Uncoordinated expression of myosin heavy chains and myosin-binding protein C isoforms in human extraocular muscles.
OBJECTIVE
To examine the distribution of myosin-binding protein C (MyBP-C) in human extraocular muscles (EOMs) and to correlate the myosin heavy chain (MyHC) and the MyBP-C composition of the fibers.


METHODS
Samples from 17 EOMs, 3 levator palpebrae (LP), and 6 limb muscles were analyzed with SDS-PAGE and immunoblot or processed for immunocytochemistry with monoclonal antibodies (mAbs) against MyBP-C-fast, MyBP-C-slow, MyHCIIa, MyHCI, MyHCsto, MyHCalpha-cardiac, and MyHCemb.


RESULTS
In the limb muscle samples, fast fibers were labeled with anti-MyBP-C-fast and anti-MyBP-C-slow, whereas the slow fibers were immunostained with anti-MyBP-C-slow only, in accordance with previous studies. In 11 EOM samples MyBP-C-fast was not detected, and weak staining with anti-MyBP-C-fast was seen only in a few fibers in the proximal part of 2 muscles. The mAb against MyBP-C-slow labeled all fibers, but fibers containing MyHCI were generally more strongly stained. In the levator palpebrae, immunostaining with anti-MyBP-C-fast was present in some fibers labeled with anti-MyHCIIa and/or anti-MyHCeom. MyBP-C-fast and -intermediate were not detected biochemically in the EOMs.


CONCLUSIONS
The lack of MyBP-C-fast and intermediate is an additional feature of the human EOM allotype. The true EOMs have a unique myofibrillar protein isoform composition reflecting their special structural and functional properties. The levator palpebrae muscle phenotype is intermediate between that of the EOMs and the limb muscles.
Kjellgren
Daniel
D
Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden; the.
Stål
Per
P
Larsson
Lars
L
Fürst
Dieter
D
Pedrosa-Domellöf
Fatima
F
D000293:Adolescent; D000328:Adult; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D009801:Oculomotor Muscles / Q000378:metabolism*; D020033:Protein Isoforms; D000099163:Myosin Binding Protein C
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D018995:Myosin Heavy Chains; D009218:Myosins; D020033:Protein Isoforms; D000099163:Myosin Binding Protein C