Phenotypic expression of 2b myosin heavy chain isoform: a comparative study among species and different muscles

摘要

Myosin is the main protein investigated in the study of muscle plasticity, and it has both structural and regulator functions in contractile apparatus (Schiaffino and Reggiani 1996). In the mammals studied so far, the expressed myosin heavy chain (MyHC) isoforms in trunk and leg/arm skeletal muscles are types 1, 2A and 2X in different percentages, while type 2B is species-specific. Indeed, this isoform is present in marsupials (Zhong et al. 2001) and in laboratory animals (Lucas et al. 2000) where it is the predominant isoform in some muscles but it is lacking in man, bovine and dog (Maccatrozzo et al. 2004, 2007; Toniolo et al. 2007). The unique exception is the pig where the 2B isoform is expressed, but only in hybrid 2X/B fibres (Toniolo et al. 2004). In the present study we wanted to examine if the 2B isoform is expressed in extraocular, laryngeal, and masticatory muscles, both at the mRNA and at the protein level. These muscles, because of their embryological origin from the pre-somitic mesoderm and for their expression of particular isoforms (EO, alpha-cardiac, and the transition isoforms present in adults) were indicated as “special” muscles.