Myosin Heavy Chain Isoforms in Equine Gluteus Medius Muscle: Comparison of mRNA and Protein Expression Profiles

The major structural protein in skeletal muscle, myosin heavy chain (MyHC), is primarily transcriptionally controlled. We compared the expression of MyHC isoforms on the mRNA and protein level in biopsies from the m. gluteus medius from adult untrained horses. In transverse sections, the majority of...

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Bibliographic Details
Published in:The journal of histochemistry and cytochemistry 2005-11, Vol.53 (11), p.1383-1390
Main Authors: Eizema, Karin, van den Burg, Maarten M.M, de Jonge, Henriette W, Dingboom, Elizabeth G, Weijs, Wim A, Everts, Maria E
Format: Article
Language:English
Subjects:
Animals
Female
Horses
Immunohistochemistry
In Situ Hybridization
Male
Muscle Fibers, Skeletal - metabolism
Muscle, Skeletal - metabolism
Myosin Heavy Chains - biosynthesis
Myosin Heavy Chains - genetics
Protein Isoforms - biosynthesis
Protein Isoforms - genetics
RNA, Messenger - biosynthesis
Transcription, Genetic
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Summary:The major structural protein in skeletal muscle, myosin heavy chain (MyHC), is primarily transcriptionally controlled. We compared the expression of MyHC isoforms on the mRNA and protein level in biopsies from the m. gluteus medius from adult untrained horses. In transverse sections, the majority of fibers showed qualitatively identical mRNA and protein expression patterns. However, coexpression of 2a and 2d/x MyHCs was substantially more common at the protein than at the mRNA level, suggesting a fine-tuning of these two genes in normal muscle not subjected to any training protocol. Because transverse sections give a limited sampling of mRNA expression in the case of uneven distribution of transcripts in a muscle fiber, we also analyzed longitudinal sections. We present, for the first time, evidence that expression of MyHC mRNA and protein was equal along the length of the fiber. Hence, mRNA expression is not regulated by differential expression of isoforms by separate myonuclei. It is concluded that the number of protein hybrid fibers in equine gluteus medius muscle is controlled by alteration of the transcription pattern uniformly along the fiber, rather than by simultaneous transcription of genes. The differences with the results in muscle of small animals and humans are discussed.
ISSN:0022-1554
1551-5044
DOI:10.1369/jhc.4A6609.2005