title: Partial deletion of AFG3L2 causing spinocerebellar ataxia type 28.
abstract: OBJECTIVE
  To identify the genetic cause of autosomal dominant spinocerebellar ataxia type 28 (SCA28) with ptosis in 2 Belgian families without AFG3L2 point mutations and further extend the clinical spectrum of SCA28 through the study of a brain autopsy, advanced MRI, and cell-based functional assays exploring the underlying disease mechanism.
  
  
  METHODS
  Two large families were clinically examined in detail. Linkage analysis and multiplex amplicon quantification were performed. A brain autopsy was obtained. Brain MRI with voxel-based morphometry and diffusion tensor imaging was performed. RNA and Western blot analysis and blue native-polyacrylamide gel electrophoresis experiments were performed.
  
  
  RESULTS
  MRI analysis demonstrated a significant cerebellar atrophy, as well as white matter degeneration in the cerebellar peduncles, corticospinal tracts, corpus callosum, and cingulum. A brain autopsy showed severe atrophy of the upper part of the cerebellar hemisphere. Ubiquitin and p62 immunoreactive intranuclear inclusions were found in cerebral and cerebellar cortical neurons, in neurons of the hippocampus, and in pontine and medullary nuclei. An identical heterozygous partial deletion of exons 14 to 16 of the AFG3L2 gene was found in both families. Additional functional assays in patient-derived cell lines revealed haploinsufficiency as the underlying disease mechanism.
  
  
  CONCLUSIONS
  Our study expands the phenotypic characterization of SCA28 by means of brain pathology and diffusion tensor imaging/voxel-based morphometry MRIs. The identification of a partial AFG3L2 deletion and the subsequent functional studies reveal loss of function as the most likely disease mechanism. Specific testing for deletions in AFG3L2 is warranted because these escape standard sequencing.
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: Smets
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Tine
authors.initials: T
authors.lastname: Deconinck
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Baets
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Sieben
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Martin
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Iris
authors.initials: I
authors.lastname: Smouts
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Shuaiyu
authors.initials: S
authors.lastname: Wang
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Franco
authors.initials: F
authors.lastname: Taroni
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Daniela
authors.initials: D
authors.lastname: Di Bella
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Van Hecke
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Parizel
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Christina
authors.initials: C
authors.lastname: Jadoul
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Robert
authors.initials: R
authors.lastname: De Potter
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Francine
authors.initials: F
authors.lastname: Couvreur
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium.
authors.forename: Elena
authors.initials: E
authors.lastname: Rugarli
authors.affiliation: From the Neurogenetics Group, VIB-Department of Molecular Genetics (K.S., T.D., J.B., I.S., P.D.J.), and Laboratories of Neurogenetics and Neuropathology, Institute Born-Bunge (K.S., T.D., J.B., A.S., J.-J.M., P.D.J.), University of Antwerp; Departments of Neurology (K.S., J.B., J.-J.M., I.S., P.D.J.) and Radiology (W.V.H., P.M.P.), Antwerp University Hospital; Department of Neurology (A.S.), Ghent University Hospital, Belgium; Biocenter (S.W., E.R.), University of Cologne; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (S.W., E.R.), Cologne, Germany; Unit of Genetics of Neurodegenerative and Metabolic Diseases (F.T., D.D.B.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Icometrix (W.V.H., P.M.P.), Leuven; Department of Neurology (C.J.), AZ Nicolaas, Sint-Niklaas; Department of Neurology (R.D.P.), AZ Sint-Lucas, Gent; and Department of Neurology (F.C.), AZ Klina, Brasschaat, Belgium. peter.dejonghe@molgen.vib-ua.be.
authors.forename: Peter
authors.initials: P
authors.lastname: De Jonghe
mesh_terms: D049069:ATP-Dependent Proteases / Q000235:genetics*; D000074183:ATPases Associated with Diverse Cellular Activities; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001284:Atrophy / Q000235:genetics / Q000473:pathology; D002460:Cell Line; D005260:Female; D057895:Haploinsufficiency / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D010641:Phenotype; D017384:Sequence Deletion / Q000235:genetics*; D020754:Spinocerebellar Ataxias / Q000151:congenital; D013132:Spinocerebellar Degenerations / Q000235:genetics* / Q000473:pathology
chemical_list: D049069:ATP-Dependent Proteases; C120699:AFG3L2 protein, human; D000074183:ATPases Associated with Diverse Cellular Activities