: a non-contractile tissue with a skeletal muscle transcriptome.
PeerJ, 2016Co-Authors: Matthew Pinch, Robert Güth, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:In most electric fish species, the electric organ (EO) derives from striated muscle cells that suppress many muscle properties. In the gymnotiform Sternopygus Macrurus, mature electrocytes, the current-producing cells of the EO, do not contain sarcomeres, yet they continue to make some cytoskeletal and sarcomeric proteins and the muscle transcription factors (MTFs) that induce their expression. In order to more comprehensively examine the transcriptional regulation of genes associated with the formation and maintenance of the contractile sarcomere complex, results from expression analysis using qRT-PCR were informed by deep RNA sequencing of transcriptomes and miRNA compositions of muscle and EO tissues from adult S. Macrurus. Our data show that: (1) components associated with the homeostasis of the sarcomere and sarcomere-sarcolemma linkage were transcribed in EO at levels similar to those in muscle; (2) MTF families associated with activation of the skeletal muscle program were not differentially expressed between these tissues; and (3) a set of microRNAs that are implicated in regulation of the muscle phenotype are enriched in EO. These data support the development of a unique and highly specialized non-contractile electrogenic cell that emerges from a striated phenotype and further differentiates with little modification in its transcript composition. This comprehensive analysis of parallel mRNA and miRNA profiles is not only a foundation for functional studies aimed at identifying mechanisms underlying the transcription-independent myogenic program in S. Macrurus EO, but also has important implications to many vertebrate cell types that independently activate or suppress specific features of the skeletal muscle program.
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Sternopygus Macrurus electric organ transcriptome and cell size exhibit insensitivity to short-term electrical inactivity.
Journal of Physiology-Paris, 2016Co-Authors: Robert Güth, Matthew Pinch, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:Electrical activity is an important regulator of cellular function and gene expression in electrically excitable cell types. In the weakly electric teleost fish Sternopygus Macrurus, electrocytes, i.e., the current-producing cells of the electric organ, derive from a striated muscle lineage. Mature electrocytes are larger than muscle fibers, do not contain sarcomeres, and are driven continuously at frequencies higher than those exerted on muscle cells. Previous work showed that the removal of electrical activity by spinal cord transection (ST) for two and five weeks led to an upregulation of some sarcomeric proteins and a decrease in electrocyte size. To test whether changes in gene transcription preceded these phenotypic changes, we determined the sensitivity of electrocyte gene expression to electrical inactivity periods of two and five days after ST. Whole tissue gene expression profiles using deep RNA sequencing showed minimal alterations in the levels of myogenic transcription factor and sarcomeric transcripts after either ST period. Moreover, while analysis of differentially expressed genes showed a transient upregulation of genes associated with proteolytic mechanisms at two days and an increase in mRNA levels of cytoskeletal genes at five days after electrical silencing, electrocyte size was not affected. Electrical inactivity also resulted in the downregulation of genes that were classified into enriched clusters associated with functions of axon migration and synapse structure. Overall, these data demonstrate that unlike tissues in the myogenic lineage in other vertebrate species, regulation of gene transcription and cell size in the muscle-like electrocytes of S. Macrurus is highly insensitive to short-term electrical inactivity. Moreover, together with data obtained from control and long-term ST studies, the present data suggest that neural input might influence post-transcriptional processes to affect the mature electrocyte phenotype.
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Mechanisms of muscle gene regulation in the electric organ of Sternopygus Macrurus.
The Journal of experimental biology, 2013Co-Authors: Robert Güth, Matthew Pinch, Graciela A UnguezAbstract:Animals perform a remarkable diversity of movements through the coordinated mechanical contraction of skeletal muscle. This capacity for a wide range of movements is due to the presence of muscle cells with a very plastic phenotype that display many different biochemical, physiological and morphological properties. What factors influence the maintenance and plasticity of differentiated muscle fibers is a fundamental question in muscle biology. We have exploited the remarkable potential of skeletal muscle cells of the gymnotiform electric fish Sternopygus Macrurus to trans-differentiate into electrocytes, the non-contractile electrogenic cells of the electric organ (EO), to investigate the mechanisms that regulate the skeletal muscle phenotype. In S. Macrurus, mature electrocytes possess a phenotype that is intermediate between muscle and non-muscle cells. How some genes coding for muscle-specific proteins are downregulated while others are maintained, and novel genes are upregulated, is an intriguing problem in the control of skeletal muscle and EO phenotype. To date, the intracellular and extracellular factors that generate and maintain distinct patterns of gene expression in muscle and EO have not been defined. Expression studies in S. Macrurus have started to shed light on the role that transcriptional and post-transcriptional events play in regulating specific muscle protein systems and the muscle phenotype of the EO. In addition, these findings also represent an important step toward identifying mechanisms that affect the maintenance and plasticity of the muscle cell phenotype for the evolution of highly specialized non-contractile tissues.
Harold H Zakon - One of the best experts on this subject based on the ideXlab platform.
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Reexpression of Myogenic Proteins in Mature Electric Organ after Removal of Neural Input
The Journal of Neuroscience, 2018Co-Authors: Graciela A Unguez, Harold H ZakonAbstract:The electric organ (EO) of the weakly electric fish Sternopygus Macrurus derives from striated myofibers that fuse and suppress many muscle properties. Mature electrocytes are larger than muscle fibers, do not contain sarcomeres, or express myosin heavy chain (MHC) or tropomyosin. Furthermore, electrocytes express keratin, a protein not expressed in muscle. In S. Macrurus the EO is driven continuously at frequencies higher than those of the intermittently active skeletal muscle. The extent to which differences in EO and muscle phenotype are accounted for by activity patterns, or innervation per se, was determined by assessing the expression of MHC, tropomyosin, and keratin 2 and 5 weeks after the elimination of (1) activity patterns by spinal transection or (2) all synaptic input by denervation. Immunohistochemical analyses showed no changes in muscle fiber phenotypes after either experimental treatment. In contrast, the keratin-positive electrocytes revealed an upregulation of MHC and tropomyosin. Nearly one-third of all electrocytes expressed MHC (35%) and tropomyosin (25%) 2 weeks after spinal transection, whereas approximately two-thirds (61%) expressed MHC 2 weeks after denervation. After 5 weeks of denervation or spinal transection, all electrocytes contained MHC and tropomyosin. Newly formed sarcomere clusters also were observed in denervated electrocytes. The MHC expressed in electrocytes corresponded to that present in a select population of muscle fibers, i.e., type II fibers. Thus, the elimination of electrical activity or all synaptic input resulted in a partial reversal of the electrocyte phenotype to an earlier developmental stage of its myogenic lineage.
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South American Weakly Electric Fish (Gymnotiformes) Are Long-Wavelength-Sensitive Cone Monochromats.
Brain Behavior and Evolution, 2016Co-Authors: Da-wei Liu, Hong Yan, Harold H ZakonAbstract:Losses of cone opsin genes are noted in animals that are nocturnal or rely on senses other than vision. We investigated the cone opsin repertoire of night-active South American weakly electric fish. We obtained opsin gene sequences from genomic DNA of 3 gymnotiforms (Eigenmannia virescens, Sternopygus Macrurus, Apteronotus albifrons) and the assembled genome of the electric eel (Electrophorus electricus). We identified genes for long-wavelength-sensitive (LWS) and medium-wavelength-sensitive cone opsins (RH2) and rod opsins (RH1). Neither of the 2 short-wavelength-sensitive cone opsin genes were found and are presumed lost. The fact that Electrophorus has a complete repertoire of extraretinal opsin genes and conservation of synteny with the zebrafish (Danio rerio) for genes flanking the 2 short-wavelength-sensitive opsin genes supports the supposition of gene loss. With microspectrophotometry and electroretinograms we observed absorption spectra consistent with RH1 and LWS but not RH2 opsins in the retinal photoreceptors of E. virescens. This profile of opsin genes and their retinal expression is identical to the gymnotiform's sister group, the catfish, which are also nocturnally active and bear ampullary electroreceptors, suggesting that this pattern likely occurred in the common ancestor of gymnotiforms and catfish. Finally, we noted an unusual N-terminal motif lacking a conserved glycosylation consensus site in the RH2 opsin of gymnotiforms, a catfish and a characin (Astyanax mexicanus). Mutations at this site influence rhodopsin trafficking in mammalian photoreceptors and cause retinitis pigmentosa. We speculate that this unusual N terminus may be related to the absence of the RH2 opsin in the cones of gymnotiforms and catfish.
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Circadian and Social Cues Regulate Ion Channel Trafficking
PLoS biology, 2009Co-Authors: Michael R. Markham, M. Lynne Mcanelly, Philip K. Stoddard, Harold H ZakonAbstract:Electric fish generate and sense electric fields for navigation and communication. These signals can be energetically costly to produce and can attract electroreceptive predators. To minimize costs, some nocturnally active electric fish rapidly boost the power of their signals only at times of high social activity, either as night approaches or in response to social encounters. Here we show that the gymnotiform electric fish Sternopygus Macrurus rapidly boosts signal amplitude by 40% at night and during social encounters. S. Macrurus increases signal magnitude through the rapid and selective trafficking of voltage-gated sodium channels into the excitable membranes of its electrogenic cells, a process under the control of pituitary peptide hormones and intracellular second-messenger pathways. S. Macrurus thus maintains a circadian rhythm in signal amplitude and adapts within minutes to environmental events by increasing signal amplitude through the rapid trafficking of ion channels, a process that directly modifies an ongoing behavior in real time.
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individual variation and hormonal modulation of a sodium channel β subunit in the electric organ correlate with variation in a social signal
Developmental Neurobiology, 2007Co-Authors: He Liu, Harold H ZakonAbstract:The sodium channel beta1 subunit affects sodium channel gating and surface density, but little is known about the factors that regulate beta1 expression or its participation in the fine control of cellular excitability. In this study we examined whether graded expression of the beta1 subunit contributes to the gradient in sodium current inactivation, which is tightly controlled and directly related to a social behavior, the electric organ discharge (EOD), in a weakly electric fish Sternopygus Macrurus. We found the mRNA and protein levels of beta1 in the electric organ both correlate with EOD frequency. We identified a novel mRNA splice form of this gene and found the splicing preference for this novel splice form also correlates with EOD frequency. Androgen implants lowered EOD frequency and decreased the beta1 mRNA level but did not affect splicing. Coexpression of each splice form in Xenopus oocytes with either the human muscle sodium channel gene, hNav1.4, or a Sternopygus ortholog, smNav1.4b, sped the rate of inactivation of the sodium current and shifted the steady-state inactivation toward less negative membrane potentials. The translational product of the novel mRNA splice form lacks a previously identified important tyrosine residue but still functions normally. The properties of the fish alpha and coexpressed beta1 subunits in the oocyte replicate those of the electric organ's endogenous sodium current. These data highlight the role of ion channel beta subunits in regulating cellular excitability.
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Androgen modulates the kinetics of the delayed rectifying K+ current in the electric organ of a weakly electric fish.
Developmental neurobiology, 2007Co-Authors: M. Lynne Mcanelly, Harold H ZakonAbstract:Weakly electric fish such as Sternopygus Macrurus utilize a unique signal production system, the electric organ (EO), to navigate within their environment and to communicate with conspecifics. The electric organ discharge (EOD) generated by the Sternopygus electric organ is quasi-sinusoidal and sexually dimorphic; sexually mature males produce long duration EOD pulses at low frequencies, whereas mature females produce short duration EOD pulses at high frequencies. EOD frequency is set by a medullary pacemaker nucleus, while EOD pulse duration is determined by the kinetics of Na+ and K+ currents in the electric organ. The inactivation of the Na+ current and the activation of the delayed rectifying K+ current of the electric organ covary with EOD frequency such that the kinetics of both currents are faster in fish with high (female) EOD frequency than those with low (male) EOD frequencies. Dihydrotestosterone (DHT) implants masculinize the EOD centrally by decreasing frequency at the pacemaker nucleus (PMN). DHT also acts at the electric organ, broadening the EO pulse, which is at least partly due to a slowing of the inactivation kinetics of the Na+ current. Here, we show that chronic DHT treatment also slows the activation and deactivation kinetics of the electric organ's delayed rectifying K+ current. Thus, androgens coregulate the time-varying kinetics of two distinct ion currents in the EO to shape a sexually dimorphic communication signal. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Robert Güth - One of the best experts on this subject based on the ideXlab platform.
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Properties of skeletal muscle in the teleost Sternopygus Macrurus are unaffected by short-term electrical inactivity
Physiological genomics, 2016Co-Authors: Robert Güth, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:Skeletal muscle is distinguished from other tissues on the basis of its shape, biochemistry, and physiological function. Based on mammalian studies, fiber size, fiber types, and gene expression profiles are regulated, in part, by the electrical activity exerted by the nervous system. To address whether similar adaptations to changes in electrical activity in skeletal muscle occur in teleosts, we studied these phenotypic properties of ventral muscle in the electric fish Sternopygus Macrurus following 2 and 5 days of electrical inactivation by spinal transection. Our data show that morphological and biochemical properties of skeletal muscle remained largely unchanged after these treatments. Specifically, the distribution of type I and type II muscle fibers and the cross-sectional areas of these fiber types observed in control fish remained unaltered after each spinal transection survival period. This response to electrical inactivation was generally reflected at the transcript level in real-time PCR and RNA-seq data by showing little effect on the transcript levels of genes associated with muscle fiber type differentiation and plasticity, the sarcomere complex, and pathways implicated in the regulation of muscle fiber size. Data from this first study characterizing the acute influence of neural activity on muscle mass and sarcomere gene expression in a teleost are discussed in the context of comparative studies in mammalian model systems and vertebrate species from different lineages.
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The myogenic electric organ of Sternopygus Macrurus: a non-contractile tissue with a skeletal muscle transcriptome.
PeerJ, 2016Co-Authors: Matthew Pinch, Robert Güth, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:In most electric fish species, the electric organ (EO) derives from striated muscle cells that suppress many muscle properties. In the gymnotiform Sternopygus Macrurus, mature electrocytes, the current-producing cells of the EO, do not contain sarcomeres, yet they continue to make some cytoskeletal and sarcomeric proteins and the muscle transcription factors (MTFs) that induce their expression. In order to more comprehensively examine the transcriptional regulation of genes associated with the formation and maintenance of the contractile sarcomere complex, results from expression analysis using qRT-PCR were informed by deep RNA sequencing of transcriptomes and miRNA compositions of muscle and EO tissues from adult S. Macrurus. Our data show that: (1) components associated with the homeostasis of the sarcomere and sarcomere-sarcolemma linkage were transcribed in EO at levels similar to those in muscle; (2) MTF families associated with activation of the skeletal muscle program were not differentially expressed between these tissues; and (3) a set of microRNAs that are implicated in regulation of the muscle phenotype are enriched in EO. These data support the development of a unique and highly specialized non-contractile electrogenic cell that emerges from a striated phenotype and further differentiates with little modification in its transcript composition. This comprehensive analysis of parallel mRNA and miRNA profiles is not only a foundation for functional studies aimed at identifying mechanisms underlying the transcription-independent myogenic program in S. Macrurus EO, but also has important implications to many vertebrate cell types that independently activate or suppress specific features of the skeletal muscle program.
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Sternopygus Macrurus electric organ transcriptome and cell size exhibit insensitivity to short-term electrical inactivity.
Journal of Physiology-Paris, 2016Co-Authors: Robert Güth, Matthew Pinch, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:Electrical activity is an important regulator of cellular function and gene expression in electrically excitable cell types. In the weakly electric teleost fish Sternopygus Macrurus, electrocytes, i.e., the current-producing cells of the electric organ, derive from a striated muscle lineage. Mature electrocytes are larger than muscle fibers, do not contain sarcomeres, and are driven continuously at frequencies higher than those exerted on muscle cells. Previous work showed that the removal of electrical activity by spinal cord transection (ST) for two and five weeks led to an upregulation of some sarcomeric proteins and a decrease in electrocyte size. To test whether changes in gene transcription preceded these phenotypic changes, we determined the sensitivity of electrocyte gene expression to electrical inactivity periods of two and five days after ST. Whole tissue gene expression profiles using deep RNA sequencing showed minimal alterations in the levels of myogenic transcription factor and sarcomeric transcripts after either ST period. Moreover, while analysis of differentially expressed genes showed a transient upregulation of genes associated with proteolytic mechanisms at two days and an increase in mRNA levels of cytoskeletal genes at five days after electrical silencing, electrocyte size was not affected. Electrical inactivity also resulted in the downregulation of genes that were classified into enriched clusters associated with functions of axon migration and synapse structure. Overall, these data demonstrate that unlike tissues in the myogenic lineage in other vertebrate species, regulation of gene transcription and cell size in the muscle-like electrocytes of S. Macrurus is highly insensitive to short-term electrical inactivity. Moreover, together with data obtained from control and long-term ST studies, the present data suggest that neural input might influence post-transcriptional processes to affect the mature electrocyte phenotype.
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Mechanisms of muscle gene regulation in the electric organ of Sternopygus Macrurus.
The Journal of experimental biology, 2013Co-Authors: Robert Güth, Matthew Pinch, Graciela A UnguezAbstract:Animals perform a remarkable diversity of movements through the coordinated mechanical contraction of skeletal muscle. This capacity for a wide range of movements is due to the presence of muscle cells with a very plastic phenotype that display many different biochemical, physiological and morphological properties. What factors influence the maintenance and plasticity of differentiated muscle fibers is a fundamental question in muscle biology. We have exploited the remarkable potential of skeletal muscle cells of the gymnotiform electric fish Sternopygus Macrurus to trans-differentiate into electrocytes, the non-contractile electrogenic cells of the electric organ (EO), to investigate the mechanisms that regulate the skeletal muscle phenotype. In S. Macrurus, mature electrocytes possess a phenotype that is intermediate between muscle and non-muscle cells. How some genes coding for muscle-specific proteins are downregulated while others are maintained, and novel genes are upregulated, is an intriguing problem in the control of skeletal muscle and EO phenotype. To date, the intracellular and extracellular factors that generate and maintain distinct patterns of gene expression in muscle and EO have not been defined. Expression studies in S. Macrurus have started to shed light on the role that transcriptional and post-transcriptional events play in regulating specific muscle protein systems and the muscle phenotype of the EO. In addition, these findings also represent an important step toward identifying mechanisms that affect the maintenance and plasticity of the muscle cell phenotype for the evolution of highly specialized non-contractile tissues.
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Wireless sensing framework for long-term measurements of electric organ discharge
2013 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2013Co-Authors: Michael Harris, Robert Güth, Evan Salazar, Vishal Nawathe, Mahmoud Sharifi, Wei Tang, Satyajayant MisraAbstract:This paper describes a customizable/extensible wireless sensor framework for long term monitoring and visualization of the electric organ discharges (EOD) of a weakly electric fish (Sternopygus Macrurus). The system developed can be used to simultaneously visualize, in near-real time, the EOD signal of multiple fish residing in separate tanks. Furthermore, the sensing mechanisms used to detect EOD are non-invasive, minimizing side effects on the fishs' natural behavior. Commercial-off-the-shelf (COTS) components are used extensively in this framework to lower cost of the system and its future enhancements. COTS components can be easily customized to support different sensors or communication methods. Experimental results involving four fish show accurate measurement of the electric field waveforms and indicate the presence of circadian rhythms in the EOD of the fish.
S R Banever - One of the best experts on this subject based on the ideXlab platform.
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chirping response of weakly electric knife fish apteronotus leptorhynchus to low frequency electric signals and to heterospecific electric fish
The Journal of Experimental Biology, 2010Co-Authors: Kent D Dunlap, B T Dibenedictis, S R BaneverAbstract:SUMMARY Brown ghost knife fish (Apteronotus leptorhynchus) can briefly increase their electric organ discharge (EOD) frequency to produce electrocommunication signals termed chirps. The chirp rate increases when fish are presented with conspecific fish or high-frequency (700–1100 Hz) electric signals that mimic conspecific fish. We examined whether A. leptorhynchus also chirps in response to artificial low-frequency electric signals and to heterospecific electric fish whose EOD contains low-frequency components. Fish chirped at rates above background when presented with low-frequency (10–300 Hz) sine-wave stimuli; at 30 and 150 Hz, the threshold amplitude for response was 1 mV cm–1. Low-frequency (30 Hz) stimuli also potentiated the chirp response to high-frequency (∼900 Hz) stimuli. Fish increased their chirp rate when presented with two heterospecific electric fish, Sternopygus Macrurus and Brachyhypopomus gauderio, but did not respond to the presence of the non-electric fish Carassius auratus. Fish chirped to low-frequency (150 Hz) signals that mimic those of S. Macrurus and to EOD playbacks of B. gauderio. The response to the B. gauderio playback was reduced when the low-frequency component (
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Chirping response of weakly electric knife fish (Apteronotus leptorhynchus) to low-frequency electric signals and to heterospecific electric fish.
The Journal of experimental biology, 2010Co-Authors: Kent D Dunlap, B T Dibenedictis, S R BaneverAbstract:Brown ghost knife fish (Apteronotus leptorhynchus) can briefly increase their electric organ discharge (EOD) frequency to produce electrocommunication signals termed chirps. The chirp rate increases when fish are presented with conspecific fish or high-frequency (700-1100 Hz) electric signals that mimic conspecific fish. We examined whether A. leptorhynchus also chirps in response to artificial low-frequency electric signals and to heterospecific electric fish whose EOD contains low-frequency components. Fish chirped at rates above background when presented with low-frequency (10-300 Hz) sine-wave stimuli; at 30 and 150 Hz, the threshold amplitude for response was 1 mV cm(-1). Low-frequency (30 Hz) stimuli also potentiated the chirp response to high-frequency ( approximately 900 Hz) stimuli. Fish increased their chirp rate when presented with two heterospecific electric fish, Sternopygus Macrurus and Brachyhypopomus gauderio, but did not respond to the presence of the non-electric fish Carassius auratus. Fish chirped to low-frequency (150 Hz) signals that mimic those of S. Macrurus and to EOD playbacks of B. gauderio. The response to the B. gauderio playback was reduced when the low-frequency component (
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Chirping response of weakly electric knife fish (Apteronotus leptorhynchus) to low-frequency electric signals and to heterospecific electric fish.
The Journal of experimental biology, 2010Co-Authors: Kent D Dunlap, B T Dibenedictis, S R BaneverAbstract:Brown ghost knife fish (Apteronotus leptorhynchus) can briefly increase their electric organ discharge (EOD) frequency to produce electrocommunication signals termed chirps. The chirp rate increases when fish are presented with conspecific fish or high-frequency (700-1100 Hz) electric signals that mimic conspecific fish. We examined whether A. leptorhynchus also chirps in response to artificial low-frequency electric signals and to heterospecific electric fish whose EOD contains low-frequency components. Fish chirped at rates above background when presented with low-frequency (10-300 Hz) sine-wave stimuli; at 30 and 150 Hz, the threshold amplitude for response was 1 mV cm(-1). Low-frequency (30 Hz) stimuli also potentiated the chirp response to high-frequency ( approximately 900 Hz) stimuli. Fish increased their chirp rate when presented with two heterospecific electric fish, Sternopygus Macrurus and Brachyhypopomus gauderio, but did not respond to the presence of the non-electric fish Carassius auratus. Fish chirped to low-frequency (150 Hz) signals that mimic those of S. Macrurus and to EOD playbacks of B. gauderio. The response to the B. gauderio playback was reduced when the low-frequency component (
Matthew Pinch - One of the best experts on this subject based on the ideXlab platform.
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The myogenic electric organ of Sternopygus Macrurus: a non-contractile tissue with a skeletal muscle transcriptome.
PeerJ, 2016Co-Authors: Matthew Pinch, Robert Güth, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:In most electric fish species, the electric organ (EO) derives from striated muscle cells that suppress many muscle properties. In the gymnotiform Sternopygus Macrurus, mature electrocytes, the current-producing cells of the EO, do not contain sarcomeres, yet they continue to make some cytoskeletal and sarcomeric proteins and the muscle transcription factors (MTFs) that induce their expression. In order to more comprehensively examine the transcriptional regulation of genes associated with the formation and maintenance of the contractile sarcomere complex, results from expression analysis using qRT-PCR were informed by deep RNA sequencing of transcriptomes and miRNA compositions of muscle and EO tissues from adult S. Macrurus. Our data show that: (1) components associated with the homeostasis of the sarcomere and sarcomere-sarcolemma linkage were transcribed in EO at levels similar to those in muscle; (2) MTF families associated with activation of the skeletal muscle program were not differentially expressed between these tissues; and (3) a set of microRNAs that are implicated in regulation of the muscle phenotype are enriched in EO. These data support the development of a unique and highly specialized non-contractile electrogenic cell that emerges from a striated phenotype and further differentiates with little modification in its transcript composition. This comprehensive analysis of parallel mRNA and miRNA profiles is not only a foundation for functional studies aimed at identifying mechanisms underlying the transcription-independent myogenic program in S. Macrurus EO, but also has important implications to many vertebrate cell types that independently activate or suppress specific features of the skeletal muscle program.
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Sternopygus Macrurus electric organ transcriptome and cell size exhibit insensitivity to short-term electrical inactivity.
Journal of Physiology-Paris, 2016Co-Authors: Robert Güth, Matthew Pinch, Manoj P. Samanta, Alexander Chaidez, Graciela A UnguezAbstract:Electrical activity is an important regulator of cellular function and gene expression in electrically excitable cell types. In the weakly electric teleost fish Sternopygus Macrurus, electrocytes, i.e., the current-producing cells of the electric organ, derive from a striated muscle lineage. Mature electrocytes are larger than muscle fibers, do not contain sarcomeres, and are driven continuously at frequencies higher than those exerted on muscle cells. Previous work showed that the removal of electrical activity by spinal cord transection (ST) for two and five weeks led to an upregulation of some sarcomeric proteins and a decrease in electrocyte size. To test whether changes in gene transcription preceded these phenotypic changes, we determined the sensitivity of electrocyte gene expression to electrical inactivity periods of two and five days after ST. Whole tissue gene expression profiles using deep RNA sequencing showed minimal alterations in the levels of myogenic transcription factor and sarcomeric transcripts after either ST period. Moreover, while analysis of differentially expressed genes showed a transient upregulation of genes associated with proteolytic mechanisms at two days and an increase in mRNA levels of cytoskeletal genes at five days after electrical silencing, electrocyte size was not affected. Electrical inactivity also resulted in the downregulation of genes that were classified into enriched clusters associated with functions of axon migration and synapse structure. Overall, these data demonstrate that unlike tissues in the myogenic lineage in other vertebrate species, regulation of gene transcription and cell size in the muscle-like electrocytes of S. Macrurus is highly insensitive to short-term electrical inactivity. Moreover, together with data obtained from control and long-term ST studies, the present data suggest that neural input might influence post-transcriptional processes to affect the mature electrocyte phenotype.
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Mechanisms of muscle gene regulation in the electric organ of Sternopygus Macrurus.
The Journal of experimental biology, 2013Co-Authors: Robert Güth, Matthew Pinch, Graciela A UnguezAbstract:Animals perform a remarkable diversity of movements through the coordinated mechanical contraction of skeletal muscle. This capacity for a wide range of movements is due to the presence of muscle cells with a very plastic phenotype that display many different biochemical, physiological and morphological properties. What factors influence the maintenance and plasticity of differentiated muscle fibers is a fundamental question in muscle biology. We have exploited the remarkable potential of skeletal muscle cells of the gymnotiform electric fish Sternopygus Macrurus to trans-differentiate into electrocytes, the non-contractile electrogenic cells of the electric organ (EO), to investigate the mechanisms that regulate the skeletal muscle phenotype. In S. Macrurus, mature electrocytes possess a phenotype that is intermediate between muscle and non-muscle cells. How some genes coding for muscle-specific proteins are downregulated while others are maintained, and novel genes are upregulated, is an intriguing problem in the control of skeletal muscle and EO phenotype. To date, the intracellular and extracellular factors that generate and maintain distinct patterns of gene expression in muscle and EO have not been defined. Expression studies in S. Macrurus have started to shed light on the role that transcriptional and post-transcriptional events play in regulating specific muscle protein systems and the muscle phenotype of the EO. In addition, these findings also represent an important step toward identifying mechanisms that affect the maintenance and plasticity of the muscle cell phenotype for the evolution of highly specialized non-contractile tissues.