Induction of inclusion formation and disruption of lamin A/C structure by premutation CGG-repeat RNA in human cultured neural cells.
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder that affects some adult carriers of pre-mutation alleles (55-200 CGG repeats) of the fragile X mental retardation 1 (FMR1) gene. FXTAS is thought to be caused by a toxic 'gain-of-function' of the expanded CGG-repeat FMR1 mRNA, which is found in the neuronal and astrocytic intranuclear inclusions associated with the disorder. Using a reporter construct with a FMR1 5' untranslated region harboring an expanded (premutation) CGG repeat, we have demonstrated that intranuclear inclusions can be formed in both primary neural progenitor cells and established neural cell lines. As with the inclusions found in post-mortem tissue, the inclusions induced by the expanded CGG repeat are alphaB-crystallin-positive; however, inclusions in culture are not associated with ubiquitin, indicating that incorporation of ubiquitinated proteins is a later event in the disease process. The absence of ubiquitinated proteins also argues against a model in which inclusion formation is due to a failure of the proteasomal degradative machinery. The presence of the expanded CGG repeat, as RNA, results in reduced cell viability as well as the disruption of the normal architecture of lamin A/C within the nucleus. This last observation, and the findings that lamin A/C is present in both the inclusions of FXTAS patients and the inclusions in cell culture, suggests that lamin A/C dysregulation may be a component of the pathogenesis of FXTAS; in particular, the Charcot-Marie-Tooth-type neuropathy associated with FXTAS may represent a functional laminopathy.
Arocena
Dolores Garcia
DG
Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Davis, CA 95616, USA.
Iwahashi
Christine K
CK
Won
Nelly
N
Beilina
Alexandra
A
Ludwig
Anna L
AL
Tassone
Flora
F
Schwartz
Philip H
PH
Hagerman
Paul J
PJ
D020121:5' Untranslated Regions / Q000633:toxicity*; D017209:Apoptosis; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D003596:Cytosine / Q000378:metabolism; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017930:Genes, Reporter / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D006151:Guanosine / Q000378:metabolism; D006801:Humans; D007381:Intermediate Filament Proteins / Q000032:analysis; D045586:Intranuclear Inclusion Bodies / Q000737:chemistry* / Q000378:metabolism; D034904:Lamin Type A / Q000032:analysis* / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000032:analysis; D009474:Neurons / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D011494:Protein Kinases / Q000032:analysis; D013234:Stem Cells / Q000378:metabolism; D014162:Transfection; D019680:Trinucleotide Repeat Expansion; D025801:Ubiquitin / Q000378:metabolism; D038203:alpha-Crystallin B Chain
D020121:5' Untranslated Regions; D003596:Cytosine; D051860:Fragile X Messenger Ribonucleoprotein 1; D049452:Green Fluorescent Proteins; D006151:Guanosine; D007381:Intermediate Filament Proteins; D034904:Lamin Type A; D009419:Nerve Tissue Proteins; D011494:Protein Kinases; D025801:Ubiquitin; D038203:alpha-Crystallin B Chain; C059215:CRYAB protein, human; C497683:FMR1 protein, human; C440308:lamin C