Mutations in the F-box only protein 7 gene (FBXO7) cause PARK15, an autosomal recessive neurodegenerative disease presenting with severe levodopa-responsive parkinsonism and pyramidal disturbances. ...Understanding the PARK15 pathogenesis might thus provide clues on the mechanisms of maintenance of brain dopaminergic neurons, the same which are lost in Parkinson's disease. The protein(s) encoded by FBXO7 remain very poorly characterized. Here, we show that two protein isoforms are expressed from the FBXO7 gene in normal human cells. The isoform 1 is more abundant, particularly in primary skin fibroblasts. Both isoforms are undetectable in cell lines from the PARK15 patient of an Italian family; the isoform 1 is undetectable and the isoform 2 is severely decreased in the patients from a Dutch PARK15 family. In human cell lines and mouse primary neurons, the endogenous or over-expressed, wild type FBXO7 isoform 1 displays mostly a diffuse nuclear localization. An intact N-terminus is needed for the nuclear FBXO7 localization, as N-terminal modification by PARK15-linked missense mutation, or N-terminus tag leads to cytoplasmic mislocalization. Furthermore, the N-terminus of wild type FBXO7 (but not of mutant FBXO7) is able to confer nuclear localization to profilin (a cytoplasmic protein). Our data also suggest that overexpressed mutant FBXO7 proteins (T22M, R378G and R498X) have decreased stability compared to their wild type counterpart. In human brain, FBXO7 immunoreactivity was highest in the nuclei of neurons throughout the cerebral cortex, intermediate in the globus pallidum and the substantia nigra, and lowest in the hippocampus and cerebellum. In conclusion, the common cellular abnormality found in the PARK15 patients from the Dutch and Italian families is the depletion of the FBXO7 isoform 1, which normally localizes in the cell nucleus. The activity of FBXO7 in the nucleus appears therefore crucial for the maintenance of brain neurons and the pathogenesis of PARK15.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Parkinson's disease (PD) is a common degenerative neurologic disorder, which is pathologically characterized by a selective degeneration of dopaminergic neurons of the substantia nigra pars compacta, ...and the presence of characteristic eosinophilic inclusions, known as Lewy-bodies in affected brain areas. The cause of PD is unknown but, in recent years, genetic factors have been implicated in the aetiology of the disease. Firstly, clinico-genetic, epidemiologic and twin studies revealed inheritable effects and questioned earlier studies which had denied such influences. Secondly, several family studies suggested autosomal-dominant inheritance of syndromes which, to variable degrees, resembled sporadic PD clinically and in some cases also neuropathologically. Recently, a disease locus has been mapped to chromosome 4q21-22 in a large Mediterranean pedigree, in which disease expression is clinically and pathologically within the spectrum of sporadic PD; being atypical only for a relatively young mean age at onset of 46 years and rapid course of 10 years from onset to death. In affected individuals of this family and of three unrelated Greek kindreds, a putative disease-causing mutation has been identified in the gene encoding alpha-synuclein. With the first variant being defined, genetic heterogeneity has become apparent, as in other families parkinsonism was not linked to the 4q-locus and was not associated with the alpha-synuclein mutation (unpublished data). We describe a different genetic locus that appears to be involved in the development of parkinsonism closely resembling sporadic PD including a similar mean age of onset (59 years in the families, 59.7 years in sporadic PD; ref. 12). This locus was detected in a group of families of European origin. In two of these families, there is genetic evidence for a common founder. The penetrance of the mutation appears to be low, most likely below 40%. This is compatible with a possible role of this locus not only in familial, but also in typical (sporadic) PD.
Genetics of parkinsonism Bonifati, Vincenzo
Parkinsonism & related disorders,
2007, 2007-00-00, 20070101, Letnik:
13
Journal Article
Recenzirano
Abstract Ten years ago, α -synuclein mutations were discovered as the first genetic cause of Parkinson's disease (PD). In the following years, linkage mapping and positional cloning studies revealed ...further highly-penetrant (Mendelian) PD-causing mutations in the parkin, DJ-1, PINK1, LRRK2 , and ATP13A2 genes, delineating a highly heterogeneous etiological scenario. Perhaps even more importantly, a low-penetrance LRRK2 mutation (Gly2019Ser) and polymorphic variants in α -synuclein and LRRK2 are emerging as relevant genetic determinants for sporadic PD in several populations. Other Mendelian genes remain to be found, but the complete resolution of the genetic architectures of the common PD forms represents the main challenge for the next decade.
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