SUBCELLULAR-LOCALIZATION OF THE HUNTINGTONS-DISEASE GENE-PRODUCT IN CELL-LINES BY IMMUNOFLUORESCENCE AND BIOCHEMICAL SUBCELLULAR FRACTIONATION

Huntington's disease is a progressive neurodegenerative disorder, whic h is caused by expansion of a polymorphic (CAG)(n) repeat in the codin g region of the Huntington's disease gene. The function of huntingtin has not been elucidated so far. Accordingly, detailed subcellular loca lization studies remain useful, In an immunohistochemical study, we ha ve reported huntingtin to be present in the cytoplasm of cells in the majority of the tissues studied, In addition, we detected a signal in the nucleus of cells in some tissues, including neuronal cells, We hav e further extended these studies in various mammalian cell lines, usin g a panel of (affinity-purified) polyclonal huntingtin antibodies in i mmunofluorescence, confocal laser scanning microscopy and biochemical subcellular fractionation studies, In mouse embryonic fibroblasts, hum an skin fibroblasts and in mouse neuroblastoma cells huntingtin was pr esent in the cytoplasm, All five antibodies, directed against differen t parts of huntingtin, also showed a signal in the nucleus, This signa l could be competed by the original antigen, The localization of hunti ngtin in both cytoplasm and nucleus, was confirmed by biochemical subc ellular fractionation studies, However, in most other studies, a nucle ar location for huntingtin has not been found, Our results suggest, ho wever, that besides its function(s) in the cytoplasm, a nuclear functi on of huntingtin at some stages of differentiation or in some phases o f the cell cycle may not be excluded.