These findings show that rAAVrh74.MCK.GALGT2 treatment of P448Lneo? muscles at an early age can inhibit the cycles of skeletal myofiber degeneration and regeneration that arise from MD. Steps of myofiber diameter likewise showed that P448Lneo? myofibers had significantly increased average myofiber diameter (Physique?3C) and reduced CV in myofiber diameter (Physique?3D) relative to untreated contralateral muscles, again indicating a lack of muscle damage and normal muscle growth. variety of forms of muscular dystrophy (MD), ranging from severe congenital forms such as Walker-Warburg syndrome (WWS), Fukuyama congenital MD, muscle eye brain disease, and congenital MD 1C and 1D to adult-onset limb girdle MDs (LGMDs), including LGMD2I, K, L, M, N, O, P, T, and U, arise from mutations in genes known to affect the glycosylation of dystroglycan with O-mannose-phosphateClinked glycans that are required for laminin binding to the dystroglycan protein.1, 2, 3, 4, 5 Because all of these disorders share improper post-translational glycosylation of dystroglycan, they are PF-4778574 collectively termed dystroglycanopathies. Dystroglycan is usually a central component of the dystrophin-associated glycoprotein (DAG) complex in striated muscles.6, 7 Dystroglycan is post-translationally processed into two proteins, and dystroglycan, that bind tightly but noncovalently to one another.6, 8 Dystroglycan is a transmembrane protein that resides within the muscle sarcolemmal membrane, whereas dystroglycan is a peripheral membraneCassociated protein. Extracellular matrix (ECM) proteins, including laminin 211, agrin, and perlecan, bind to dystroglycan, whereas the intracellular domain name of dystroglycan binds to cytoskeletal-associated proteins, including dystrophin utrophin and plectin 1, which in turn bind to filamentous actin and/or microtubules.7, 9 As such, dystroglycan serves as a vital link within the membrane to connect the ECM, particularly laminin 211 that is a principal component of the basal lamina that surrounds every skeletal myofiber in the adult,10, 11 PF-4778574 through the membrane to the intracellular filamentous actin cytoskeleton. ECM proteins bind dystroglycan through the O-mannose-phosphateClinked oligosaccharide structures present in its mucin-like domain name,2 and mutations in well more than a dozen genes that control dystroglycan glycosylation give rise to congenital or limb girdle forms of MD.3, 4 In their most severe forms, including WWS, Fukuyama congenital MD, and muscle eye brain disease, dystroglycanopathies not only affect skeletal muscle but also vision and brain development, leading to lissencephalic changes PSEN1 in the cerebral cortex due to defects in the glial limitans-pial basement membrane and to ocular malformations that can include retinal detachment.12, 13, 14 One gene that when mutated can give rise to dystroglycanopathies is fukutin-related protein, which is encoded by the gene. mutations have been reported to cause WWS, congenital MD 1C, and LGMD2I, with the more severe clinical phenotypes typically being associated with mutations that further affect the glycosylation of dystroglycan and laminin binding to dystroglycan.15, 16, 17, 18, 19 Mutations in and fukutin (shares homology and from which got its name,20, 21 both can give rise to forms of either congenital MD or LGMD.22, 23 Recently, both FKRP and fukutin have been shown to possess ribitol 5-phosphate transferase activity, and a tandem ribitol 5-phosphate moiety was shown to be present on dystroglycan on which laminin binding glycans could be synthesized and which are themselves absent in FKRP-, fukutin-, and isoprenoid synthase domain name containingCdeficient cells.24 Lu and colleagues25 have designed a series of mouse knockin models of disease-relevant human mutations that give rise to varying degrees of muscle disease pathology and dysfunction. Introduction of the P448L mutation, in the presence of a neomycin gene cassette, gives rise to severe muscle pathology consistent with WWS,26 whereas deletion of the neo cassette from the P448L knockin allele gives rise to a milder disease spectrum more analogous to LGMD2I, with adult onset muscle necrosis and evidence of muscle damage and regeneration, coupled with inflammation, fibrosis, and muscle wasting.25 PF-4778574 This mouse model, like human LGMD2I, shows reduced functional glycosylation of dystroglycan in both heart and skeletal muscles, whereas dystroglycan protein is expressed at or near normal levels.19 Here, we have used the neo-deleted version of the P448L mouse model (P448Lneo?) to assess the value of a particular gene therapy for patients with LGMD2I.19, 25 Although defects in dystroglycan glycosylation can give rise to forms of MD, other enzymes that glycosylate dystroglycan, when overexpressed, can significantly increase muscle protection and prevent muscle pathology. One such approach involves overexpression of (formerly gene encodes a 1 to 4 N-acetylgalactosaminyl transferase.
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