Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of motor innervation in the expression of beta-galactosidase targeted to the nucleus (nls beta gal) under the control of a chicken muscle acetylcholine receptor alpha-subunit promoter of 850 bp was investigated using two lines of transgenic mice. After birth, nls beta gal was transiently expressed in the endplate areas of extensor digitorum longus, tibialis anterior and diaphragm muscles. In the adult, denervation of several fast twitch muscles caused a burst of transgene expression which started at endplates and displayed defined though transient spatio-temporal patterns; in the slow soleus muscle, no regular patterns were observed. Thus, in vivo, the 850 bp promoter confers preferential expression of nls LacZ in the motor endplates of newborn mice and, in addition, directs expression of nls LacZ in denervated adult muscles.
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PMID:Regulation of an acetylcholine receptor LacZ transgene by muscle innervation. 148 67

We have obtained transgenic mice expressing nuclearly targeted beta-galactosidase (nls-beta-gal) under the control of a chicken acetylcholine receptor alpha-subunit promoter. The expression of the transgene was detected in early somites, starting before embryonic day 9.5. In 13-day embryos, the expression pattern of the transgene closely paralleled that of the endogenous mouse alpha-subunit gene, assessed by in situ hybridization. Our results illustrate, with single-cell resolution, the tissue specificity of this alpha-subunit promoter during embryogenesis. After birth, the overall beta-galactosidase activity rapidly decreased with age. However, in diaphragms of newborn animals, beta-galactosidase activity selectively persisted in nuclei underlying the motor endplates. The latter were revealed by an acetylcholinesterase stain. Nls-beta-gal was also visualized by indirect immunofluorescence, while endplates were labelled with fluorescent alpha-bungarotoxin. Confocal microscopy unambiguously identified the more intensely stained nuclei as synaptic 'fundamental nuclei', and allowed estimates of relative staining levels. Thus an 842 bp acetylcholine receptor gene promoter confers preferential synaptic expression to a reporter gene within myofibres in vivo.
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PMID:An acetylcholine receptor alpha-subunit promoter conferring preferential synaptic expression in muscle of transgenic mice. 190 Apr 67

The effects of denervation were investigated in mice with transgenes containing promoter elements from the muscle acetylcholine receptor epsilon- and alpha-subunit genes. The promoter sequences were coupled to a nuclear localization signal-beta-galactosidase fusion gene (nlacZ) as a reporter. While many postsynaptic specializations form in the embryo, expression of the epsilon subunit is induced during the first two postnatal weeks. When muscles were denervated at birth, before the onset of epsilon expression, epsilon nlacZ still appeared at the former synaptic sites on schedule. This result suggests that the nerve leaves a localized "trace" in the muscle that can continue to regulate transcription. An additional finding was that epsilon nlacZ expression was much stronger in denervated than in intact muscles. This suggests that the epsilon promoter is similar to the other subunits in containing elements that are activated on cessation of neural activity. However, even after denervation, epsilon nlacZ expression was always confined to the synaptic region whereas alpha nlacZ expression increased in nuclei along the entire length of the fiber. This suggests that while the epsilon gene is similar in its activity dependence to other subunit genes, it is unique in that local nerve-derived signals are essential for its expression. Consequently, inactivity enhances epsilon expression only in synaptic nuclei where such signals are present, but enhances expression throughout the muscle fiber. Truncations and an internal deletion of the epsilon promoter indicate that cis-elements essential for the response to synaptic signals are contained within 280 bp of the transcription start site. In contrast to these results in young animals, denervation in older animals leads to an unexpected reduction in nlacZ activity. However, mRNA measurements indicated that transgene expression was increased in these animals. This discordance between nlacZ mRNA and enzyme activity, demonstrates a previously unknown limitation of nlacZ as a reporter gene in transgenic animals.
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PMID:Neural regulation of muscle acetylcholine receptor epsilon- and alpha-subunit gene promoters in transgenic mice. 825 48

The adult neuromuscular junction displays an accumulation of both the acetylcholine receptor (AChR) protein in the subneural domain of the post-synaptic membrane and the mRNAs coding for all its subunits at the level of the subjunctional "fundamental nuclei." In the course of end plate development, the epsilon-subunit, at variance with other subunits, becomes exclusively expressed at the level of the fundamental nuclei, yet at a rather late stage (around birth). To analyze the promoter region of the epsilon-subunit gene which directs its specific expression at the synapse, we used a quantitative transient in vivo expression assay in intact muscle tissue using constructs of the epsilon-subunit promoter placed upstream of the beta-galactosidase reporter gene. One crucial element for synapse-specific expression was detected between the -11 and -6 positions. Disruption of this element, either by a scanning mutation or single base mutations, greatly diminishes, or even completely inhibits, preferential expression of the transgene at the end plate. Gel shift experiments reveal the presence of a complex in nuclear muscle extracts that bind the core sequence of this element. The identification of such a site opens the possibility to identify regulatory factors responsible for compartmentalized expression at the neuromuscular junction.
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PMID:Identification of an element crucial for the sub-synaptic expression of the acetylcholine receptor epsilon-subunit gene. 866 16

During the development of the mammalian neuromuscular junction, acetylcholine receptors (AChRs) become localized to the postsynaptic muscle membrane. As this process nears completion, the fetal form of the receptor, containing a gamma subunit (composition alpha 2 beta gamma delta) is gradually replaced by an epsilon subunit-containing adult form (alpha 2 beta epsilon delta). To understand how this transition is controlled, we compared the expression and regulation of the AChR gamma and epsilon subunits in developing, adult, and cultured muscles. Immunostaining with subunit-specific antibodies showed that replacement of gamma subunit- by epsilon subunit-containing AChRs occurs largely during the first postnatal week in fast-twitch muscles, and occurs homogeneously throughout individual endplates. In the slow-twitch soleus, however, this transition is delayed, and in the multiply innervated slow fibers of extraocular muscle, gamma subunit expression persists into adulthood. The transcriptional bases of the AChR subunit transition, and of these intermuscular variations, were demonstrated in mice bearing transgenes containing promoter elements from the AChR gamma and epsilon subunit genes, each coupled to a nuclear-localized beta-galactosidase (nlacZ) reporter. We show that transgene expression is stimulated by the nerve-derived inducer of AChR expression, ARIA, in myotubes cultured from gamma-nlacZ as well as epsilon-nlacZ mice. However, the expression of gamma-nlacZ, but not epsilon-nlacZ, is increased by treatment of myotubes with TTX, and the ARIA sensitivity of gamma-nlacZ is dependent on the electrical state of the myotube. Thus, the promoters of the gamma and epsilon subunit genes may integrate ARIA- and activity-dependent signals in different ways to generate their complementary patterns of expression.
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PMID:Maturation of the acetylcholine receptor in skeletal muscle: regulation of the AChR gamma-to-epsilon switch. 887 66

In adult muscle, transcription of the nicotinic acetylcholine receptor (AChR) is restricted to the nuclei located at the neuromuscular junction. The N-box, a new promoter element, was identified recently and shown to contribute to this compartmentalized synaptic expression of the AChR delta- and epsilon-subunits. We demonstrate that the N-box mediates transcriptional activation in cultured myotubes and identify the transcription factor that binds to the N-box as a heterooligomer in myotubes and adult muscle. The GABP (GA-binding protein) alpha-subunit belongs to the Ets family of transcription factors, whereas the beta-subunit shares homology with IkappaB and Drosophila Notch protein. GABP binding specificity to mutated N-box in vitro strictly parallels the sequence requirement for beta-galactosidase targeting to the endplate in vivo. In situ hybridization studies reveal that the mRNAs of both GABP subunits are abundant in mouse diaphragm, with preferential expression of the alpha-subunit at motor endplates. In addition, heregulin increases GABPalpha protein levels and regulates phosphorylation of both subunits in cultured chick myotubes. Finally, dominant-negative mutants of either GABPalpha or GABPbeta block heregulin-elicited transcriptional activation of the AChR delta and epsilon genes. These findings establish the expected connection with a presynaptic trophic factor whose release contributes to the accumulation of AChR subunit mRNAs at the motor endplate.
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PMID:Implication of a multisubunit Ets-related transcription factor in synaptic expression of the nicotinic acetylcholine receptor. 960 90

Myasthenia gravis (MG) is an autoimmune disease targeting the skeletal muscle acetylcholine receptor (AChR). Although the autoantigen is present in the thymus, it is not tolerated in MG patients. In addition, the nature of the cell bearing the autoantigen is controversial. To approach these questions, we used two lineages of transgenic mice in which the beta-galactosidase (beta-gal) gene is under the control of a 842-bp (Tg1) or a 3300-bp promoter fragment (Tg2) of the chick muscle alpha subunit AChR gene. In addition to expression in muscle cells, thymic expression was observed in both mouse lines (mainly in myoid cells in Tg1 and myoid cells and epithelial cells in Tg2). After challenge with beta-gal, Tg1 mice produced Th2-dependent anti-beta-gal antibodies, while Tg2 mice were almost unresponsive. By contrast, in a proliferation assay both Tg lines were unresponsive to beta-gal. Cells from Tg1 mice produce Th2-dependent cytokine whereas cells from Tg2 mice were nonproducing in response to beta-gal. These data indicate that the level of expression in Tg1 mice could be sufficient to induce tolerance of Th1 cells but not of Th2 cells, while both populations are tolerated in Tg2 mice. These findings are compatible with the hypothesis that AChR expression is not sufficiently abundant in MG thymus to induce a full tolerance.
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PMID:An acetylcholine receptor alpha subunit promoter confers intrathymic expression in transgenic mice. Implications for tolerance of a transgenic self-antigen and for autoreactivity in myasthenia gravis. 961 5

We studied the behavior of myogenic progenitors from donor desmin(+/-) LacZ embryos after implantation into tibialis anterior muscle of 2-month-old mouse hosts. Myogenic progenitors were collected from 10-day post-coital mouse embryo somite dermomyotomes (DMs), forelimb buds (LBs), and trunks. The replacement of desmin by the LacZ coding sequence allowed specific monitoring of beta-galactosidase expression in donor myogenic cells. Immunostaining for myosin heavy chain and laminin expression was performed together with acetylcholine receptor histochemistry on sections of implanted muscle. Myogenic progenitors generated from DM, LB, and trunk were able to proliferate and adopt a myogenic pathway after transplantation into adult mouse muscle. Although their development appeared to be limited for DM and LB cell transplantation, the differentiation of myogenic progenitors occurred readily with trunk cell injection, suggesting that cell types associated with DM cells were involved in long-term myofiber differentiation (21 day). When neural tube/notochord (NTN) or sclerotomal (S) cells were co-transplanted with DM cells, myogenic nuclei were produced, indicating that both NTN and S are required for the differentiation of DMs grafted into adult muscle. These data are consistent with the differentiation of neural tissues and bone from NTN and S, respectively, and with the development of anatomic relations among all in vivo-differentiated tissues. These results suggest that embryonic trunk cells can be used to repair different types of injured tissues (especially skeletal muscle) under appropriate environmental conditions.
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PMID:Developmental behavior of embryonic myogenic progenitors transplanted into adult muscle as revealed by desmin LacZ recombinant gene. 1450 Jun 93