Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We reviewed six cases of rhabdomyosarcoma as a rare second primary malignancy in children with bilateral retinoblastoma after irradiation treatment. The patients comprised four females and two males (age range 1 year 4 months-7 years 11 months). Second tumors arose in the temporal muscle inside or close to the previously irradiated fields. All the children were alive and well 24-72 months after diagnosis. Microscopic examination showed proliferation of closely packed, small round cells with scanty cytoplasm, coarse nuclear chromatin, and increased mitotic activity without a myxoid background nor obvious alveolar architecture. The most characteristic feature was the presence of rosette-like structures in four tumors. Immunoreactivity for many skeletal muscle markers was evident, including desmin (six of six), muscle-specific actin (HHF35) (six of six), sarcomeric actin (six of six), myogenin (six of six), vimentin (six of six), and myoglobin (three of six). On reverse transcriptase-polymerase chain reaction examination, three second tumors lacked specific chimeric transcripts for alveolar rhabdomyosarcoma and Ewing's sarcoma. Unexpectedly, variable reactivity for neurofilament (150 kd) was identified in six of six second tumors as well as 15 of 20 sporadic primary rhabdomyosarcomas (75%) examined as controls, the result being confirmed by Western blot analysis. In addition, staining for retinoblastoma-susceptibility gene protein was negative in all second tumors, in contrast to positivity in 14 of 17 sporadic primary tumors (82%). This finding suggests that retinoblastoma-susceptibility gene abnormalities could be associated with the development of second primary rhabdomyosarcoma. We consider that knowledge of the occurrence of rhabdomyosarcoma and appropriate immunohistochemical study are helpful for avoiding a misdiagnosis of recurrent retinoblastoma or Ewing's sarcoma when encountering patients with a history of bilateral retinoblastoma who developed second small round cell neoplasms.
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PMID:Second primary rhabdomyosarcomas in patients with bilateral retinoblastoma: a clinicopathologic and immunohistochemical study. 980 27

To clarify the acquisition of the adult muscle pattern in Xenopus laevis, in situ hybridization and reverse transcriptase-polymerase chain reaction were used to correlate the time course of gene expression for myogenic regulatory factors (Myf-5, MyoD, and myogenin) with the expression of contractile protein (myosin heavy chain; MHC) genes during hindlimb formation compared with their expression in dorsal body muscles. After the precocious expression of Myf-5 and MyoD mRNA in limb bud (stage 50), myogenin mRNA strongly accumulated later at paddle stages (stages 52/53) concomitantly with the accumulation of both the larval and the adult MHC mRNAs. In dorsal body muscles, as early as stage 52, myogenin transcripts accumulated in a few small, secondary myofibers expressing the adult MHC mRNA that were located along the dorsomedial edge, but they were never detected in the large, primary myofibers of the body expressing the larval MHC mRNA. During metamorphosis, the areas expressing both the adult MHC and the myogenin transcripts gradually expanded from the dorsomedial edge to the ventral side of the dorsal body muscles, accounting for the progression of the secondary "adult" myogenesis described previously (Nishikawa and Hayashi [1994] Dev. Biol. 165:86-94). This work shows that, in Xenopus, the accumulation of myogenin mRNA is restricted to secondary myogenesis, including the formation of new muscles in developing limbs as well as in dorsal muscles during body remodeling. This shows that myogenin is not required for primary myogenesis, and it suggests a crucial role for myogenin in the terminal differentiation program, including myoblast fusion and the activation of adult-type muscle genes.
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PMID:Expression of myogenic regulatory factors during muscle development of Xenopus: myogenin mRNA accumulation is limited strictly to secondary myogenesis. 982 66

Myogenic cell differentiation is induced by Arg(8)-vasopressin, whereas high cAMP levels and protein kinase A (PKA) activity inhibit myogenesis. We investigated the role of type 4 phosphodiesterase (PDE4) during L6-C5 myoblast differentiation. Selective PDE4 inhibition resulted in suppression of differentiation induced by vasopressin. PDE4 inhibition prevented vasopressin-induced nuclear translocation of the muscle-specific transcription factor myogenin without affecting its overall expression level. The effects of PDE4 inhibition could be attributed to an increase of cAMP levels and PKA activity. RNase protection, reverse transcriptase PCR, immunoprecipitation, Western blot, and enzyme activity assays demonstrated that the PDE4D3 isoform is the major PDE4 expressed in L6-C5 myoblasts and myotubes, accounting for 75% of total cAMP-hydrolyzing activity. Vasopressin cell stimulation caused a biphasic increase of PDE4 activity, which peaked at 2 and 15 min and remained elevated for 48 h. In the continuous presence of vasopressin, cAMP levels and PKA activity were lowered. PDE4D3 overexpression increased spontaneous and vasopressin-dependent differentiation of L6-C5 cells. These results show that PDE4D3 plays a key role in the control of cAMP levels and differentiation of L6-C5 cells. Through the modulation of PDE4 activity, vasopressin inhibits the cAMP signal transduction pathway, which regulates myogenesis possibly by controlling the subcellular localization of myogenin.
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PMID:Involvement of type 4 cAMP-phosphodiesterase in the myogenic differentiation of L6 cells. 1058 63

In adult Xenopus laevis, we analyzed, using reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization, the influence of long-term muscle denervation on the accumulation of MRF4 and myogenin transcripts. The brachial muscle was denervated by cutting the brachial nerve and was examined after 4 months. MRF4 mRNA levels decreased about two-fold in denervated muscle as compared with contralateral muscle. Myogenin mRNA levels, by contrast, were induced about five-fold by denervation. This report shows that muscle denervation persistently reduces the levels of MRF4 transcripts suggesting that MRF4 expression may be induced by innervation and hence may be involved in mediating transcriptional responses to innervation. The up-regulation of myogenin by denervation suggests that myogenin expression may compensate for the down-regulation of MRF4 gene.
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PMID:Long-term denervation modulates differentially the accumulation of myogenin and MRF4 mRNA in adult Xenopus muscle. 1062 21

Satellite cells isolated from fast tibialis anterior (TA) and slow soleus (SOL) rat muscles were cultivated on matrigel, and treated with acidic fibroblast growth factor (aFGF). The following observations were made: 1) aFGF-treated cultures exhibited enhanced proliferation as mirrored by a twofold increase in DNA content. 2) Compared to the untreated cultures, myotubes in the aFGF cultures were larger; 3) Using reverse transcriptase polymerase chain reaction (RT-PCR) and northern blot analyses, we observed enhanced expression of all adult myosin heavy chain (MHC) isoforms, as well as of myogenin. These findings indicate that, under the culture conditions used, aFGF has a stimulatory effect on proliferation but also on maturation and differentiation of satellite cells. Furthermore, transcript levels of FGF receptor 1 (FGFR1) and 4 (FGFR4) isoforms, as well as of aFGF and bFGF were assessed by RT-PCR. aFGF-treated myotubes displayed increased expression of aFGF and bFGF, suggesting a paracrine effect of exogenous aFGF. In this regard, SOL-derived cultures responded more strongly than TA-derived cultures. The effects of aFGF treatment on the two receptors consisted of a decrease in FGFR1 and an increase in FGFR4 mRNA levels in 5-day-old cultures. In 8-day-old TA cultures, effects of FGF were similar to those in 5-day-old cultures. 8-day FGF-treated SOL cultures treated with FGF for 8 days exhibited higher FGFR1 and FGFR4 mRNA levels than the respective untreated cultures. Compared to 5 day-treated cultures, FGFR1 increased and FGFR4 decreased. This led to a shift in the ratio of FGFR1 to FGFR4 in the FGF-treated cultures which may explain the ability of satellite cells to differentiate under the influence of aFGF.
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PMID:Evidence that acidic fibroblast growth factor promotes maturation of rat satellite-cell-derived myotubes in vitro. 1063 13

Rhabdomyosarcomas are a heterogeneous group of tumors with respect to their molecular basis, degree of differentiation, histology, and clinical behavior. Because of the wide variation of tumor morphology, it is often difficult to distinguish between the distinct subtypes of rhabdomyosarcomas. By using cryosections of tumor specimens and immunohistochemistry, in the present study we show that strong expression of myogenin in rhabdomyosarcoma is associated with alveolar histology (P = <0.0001, Fisher's exact test). Although staining for myogenin was observed in 22 of 26 rhabdomyosarcomas, all alveolar rhabdomyosarcomas (nine of nine) showed high levels of staining for myogenin, as defined by the frequency and intensity of staining of the tumor cells. The staining pattern suggests that the tumor cells are clonally derived from myogenin-positive progenitor cells. In contrast, most embryonal rhabdomyosarcomas (13 of 15) were either negative or showed a low level of staining for myogenin. In these tumors a larger proportion of tumor cells were distinctly negative for myogenin. Six of seven alveolar rhabdomyosarcomas that strongly stained for myogenin were also positive for Pax3-7/Forkhead (FKHR) by polymerase chain reaction/reverse transcriptase-polymerase chain reaction. One of two embryonal rhabdomyosarcomas that strongly stained for myogenin was retrospectively found to be positive for Pax3/FKHR transcripts. Quantitative analysis for myogenin by Western blotting using a smaller subset of rhabdomyosarcomas revealed that in general there was a good correlation between immunohistochemical staining and Western blotting (P = 0.01, Pearson Correlation), although the former technique was more sensitive for detecting tumors with low levels of the protein. On average, alveolar rhabdomyosarcomas expressed at least threefold more myogenin than embryonal rhabdomyosarcomas. Our data show that staining for myogenin will be a simple, rapid, and accurate adjunct for distinguishing between alveolar and embryonal rhabdomyosarcomas. We propose that embryonal rhabdomyosarcomas result from an early block in myogenesis, before the expression of myogenin. In contrast, we propose that alveolar rhabdomyosarcomas either originate from a late block in myogenesis (after expression of myogenin) or that the pathological mechanisms involved in these neoplasms also induce strong expression of this protein.
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PMID:Strong immunostaining for myogenin in rhabdomyosarcoma is significantly associated with tumors of the alveolar subclass. 1066 68

While the role of myogenic regulatory factors (MRFs) in skeletal myogenesis has been well evaluated in limb and trunk muscles, very little is known about their role in tongue myogenesis. Here the expression of MRF mRNA in mouse tongue muscle was examined during development from embryonic day (E)11 to birth and compared them with that in hind-limb muscle. Desmin, muscle creatine kinase and troponin C mRNAs were used as markers for myoblast determination, myotubule formation and myofibre maturation, respectively. The mRNA quantities were determined by competitive reverse transcriptase-polymerase chain reaction. The expression profile of desmin mRNA indicated that myoblast determination occurred before E11 in both the tongue and hind-limb muscles; the profile of muscle creatine kinase and troponin C mRNAs indicated that myotubule formation and myofibre maturation began between E11 and 13 in both tongue and hind-limb muscles, but ended 2 days earlier in the tongue than in the hind limb. Expression of myoD and myogenin mRNAs began at E11, increased, and showed peak values earlier in the tongue muscle (E13) than in the hind-limb muscle (E15). Expression of MRF4 mRNA appeared earlier in the tongue (E13) than in the hind-limb muscle (E15) and increased in both muscles after that. These results suggest that myotubule formation and myofibre maturation in the tongue muscle progress faster than in the hind-limb muscle, a result of earlier expression of myoD, myogenin, and MRF4 in response to earlier functional demands such as suckling immediately after birth.
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PMID:Expression of myogenic regulatory factors during the development of mouse tongue striated muscle. 1066 94

Rhabdomyosarcomas (RMSs) are classified into embryonal (ERMS), alveolar (ARMS), and pleomorphic (PRMS) subtypes. ERMS, including botryoid variants, typically occurs in young children, ARMS typically occurs in older children and young adults, and PRMS occurs in older adults. Although ARMSs show thin fibrous bands separating nests of cells, abundant extracellular matrix production is rare in RMS. In the course of reviewing hyalinizing sarcomas we discovered a distinctive RMS in adults that closely mimicked osteosarcoma or chondrosarcoma because of the extensive matrix production. Four RMSs with hyalinized matrix were retrieved from our files. These cases were evaluated with respect to patient age and sex, tumor site and size, growth pattern, nuclear grade, cellularity, mitotic figures/20 high power fields, vascular invasion, necrosis, the presence of rhabdomyoblasts, multinucleated cells, and alveolar growth pattern. Immunohistochemistry for desmin, myogenin, MyoD1, actin, cytokeratin, S-100 protein, collagen II, and CD99 was performed. Reverse transcriptase polymerase chain reaction for the ARMS-associated PAX3/FKHR and PAX7/PKHF was also performed on three cases. The cases involved the forearm, hand, orbit, and nasopharynx of a 40-year-old woman, a 50-year-old man, an 18-year-old man, and a 21-year-old man, respectively. The tumors ranged from 3.7 to 8 cm and consisted of lobules and infiltrating cords of small round malignant cells embedded in a densely hyalinized matrix having both a chondroid and osteoid-like appearance. No definite lacunae or matrix calcification was present. An alveolar pattern was only present focally, and tumor giant cells were not present. One case had a single focus of rhabdomyoblastic differentiation with strap cells. Mitotic activity was >20 mitotic figures/20 high power fields in three of four cases. Immunohistochemically, one case strongly expressed desmin, whereas three cases expressed it focally, with a dot-like pattern. Myogenin was only focally positive, but MyoD1 was present in nearly every cell of each case. Two cases expressed actin and one expressed CD99. No case expressed cytokeratin, S-100 protein, or collagen II. Only one case contained adequate RNA for reverse transcriptase polymerase chain reaction, and this case was negative for the ARMS-associated gene fusions. Follow-up showed one patient to be dead of metastatic disease at 60 months despite intensive therapy, another patient to be disease free at 26 months, and the third patient to be disease free at 5 months. The fourth case is recent. These cases are a distinctive-appearing rhabdomyosarcoma easily mistaken for variants of chondrosarcoma, osteosarcoma, or even sclerosing epithelioid fibrosarcoma because of their hyalinizing appearance compounded by their typically focal and dot-like desmin expression. These four cases are essentially identical to the three unusual RMSs recently reported by Mentzel and Katenkamp as "sclerosing, pseudovascular rhabdomyosarcoma in adults." Although the focal alveolar architecture and the primitive cytologic appearance of these hyalinizing RMS suggest a relationship with ARMS, the presence of abundant strap cells in one case, the predominant expression of MyoD1 rather than myogenin, and the absence of ARMS-associated fusions genes point more strongly toward a variant of ERMS. However, the late adult age in two cases is unusual for both EMRS and ARMS, suggesting that sclerosing RMS may prove to be a distinct subtype of RMS. Study of additional cases will be necessary to more fully elucidate its place among RMS and its prognostic significance.
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PMID:Sclerosing rhabdomyosarcoma in adults: report of four cases of a hyalinizing, matrix-rich variant of rhabdomyosarcoma that may be confused with osteosarcoma, chondrosarcoma, or angiosarcoma. 1221 74

Human umbilical cord blood (UCB) has been regarded as an alternative source for cell transplantation and cell therapy because of its hematopoietic and nonhematopoietic (mesenchymal) potential. Although there has been debate about whether mesenchymal stem cells (MSCs) are invariably present in UCB, several reports showed that MSC-like cells could be consistently derived from human UCB and, moreover, could differentiate into various cells of a mesodermal origin. However, it remains unclear whether these UCB-derived MSCs are also capable of differentiating into skeletal muscle cells. In this study, we isolated MSCs from human UCB and induced them to differentiate into skeletal muscle cells. During cell culture expansion, UCB-derived mononuclear cells gave rise to adherent layers of fibroblast-like cells expressing MSC-related antigens such as SH2, SH3, alpha-smooth muscle actin, CD13, CD29, and CD49e. More important, when these UCB-derived MSCs were incubated in promyogenic conditions for up to 6 weeks, they expressed myogenic markers in accordance with myogenic differentiation pattern. Both flow cytometric and reverse transcriptase-polymerase reaction analyses showed that two early myogenic markers, MyoD and myogenin, were expressed after 3 days of incubation but not after 2 weeks. At week 6, more than half of UCB-derived MSCs expressed myosin heavy chain, a late myogenic marker. Our results demonstrate that UCB-derived MSCs possess a potential of skeletal myogenic differentiation and also imply that these cells could be a suitable source for skeletal muscle repair and a useful tool of muscle-related tissue engineering.
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PMID:Skeletal myogenic differentiation of mesenchymal stem cells isolated from human umbilical cord blood. 1527 7

Rhabdomyosarcoma is the most common soft tissue malignancy in children but is rare in adults. The latest World Health Organization classification of soft tissue tumors recognizes embryonal, alveolar, and pleomorphic rhabdomyosarcomas. More recently, a sclerosing variant of rhabdomyosarcoma has been recognized and reported in seven adult patients. We describe a pediatric case of sclerosing rhabdomyosarcoma presenting as a sacral mass in a 3-year-old girl. Morphologically, the tumor showed a prominent sclerosing hyaline matrix and demonstrated pseudovascular and microalveolar architectural foci. Focal positivity was seen with desmin, smooth muscle actin, and myogenin. MyoD1 showed uniform diffuse nuclear staining. Fusion transcripts were not demonstrated by reverse transcriptase-polymerase chain reaction analysis. The histology, immunohistochemistry, and molecular genetics matched those reported in the seven adult cases of sclerosing rhabdomyosarcoma. This is the first case report, to our knowledge, of this rare tumor arising in the pediatric age group, and we compare the features with those reported in adult sclerosing rhabdomyosarcoma.
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PMID:Sclerosing rhabdomyosarcoma in childhood: case report and review of the literature. 1580 20


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