title: Transgenic Rescue of the LARGEmyd Mouse: A LARGE Therapeutic Window?
abstract: LARGE is a glycosyltransferase involved in glycosylation of α-dystroglycan (α-DG). Absence of this protein in the LARGEmyd mouse results in α-DG hypoglycosylation, and is associated with central nervous system abnormalities and progressive muscular dystrophy. Up-regulation of LARGE has previously been proposed as a therapy for the secondary dystroglycanopathies: overexpression in cells compensates for defects in multiple dystroglycanopathy genes. Counterintuitively, LARGE overexpression in an FKRP-deficient mouse exacerbates pathology, suggesting that modulation of α-DG glycosylation requires further investigation. Here we demonstrate that transgenic expression of human LARGE (LARGE-LV5) in the LARGEmyd mouse restores α-DG glycosylation (with marked hyperglycosylation in muscle) and that this corrects both the muscle pathology and brain architecture. By quantitative analyses of LARGE transcripts we also here show that levels of transgenic and endogenous LARGE in the brains of transgenic animals are comparable, but that the transgene is markedly overexpressed in heart and particularly skeletal muscle (20-100 fold over endogenous). Our data suggest LARGE overexpression may only be deleterious under a forced regenerative context, such as that resulting from a reduction in FKRP: in the absence of such a defect we show that systemic expression of LARGE can indeed act therapeutically, and that even dramatic LARGE overexpression is well-tolerated in heart and skeletal muscle. Moreover, correction of LARGEmyd brain pathology with only moderate, near-physiological LARGE expression suggests a generous therapeutic window.
authors.affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: J C W
authors.initials: JC
authors.lastname: Hildyard
authors.affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: E
authors.initials: E
authors.lastname: Lacey
authors.affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: H
authors.initials: H
authors.lastname: Booler
authors.affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Hopkinson
authors.affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: D J
authors.initials: DJ
authors.lastname: Wells
authors.affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: S C
authors.initials: SC
authors.lastname: Brown
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D049030:Dystroglycans / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000378:metabolism; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics* / Q000378:metabolism
chemical_list: D049030:Dystroglycans; C502747:Large1 protein, mouse; D017351:N-Acetylglucosaminyltransferases