Identification and localization of ataxin-7 in brain and retina of a patient with cerebellar ataxia type II using anti-peptide antibody.
Autosomal dominant cerebellar ataxias (ADCAs) are a complex group of neurodegenerative disorders characterized by progressive degeneration of the cerebellum, brain stem and spinal cord. The spinocerebellar ataxia type 7 (SCA7) is associated with pigmentary macular dystrophy and retinal degeneration leading to blindness caused by a CAG/polyglutamine (polyGln) expansion in the coding region of the SCA7 gene/protein. The SCA7 gene codes for ataxin-7, a protein of unknown function. To investigate its cellular and subcellular localization, we have developed a sequence-specific polyclonal antibody against the N-terminal part of the protein. Immunohistochemical analysis indicated that ataxin-7 accumulates as single nuclear inclusion (NI) in the cells of the brain and retina of a SCA7 patient but not of controls. The 1C2 antibody, directed against expanded polyGln, confirmed the aggregation of mutant ataxin-7 in these NIs. Furthermore, ubiquitin was found in these aggregates, suggesting that mutant ataxin-7 is a target for ubiquitin-dependent proteolysis, but resistant to removal. Electron microscopic studies using immunogold labeling showed that ataxin-7 immunoreactive NIs appear as dense aggregates containing a mixture of granular and filamentary structures. Together, these data confirm the presence of NIs in brain and retina of a SCA7 patient, a common characteristic of disorders caused by expanded CAG/polyGln repeats.
Mauger
C
C
Department of Molecular Genetics, Flanders Interuniversity Institute for Biotechnology (VIB), Belgium.
Del-Favero
J
J
Ceuterick
C
C
Lübke
U
U
van Broeckhoven
C
C
Martin
J
J
D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D000067719:Ataxin-7; D001923:Brain Chemistry; D002524:Cerebellar Ataxia / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D002675:Child, Preschool; D017809:Fatal Outcome; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000276:immunology; D011149:Pons / Q000737:chemistry*; D012160:Retina / Q000737:chemistry* / Q000648:ultrastructure
C000593829:ATXN7 protein, human; D000911:Antibodies, Monoclonal; D000067719:Ataxin-7; D009419:Nerve Tissue Proteins