Temporal and Spatial Expression of Distinct Troponin T Genes in Embryonic/Larval Tail Striated Muscle and Adult Body Wall Smooth Muscle of Ascidian

Cell Structure and Function

Takashi Obinata¹  Takeshi Endo¹  Ken Matsumoto¹  Go Katsura¹  Taro Hama¹  Yukio Ohtsuka¹ 

[1] Department of Biology, Faculty of Science, Chiba University

关键词: troponin T;    ascidian;    smooth muscle;    striated muscle;    nuclear localization;   

DOI  :  10.1247/csf.22.197

学科分类：分子生物学，细胞生物学和基因

来源: Japan Society for Cell Biology

【 摘 要 】

References(26)Cited-By(1)During development of the ascidian Halocynthia roretzi, the tadpole larva hatched from the tailbud embryo metamorphoses to the adult with a body wall muscle. Although the adult body wall muscle is morphologically nonsarcomeric smooth muscle, it contains a troponin complex consisting of three subunits (T, I, and C) as do vertebrate striated muscles. Different from vertebrate troponins, however, the smooth muscle troponin promotes actin-myosin interaction in the presence of high concentration of Ca2+, and this promoting property is attributable to troponin T. To address whether the embryonic/larval tail striated muscle and the adult smooth muscle utilize identical or different regulatory machinery, we cloned troponin T cDNAs from each cDNA library. The embryonic and the adult troponin Ts were encoded by distinct genes and shared only <60% identity with each other. These isoforms were specifically expressed in the embryonic/larval tail striated muscle and the adult smooth muscle, respectively. These results may imply that these isoforms regulate actin-myosin interaction in different manners. The adult troponin T under forced expression in mouse fibroblasts was unexpectedly located in the nuclei. However, a truncated protein with a deletion including a cluster of basic amino acids colocalized with tropomyosin on actin filaments. Thus, complex formation with troponin I and C immediately after the synthesis is likely to be essential for the protein to properly localize on the thin filaments.

【 授权许可】

Unknown