Role of innervation, excitability, and myogenic factors in the expression of the muscular chloride channel ClC-1. A study on normal and myotonic muscle

Item Type:	Article
Title:	Role of innervation, excitability, and myogenic factors in the expression of the muscular chloride channel ClC-1. A study on normal and myotonic muscle
Creators Name:	Klocke, R. and Steinmeyer, K. and Jentsch, T.J. and Jockusch, H.
Abstract:	The muscular chloride channel (ClC-1) is essential for a normal excitability of mature mammalian muscle fibers; inactivation of the corresponding gene by mutations leads to hyperexcitability of muscle, the hallmark of the disease myotonia. In the mouse, there is very little ClC-1 mRNA in myotubes, and its concentration increases steeply during postnatal development, suggesting a role of the motor nerve in ClC-1 expression. We investigated the response of the expression of the corresponding gene Clc-1 to different patterns of muscle activity as controlled by sarcolemmal excitability and by innervation. In rat and mouse, the level of ClC-1 mRNA was higher in fast (extensor digitorum longus) than in slow (soleus) muscle. Myotonia in the ADR mouse is caused by an insertional mutation leading to the adr allele of the Clc-1 gene and to grossly abnormal ClC-1 mRNAs. Nevertheless, in +/adr heterozygous, phenotypically wild type (WT) animals, the expression levels of both alleles correspond to the gene dosage. However, in the myotonic ADR mouse in which both Clc-1 genes are defective, ClC-1 mRNA levels in slow muscle were nearly as high as in WT fast muscle. In WT muscle, denervation within 2 days caused a drastic reduction of the ClC-1 mRNA level and at the same time an increase of myogenin and MyoD mRNAs. Neither effect of denervation was observed in myotonic mice (homozygous for the alleles adr or adrK), suggesting that spontaneous electrical activity of the hyperexcitable sarcolemma may substitute for nerve activity. Furthermore, potential MyoD/myogenin-binding sequence motifs were identified in the 5' regulatory region of the Clc-1 gene. These findings suggest that the activity-dependent regulation of the muscular chloride channel 1 gene is mediated by myogenic factors.
Keywords:	Amino Acid Sequence, Base Sequence, Chloride Channels, Creatine Kinase, Gene Expression, Heterozygote, Molecular Sequence Data, Muscle Denervation, MyoD Protein, Myogenin, Myotonia, Genetic Promoter Regions, Messenger RNA, Wistar Rats, Nicotinic Receptors, Sequence Alignment, Nucleic Acid Sequence Homology, Time Factors, Animals, Mice, Rats
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	269
Number:	44
Page Range:	27635-27639
Date:	4 November 1994
Official Publication:	http://www.jbc.org/content/269/44/27635.abstract
PubMed:	View item in PubMed

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