title: Loss of beta-III spectrin leads to Purkinje cell dysfunction recapitulating the behavior and neuropathology of spinocerebellar ataxia type 5 in humans.
abstract: Mutations in SPTBN2, the gene encoding beta-III spectrin, cause spinocerebellar ataxia type 5 in humans (SCA5), a neurodegenerative disorder resulting in loss of motor coordination. How these mutations give rise to progressive ataxia and what the precise role beta-III spectrin plays in normal cerebellar physiology are unknown. We developed a mouse lacking full-length beta-III spectrin and found that homozygous mice reproduced features of SCA5 including gait abnormalities, tremor, deteriorating motor coordination, Purkinje cell loss, and cerebellar atrophy (molecular layer thinning). In vivo analysis reveals an age-related reduction in simple spike firing rate in surviving beta-III(-/-) Purkinje cells, whereas in vitro studies show these neurons to have reduced spontaneous firing, smaller sodium currents, and dysregulation of glutamatergic neurotransmission. Our data suggest an early loss of EAAT4- (protein interactor of beta-III spectrin) and a subsequent loss of GLAST-mediated uptake may play a role in neuronal pathology. These findings implicate a loss of beta-III spectrin function in SCA5 pathogenesis and indicate that there are at least two physiological effects of beta-III spectrin loss that underpin a progressive loss of inhibitory cerebellar output, namely an intrinsic Purkinje cell membrane defect due to reduced sodium currents and alterations in glutamate signaling.
authors.affiliation: The Centre for Integrative Physiology, The University of Edinburgh, George Square, Edinburgh EH8 9XD, United Kingdom.
authors.forename: Emma M
authors.initials: EM
authors.lastname: Perkins
authors.forename: Yvonne L
authors.initials: YL
authors.lastname: Clarkson
authors.forename: Nancy
authors.initials: N
authors.lastname: Sabatier
authors.forename: David M
authors.initials: DM
authors.lastname: Longhurst
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Millward
authors.forename: Jennifer
authors.initials: J
authors.lastname: Jack
authors.forename: Junko
authors.initials: J
authors.lastname: Toraiwa
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Watanabe
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Rothstein
authors.forename: Alastair R
authors.initials: AR
authors.lastname: Lyndon
authors.forename: David J A
authors.initials: DJ
authors.lastname: Wyllie
authors.forename: Mayank B
authors.initials: MB
authors.lastname: Dutia
authors.forename: Mandy
authors.initials: M
authors.lastname: Jackson
mesh_terms: D000200:Action Potentials / Q000235:genetics; D000818:Animals; D001284:Atrophy / Q000235:genetics; D002531:Cerebellum / Q000473:pathology; D005684:Gait / Q000235:genetics; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009043:Motor Activity / Q000235:genetics*; D011689:Purkinje Cells / Q000378:metabolism* / Q000473:pathology*; D013049:Spectrin / Q000172:deficiency* / Q000235:genetics; D020754:Spinocerebellar Ataxias / Q000235:genetics* / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D014202:Tremor / Q000235:genetics
chemical_list: C495133:SPTBN2 protein, human; D013049:Spectrin