title: Apolipoprotein E and apolipoprotein E messenger RNA in muscle of inclusion body myositis and myopathies.
abstract: Sporadic inclusion body myositis and the hereditary inclusion body myopathies are severe, progressive muscle diseases, characterized pathologically by vacuolated muscle fibers containing paired helical filaments. We immunostained muscle biopsy specimens from sporadic inclusion body myositis, hereditary inclusion body myopathy, disease control, and normal patients with several antibodies against apolipoprotein E (ApoE). Approximately 80 to 90% of the vacuolated muscle fibers of sporadic inclusion body myositis contained well-defined, strongly immunoreactive ApoE inclusions. In hereditary inclusion body myopathy, only rare vacuolated fibers had immunoreactive inclusions, whereas most had diffuse cytoplasmic ApoE immunoreactivity. Ultrastructurally, ApoE immunoreactivity in sporadic myositis was localized mainly to the paired helical filaments. By contrast, in the hereditary form, ApoE immunoreactivity occurred on material in close proximity to the paired helical filaments, but never was on the paired helical filaments. In both muscle diseases, ApoE was also on the 6- to 10-nm filaments and amorphous material. In the sporadic form, ApoE-immunoreactive deposits colocalized with Congo red-positive deposits; however, in muscle fibers from patients with hereditary disease there was no congophilia. ApoE messenger RNA was not detectable in muscle fibers from patients with hereditary or sporadic disease but was expressed abundantly in muscle macrophages. In all control and inclusion body myositis or myopathy biopsy specimens, ApoE immunoreactivity was strong at the postsynaptic domain of neuromuscular junctions; nonjunctional regions of normal fibers were negative for ApoE. ApoE immunoreactivity occurred diffusely in regenerating muscle fibers, a subset of which had detectable ApoE messenger RNA.
authors.affiliation: University of Southern California Neuromuscular Center, Department of Neurology, University of Southern California School of Medicine, Good Samaritan Hospital, Los Angeles 90017-1912, USA.
authors.forename: M
authors.initials: M
authors.lastname: Mirabella
authors.forename: R B
authors.initials: RB
authors.lastname: Alvarez
authors.forename: W K
authors.initials: WK
authors.lastname: Engel
authors.forename: K H
authors.initials: KH
authors.lastname: Weisgraber
authors.forename: V
authors.initials: V
authors.lastname: Askanas
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D001057:Apolipoproteins E / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D009220:Myositis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018979:Myositis, Inclusion Body / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D012333:RNA, Messenger