title: Adeno-Associated Virus-Mediated Mini-Agrin Delivery Is Unable to Rescue Disease Phenotype in a Mouse Model of Limb Girdle Muscular Dystrophy Type 2I.
abstract: Agrin is a basement membrane-specific proteoglycan that can regulate orientation of cytoskeleton proteins and improve function of dystrophic skeletal muscle. In skeletal muscle, agrin binds with high affinity to laminin(s) and α-dystroglycan (α-DG), an integral part of the dystrophin-glycoprotein complex. Miniaturized forms of agrin (mAgrin) have been shown to ameliorate disease pathology in a laminin-α2 knockout mouse model of muscular dystrophy, acting as a link between α-DG and laminin(s). Here, we test whether mAgrin might also improve pathologies associated with FKRP-related dystroglycanopathies, another form of muscular dystrophy characterized by weak interactions between muscle and basement membranes. We demonstrate in vitro that mAgrin enhances laminin binding to primary myoblasts and fibroblasts from an FKRP mutant mouse model and that this enhancement is abrogated when mAgrin is in molar excess relative to laminin. However, in vivo delivery of mAgrin via adeno-associated virus (AAV) into FKRP mutant mice was unable to improve dystrophic phenotypes, both histologically and functionally. These results likely reflect insufficient binding of mAgrin to hypoglycosylated α-DG on muscle fibers and possibly abrogation of binding from molar excess of overexpressed AAV-delivered mAgrin. Further exploration of mAgrin modification is necessary to strengthen its binding to other membrane components, including hypoglycosylated α-DG, for potential therapeutic applications.
authors.affiliation: McColl-Lockwood Laboratory for Muscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Carolinas Healthcare System, Charlotte, North Carolina.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Vannoy
authors.affiliation: Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
authors.forename: Haowen
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Division of Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
authors.forename: Chunping
authors.initials: C
authors.lastname: Qiao
authors.affiliation: Division of Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
authors.forename: Xiao
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. Electronic address: abang@sbpdiscovery.org.
authors.forename: Anne G
authors.initials: AG
authors.lastname: Bang
authors.affiliation: McColl-Lockwood Laboratory for Muscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Carolinas Healthcare System, Charlotte, North Carolina. Electronic address: qi.lu@carolinashealthcare.org.
authors.forename: Qi L
authors.initials: QL
authors.lastname: Lu
mesh_terms: D018171:Agrin / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D000229:Dependovirus; D015316:Genetic Therapy / Q000379:methods*; D007150:Immunohistochemistry; D007797:Laminin / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D049288:Muscular Dystrophies, Limb-Girdle; D009137:Muscular Dystrophy, Animal / Q000473:pathology / Q000628:therapy*; D010641:Phenotype; D011485:Protein Binding
chemical_list: D018171:Agrin; D007797:Laminin