Utrophin mRNA Expression in Muscle Is Not Restricted to the Neuromuscular Junction

Utrophin is normally present exclusively in synaptic regions of skeletal muscle fibers, although it is expressed extrasynaptically in certain pathological situations, where it has been proposed to compensate for the absence of dystrophin in Duchenne muscular dystrophy patients andmdxmice. Recently t...

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Bibliographic Details
Published in:Molecular and cellular neuroscience 1998-04, Vol.10 (5-6), p.229-242
Main Authors: Vater, Ruth, Young, Carol, Anderson, Louise V.B., Lindsay, Susan, Blake, Derek J., Davies, Kay E., Zuellig, Richard, Slater, Clarke R.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Autoradiography
Cell Nucleus - metabolism
Cytoskeletal Proteins - genetics
Female
Immunohistochemistry
In Situ Hybridization
Membrane Proteins - genetics
Molecular Sequence Data
Muscle, Skeletal - innervation
Muscle, Skeletal - metabolism
Neuromuscular Junction - metabolism
Rats
Rats, Wistar
RNA, Messenger - analysis
RNA, Messenger - biosynthesis
Utrophin
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Summary:Utrophin is normally present exclusively in synaptic regions of skeletal muscle fibers, although it is expressed extrasynaptically in certain pathological situations, where it has been proposed to compensate for the absence of dystrophin in Duchenne muscular dystrophy patients andmdxmice. Recently there have been conflicting reports regarding the preferential expression of utrophin mRNA at the neuromuscular junction. Usingin situhybridization with RNA probes, we show a clear accumulation of autoradiographic labeling at more than 90% of neuromuscular junctions (identified by histochemical demonstration of cholinesterase activity). The intensity of this labeling is proportional to the number of junctional myonuclei in the section. Some clusters of labeling were found associated with nonmuscle nuclei (e.g., blood vessels, nerves), where utrophin is present. In addition, labeling for utrophin mRNA was associated with about 25% of extrajunctional myonuclei, where the protein is not present. The mean labeling per nucleus at junctional myonuclei was at least 10 times greater than at extrajunctional myonuclei. We discuss the possible regulatory mechanisms involved in the heterogeneous expression of utrophin mRNA in skeletal muscle.
ISSN:1044-7431
1095-9327
DOI:10.1006/mcne.1998.0661