Molecular and cellular biological study on muscle differentiation and plasticity.

点击翻译按钮获取中文摘要

1. Dynamics of myoproteins : By using microinjection, photobleaching and immunofluorescence, it was found that nebulin plays an important role for incorporation of actin into and exchange of actin in nascent myofibrils, but connectin does not have such a role. It was also found that difference exists in exchangeability between actin and α-actinin. This difference seems to be related to the formation of I-Z-I structures of myofibrils.2. Developmental relationship between myoproteins during myofibrillogenesis : Immunofluorescence microscopy of embryonic muscle revealed that myomesin, connectin and C-protein play an important role for assembly and regular alignment of myosin molecules. A mechnism works to remove transiently expressed embryonic isoforms (nonmuscle actin and cardiac C-protein) from functional structures after they play some unknown role (s) for structure formation.3. Studies on actin-binding and myosin-binding proteins in developing muscle : 1) Expression profile of muscle-type cofilin, an actin-binding protein characteristic of muscle, was clarified during myogenesis in mouse fetus by in situ hybridization methods. 2) A unique C-protein variant has been discovered, which is expressed more abundantly in atrium of aged mice. It was revealed that this protein interacts only weekly with myosin and connectin with recombinant protein.4. Characteristcs of myofibers in masseter muscle of mice during postnatal growth period : The purpose of this study was to investigate the differentiation of myosin heavy chain (MHC) isoforms during postnatal development of mouse masseter muscle. Expression of MHC-2b in masseter occurs in accordance with the weaning period. This fact suggests that transformation from suckling to mastication effects to change MHC isoforms at this period.