Models of the dystrophin-glycoprotein complex do not reconcile the novel sparing of extraocular muscle in muscular dystrophy. Extraocular muscle sparing in Duchenne muscular dystrophy implies the existence of adaptive properties in these muscles that may extend protection to other neuromuscular diseases. We studied the extraocular muscle morphology and dystrophin-glycoprotein complex organization in murine targeted deletion of the γ-sarcoglycan (gsg-/-) and δ-sarcoglycan (dsg-/-) genes, two models of autosomal recessive limb girdle muscular dystrophy. In contrast to limb and diaphragm, the principal extraocular muscles were intact in gsg-/- and dsg-/- mice. However, central nucleated, presumptive regenerative, fibers were seen in the accessory extraocular muscles (retractor bulbi, levator palpebrae superioris) of both strains. Skeletal muscles of gsg-/- mice exhibited in vivo Evans Blue dye permeability, while the principal extraocular muscles did not. Disruption of γ-sarcoglycan produced secondary displacement of α- and β-sarcoglycans in the extraocular muscles. The intensity of immunofluorescence for dystrophin and α- and β-dystroglycan also appeared to be slightly reduced. Utrophin localization was unchanged. The finding that sarcoglycan disruption was insufficient to elicit alterations in extraocular muscle suggests that loss of mechanical stability and increased sarcolemmal permeability are not inevitable consequences of mutations that disrupt the dystrophin-glycoprotein complex organization and must be accounted for in models of muscular dystrophy.
|Number of pages||11|
|State||Published - 2001|
Bibliographical noteFunding Information:
The authors would like to thank Beth Ann Benetz and Hank Skladanowski for invaluable assistance with illustration preparation. Studies were supported by grants from the National Institutes of Health (R01 EY09834 and R01 EY12779 to JDP and R01 HL61322 to EMM), the Muscular Dystrophy Association (JDP and EMM), an unrestricted grant from Research to Prevent Blindness, a Research to Prevent Blindness Senior Scientific Investigator Award (JDP), a Charles E. Culpeper Medical Scholar award (EMM), the Ohio Lions Eye Research Foundation (JDP and FHA), American Heart Association Midwest Affiliate fellowship (AAH), the CWRU Visual Science Research Fund (JDP), and the Evenor Armington Fund (JDP and FHA), and a Research Resources award from the Howard Hughes Medical Institute to the University of Chicago Biological Sciences Division (EMM). JDP is Carl F. Asseff, M.D. Professor of Ophthalmology. Histological data were obtained with the assistance of the core facilities of the CWRU Visual Sciences Research Center (P30 EY11373).
- Extraocular muscle
- Muscular dystrophy
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health
- Clinical Neurology