Section 10
Chapter 9,880

In vivo regulation of the b-myosin heavy chain gene in soleus muscle of suspended and weight-bearing rats

Giger, J.M.; Haddad, F.; Qin, A.X.

American Journal of Physiology 278(6): 153-C1161


ISSN/ISBN: 0363-6143
Accession: 009879353

Download citation:  

In the weight-bearing hindlimb soleus muscle of the rat, [similar] 90% of muscle fibers express the b-myosin heavy chain (b-MHC) isoform protein. Hindlimb suspension (HS) causes the MHC isoform population to shift from btoward the fast MHC isoforms. Our aim was to establish a model to test the hypothesis that this shift in expression is transcriptionally regulated through specific cis elements of the b-MHC promoter. With the use of a direct gene transfer approach, we determined the activity of different length b-MHC promoter fragments, linked to a firefly luciferase reporter gene, in soleus muscle of control and HS rats. In weight-bearing rats, the relative luciferase activity of the longest b-promoter fragment (-3500 bp) was threefold higher than the shorter promoter constructs, which suggests that an enhancer sequence is present in the upstream promoter region. After 1 wk of HS, the reporter activities of the -3500-, -914-, and -408-bp promoter constructs were significantly reduced ([similar] 40%), compared with the control muscles. However, using the -215-bp construct, no differences in promoter activity were observed between HS and control muscles, which indicates that the response to HS in the rodent appears to be regulated within the -408 and -215 bp of the promoter. Reprinted by permission of the publisher.

PDF emailed within 1 workday: $29.90