Molecular and cellular biological study on muscle differentiation and plasticity.

1. 肌蛋白动力学：通过显微注射、光漂白和免疫荧光等方法发现，在新生肌原纤维中，nebulin对肌动蛋白的掺入和肌动蛋白的交换起着重要的作用，而connectin则没有这种作用。肌动蛋白与α-肌动蛋白的互换性也存在差异。这种差异似乎与肌原纤维I-Z-I结构的形成有关。肌原纤维形成过程中肌蛋白的发育关系：胚胎肌免疫荧光显微镜显示，肌凝蛋白、连接蛋白和c蛋白对肌凝蛋白分子的组装和规则排列起重要作用。有一种机制可以将瞬时表达的胚胎同种异构体（非肌肉肌动蛋白和心脏c蛋白）从功能结构中移除，因为它们在结构形成中起着一些未知的作用。肌动蛋白结合蛋白和肌球蛋白结合蛋白在肌肉发育中的研究：1)通过原位杂交方法，明确了肌动蛋白结合蛋白肌肉型cofilin在小鼠胎儿肌肉发育过程中的表达谱。2)发现了一种独特的c蛋白变异，该变异在老年小鼠心房中表达更为丰富。结果表明，该蛋白每周仅与肌凝蛋白和连接蛋白相互作用。出生后小鼠咬肌肌纤维的特征：本研究旨在探讨出生后小鼠咬肌发育过程中肌球蛋白重链（MHC）亚型的分化情况。咀嚼肌中MHC-2b的表达与断奶期一致。这一事实表明，从哺乳到咀嚼的转变影响了这一时期MHC亚型的变化。

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.