A single nucleotide polymorphism in the 3'UTR of the SNCA gene encoding alpha-synuclein is a new potential susceptibility locus for Parkinson disease.
ABSTRACT In Parkinson disease, the second most common neurodegenerative disorder in humans, increased alpha-synuclein (SNCA) levels are pathogenic, as evidenced by gene copy number mutations and increased alpha-synuclein levels detected in some familial and sporadic PD cases, respectively. Gene expression can be regulated at the post-transcriptional level by elements in the 3' untranslated region (3'UTR) of mRNAs. The goal of this study was to determine whether the 3'UTR of human SNCA can affect gene expression. Comparative sequence analysis revealed very high conservation across the entire 3'UTR of human SNCA over millions of years, suggesting the presence of multiple functionally important domains. EST and RT-PCR analyses showed that four different polyadenylation events occur in the 3'UTR of human SNCA. Finally, using luciferase assays, we examined the effect of the minor allele of five naturally occurring single nucleotide polymorphisms (SNPs) in the 3'UTR of SNCA on gene expression. The minor allele of SNP rs17016074 increased luciferase expression by 32% in a transient transfection assay in SHSY5Y neuroblastoma cells. Understanding the role of the 3'UTR of human SNCA and identifying functionally important naturally occurring SNPs using reporter assays can complement disease association studies in humans, uncovering potential susceptibility or protective polymorphisms in Parkinson disease. Our findings demonstrate that the 3'UTR of human SNCA, as a whole, and rs17016074, in particular, are loci of potential clinical importance for Parkinson disease.
Article: Sequence and position requirements for uridylate-rich downstream elements of polyadenylation signals.[show abstract] [hide abstract]
ABSTRACT: We have defined the positional and sequence requirements of U-rich downstream elements using a simian virus 40 late polyadenylation signal containing a substituted downstream region. A UUUUU element will significantly increase the efficiency of 3' end processing when placed between 6 and 25 bases downstream from the cleavage site. Positions in this interval closer than 15 bases from the cleavage site, however, were noticeably less efficient. Placement of the UUUUU element between +20 and +25 caused a partial shift in cleavage site usage to a CA motif at +4. Mutational analysis indicated that the sequence requirements at individual positions of the UUUUU element were somewhat flexible. Changing more than one base of the UUUUU sequence, however, severely diminished the ability of the element to mediate efficient 3' end processing. Finally, although hnRNP C proteins specifically interact with U-rich sequences, this protein--RNA interaction is not required for efficient in vitro polyadenylation.Nucleic Acids Research 08/1994; 22(13):2525-31. · 8.03 Impact Factor
Article: Patients homozygous and heterozygous for SNCA duplication in a family with parkinsonism and dementia.[show abstract] [hide abstract]
ABSTRACT: Multiplication of the alpha-synuclein gene (SNCA) (OMIM 163890) has been identified as a causative mutation in hereditary Parkinson disease or dementia with Lewy bodies. To determine the genetic, biochemical, and neuropathologic characteristics of patients with autopsy-confirmed autosomal dominant Lewy body disease, with particular reference to the dosage effects of SNCA. Four-generation family study. Academic research. Patients We fractionated samples extracted from frozen brain tissues of 4 patients for biochemical characterization, followed by immunoblot analysis. We determined the dosages of SNCA and its surrounding genes by quantitative polymerase chain reaction analysis. Quantitative polymerase chain reaction analysis revealed that 3 patients were heterozygous for SNCA duplication and 1 patient was homozygous for SNCA duplication. The homozygous patient showed earlier age at onset and earlier death, with more severe cognitive impairment than the heterozygous patients. Biochemical analysis revealed that phosphorylated alpha-synuclein accumulated in the sarkosyl-insoluble urea-extracted fraction of the brains of the patients. Pathologically confirmed Lewy body disease clinically characterized by progressive parkinsonism and cognitive dysfunction is caused by SNCA duplication. The homozygous patient demonstrated the most severe phenotype, suggesting that SNCA dosage has a considerable effect on disease phenotype even within a family. SNCA duplication results in the hyperaccumulation of phosphorylated alpha-synuclein in the brains of patients.Archives of neurology 05/2008; 65(4):514-9. · 6.31 Impact Factor
Article: Elevated alpha-synuclein mRNA levels in individual UV-laser-microdissected dopaminergic substantia nigra neurons in idiopathic Parkinson's disease.[show abstract] [hide abstract]
ABSTRACT: The presynaptic protein alpha-synuclein is involved in several neurodegenerative diseases, including Parkinson's disease (PD). In rare familial forms of PD, causal mutations (PARK1) as well as multiplications (PARK4) of the alpha-synuclein gene have been identified. In sporadic, idiopathic PD, abnormal accumulation and deposition of alpha-synuclein might also cause degeneration of dopaminergic midbrain neurons, the clinically most relevant neuronal population in PD. Thus, cell-specific quantification of alpha-synuclein expression-levels in dopaminergic neurons from idiopathic PD patients in comparison to controls would provide essential information about contributions of alpha-synuclein to the etiology of PD. However, a number of previous studies addressing this question at the tissue-level yielded varying results regarding alpha-synuclein expression. To increase specificity, we developed a cell-specific approach for mRNA quantification that also took into account the important issue of variable RNA integrities of the individual human postmortem brain samples. We demonstrate that PCR -amplicon size can confound quantitative gene-expression analysis, in particular of partly degraded RNA. By combining optimized UV-laser microdissection- and quantitative RT-PCR-techniques with suitable PCR assays, we detected significantly elevated alpha-synuclein mRNA levels in individual, surviving neuromelanin- and tyrosine hydroxylase-positive substantia nigra dopaminergic neurons from idiopathic PD brains compared to controls. These results strengthen the pathophysiologic role of transcriptional dysregulation of the alpha-synuclein gene in sporadic PD.Nucleic Acids Research 05/2008; 36(7):e38. · 8.03 Impact Factor