(Introduction)
PARK9, firstly reported as Kufor-Rakeb syndrome by al-Din et al. in 1994, is the autosomal recessive juvenile onset familial Parkinson's disease that is characterized by L-DOPA responsive parkinsonism, cognitive dysfunction, pyramidal signs and myoclonus. The gene responsible for PARK9 was recently identified as ATP13A2 which encodes 1180 amino acid, and its protein product ATP13A2 was found to have 10 transmembrane domains and locate in the lysosome as P-type ATPase. It is assumed that loss of the lysosomal function as well as gain of toxic function by mutant ATP13A2 were responsible for the neuronal loss in PARK9, although the precise mechanism of it is not well understood.

(Methods)
To reveal the mechanism of neuronal loss in PARK9, we created ATP13A2 mutant medaka by TILLING (Tilling is Targetting Induced Local Lesions In Genome) method using ENU mutagen.

(Results and Conclusion)
The point mutation in the ATP13A2 mutant medaka was located in the intron between exon 12 and 13 (IVS13, T-C, +2), and causes exon 13 skipping in the ATP13A2 gene transcription, that is relevant to human PARK9 cases. Aged ATP13A2 mutant medaka showed reduced dopamine content and the decreased number of TH+ neurons in the midbrain, suggesting that ATP13A2 mutant medaka could be a good PD model. Although the α-synuclein accumulation by ATP13A2 knockdown in mice primary cortical neurons was reported, it still remains unknown whether it is true or not in vivo, especially in vertebrates. Now we are performing biochemical and immunohistochemical analysis including α-synuclein immnostaining and evaluation of lysosomal functions in ATP13A2 mutation medaka to confirm the relationship among the dysfunction of ATP13A2, lysosomal dysfunction and α-synuclein accumulation in vivo.