Parkinson's disease is a common neurodegenerative disease affecting over half a million Americans. Current therapies improve motor function, but they have significant side effects and do not slow disease progression. The discovery of genes responsible for hereditary parkinsonism has sparked interest in the role of these genes and the associated metabolic pathways in the more common, sporadic form of the disease. Animal models that faithfully reproduce key aspects of human disease permit testing of hypotheses and evaluation of new therapies. Our goal is to identify the gene causing canine multiple system degeneration (CMSD), a hereditary movement disorder of dogs, and develop it as a novel animal model of parkinsonism. Our hypothesis is that a mutation in the canine PARK2 gene causes progressive loss of dopaminergic cells in CMSD. Our preliminary studies have mapped the CMSD locus to a 5.1 Mb segment of the canine genome which includes PARK2. PARK2 mutations are the most common cause of familial parkinsonism. Inactivation of parkin (PARK2) in mice, however, fails to produce parkinsonism, thus a better animal model is needed.
Our specific aims are to: 1) Validate CMSD as a robust model of parkinsonism. Dogs with CMSD develop signs of parkinsonism and preliminary results suggest loss of dopaminergic neurons. We will confirm loss of dopaminergic neurons in the substantia nigra of CMSD dogs by immunohistochemistry and catecholamine assays. We will also determine if inclusion bodies in CMSD share immunohistochemical and ultrastructural characteristics of the inclusions found in Parkinson's disease (Lewy bodies). 2) Identify the gene responsible for CMSD. We have resequenced the coding regions of PARK2 and excluded simple deletions or missense mutations of PARK2 as a cause of CMSD; however, exon duplications are also reported in human disease. We will determine if there is decreased or aberrant PARK2 expression from the mutant allele by showing partial or complete loss of the mutant allele in mRNA from a CMSD dog and by demonstrating decreased or variant PARK2 mRNA in tissues from affected dogs. In addition, we will use multiplexed amplifiable probe hybridization to detect exon duplication of the canine PARK2 gene in CMSD. 3) Establish a viable research colony. We identified the CMSD locus in private kennels who have donated breeding stock. To utilize the model to answer basic questions about the pathogenesis and prevention of dopaminergic cell loss, the mutation must be preserved in a viable research colony. We will add to our breeding stock and conduct a breeding program to ensure future availability of the model. Parkinson's disease is a common neurodegenerative disease affecting over half a million Americans. Current therapies improve motor function, but they have significant side effects and do not slow disease progression. This research will develop a novel animal model of the disease which can be used to test theories about the cause and develop new therapies. ? ? ?
