Transcription factor Pitx3 mutant mice as a model for Parkinson’s disease

BACKGROUND Parkinson’s disease (PD) is a common, age-dependent degenerative neurological disorder impairing motor control function and cognition. A key pathology of PD is a degeneration of the nigrostriatal dopamine system, leading to a severe dopamine denervation in the striatum and dynsfunction of the striatal neural circuits. OBJECTIVE To better understand the pathophysiology of the nigrostriatal dopamine denervation and to discover better treatments, animal PD models are needed. METHODS The authors’ original research on the transcription factor Pitx3 null mutant mice and the relevant literature were reviewed. RESULTS An important feature of an animal PD model is the severe, PD-like nigrostriatal dopamine denervation. This feature is provided in the transcription factor Pitx3 null mutant mice. These mice have a severe and bilateral nigral dopamine neuron loss and dopamine denervation in the dorsal striatum, while the dopamine neuron loss in the ventral tegmental area and dopamine denervation in the ventral striatum are moderate, creating a dorsal-ventral dopamine loss gradient and mimicking the dopamine denervation pattern in PD. Pitx3 null mice show motor function deficits in the balance beam and pole tests and these deficits are reversed by L-3,4-dihydroxyphenylalanine (L-dopa). These mice also show impaired cognitive functions as indicated by reduced motor learning and avoidance memory. L-dopa, D1 agonists and, to a lesser extent, D2 agonists, induce normal horizontal movements (walking) and also dyskinesia-like movements consisting of vertical body trunk movements and waving paw movements. CONCLUSION The easy-to-maintain Pitx3 null mice with an autogenic, consistent and gradient dopamine denervation are a convenient and suitable mouse model to study the consequences of dopamine loss in PD and to test dopaminergic replacement therapies for PD.