Coexpression of myosin heavy chain 2b with myosin heavy chain 1-fact or artefact ?
Résumé
In skeletal muscle, pure fibres expressing one myosin heavy chain (MyHC) isoform, and intermediate fibres, expressing two and exceptionally three MyHCs have been described. When skeltal muscle adapts its fibre profile to changed functional demands MyHC isoform transformation follows the pathway: MyHC-1↔MyHC-2a↔MyHC-2x/d↔MyHC-2b. Therefore, in hybrid fibres only successive isoforms from the proposed pathway should coexist. However, jump fibres in which MyHC-1 is co-expressed with MyHC-2x/d have been described recently. The present study describes possible coexpression of MyHC-1with MyHC-2b in transforming as well as in normal control mouse and rat muscle fibres. The study is only descriptive and provides not sufficient proof to exclude the possible artefact resulting from unknown technical reasons.