Local Transcriptional Control of Utrophin Expression at the Neuromuscular Synapse

doi:10.1074/jbc.272.13.8117

Local Transcriptional Control of Utrophin Expression at the Neuromuscular Synapse*

From the Departments of ^‡ Physiology, and
** Pharmacology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, the
^¶ Department of Biochemistry, Genetics Unit, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom, and
^‡‡ Biologie Cellulaire des Membranes, Institut Jacques Monod, CNRS, Université Denis Diderot, 2 Place Jussieu, 75251 Paris Cédex 05, France

^§§ Scholar of the Medical Research Council of Canada. To whom correspondence should be addressed:
Dept. of Physiology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd., Ottawa, Ontario, Canada K1H 8M5.
Tel.: 613-562-5800 (Ext. 8383); Fax: 613-562-5434; E-mail: bjasmin{at}danis.med.uottawa.ca

Abstract

Recently, the use of a transgenic mouse model system for Duchenne muscular dystrophy has demonstrated the ability of utrophin to functionally replace dystrophin and alleviate the muscle pathology (see Tinsley, J. M., Potter, A. C., Phelps, S. R., Fisher, R., Trickett, J. I., and Davies, K. E. (1996) Nature 384, 349–353). However, there is currently a clear lack of information concerning the regulatory mechanisms presiding over utrophin expression during normal myogenesis and synaptogenesis. Using in situ hybridization, we show that utrophin mRNAs selectively accumulate within the postsynaptic sarcoplasm of adult muscle fibers. In addition, we demonstrate that a 1.3-kilobase fragment of the human utrophin promoter is sufficient to confer synapse-specific expression to a reporter gene. Deletion of 800 base pairs from this promoter fragment reduces the overall expression of the reporter gene and abolishes its synapse-specific expression. Finally, we also show that utrophin is present at the postsynaptic membrane of ectopic synapses induced to form at sites distant from the original neuromuscular junctions. Taken together, these results indicate that nerve-derived factors regulate locally the transcriptional activation of the utrophin gene in skeletal muscle fibers and that myonuclei located in extrasynaptic regions are capable of expressing utrophin upon receiving appropriate neuronal cues.

Footnotes

↵^§ Arthur Minden Predoctoral Fellow of the Muscular Dystrophy Association of Canada.
↵^∥ Supported by the Muscular Dystrophy Association of Great Britain and Northern Ireland.
↵* This work was supported in part by the Muscular Dystrophy Association of America (to B. J. J.), l'Association Française contre les Myopathies (to B. J. J. and J. C.), and the Medical Research Council of Canada (to B. J. J.) and the United Kingdom (to K. E. D.). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

DMD

Duchenne muscular dystrophy

AChE

acetylcholinesterase

AChR

acetylcholine receptor

TA

tibialis anterior

kb

kilobase(s)

bp

base pair(s).
↵²B. J. Jasmin et al., unpublished observations.
- Received December 20, 1996.