Genes in familial parkinsonism and their role in sporadic Parkinson's disease.

For several decades there has been a controversy on the contribution of genetic factors to the pathogenesis of sporadic idiopathic Parkinson's disease (PD). The identification of families in which typical parkinsonism is inherited as an autosomal dominant or recessive trait sheds light on genes that cause phenotypes resembling sporadic PD. These genes are involved in molecular pathways leading to neurodegeneration and dysfunction of the nigrostriatal system. The present article gives insight into molecular pathways to neurodegeneration deciphered by the functional characterization of five genes identified in inherited forms of typical levodopa-responsive parkinsonism. There is increasing evidence that genes involved in monogenic forms of the disease may act as susceptibility factors also in the common sporadic form of PD. Transgenic animal models based on disease genes identified in monogenic forms of typical parkinsonism replicate important features of PD including protein aggregation and progressive motor symptoms. This implicates novel perspectives for neuroprotective therapeutic approaches that might be beneficial also to sporadic PD.