Organization of connectin/titin filaments in sarcomeres of differentiating chicken skeletal muscle cells.
Very long, elastic connectin/titin molecules position the myosin filaments at the center of a sarcomere by linking them to the Z line. The behavior of the connectin filaments during sarcomere formation in differentiating chicken skeletal muscle cells was observed under a fluorescent microscope using the antibodies to the N terminal (located in the Z line), C terminal (M line), and C zone (myosin filament) regions ofconnectin and was compared to the incorporation of alpha-actinin and myosin into forming sarcomeres. In early stages of differentiating muscle cells, the N terminal region of connectin was incorporated into a stress fiber-like structure (SFLS) together with alpha-actinin to form dots, whereas the C terminal region was diffusely distributed in the cytoplasm. When both the C and N terminal regions formed striations in young myofibrils, the epitope to the C zone of A-band region, that is the center between the A-I junction and the M-line, initially was diffuse in appearance and later formed definite striations. It appears that it took some time for the N and C terminal regions of connectin to form a regular organization in a sarcomere. Thus the two ends of the connectin filaments were first fixed followed by the specific binding of the middle portion onto the myosin filament during sarcomere formation.
Soeno
Y
Y
Department of Biology, Faculty of Science, Chiba University, Japan.
Yajima
H
H
Kawamura
Y
Y
Kimura
S
S
Maruyama
K
K
Obinata
T
T
D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo; D064211:Connectin; D005455:Fluorescent Antibody Technique; D016253:Microscopy, Immunoelectron; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology* / Q000196:embryology / Q000648:ultrastructure; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*
D064211:Connectin; D009124:Muscle Proteins; D011494:Protein Kinases