Striated muscle tropomyosin-enriched microfilaments of developing muscles of chicken embryos.
The striated muscle tropomyosin-enriched microfilaments were isolated from developing muscles in ovo by the previously described method with a monoclonal antibody against striated muscle isoforms of tropomyosin (Lin & Lin, 1986). Two-dimensional gel analysis of the isolated microfilaments from developing heart, thigh and breast muscles revealed the coexistence of non-muscle isoforms of tropomyosin and actin throughout all stages of embryogenesis. A small but significant amount of skeletal muscle isoforms (alpha, beta) of tropomyosins and their phosphorylated forms was detected in the microfilaments isolated from hearts of 6-15-day-old embryos. These skeletal isoforms of tropomyosins disappeared after this stage of embryogenesis. In addition, we also detected both embryonic and adult isoforms of troponin T in early developing hearts. In developing thigh and breast muscles, the presence of non-muscle tropomyosin isoforms 2, 3a and 3b in the isolated microfilaments was apparent. The contents of tropomyosin isoform 2 were decreased with development and this non-muscle isoform completely disappeared at the 15th day of embryogenesis. On the other hand, the non-muscle tropomyosin isoforms 3a and 3b were present throughout all stages of development. Double-label immunofluorescence microscopy with monoclonal CH1 (anti-striated muscle isoforms of tropomyosin) and CG beta 6 (anti-non-muscle isoforms of tropomyosin) on the isolated, glycerinated skeletal and cardiac muscle cells of 10-day-old or 13-day-old embryos confirmed the colocalization of muscle and non-muscle isoforms of tropomyosins within the same cells. These results suggest that different isoforms of actin and tropomyosin can assemble into a class of microfilaments (i.e. striated muscle tropomyosin-enriched microfilaments) in ovo, which may transform into the thin filaments of mature muscle cells.
Department of Anatomy, College of Medicine, National Taiwan University, Taipei.
S M
SM
Wang
S H
SH
Wang
J L
JL
Lin
J J
JJ
Lin
D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure*; D000199:Actins / Q000276:immunology / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002642:Chick Embryo; D003599:Cytoskeleton / Q000648:ultrastructure*; D004586:Electrophoresis; D005455:Fluorescent Antibody Technique; D006321:Heart / Q000196:embryology; D009132:Muscles / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D010210:Papillary Muscles / Q000378:metabolism / Q000648:ultrastructure; D014335:Tropomyosin / Q000276:immunology / Q000378:metabolism*
D000199:Actins; D000911:Antibodies, Monoclonal; D014335:Tropomyosin