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First published online August 3, 2006
Journal of Experimental Biology 209, 3209-3218 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02365
Decreased expression of myogenic transcription factors and myosin heavy chains in Caenorhabditis elegans muscles developed during spaceflight
1 Japan Aerospace Exploration Agency, 2-1-1, Sengen, Tsukuba, Ibaraki
305-8505, Japan
2 Ames Research Center, National Aeronautics and Space Administration, M/S
239-11, Moffett Field, CA 94035-1000, USA
3 Advanced Engineering Services Co. Ltd., Tsukuba Mitsui Building, 1-6-1,
Takezono, Tsukuba, Ibaraki 305-0032, Japan
4 Graduate School of Life Sciences, Tohoku University, Sendai 980-8577,
Japan
* Author for correspondence (e-mail: higashibata.akira{at}jaxa.jp)
Accepted 5 June 2006
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Summary |
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Key words: spaceflight, muscle remodeling, Caenorhabditis elegans, myosin heavy chain, development
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Introduction |
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TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
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). When exposed to the microgravity of spaceflight,
muscles developed on Earth have been shown to display changes in morphology,
contractile function and myosin heavy chain (MHC) gene expression
(Caiozzo et al., 1994;
Caiozzo et al., 1996;
Criswell et al., 1996;
Day et al., 1995;
Edgerton et al., 1995;
Fitts et al., 2000;
Harrison et al., 2003).
Recently, it was shown that cultured embryonic avian muscle cells are directly
responsive to spaceflight, undergoing atrophy as the result of decreased
protein synthesis (Vandenburgh et al.,
1999). The observation that MHC levels were decreased postflight
relative to control cultures suggests that muscles developing in microgravity
express less MHC.
Cultured muscle cells lack innervation, which is required for proper muscle
development and to prevent muscle atrophy in vivo
(Szewczyk and Jacobson, 2005).
Therefore, studies of muscle development or atrophy in whole animals are
required to confirm results obtained with cultured cells. Muscles of the
nematode Caenorhabditis elegans have been studied extensively, and
show significant similarity to vertebrate muscles. The principal muscles in
C. elegans are the body wall and pharyngeal muscles
(Epstein et al., 1974). Body
wall muscle is analogous to vertebrate skeletal muscle and functions to allow
locomotion. In body wall muscle, myogenesis appears to be controlled by the
helix-loop-helix transcription factor HLH-1
(Chen et al., 1994;
Krause, 1995), which controls
the expression of two MHC isoforms [MHC A and B encoded by myo-3 and
unc-54, respectively (Dibb et
al., 1985; Epstein et al.,
1974; Karn et al.,
1983; MacLeod et al.,
1981; Miller et al.,
1986)]. The pharyngeal muscles function rhythmically in feeding
and possibly pseudocoelomic circulation. They are analogous to vertebrate
cardiac muscle, and contain two MHC isoforms [MHC C and D, encoded by
myo-2 and myo-1, respectively
(Ardizzi and Epstein, 1987;
Miller et al., 1986)]. In
developing pharyngeal muscle, these MHCs appear to be regulated by the
cooperative action of transcription factors PEB-1, PHA-4 and CEH-22
(Gaudet and Mango, 2002;
Kalb et al., 2002;
Okkema and Fire, 1994;
Okkema et al., 1997). The
transcriptional regulation of C. elegans myosin genes is in many
respects similar to that of vertebrates. However, both body wall and
pharyngeal muscle also contain the invertebrate paramyosin core protein
encoded by unc-15 (Epstein et
al., 1985; Kagawa et al.,
1989). The extensive similarities to mammalian muscle have allowed
C. elegans to be developed as a small animal model for studies of a
number of types of muscle atrophy, including muscular dystrophy
(Grisoni et al., 2002),
starvation (Zdinak et al.,
1997), denervation (Szewczyk
et al., 2000), growth factor alterations
(Szewczyk and Jacobson, 2003),
aging (Fisher, 2004) and
altered function of myosin chaperones
(Hoppe et al., 2004). C.
elegans has also been developed as a model for studies of spaceflight
effects on physiology (Hartman et al.,
2001; Nelson et al.,
1994a; Nelson et al.,
1994b). In this study, we therefore employed space flown C.
elegans to confirm and extend the findings made with cultured embryonic
avian muscle cells.
In this report we demonstrate that muscles of C. elegans that developed in space, during the European Space Agency (ESA) DELTA mission, display decreased expression of the transcription factors controlling both body wall and pharyngeal muscle myogenesis as well as decreased expression of muscle-specific MHCs. These results demonstrate that the changes previously observed in cultured embryonic avian muscle cell development in space also occur in vivo in the nematode C. elegans. Our results suggest that altered MHC expression is a highly conserved molecular response to spaceflight and can be studied in small genetic model organisms. Furthermore, decreased protein synthesis in developing muscle implies that, in space, a reduction in muscle repair and remodeling may underlie at least a portion of spaceflight-induced muscle atrophy.
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Materials and methods |
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TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
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)] for 1
month at 20°C. Approximately 10 000 worms of mixed larval stage were
transferred into 2.5 ml culture bags containing fresh CeMM. A total of 40 ml
of culture bags were enclosed in a vented EC-1 (the Biorack Experiment
Container type 1, developed by Professor Eberhard Horn from Ulm, Germany),
which allows air exchange between the environment and the experimental culture
bags. EC-1s were placed inside KUBIK, a modular incubator developed by the
European Space Agency (ESA) for spaceflight experiments that can ensure a
temperature rise from 6°C to 37°C by 1°C increments
(http://www.esa.int/esaHS/SEMS9D638FE_iss_0.html).
Nematodes in EC-1 containers were cultured in KUBIK at 12°C for 5 days and
then at 12°C for the 2 days immediately preceding launch in the Soyuz
spacecraft. After launch, the worms were kept at 20°C in KUBIK
accommodated in the Soyuz spacecraft until the spacecraft had docked with the
International Space Station (ISS). The flight worms were cultured in KUBIK at
20°C for 10 days, and after landing they were immediately frozen in liquid
nitrogen. A full description of the ICE-FIRST experimental design and hardware
has been submitted for publication elsewhere.
Extraction of total RNA
After thawing the samples, worms were washed twice with M9 buffer
(Sulston and Hodgkin, 1988) to
remove CeMM. The worms were repeatedly frozen and thawed five times. Total RNA
from the space flown and ground control worms was extracted using an Isogen
RNA purification kit (Wako Pure Chemicals, Osaka, Japan) following the
manufacturer's protocol. The concentration and purity of extracted RNA were
determined using an Agilent 2100 Bioanalyzer (Agilent Technologies, Palo Alto,
CA, USA). The gene expression profile was analyzed using the Affymetrix
GeneChip C. elegans Genome Array (22,150 gene species, 22,500 element
array) (Affymetrix, Santa Clara, CA, USA) performed by the Dragon Genomics
Center (TaKaRa Bio Inc., Shiga, Japan).
Real-time quantitative PCR
To measure the expression differences of muscle-related genes between
ground control worms and space-flown worms, real-time PCR was performed. The
preparation of cDNA was carried out using ExScript RT reagent kit (TaKaRa Bio)
and iCycler thermal cycler (Bio-Rad Laboratories, Inc., Hercules, CA, USA).
Subsequently the preparation of the reaction mixture for measuring the cDNA
quantity was performed using Premix EX Taq (TaKaRa Bio) according to the
manufacturer's instructions. Reaction and fluorescence monitoring were done
using a Smart Cycler real-time PCR system with Smart Cycler software version
2.0C (Cepheid, Sunnyvale, CA, USA). The following primer pairs were used for
PCR amplification: gpd-2 (5'-ACCGGAGTCTTCACCACCATC-3' and
5'-ACGACTACGAGGTTACAAGCA-3'), act-3
(5'-ACGAACATTGGAGCATCAGCA-3' and
5'-TCAATTGGGTACTTGAGGGTAAGG-3'), hlh-1
(5'-GAGCACACCAAATGCCACAGA-3' and
5'-CTCCGCCAGCAGTAGACGTT-3'), myo-3
(5'-AAAGGTCAAGCCAATGCTCAA-3' and
5'-TCTTCAACCAAATCGGCAAC-3'), unc-54
(5'-CCCGACTTGAGGACGAACA-3' and
5'-AGCCTTGGAACGGGATTGAC-3'), peb-1
(5'-TGCGATTAGCGTGAGCAGTATG-3' and
5'-TGTCTGGATTGTATCGGACAAATGA-3'), pha-4
(5'-ATCTTGGCCTAATTGACCCATC-3' and
5'-TCATCTGTGCTTGCGTGGTT-3'), myo-1
(5'-GGTCCGTCAAGAACAAGAGCA-3' and
5'-ATCATGGCACGTTCAGCATC-3'), myo-2
(5'-CAAGCAACGTCCACGTGAAGA-3' and
5'-CTCCGAGTCAATTCCGAAGCA-3') and unc-15
(5'-CGCCGATCTTGGATCACTCA-3' and
5'-GGCACGCTCACGTTCAACTC-3'). Each amplification was performed in
triplicate. Values were statistically analyzed using PRISM software (GraphPad
software Inc., San Diego, CA, USA). Significance was accepted at
P<0.05.
Western blotting
To determine the steady-state levels of myosin proteins, western blots were
performed in triplicate. Total protein was extracted using two-dimensional
(2D) extraction solution [7 mol l-1 urea (Wako Pure Chemicals,
Osaka, Japan), 2 mol l-1 thiourea (Wako), 4% (w/v) CHAPS (Dojin,
Osaka, Japan), 0.5% (v/v) carrier ampholyte (Bio-Rad), 40 mmol l-1
dithiothreitol (Nacalai Tesque, Kyoto, Japan)]. Total protein concentration
was determined by using a 2D Quant Kit (Amersham Biosciences, Piscataway, NJ,
USA). 110 µg of total protein was collected from approximately 40 000 worms
of each ground control and space flown sample. The sample solution was
prepared to contain 0.2 µg µl-1 total protein. An equal
volume of 2x Laemmli sample buffer was added to the sample solution. The
samples were boiled for 5 min and sonicated for 1 min. Samples containing 2
µg of protein per lane were electrophoresed on an SDS-polyacrylamide gel
(5-10%, Bio-Rad) and blotted onto a Hybond-P membrane (Amersham) at 15 V for
60 min. The membrane was washed with blocking solution [5% (w/v) non-fat dried
milk, 0.05% (w/v) Tween 20, 100 mmol l-1 Tris-HCl (pH 7.5), and 500
mmol l-1 NaCl]. MHC B and C were detected using an anti-MHC B and C
mouse monoclonal antibody (5-12; 1:1,000 dilution), and paramyosin was
detected using an anti-paramyosin rabbit polyclonal antibody (1:10 000
dilution). Both antibodies were kindly provided by Dr Kagawa. Anti-GAPDH
antibody (1:1 000 dilution) (Imgenex, San Diego, CA, USA) was used to detect
GAPDH as an internal standard. Anti-mouse IgG horseradish
peroxidase-conjugated mouse anti-goat IgG (Pierce, Rockford, IL, USA) and
anti-rabbit IgG horseradish peroxidase linked whole antibody from donkey
(Amersham) were used as the secondary antibodies. Each secondary antibody was
used at a 1:10 000 dilution. After treatment using and ECL Plus
chemiluminescence detection kit (Amersham), immunoreactive proteins were
detected using a VersaDoc chemiluminesence detection system (Bio-Rad). Values
were statistically analyzed using PRISM software (GraphPad). Significance was
accepted at P<0.05.
Movement assay
Live animals were video recorded at the landing site within 2 h of return
utilizing a ProScope [Bodelin Technologies, Lake Oswego, OR, USA
(http://www.theproscope.com)].
Animals were placed in a temperature controlled chamber at 20°C and
allowed to equilibrate before videos were recorded. Bright-field illumination
was achieved using a battery powered LED housed inside a 60 mm Petri dish.
Samples were placed upon this Petri dish and recorded on a battery powered PC
using the ProScope at high magnification (approximately 40x total
magnification). Proper focal depth was achieved utilizing a custom plastic
housing designed by Dr Conley for the ProScope, with oblique incident
illumination. Videos were used to determine movement rates using the
previously described swim test (Szewczyk
et al., 2002). Ten randomly selected animals from each condition
were evaluated, and the movement rate of each animal was measured 10 times.
Sample videos can be found at
http://weboflife.nasa.gov/celegans/questionsice.htm.
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Results |
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Some muscle related genes show decreased expression after spaceflight by microarray analysis
DNA microarray analyses of muscle-related genes were performed using the
Affymetrix GeneChip C. elegans Genome Array.
Fig. 1 shows the full genome
scatter plot of gene expression, comparing the flight worms and the ground
controls. Colored symbols (triangles, open and closed squares) are genes
involved in muscle development. Muscle-related genes that showed lower
expression flags in flight worms rather than in ground control worms are
indicated by closed square symbols. This group includes important genes
involved in muscle development such as MHCs, troponins, tropomyosins.
Muscle-related genes for which there was no difference in expression between
control and flight worms are showed by open square symbols. Closed triangles
indicate the genes of transcription factors involved in expression of MHCs.
The expression change in muscle-related genes, as indicated by DNA microarray,
are summarized in Table 2A. The
expression levels of myo-1, -2, -3 and unc-54 genes that
encode myosin heavy chains (MHC D, C, A and B, respectively) and
unc-15 that encodes paramyosin, were all decreased in the space flown
worms. Expression of the transcription factors controlling the expression of
these genes was likewise decreased. Transcription of myo-3 and
unc-54 in the body wall muscle is regulated by CeMyoD
(HLH-1/hlh-1), which showed a modest decrease. Transcription of
myo-1 and -2 in pharyngeal muscle is controlled by
ceh-22, peb-1 and pha-4, which decreased significantly in
space flown worms (Table 2B).
Statistically significant reductions in transcript levels of genes essential
to muscle structure were not limited to the MHCs
(Table 2A). The genes encoding
troponins and tropomyosins were also significantly decreased, specifically,
tnc-2 (troponin C), tnt-2, -3, -4 (troponin T) and
lev-11 (tropomyosin).
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Real-time quantitative PCR confirms that myosin-related genes show decreased transcript levels after spaceflight
DNA microarrays are a semi-quantitative and an imprecise tool for examining
expression differences. To confirm and evaluate more quantitatively the
expression differences predicted by the DNA microarrays, real-time
quantitative PCR was performed. The gene encoding one of three predicted
glyceraldehyde-3-phosphate dehydrogenases, gpd-2, is expressed in
muscle and is considered a `housekeeping gene' that should be expressed at a
steady level under most conditions, including spaceflight. We used
gpd-2 as an internal standard against which to normalize these
quantitative PCR data. The body wall muscle-specific myo-3 and
unc-54 were decreased 73.3% and 22.6%, respectively, in the space
flown worms (Fig. 2). The
myogenic transcription factor hlh-1 was also decreased compared with
that of ground control worms. The expression levels of pharyngeal
muscle-specific myo-2 and myo-1 were decreased, 49.0% and
10.8%, respectively. The transcription factors controlling expression of these
MHC genes, pha-4 and peb-1, also decreased in the space
flown worms (51.8% and 16.7%, respectively). These results qualitatively
validate and confirm the observations made using the DNA microarray analysis,
and give a quantitative evaluation of the extent of decreased mRNA
expression.
MHC and paramyosin protein levels are reduced after spaceflight as measured by western blot
To establish whether the observed changes in mRNA level are reflected in
the steady-state levels of myosin-associated proteins, we quantified the
amount of MHC B, C and paramyosin by 2D (not shown) and triplicate western
blot analysis using GAPDH as an internal standard (see Materials and methods).
GAPDH is the protein product of gpd-2, which was used as an internal
standard for the real-time PCR. The density of the MHC and paramyosin bands
decreased 10% in the space-flown worms relative to the control worms, but
GAPDH levels were not significantly altered
(Fig. 3). These results both
confirm the observations made by DNA microarray and real-time PCR analyses,
and document that those changes are in fact reflected at the protein
level.
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Space flown C. elegans display reduced movement after landing
The observed decreases in MHC expression might be predicted to produce
defects in muscle contractility. To evaluate whether the returned animals
displayed any defects in movement, we examined the video footage recorded
immediately after landing. Ten animals randomly selected from one sample moved
with a velocity of 90±9 waves min-1 [mean ± standard
deviation for 100 observations (10 animals each observed 10 times)]. Ten
animals randomly selected from the matched ground controls had a velocity of
112±8 waves min-1; not significantly different than animals
under standard culture conditions (120±10 waves min-1).
These results demonstrate that space flown C. elegans displayed a
small but significant movement defect.
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Discussion |
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TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
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;
Epstein et al., 1974;
MacLeod et al., 1981;
Miller et al., 1986;
Waterston et al., 1977). MHC B
localizes in the terminal portion of thick filaments
(Miller, 3rd et al., 1983;
Miller et al., 1986), and is
the major MHC isoform as measured by molar proportion
(Honda and Epstein, 1990). MHC
C and D, encoded by myo-2 and myo-1 respectively, localize
to pharyngeal muscle and are required for eating
(Ardizzi and Epstein, 1987;
Miller et al., 1986). Despite
the differences in tissue expression and function, the results from DNA
microarray, quantitative PCR, and western blot analyses all indicate that
expression of MHC genes is decreased in response spaceflight. As expected for
methodological reasons (microarrays are subject to more quantitative
variability), the DNA microarray and quantitative real-time PCR results agree
qualitatively but not quantitatively. These data suggest that MHC gene
expression is influenced by microgravity at the level of transcription. Given
the different cellular locations and functions of these four MHCs, our results
suggest that MHC gene expression is influenced by microgravity independent
from MHC localization or function.
In vertebrates, MyoD, a basic helix-loop-helix protein (bHLH), has been
identified as a myogenic factor playing a critical role in the determination
and differentiation of skeletal muscle
(Davis et al., 1987). This
transcription factor has been proposed as a putative target for degradation in
response to intramuscular atrophy inducing signaling events on Earth
(Szewczyk and Jacobson, 2005).
C. elegans has a body wall muscle-specific transcription factor,
CeMyoD, that is also a helix-loop-helix type transcription factor
(Chen et al., 1994;
Krause, 1995). Pharyngeal
muscle-specific transcription factors are peb-1, pha-4 and
ceh-22 (Gaudet and Mango,
2002; Kalb et al.,
2002; Okkema and Fire,
1994; Okkema et al.,
1997). Transcripts encoding all of these transcription factors
were significantly decreased in the space flown worms, consistent with our
hypothesis that microgravity is influencing MHC protein expression at the
level of transcription. Based upon decreased mRNA levels, the regulation of
these transcription factors also appears to be at the level of transcription,
even more so given that mRNA may be more, not less, stable in response to
spaceflight. Elucidating the mechanism for microgravity depression of myogenic
transcription factors is an important area for future research.
In our DNA microarray, two ubiquitin ligases show increased level of
expression. Each of these skr genes is predicted to encode a homolog
of Skp1 in S. cerevisiae, a core component of the SCF
(Skp1/Cullin1/F-box) ubiquitin-ligase complex that facilitates
ubiquitin-mediated protein degradation
(Nayak et al., 2002).
Currently, the function of skr-6 and skr-18 remain to be
established in vivo. Skp1-containing complexes can bind
muscle-specific F-box proteins, for example atrogin-1, and induce muscle
atrophy in vertebrates (Bodine et al.,
2001; Gomes et al.,
2001). In denervated muscle of rats, mRNA levels of MHC I were
decreased whereas mRNA level of atrogin-1 was significantly increased,
although a causal relation of these altered levels of expression was not
examined (Horinouchi et al.,
2005). It may be of interest to determine if skr-6 or
skr-18, for which RNAi results in altered movement
(Simmer et al., 2003),
contributes to muscle atrophy in C. elegans.
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A functional consequence of decreased body-wall MHC or myogenic
transcription factor gene expression, as determined by RNAi experiments, is
decreased locomotion (Simmer et al.,
2003). Therefore, our observation of decreased MHC levels is
sufficient to explain the observed decreased locomotion, at the population
level. However, alternative explanations such as decreased arginine kinase
expression (the nematode orthologue of creatine kinase) or increased
degradation facilitated by skr-6 or skr-18, could also
explain our observations. Data obtained at the level individual worms will be
required to ask and answer questions regarding the specific nature of the
relationship between MHC levels and decreased locomotion. Although future
studies during spaceflight are required to answer such questions, our results
suggest that small genetic model organisms, such as C. elegans, can
be employed usefully in such studies.
Decreased contractile demand may not underlie the observed decrease in MHC expression
Past studies in vertebrates have shown shifts in MHC isoform-based fiber
types in response to spaceflight (Kischel
et al., 2001; Widrick et al.,
1999). Here we report that spaceflight also influences MHC
expression in developing C. elegans nematodes. As in vertebrates,
C. elegans MHCs are essential and major molecules of sarcomeric thick
filaments (Epstein et al.,
1974). The observation that in C. elegans, as in
vertebrates, MHC expression is altered in response to spaceflight suggests
that the mechanisms monitoring MHC expression requirements are highly
conserved.
Reduced workload is believed to be a primary cause of atrophy associated
with spaceflight (di Prampero and Narici,
2003), and has resulted in many physiologists renaming postural
muscles `antigravity' muscles. However, two observations suggest there was not
a decreased contractile demand in C. elegans muscles during
development. First, there is a strong contractile demand place upon body wall
muscle in order to molt and complete development successfully
(Frand et al., 2005). Second,
pharyngeal muscle contraction, like cardiac muscle contraction, is rhythmic
and required throughout life. Defects in pharyngeal contraction disrupt
developmental timing (Lakowski and Hekimi,
1998). Because developmental timing was unaffected in response to
spaceflight (N.J.S. and C.A.C., unpublished observations) it seems unlikely
that there was a large decrease in contractile activity in either body wall or
pharyngeal muscle. At present, our results with C. elegans lacking
`antigravity' muscle suggest that reduced contractile activity, per
se, is not the only underlying cause of spaceflight-induced muscle
alterations. Furthermore, the observation that atrophy in response to
spaceflight is not limited to `antigravity' skeletal muscle, but also occurs
in vascular smooth muscle and cardiac muscle
(Goldstein et al., 1998;
Zhang et al., 2001), suggests
that such non contractile activity-based mechanisms for muscle alteration may
be highly conserved.
Altered muscle development in flight may contribute to spaceflight induced muscle atrophy
Muscle atrophy in response to space flight can become a serious medical
condition, for which the development of countermeasures is essential. Current
countermeasures (e.g. exercise) are known to be relatively ineffective
(Adams et al., 2003). It may be
that we have simply not yet developed the optimal exercise regimen to combat
spaceflight-induced muscle atrophy. However, there is growing evidence that
decreased use may not be the only cause of muscle atrophy in response to
spaceflight. For example, past observations show that vascular and cardiac
muscles also undergo atrophy (Zhang et
al., 2001) and that cultured embryonic muscle is intrinsically
sensitive to the effects of spaceflight
(Vandenburgh et al., 1999).
Here, we have shown that C. elegans muscles are also intrinsically
sensitive to the effects of spaceflight, specifically, that developing
nematode muscles decrease myogenic transcription factor and MHC expression
during spaceflight. Our observations appear to complement the past
observations of decreased MHC expression seen in developing chick muscle cells
(Vandenburgh et al., 1999) and
decreased MyoD expression seen in developing rat muscles
(Inobe et al., 2002). These
results suggest not only that decreased MHC expression observed in vertebrate
muscles during spaceflight may be due to decreased levels of myogenic
transcription factors, but also that muscle metabolism in flight (e.g. normal
fiber turnover, repair) will produce `atrophic' muscle as the result of
decreased levels of myogenic transcription factors. The recent observation in
rats that genes involved in regulation of muscle satellite cell reproduction
are downregulated during spaceflight
(Taylor et al., 2002) is
consistent with this hypothesis. Although future studies to confirm this
hypothesis are required, these transcription factors are likely to represent
targets for countermeasure development. Such small-molecule countermeasures
may also become more broadly useful in the treatment of muscle atrophy induced
by bedrest, aging and a number of clinical conditions.
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Acknowledgments |
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Footnotes |
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Present address: University of Pittsburgh, Department of Biological
Sciences, A234 Langley Hall, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA 
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References |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Adams, G. R., Caiozzo, V. J. and Baldwin, K. M.
(2003). Skeletal muscle unweighting: spaceflight and ground-based
models. J. Appl. Physiol.
95,2185
-2201.
Ardizzi, J. P. and Epstein, H. F. (1987).
Immunochemical localization of myosin heavy chain isoforms and paramyosin in
developmentally and structurally diverse muscle cell types of the nematode
Caenorhabditis elegans. J. Cell Biol.
105,2763
-2770.
Bodine, S. C., Latres, E., Baumhueter, S., Lai, V. K., Nunez,
L., Clarke, B. A., Poueymirou, W. T., Panaro, F. J., Na, E., Dharmarajan, K.
et al. (2001). Identification of ubiquitin ligases required
for skeletal muscle atrophy. Science
294,1704
-1708.
Caiozzo, V. J., Baker, M. J., Herrick, R. E., Tao, M. and
Baldwin, K. M. (1994). Effect of spaceflight on skeletal
muscle: mechanical properties and myosin isoform content of a slow muscle.
J. Appl. Physiol. 76,1764
-1773.
Caiozzo, V. J., Haddad, F., Baker, M. J., Herrick, R. E.,
Prietto, N. and Baldwin, K. M. (1996). Microgravity-induced
transformations of myosin isoforms and contractile properties of skeletal
muscle. J. Appl. Physiol.
81,123
-132.
Chen, L., Krause, M., Sepanski, M. and Fire, A. (1994). The Caenorhabditis elegans MYOD homologue HLH-1 is essential for proper muscle function and complete morphogenesis. Development 120,1631 -1641.[Abstract]
Criswell, D. S., Carson, J. A. and Booth, F. W. (1996). Regulation of contractile protein gene expression in unloaded mouse skeletal muscle. J. Gravit. Physiol. 3, 58-60.[Medline]
Davis, R. L., Weintraub, H. and Lassar, A. B. (1987). Expression of a single transfected cDNA converts fibroblasts to myoblasts. Cell 51,987 -1000.[CrossRef][Medline]
Day, M. K., Allen, D. L., Mohajerani, L., Greenisen, M. C., Roy, R. R. and Edgerton, V. R. (1995). Adaptations of human skeletal muscle fibers to spaceflight. J. Gravit. Physiol. 2,P47 -P50.[Medline]
di Prampero, P. E. and Narici, M. V. (2003). Muscles in microgravity: from fibres to human motion. J. Biomech. 36,403 -412.[CrossRef][Medline]
Dibb, N. J., Brown, D. M., Karn, J., Moerman, D. G., Bolten, S. L. and Waterston, R. H. (1985). Sequence analysis of mutations that affect the synthesis, assembly and enzymatic activity of the unc-54 myosin heavy chain of Caenorhabditis elegans. J. Mol. Biol. 183,543 -551.[CrossRef][Medline]
Edgerton, V. R., Zhou, M. Y., Ohira, Y., Klitgaard, H., Jiang,
B., Bell, G., Harris, B., Saltin, B., Gollnick, P. D., Roy, R. R. et al.
(1995). Human fiber size and enzymatic properties after 5 and 11
days of spaceflight. J. Appl. Physiol.
78,1733
-1739.
Epstein, H. F., Waterston, R. H. and Brenner, S. (1974). A mutant affecting the heavy chain of myosin in Caenorhabditis elegans. J. Mol. Biol. 90,291 -300.[CrossRef][Medline]
Epstein, H. F., Miller, D. M., 3rd, Ortiz, I. and Berliner, G.
C. (1985). Myosin and paramyosin are organized about a newly
identified core structure. J. Cell Biol.
100,904
-915.
Fisher, A. L. (2004). Of worms and women: sarcopenia and its role in disability and mortality. J. Am. Geriatr. Soc. 52,1185 -1190.[CrossRef][Medline]
Fitts, R. H., Desplanches, D., Romatowski, J. G. and Widrick, J. J. (2000). Spaceflight effects on single skeletal muscle fiber function in the rhesus monkey. Am. J. Physiol. 279,R1546 -R1557.
Fitts, R. H., Riley, D. R. and Widrick, J. J. (2001). Functional and structural adaptations of skeletal muscle to microgravity. J. Exp. Biol. 204,3201 -3208.[Medline]
Frand, A. R., Russel, S. and Ruvkun, G. (2005). Functional genomic analysis of C. elegans molting. PLoS Biol. 3,e312 .[CrossRef][Medline]
Gaudet, J. and Mango, S. E. (2002). Regulation
of organogenesis by the Caenorhabditis elegans FoxA protein PHA-4.
Science 295,821
-825.
Goldstein, M. A., Cheng, J. and Schroeter, J. P. (1998). The effects of increased gravity and microgravity on cardiac morphology. Aviat. Space Environ. Med. 69,A12 -A16.[Medline]
Gomes, M. D., Lecker, S. H., Jagoe, R. T., Navon, A. and
Goldberg, A. L. (2001). Atrogin-1, a muscle-specific F-box
protein highly expressed during muscle atrophy. Proc. Natl. Acad.
Sci. USA 98,14440
-14445.
Grisoni, K., Martin, E., Gieseler, K., Mariol, M. C. and Segalat, L. (2002). Genetic evidence for a dystrophin-glycoprotein complex (DGC) in Caenorhabditis elegans.Gene 294,77 -86.[CrossRef][Medline]
Harrison, B. C., Allen, D. L., Girten, B., Stodieck, L. S.,
Kostenuik, P. J., Bateman, T. A., Morony, S., Lacey, D. and Leinwand, L.
A. (2003). Skeletal muscle adaptations to microgravity
exposure in the mouse. J. Appl. Physiol.
95,2462
-2470.
Hartman, P. S., Hlavacek, A., Wilde, H., Lewicki, D., Schubert, W., Kern, R. G., Kazarians, G. A., Benton, E. V., Benton, E. R. and Nelson, G. A. (2001). A comparison of mutations induced by accelerated iron particles versus those induced by low earth orbit space radiation in the FEM-3 gene of Caenorhabditis elegans. Mutat. Res. 474, 47-55.[Medline]
Honda, S. and Epstein, H. F. (1990). Modulation
of muscle gene expression in Caenorhabditis elegans: differential
levels of transcripts, mRNAs, and polypeptides for thick filament proteins
during nematode development. Proc. Natl. Acad. Sci.
USA 87,876
-880.
Hoppe, T., Cassata, G., Barral, J. M., Springer, W., Hutagalung, A. H., Epstein, H. F. and Baumeister, R. (2004). Regulation of the myosin-directed chaperone UNC-45 by a novel E3/E4-multiubiquitylation complex in C. elegans. Cell 118,337 -349.[CrossRef][Medline]
Horinouchi, H., Kumamoto, T., Kimura, N., Ueyama, H. and Tsuda, T. (2005). Myosin loss in denervated rat soleus muscle after dexamethasone treatment. Pathobiology 72,108 -116.[CrossRef][Medline]
Inobe, M., Inobe, I., Adams, G. R., Baldwin, K. M. and Takeda,
S. (2002). Effects of microgravity on myogenic factor
expressions during postnatal development of rat skeletal muscle. J.
Appl. Physiol. 92,1936
-1942.
Kagawa, H., Gengyo, K., McLachlan, A. D., Brenner, S. and Karn, J. (1989). Paramyosin gene (unc-15) of Caenorhabditis elegans. Molecular cloning, nucleotide sequence and models for thick filament structure. J. Mol. Biol. 207,311 -333.[CrossRef][Medline]
Kalb, J. M., Beaster-Jones, L., Fernandez, A. P., Okkema, P. G., Goszczynski, B. and McGhee, J. D. (2002). Interference between the PHA-4 and PEB-1 transcription factors in formation of the Caenorhabditis elegans pharynx. J. Mol. Biol. 320,697 -704.[CrossRef][Medline]
Karn, J., Brenner, S. and Barnett, L. (1983).
Protein structural domains in the Caenorhabditis elegans unc-54
myosin heavy chain gene are not separated by introns. Proc. Natl.
Acad. Sci. USA 80,4253
-4257.
Kischel, P., Stevens, L., Montel, V., Picquet, F. and Mounier,
Y. (2001). Plasticity of monkey triceps muscle fibers in
microgravity conditions. J. Appl. Physiol.
90,1825
-1832.
Krause, M. (1995). MyoD and myogenesis in C. elegans. BioEssays 17,219 -228.[CrossRef][Medline]
Lakowski, B. and Hekimi, S. (1998). The
genetics of caloric restriction in Caenorhabditis elegans. Proc.
Natl. Acad. Sci. USA 95,13091
-13096.
MacLeod, A. R., Karn, J. and Brenner, S. (1981). Molecular analysis of the unc-54 myosin heavy-chain gene of Caenorhabditis elegans. Nature 291,386 -390.[CrossRef][Medline]
Miller, D. M., 3rd, Ortiz, I., Berliner, G. C. and Epstein, H. F. (1983). Differential localization of two myosins within nematode thick filaments. Cell 34,477 -490.[CrossRef][Medline]
Miller, D. M., Stockdale, F. E. and Karn, J.
(1986). Immunological identification of the genes encoding the
four myosin heavy chain isoforms of Caenorhabditis elegans. Proc.
Natl. Acad. Sci. USA 83,2305
-2309.
Nayak, S., Santiago, F. E., Jin, H., Lin, D., Schedl, T. and Kipreos, E. T. (2002). The Caenorhabditis elegans Skp1-related gene family: diverse functions in cell proliferation, morphogenesis, and meiosis. Curr. Biol. 12,277 -287.[CrossRef][Medline]
Nelson, G. A., Schubert, W. W., Kazarians, G. A. and Richards, G. F. (1994a). Development and chromosome mechanics in nematodes: results from IML-1. Adv. Space Res. 14,209 -214.[CrossRef][Medline]
Nelson, G. A., Schubert, W. W., Kazarians, G. A., Richards, G. F., Benton, E. V., Benton, E. R. and Henke, R. (1994b). Radiation effects in nematodes: results from IML-1 experiments. Adv. Space Res. 14,87 -91.[Medline]
Okkema, P. G. and Fire, A. (1994). The Caenorhabditis elegans NK-2 class homeoprotein CEH-22 is involved in combinatorial activation of gene expression in pharyngeal muscle. Development 120,2175 -2186.[Abstract]
Okkema, P. G., Ha, E., Haun, C., Chen, W. and Fire, A. (1997). The Caenorhabditis elegans NK-2 homeobox gene ceh-22 activates pharyngeal muscle gene expression in combination with pha-1 and is required for normal pharyngeal development. Development 124,3965 -3973.[Abstract]
Simmer, F., Moorman, C., van der Linden, A. M., Kuijk, E., van den Berghe, P. V., Kamath, R. S., Fraser, A. G., Ahringer, J. and Plasterk, R. H. (2003). Genome-wide RNAi of C. elegans using the hypersensitive rrf-3 strain reveals novel gene functions. PLoS Biol. 1,E12 .[Medline]
Sulston, J. and Hodgkin, J. (1988). Method. In The Nematode Caenorhabditis elegans (ed. W. B. Wood), p. 589. New York: Cold Spring Harbor Laboratory Press.
Szewczyk, N. J. and Jacobson, L. A. (2003). Activated EGL-15 FGF receptor promotes protein degradation in muscles of Caenorhabditis elegans. EMBO J. 22,5058 -5067.[CrossRef][Medline]
Szewczyk, N. J. and Jacobson, L. A. (2005). Signal-transduction networks and the regulation of muscle protein degradation. Int. J. Biochem. Cell Biol. 37,1997 -2011.[CrossRef][Medline]
Szewczyk, N. J., Hartman, J. J., Barmada, S. J. and Jacobson, L. A. (2000). Genetic defects in acetylcholine signalling promote protein degradation in muscle cells of Caenorhabditis elegans.J. Cell Sci. 113,2003 -2010.[Abstract]
Szewczyk, N. J., Peterson, B. K. and Jacobson, L. A.
(2002). Activation of Ras and the MAP kinase pathway promotes
protein degradation in muscle cells of Caenorhabditis elegans. Mol.
Cell. Biol. 22,4181
-4188.
Szewczyk, N. J., Kozak, E. and Conley, C. A. (2003). Chemically defined medium and Caenorhabditis elegans.BMC Biotechnol. 3,19 .[CrossRef][Medline]
Taylor, W. E., Bhasin, S., Lalani, R., Datta, A. and Gonzalez-Cadavid, N. F. (2002). Alteration of gene expression profiles in skeletal muscle of rats exposed to microgravity during a spaceflight. J. Gravit. Physiol. 9, 61-70.[Medline]
Vandenburgh, H., Chromiak, J., Shansky, J., Del Tatto, M. and
Lemaire, J. (1999). Space travel directly induces skeletal
muscle atrophy. FASEB J.
13,1031
-1038.
Waterston, R. H., Fishpool, R. M. and Brenner, S. (1977). Mutants affecting paramyosin in Caenorhabditis elegans. J. Mol. Biol. 117,679 -697.[CrossRef][Medline]
Widrick, J. J., Knuth, S. T., Norenberg, K. M., Romatowski, J. G., Bain, J. L., Riley, D. A., Karhanek, M., Trappe, S. W., Trappe, T. A., Costill, D. L. et al. (1999). Effect of a17 day spaceflight on contractile properties of human soleus muscle fibres. J. Physiol. 516, 915-930.
Zdinak, L. A., Greenberg, I. B., Szewczyk, N. J., Barmada, S. J., Cardamone Rayner, M., Hartman, J. J. and Jacobson, L. A. (1997). Transgene-coded chimeric proteins as reporters of intracellular proteolysis: starvation-induced catabolism of a lacZ fusion protein in muscle cells of Caenorhabditis elegans. J. Cell Biochem. 67,143 -153.[CrossRef][Medline]
Zhang, L. F., Yu, Z. B., Ma, J. and Mao, Q. W. (2001). Peripheral effector mechanism hypothesis of postflight cardiovascular dysfunction. Aviat. Space Environ. Med. 72,567 -575.[Medline]
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