SV40 microRNA miR-S1-3p Downregulates the Expression of T Antigens to Control Viral DNA Replication, and TNFα and IL-17F Expression.

SV40-encoded microRNA (miRNA), miR-S1, downregulates the large and small T antigens (LTag and STag), which promote viral replication and cellular transformation, thereby presumably impairing LTag and STag functions essential for the viral life cycle. To explore the functional significance of miR-S1-mediated downregulation of LTag and STag as well as the functional roles of miR-S1, we evaluated viral DNA replication and proinflammatory cytokine induction in cells transfected with simian virus 40 (SV40) genome plasmid and its mutated form lacking miR-S1 expression. The SV40 genome encodes two mature miR-S1s, miR-S1-3p and miR-S1-5p, of which miR-S1-3p is the predominantly expressed form. MiR-S1-3p exerted strong repressive effects on a reporter containing full-length sequence complementarity, but only marginal effect on one harboring a sequence complementary to its seed sequence. Consistently, miR-S1-3p downregulated LTag and STag transcripts with complete sequence complementarity through miR-S1-3p-Ago2-mediated mRNA decay. Transfection of SV40 plasmid induced higher DNA replication and lower LTag and STag transcripts in most of the examined cells compared to that miR-S1-deficient SV40 plasmid. However, miR-S1 itself did not affect DNA replication without the downregulation of LTag transcripts. Both LTag and STag induced the expression of tumor necrosis factor α (TNFα) and interleukin (IL)-17F, which was slightly reduced by miR-S1 due to miR-S1-mediated downregulation of LTag and STag. Forced miR-S1 expression did not affect TNFα expression, but increased IL-17F expression. Overall, our findings suggest that miR-S1-3p is a latent modifier of LTag and STag functions, ensuring efficient viral replication and attenuating cytokine expression detrimental to the viral life cycle.

Distal regulatory element of the STAT1 gene potentially mediates positive feedback control of STAT1 expression.

We previously identified a distal regulatory element located approximately 5.5-kb upstream of the signal transducer and activator of transcription 1 (STAT1) gene, thereafter designating it as 5.5-kb upstream regulatory region (5.5URR). In this study, we investigated the functional roles of 5.5URR in the transcriptional regulation of STAT1 gene. A chromosome conformation capture assay indicated physical interaction of 5.5URR with the STAT1 core promoter. In luciferase reporter assays, 5.5URR-combined STAT1 core promoter exhibited significant increase in reporter activity enhanced by forced STAT1 expression or interferon (IFN) treatment, but STAT1 core promoter alone did not. The 5.5URR contained IFN-stimulated response element and GAS sites, which bound STAT1 complexes in electrophoretic mobility shift assays. Consistently, chromatin immunoprecipitation (ChIP) assays of HEK293 cells with Halo-tagged STAT1 expression indicated the association of Halo-tagged STAT1 with 5.5URR. ChIP assays with IFN treatment demonstrated that IFNs promoted the recruitment of Halo-tagged STAT1 to 5.5URR. Forced STAT1 expression or IFN treatment increased the expression of endogenous STAT1 and other IFN signaling pathway components, such as STAT2, IRF9 and IRF1, besides IFN-responsive genes. Collectively, the results suggest that 5.5URR may provide a regulatory platform for positive feedback control of STAT1 expression possibly to amplify or sustain the intracellular IFN signals.

JAZF1 promotes proliferation of C2C12 cells, but retards their myogenic differentiation through transcriptional repression of MEF2C and MRF4-Implications for the role of Jazf1 variants in oncogenesis and type 2 diabetes.

Single-nucleotide polymorphisms associated with type 2 diabetes (T2D) have been identified in Jazf1, which is also involved in the oncogenesis of endometrial stromal tumors. To understand how Jazf1 variants confer a risk of tumorigenesis and T2D, we explored the functional roles of JAZF1 and searched for JAZF1 target genes in myogenic C2C12 cells. Consistent with an increase of Jazf1 transcripts during myoblast proliferation and their decrease during myogenic differentiation in regenerating skeletal muscle, JAZF1 overexpression promoted cell proliferation, whereas it retarded myogenic differentiation. Examination of myogenic genes revealed that JAZF1 overexpression transcriptionally repressed MEF2C and MRF4 and their downstream genes. AMP deaminase1 (AMPD1) was identified as a candidate for JAZF1 target by gene array analysis. However, promoter assays of Ampd1 demonstrated that mutation of the putative binding site for the TR4/JAZF1 complex did not alleviate the repressive effects of JAZF1 on promoter activity. Instead, JAZF1-mediated repression of Ampd1 occurred through the MEF2-binding site and E-box within the Ampd1 proximal regulatory elements. Consistently, MEF2C and MRF4 expression enhanced Ampd1 promoter activity. AMPD1 overexpression and JAZF1 downregulation impaired AMPK phosphorylation, while JAZF1 overexpression also reduced it. Collectively, these results suggest that aberrant JAZF1 expression contributes to the oncogenesis and T2D pathogenesis.

MicroRNA-1 targets Slug and endows lung cancer A549 cells with epithelial and anti-tumorigenic properties.

MicroRNA-1 (miR-1) has recently been suggested to function as a tumor suppressor. Its functional relevance was assessed by exploring structural and tumorigenic properties of lung cancer A549 cells stably transduced with retrovirus containing pre-miR-1. A549 cells overexpressing miR-1 exhibited a significant morphological change from a mesenchymal to an epithelial phenotype characterized by cell polarization and intercellular junctions. The cells showed increased expression of E-cadherin, which colocalized with cortical actin filaments and vinculin to form typical adherens junction at the apical regions of intercellular borders. Additionally, they exhibited occludin-positive tight junctions at similar apical regions. Moreover, their migratory and invasive activities were inhibited, and their sensitivity to doxorubicin was increased slightly compared to control mock-infected cells. These structural and tumorigenic properties induced by miR-1 were associated with the reduced expression of Slug, which was a transcriptional repressor of E-cadherin or an inducer of epithelial-to-mesenchymal transition. Consistently, Slug was identified as a miR-1 target by bioinformatics and a luciferase reporter assay with plasmids containing luciferase-Slug 3'UTR. Collectively, the data presented here suggest that re-expression of miR-1 may be an effective therapy that prevents cancer malignancy by converting cells from a mesenchymal phenotype to an epithelial phenotype via the downregulation of Slug.

Transduction efficiency and immune response associated with the administration of AAV8 vector into dog skeletal muscle.

Recombinant adeno-associated virus (rAAV)-mediated gene transfer is an attractive approach to the treatment of Duchenne muscular dystrophy (DMD). We investigated the muscle transduction profiles and immune responses associated with the administration of rAAV2 and rAAV8 in normal and canine X-linked muscular dystrophy in Japan (CXMD(J)) dogs. rAAV2 or rAAV8 encoding the lacZ gene was injected into the skeletal muscles of normal dogs. Two weeks after the injection, we detected a larger number of beta-galactosidase-positive fibers in rAAV8-transduced canine skeletal muscle than in rAAV2-transduced muscle. Although immunohistochemical analysis using anti-CD4 and anti-CD8 antibodies revealed less T-cell response to rAAV8 than to rAAV2, beta-galactosidase expression in rAAV8-injected muscle lasted for <4 weeks with intramuscular transduction. Canine bone marrow-derived dendritic cells (DCs) were activated by both rAAV2 and rAAV8, implying that innate immunity might be involved in both cases. Intravenous administration of rAAV8-lacZ into the hind limb in normal dogs and rAAV8-microdystrophin into the hind limb in CXMD(J) dogs resulted in improved transgene expression in the skeletal muscles lasting over a period of 8 weeks, but with a declining trend. The limb perfusion transduction protocol with adequate immune modulation would further enhance the rAAV8-mediated transduction strategy and lead to therapeutic benefits in DMD gene therapy.

Selective vacuolar degeneration in dystrophin-deficient canine Purkinje fibers despite preservation of dystrophin-associated proteins with overexpression of Dp71.

BACKGROUND: Respiratory support therapy significantly improves life span in patients with Duchenne muscular dystrophy; cardiac-related fatalities, including lethal arrhythmias, then become a crucial issue. It is therefore important to more thoroughly understand cardiac involvement, especially pathology of the conduction system, in the larger Duchenne muscular dystrophy animal models such as dystrophic dogs. METHODS AND RESULTS: When 10 dogs with canine X-linked muscular dystrophy in Japan (CXMD(J)) were examined at the age of 1 to 13 months, dystrophic changes of the ventricular myocardium were not evident; however, Purkinje fibers showed remarkable vacuolar degeneration as early as 4 months of age. The degeneration of CXMD(J) Purkinje fibers was coincident with overexpression of Dp71 at the sarcolemma and translocation of mu-calpain to the cell periphery near the sarcolemma or in the vacuoles. Immunoblotting of the microdissected fraction showed that mu-calpain-sensitive proteins such as desmin and cardiac troponin-I or -T were selectively degraded in the CXMD(J) Purkinje fibers. Utrophin was highly upregulated in the earlier stage of CXMD(J) Purkinje fibers, but the expression was dislocated when vacuolar degeneration was recognized at 4 months of age. Nevertheless, the expression of dystrophin-associated proteins alpha-, beta-, gamma-, and delta-sarcoglycans and beta-dystroglycan was well maintained at the sarcolemma of Purkinje fibers. CONCLUSIONS: Selective vacuolar degeneration of Purkinje fibers was found in the early stages of dystrophin deficiency. Dislocation of utrophin besides upregulation of Dp71 can be involved with this pathology. The degeneration of Purkinje fibers can be associated with the distinct deep Q waves in ECG and fatal arrhythmia seen in dystrophin deficiency.

Alpha1-syntrophin-deficient skeletal muscle exhibits hypertrophy and aberrant formation of neuromuscular junctions during regeneration.

Alpha1-syntrophin is a member of the family of dystrophin-associated proteins; it has been shown to recruit neuronal nitric oxide synthase and the water channel aquaporin-4 to the sarcolemma by its PSD-95/SAP-90, Discs-large, ZO-1 homologous domain. To examine the role of alpha1-syntrophin in muscle regeneration, we injected cardiotoxin into the tibialis anterior muscles of alpha1-syntrophin-null (alpha1syn-/-) mice. After the treatment, alpha1syn-/- muscles displayed remarkable hypertrophy and extensive fiber splitting compared with wild-type regenerating muscles, although the untreated muscles of the mutant mice showed no gross histological change. In the hypertrophied muscles of the mutant mice, the level of insulin-like growth factor-1 transcripts was highly elevated. Interestingly, in an early stage of the regeneration process, alpha1syn-/- mice showed remarkably deranged neuromuscular junctions (NMJs), accompanied by impaired ability to exercise. The contractile forces were reduced in alpha1syn-/- regenerating muscles. Our results suggest that the lack of alpha1-syntrophin might be responsible in part for the muscle hypertrophy, abnormal synapse formation at NMJs, and reduced force generation during regeneration of dystrophin-deficient muscle, all of which are typically observed in the early stages of Duchenne muscular dystrophy patients.

MicroRNA-206 is highly expressed in newly formed muscle fibers: implications regarding potential for muscle regeneration and maturation in muscular dystrophy.

miR-1, miR-133a, and miR-206 are muscle-specific microRNAs expressed in skeletal muscles and have been shown to contribute to muscle development. To gain insight into the pathophysiological roles of these three microRNAs in dystrophin-deficient muscular dystrophy, their expression in the tibialis anterior (TA) muscles of mdx mice and CXMD(J) dogs were evaluated by semiquantitative RT-PCR and in situ hybridization. Their temporal and spatial expression patterns were also analyzed in C2C12 cells during muscle differentiation and in cardiotoxin (CTX)-injured TA muscles to examine how muscle degeneration and regeneration affect their expression. In dystrophic TA muscles of mdx mice, miR-206 expression was significantly elevated as compared to that in control TA muscles of age-matched B10 mice, whereas there were no differences in miR-1 or miR-133a expression between B10 and mdx TA muscles. On in situ hybridization analysis, intense signals for miR-206 probes were localized in newly formed myotubes with centralized nuclei, or regenerating muscle fibers, but not in intact pre-degenerated fibers or numerous small mononucleated cells, possibly proliferating myoblasts and inflammatory infiltrates. Similar increased expression of miR-206 was also found in C2C12 differentiation and CTX-induced regeneration, in which differentiated myotubes or regenerating fibers showed abundant expression of miR-206. However, CXMD(J) TA muscles contained smaller amounts of miR-206, miR-1, and miR-133a than controls. They exhibited more severe and more progressive degenerative alterations than mdx TA muscles. Taken together, these observations indicated that newly formed myotubes showed markedly increased expression of miR-206, which might reflect active regeneration and efficient maturation of skeletal muscle fibers.

Dystrophin deficiency in canine X-linked muscular dystrophy in Japan (CXMDJ) alters myosin heavy chain expression profiles in the diaphragm more markedly than in the tibialis cranialis muscle.

BACKGROUND: Skeletal muscles are composed of heterogeneous collections of muscle fiber types, the arrangement of which contributes to a variety of functional capabilities in many muscle types. Furthermore, skeletal muscles can adapt individual myofibers under various circumstances, such as disease and exercise, by changing fiber types. This study was performed to examine the influence of dystrophin deficiency on fiber type composition of skeletal muscles in canine X-linked muscular dystrophy in Japan (CXMDJ), a large animal model for Duchenne muscular dystrophy. METHODS: We used tibialis cranialis (TC) muscles and diaphragms of normal dogs and those with CXMDJ at various ages from 1 month to 3 years old. For classification of fiber types, muscle sections were immunostained with antibodies against fast, slow, or developmental myosin heavy chain (MHC), and the number and size of these fibers were analyzed. In addition, MHC isoforms were detected by gel electrophoresis. RESULTS: In comparison with TC muscles of CXMDJ, the number of fibers expressing slow MHC increased markedly and the number of fibers expressing fast MHC decreased with growth in the affected diaphragm. In populations of muscle fibers expressing fast and/or slow MHC(s) but not developmental MHC of CXMDJ muscles, slow MHC fibers were predominant in number and showed selective enlargement. Especially, in CXMDJ diaphragms, the proportions of slow MHC fibers were significantly larger in populations of myofibers with non-expression of developmental MHC. Analyses of MHC isoforms also indicated a marked increase of type I and decrease of type IIA isoforms in the affected diaphragm at ages over 6 months. In addition, expression of developmental (embryonic and/or neonatal) MHC decreased in the CXMDJ diaphragm in adults, in contrast to continuous high-level expression in affected TC muscle. CONCLUSION: The CXMDJ diaphragm showed marked changes in fiber type composition unlike TC muscles, suggesting that the affected diaphragm may be effectively adapted toward dystrophic stress by switching to predominantly slow fibers. Furthermore, the MHC expression profile in the CXMDJ diaphragm was markedly different from that in mdx mice, indicating that the dystrophic dog is a more appropriate model than a murine one, to investigate the mechanisms of respiratory failure in DMD.

Activation and localization of matrix metalloproteinase-2 and -9 in the skeletal muscle of the muscular dystrophy dog (CXMDJ).

BACKGROUND: Matrix metalloproteinases (MMPs) are key regulatory molecules in the formation, remodeling and degradation of all extracellular matrix (ECM) components in both physiological and pathological processes in various tissues. The aim of this study was to examine the involvement of gelatinase MMP family members, MMP-2 and MMP-9, in dystrophin-deficient skeletal muscle. Towards this aim, we made use of the canine X-linked muscular dystrophy in Japan (CXMDJ) model, a suitable animal model for Duchenne muscular dystrophy. METHODS: We used surgically biopsied tibialis cranialis muscles of normal male dogs (n = 3) and CXMDJ dogs (n = 3) at 4, 5 and 6 months of age. Muscle sections were analyzed by conventional morphological methods and in situ zymography to identify the localization of MMP-2 and MMP-9. MMP-2 and MMP-9 activity was examined by gelatin zymography and the levels of the respective mRNAs in addition to those of regulatory molecules, including MT1-MMP, TIMP-1, TIMP-2, and RECK, were analyzed by semi-quantitative RT-PCR. RESULTS: In CXMDJ skeletal muscle, multiple foci of both degenerating and regenerating muscle fibers were associated with gelatinolytic MMP activity derived from MMP-2 and/or MMP-9. In CXMDJ muscle, MMP-9 immunoreactivity localized to degenerated fibers with inflammatory cells. Weak and disconnected immunoreactivity of basal lamina components was seen in MMP-9-immunoreactive necrotic fibers of CXMDJ muscle. Gelatinolytic MMP activity observed in the endomysium of groups of regenerating fibers in CXMDJ did not co-localize with MMP-9 immunoreactivity, suggesting that it was due to the presence of MMP-2. We observed increased activities of pro MMP-2, MMP-2 and pro MMP-9, and levels of the mRNAs encoding MMP-2, MMP-9 and the regulatory molecules, MT1-MMP, TIMP-1, TIMP-2, and RECK in the skeletal muscle of CXMDJ dogs compared to the levels observed in normal controls. CONCLUSION: MMP-2 and MMP-9 are likely involved in the pathology of dystrophin-deficient skeletal muscle. MMP-9 may be involved predominantly in the inflammatory process during muscle degeneration. In contrast, MMP-2, which was activated in the endomysium of groups of regenerating fibers, may be associated with ECM remodeling during muscle regeneration and fiber growth.

Cardiac involvement in Beagle-based canine X-linked muscular dystrophy in Japan (CXMDJ): electrocardiographic, echocardiographic, and morphologic studies.

BACKGROUND: Cardiac mortality in Duchenne muscular dystrophy (DMD) has recently become important, because risk of respiratory failure has been reduced due to widespread use of the respirator. The cardiac involvement is characterized by distinctive electrocardiographic abnormalities or dilated cardiomyopathy, but the pathogenesis has remained obscure. In research on DMD, Golden retriever-based muscular dystrophy (GRMD) has attracted much attention as an animal model because it resembles DMD, but GRMD is very difficult to maintain because of their severe phenotypes. We therefore established a line of dogs with Beagle-based canine X-linked muscular dystrophy in Japan (CXMDJ) and examined the cardiac involvement. METHODS: The cardiac phenotypes of eight CXMDJ and four normal male dogs 2 to 21 months of age were evaluated using electrocardiography, echocardiography, and histopathological examinations. RESULTS: Increases in the heart rate and decreases in PQ interval compared to a normal littermate were detected in two littermate CXMDJ dogs at 15 months of age or older. Distinct deep Q-waves and increase in Q/R ratios in leads II, III, and aVF were detected by 6-7 months of age in all CXMDJ dogs. In the echocardiogram, one of eight of CXMDJ dogs showed a hyperechoic lesion in the left ventricular posterior wall at 5 months of age, but the rest had not by 6-7 months of age. The left ventricular function in the echocardiogram indicated no abnormality in all CXMDJ dogs by 6-7 months of age. Histopathology revealed myocardial fibrosis, especially in the left ventricular posterobasal wall, in three of eight CXMDJ dogs by 21 months of age. CONCLUSION: Cardiac involvement in CXMDJ dogs is milder and has slower progression than that described in GRMD dogs. The distinct deep Q-waves have been ascribed to myocardial fibrosis in the posterobasal region of the left ventricle, but our data showed that they precede the lesion on echocardiogram and histopathology. These findings imply that studies of CXMDJ may reveal not only another causative mechanism of the deep Q-waves but also more information on the pathogenesis in the dystrophin-deficient heart.

Major clinical and histopathological characteristics of canine X-linked muscular dystrophy in Japan, CXMDJ.

Canine X-linked muscular dystrophy (CXMD), which was found in a colony of golden retriever, is caused by a mutation in the dystrophin gene and it is a useful model of Duchenne muscular dystrophy (DMD). To investigate the pathogenesis and to develop therapy of DMD, we have established a beagle-based CXMD colony in Japan (CXMDJ) and examined their phenotypes. The mortality by 3 days of age in the third generation (G3) of CXMDJ dogs, 32.3%, was considerably higher than that in normal G3 littermates, 13.3%. Serum creatine kinase (CK) levels of G3 CXMDJ were significantly higher than that of normal male dogs with two peaks: at shortly after birth and around 2 months of age. Diaphragm muscle involvement occurred shortly after birth and was more severe than that of limb muscles. Stress during whelping might be associated with the neonatal death and respiratory muscle involvement. Gait disturbance was also noticed after 2 months of age. The involvement of limb and temporal muscles was observed from 2 months of age, which corresponded with the second peak of serum CK. Macroglossia, dysphagia, drooling and jaw joint contracture were overt from 4 months of age. We noticed severe macroglossia and hypertrophy of the sublingual muscles at the age of 12 months, and these were important features of this model, because dysphagia is one of major symptoms in older DMD patients. Overall, the phenotypes of CXMDJ were roughly identical to those of CXMD dogs in the literature. Beagle-based CXMDJ is smaller and easier to handle than golden retriever, therefore they are a useful model for DMD.

Interleukin 6 induces overexpression of the sarcolemmal utrophin in neonatal mdx skeletal muscle.

Duchenne muscular dystrophy (DMD) is an X-linked lethal disorder caused by a defect in the DMD gene, which encodes the cytoskeletal protein dystrophin. Utrophin is an autosomal homolog of the DMD gene product dystrophin, and augmented expression of endogenous utrophin is expected to provide an alternative therapeutic approach to DMD. We previously reported that an immune response against a beta-galactosidase-expressing adenovirus vector, AxCALacZ, resulted in an accumulation of endogenous utrophin on the extrasynaptic sarcolemma in dystrophin-deficient mdx mice. To determine which cytokine is involved in the regulation of utrophin expression, we directly injected several cytokines separately into neonatal mdx muscles and tested whether the expression of utrophin is increased on the sarcolemma. Importantly, among the cytokines tested, solely interleukin 6 (IL-6) successfully increased expression of utrophin. Moreover, the increase in utrophin mRNA was detected in recombinant IL-6-injected mdx muscles by quantitative real-time reverse transcriptase-polymerase chain reaction. Further, IL-6 expression was elevated in AxCALacZ-infected mdx muscle at an early stage, and anti-IL-6 receptor (IL-6R) antibody treatment blocked enhanced utrophin expression in AxCALacZ-infected mdx muscle. We should point out, however, that overexpression of utrophin due to recombinant IL-6 treatment lasted only 1 week. In addition, expression of utrophin was not evident in normal C57BL/10 neonatal muscles injected with IL-6. Taken together, these results suggest that IL-6 can induce overexpression of utrophin on the extrasynaptic sarcolemma but requires preexisting factors in neonatal mdx muscle to fully regulate utrophin expression.

Development of a safe oral Abeta vaccine using recombinant adeno-associated virus vector for Alzheimer's disease.

A new oral vaccine for Alzheimer's disease was developed using recombinant adeno-associated virus vector carrying Abeta cDNA (AAV/Abeta). Oral administration of the vaccine without adjuvant induced the expression and secretion of Abeta1-43 or Abeta1-21 in the epithelial cell layer of the intestine in amyloid precursor protein transgenic mice. Serum antibody levels were elevated for more than six months, while T cell proliferative responses to Abeta was not detected. Brain Abeta burden was significantly decreased compared to the control without inflammatory changes. This oral AAV/Abeta vaccine seems to be promising for prevention and treatment of Alzheimer's disease.

Canine X-linked muscular dystrophy in Japan (CXMDJ).

The purpose of this study was to develop a strain of canine X-linked muscular dystrophy (CXMD), a model of Duchenne muscular dystrophy, in Japan. A female beagle was artificially inseminated with frozen-thawed spermatozoa derived from an affected golden retriever. Subsequently, two carrier female dogs (G1 carriers) and four normal male littermates were produced. Thereafter, the two G1 carriers were mated with beagle sires. As a result, each bitch whelped three times, and out of 54 pups, 17 affected male descendants, and 11 carrier female descendants (G2 carriers) were detected. One G2 carrier was then mated with a beagle sire and 15 pups in two whelpings were produced, including five affected males and four carrier females (G3 carriers). A total of 10 female beagles were artificially inseminated to evaluate the fertility of the frozen-thawed spermatozoa from the two affected dogs. The whelping rates of the two affected dogs were 4/5 and the litter sizes were 5.0 +/- 1.41 and 6.0 +/- 0.82, respectively. These results indicate that a canine X-linked muscular dystrophy colony has been established in Japan. We called them CXMDJ.

Initial pulmonary respiration causes massive diaphragm damage and hyper-CKemia in Duchenne muscular dystrophy dog.

The molecular mechanism of muscle degeneration in a lethal muscle disorder Duchene muscular dystrophy (DMD) has not been fully elucidated. The dystrophic dog, a model of DMD, shows a high mortality rate with a marked increase in serum creatine kinase (CK) levels in the neonatal period. By measuring serum CK levels in cord and venous blood, we found initial pulmonary respiration resulted in massive diaphragm damage in the neonates and thereby lead to the high serum CK levels. Furthermore, molecular biological techniques revealed that osteopontin was prominently upregulated in the dystrophic diaphragm prior to the respiration, and that immediate-early genes (c-fos and egr-1) and inflammation/immune response genes (IL-6, IL-8, COX-2, and selectin E) were distinctly overexpressed after the damage by the respiration. Hence, we segregated dystrophic phases at the molecular level before and after mechanical damage. These molecules could be biomarkers of muscle damage and potential targets in pharmaceutical therapies.

A conserved regulatory element located far downstream of the gls locus modulates gls expression through chromatin loop formation during myogenesis.

Chromatin loops formed between distant regulatory elements and promoters modulate gene expression. We identified a novel distant regulatory element located approximately 120kb downstream of the gls promoter, and examined its regulatory relevance to gls gene expression in C2C12 cells by a chromosome conformation capture assay. The distant element physically interacted with the gls promoter in myoblasts but not in myotubes. Semiquantitative analysis by real-time PCR showed more abundant gls transcripts in myoblasts than in myotubes. These findings suggest that this distant element differentially regulates gls gene expression through dynamic formation and abrogation of a chromatin loop during myogenesis.

Plectin 1 links intermediate filaments to costameric sarcolemma through beta-synemin, alpha-dystrobrevin and actin.

In skeletal muscles, the sarcolemma is possibly stabilized and protected against contraction-imposed stress by intermediate filaments (IFs) tethered to costameric sarcolemma. Although there is emerging evidence that plectin links IFs to costameres through dystrophin-glycoprotein complexes (DGC), the molecular organization from plectin to costameres still remains unclear. Here, we show that plectin 1, a plectin isoform expressed in skeletal muscle, can interact with beta-synemin, actin and a DGC component, alpha-dystrobrevin, in vitro. Ultrastructurally, beta-synemin molecules appear to be incorporated into costameric dense plaques, where they seem to serve as actin-associated proteins rather than IF proteins. In fact, they can bind actin and alpha-dystrobrevin in vitro. Moreover, in vivo immunoprecipitation analyses demonstrated that beta-synemin- and plectin-immune complexes from lysates of muscle light microsomes contained alpha-dystrobrevin, dystrophin, nonmuscle actin, metavinculin, plectin and beta-synemin. These findings suggest a model in which plectin 1 interacts with DGC and integrin complexes directly, or indirectly through nonmuscle actin and beta-synemin within costameres. The DGC and integrin complexes would cooperate to stabilize and fortify the sarcolemma by linking the basement membrane to IFs through plectin 1, beta-synemin and actin. Besides, the two complexes, together with plectin and IFs, might have their own functions as platforms for distinct signal transduction.

AAV vector-mediated microdystrophin expression in a relatively small percentage of mdx myofibers improved the mdx phenotype.

Duchenne muscular dystrophy (DMD) is a lethal disorder of skeletal muscle caused by mutations in the dystrophin gene. Adeno-associated virus (AAV) vector-mediated gene therapy is a promising approach to the disease. Although a rod-truncated microdystrophin gene has been proven to ameliorate dystrophic phenotypes, the level of microdystrophin expression required for effective gene therapy by an AAV vector has not been determined yet. Here, we constructed a recombinant AAV type 2 vector, AAV2-MCKDeltaCS1, expressing microdystrophin (DeltaCS1) under the control of a muscle-specific MCK promoter and injected it into TA muscles of 10-day-old and 5-week-old mdx mice. AAV2-MCKDeltaCS1-mediated gene transfer into 5-week-old mdx muscle resulted in extensive and long-term expression of microdystrophin and significantly improved force generation. Interestingly, 10-day-old injected muscle expressed microdystrophin in a limited number of myofibers but showed hypertrophy of microdystrophin-positive muscle fibers and considerable recovery of contractile force. Thus, we concluded that AAV2-MCKDeltaCS1 could be a powerful tool for gene therapy of DMD.

Muscle regeneration by reconstitution with bone marrow or fetal liver cells from green fluorescent protein-gene transgenic mice.

The myogenic potential of bone marrow and fetal liver cells was examined using donor cells from green fluorescent protein (GFP)-gene transgenic mice transferred into chimeric mice. Lethally irradiated X-chromosome-linked muscular dystrophy (mdx) mice receiving bone marrow cells from the transgenic mice exhibited significant numbers of fluorescence(+) and dystrophin(+) muscle fibres. In order to compare the generating capacity of fetal liver cells with bone marrow cells in neonatal chimeras, these two cell types from the transgenic mice were injected into busulfantreated normal or mdx neonatal mice, and muscular generation in the chimeras was examined. Cardiotoxin-induced (or -uninduced, for mdx recipients) muscle regeneration in chimeras also produced fluorescence(+) muscle fibres. The muscle reconstitution efficiency of the bone marrow cells was almost equal to that of fetal liver cells. However, the myogenic cell frequency was higher in fetal livers than in bone marrow. Among the neonatal chimeras of normal recipients, several fibres expressed the fluorescence in the cardiotoxin-untreated muscle. Moreover, fluorescence(+) mononuclear cells were observed beneath the basal lamina of the cardiotoxin-untreated muscle of chimeras, a position where satellite cells are localizing. It was also found that mononuclear fluorescence(+) and desmin(+) cells were observed in the explantation cultures of untreated muscles of neonatal chimeras. The fluorescence(+) muscle fibres were generated in the second recipient mice receiving muscle single cells from the cardiotoxin-untreated neonatal chimeras. The results suggest that both bone marrow and fetal liver cells may have the potential to differentiate into muscle satellite cells and participate in muscle regeneration after muscle damage as well as in physiological muscle generation.