Exacerbation of sensorimotor dysfunction in mice deficient in Atp13a2 and overexpressing human wildtype alpha-synuclein.

Loss of function mutations in the gene ATP13A2 are associated with Kufor-Rakeb Syndrome and Neuronal Ceroid Lipofuscinosis, the former designated as an inherited form of Parkinson's disease (PD). The function of ATP13A2 is unclear but in vitro studies indicate it is a lysosomal protein and may interact with the presynaptic protein alpha-synuclein (aSyn) and certain heavy metals. Accumulation of aSyn is a major component of lewy bodies, the pathological hallmark of PD. Atp13a2-deficient (13a2) mice develop age-dependent sensorimotor deficits, and accumulation of insoluble aSyn in the brain. To better understand the interaction between ATP13A2 and aSyn, double mutant mice with loss of Atp13a2 function combined with overexpression of human wildtype aSyn were generated. Female and male wildtype (WT), 13a2, aSyn, and 13a2-aSyn mice were tested on a battery of sensorimotor tests including adhesive removal, challenging beam traversal, spontaneous activity, gait, locomotor activity, and nest-building at 2, 4, and 6 months of age. Double mutant mice showed an earlier onset and accelerated alterations in sensorimotor function that were age, sex and test-dependent. Female 13a2-aSyn mice showed early and progressive dysfunction on the beam and in locomotor activity. In males, 13a2-aSyn mice showed more severe impairments in spontaneous activity and adhesive removal. Sex differences were also observed in aSyn and 13a2-aSyn mice on the beam, cylinder, and adhesive removal tests. In other tasks, double mutant mice displayed deficits similar to aSyn mice. These results indicate loss of Atp13a2 function exacerbates the sensorimotor phenotype in aSyn mice in an age and sex-dependent manner.

The effect of manganese exposure in Atp13a2-deficient mice.

Loss of function mutations in the P5-ATPase ATP13A2 are associated with Kufor-Rakeb Syndrome and Neuronal Ceroid Lipofuscinosis. While the function of ATP13A2 is unclear, in vitro studies suggest it is a lysosomal protein that interacts with the metals manganese (Mn) and zinc and the presynaptic protein alpha-synuclein. Loss of ATP13A2 function in mice causes sensorimotor deficits, enhanced autofluorescent storage material, and accumulation of alpha-synuclein. The present study sought to determine the effect of Mn administration on these same outcomes in ATP13A2-deficient mice. Wildtype and ATP13A2-deficient mice received saline or Mn at 5-9 or 12-19 months for 45days. Sensorimotor function was assessed starting at day 30. Autofluorescence was quantified in multiple brain regions and alpha-synuclein protein levels were determined in the ventral midbrain. Brain Mn, iron, zinc, and copper concentrations were measured in 5-9 month old mice. The results show Mn enhanced sensorimotor function, increased autofluorescence in the substantia nigra, and increased insoluble alpha-synuclein in the ventral midbrain in older ATP13A2-deficient mice. In addition, the Mn regimen used increased Mn concentration in the brain and levels were higher in Mn-treated mutants than controls. These results indicate loss of ATP13A2 function leads to increased sensitivity to Mn in vivo.

Assessment of sensorimotor function in mouse models of Parkinson's disease.

Sensitive and reliable behavioral outcome measures are essential to the evaluation of potential therapeutic treatments in preclinical trials for many neurodegenerative diseases. In Parkinson's disease, sensorimotor tests sensitive to varying degrees of nigrostriatal dysfunction are fundamental for testing the efficacy of potential therapeutics. Reliable and quite elegant sensorimotor measures exist for rats, however many of these tests measure sensorimotor asymmetry within the rat and are not entirely suitable for the newer genetic mouse models of PD. We have put together a battery of sensorimotor tests inspired by the sensitive tests in rats and adapted for mice. The test battery highlighted in this study is chosen for a) its sensitivity in a wide variety of mouse models of PD, b) its ease in implementing into a study, and c) its low expense. These tests have proven useful in characterizing novel genetic mouse models of PD as well as in testing potential disease-modifying therapies.

Atp13a2-deficient mice exhibit neuronal ceroid lipofuscinosis, limited α-synuclein accumulation and age-dependent sensorimotor deficits.

Mutations in ATP13A2 (PARK9), encoding a lysosomal P-type ATPase, are associated with both Kufor-Rakeb syndrome (KRS) and neuronal ceroid lipofuscinosis (NCL). KRS has recently been classified as a rare genetic form of Parkinson's disease (PD), whereas NCL is a lysosomal storage disorder. Although the transport activity of ATP13A2 has not been defined, in vitro studies show that its loss compromises lysosomal function, which in turn is thought to cause neuronal degeneration. To understand the role of ATP13A2 dysfunction in disease, we disrupted its gene in mice. Atp13a2(-/-) and Atp13a2(+/+) mice were tested behaviorally to assess sensorimotor and cognitive function at multiple ages. In the brain, lipofuscin accumulation, α-synuclein aggregation and dopaminergic pathology were measured. Behaviorally, Atp13a2(-/-) mice displayed late-onset sensorimotor deficits. Accelerated deposition of autofluorescent storage material (lipofuscin) was observed in the cerebellum and in neurons of the hippocampus and the cortex of Atp13a2(-/-) mice. Immunoblot analysis showed increased insoluble α-synuclein in the hippocampus, but not in the cortex or cerebellum. There was no change in the number of dopaminergic neurons in the substantia nigra or in striatal dopamine levels in aged Atp13a2(-/-) mice. These results show that the loss of Atp13a2 causes sensorimotor impairments, α-synuclein accumulation as occurs in PD and related synucleinopathies, and accumulation of lipofuscin deposits characteristic of NCL, thus providing the first direct demonstration that null mutations in Atp13a2 can cause pathological features of both diseases in the same organism.