Age-dependent degeneration of midbrain dopaminergic (mDA) neurons underlies the cognitive and motor symptoms of Parkinson’s disease. Havrda et al. previously reported that mice that lack the transcription factor Id2, which is expressed in the developing CNS, have fewer dopaminergic neurons in the olfactory bulb and reduced olfactory discrimination, a preclinical marker of Parkinson’s disease. Now, the researchers report that Id2−/− mice exhibit age-dependent degeneration of mDA neurons that is associated with changes in locomotor activity. Young Id2−/− mice had reduced dopamine transporter (DAT) expression, a biomarker of Parkinson’s disease. Moreover, DAT expression was found to be dependent on Id2 expression in an in vitro dopaminergic neuron differentiation model. Thus, the Id2−/− mouse represents a new model in which to study the progression and treatment of neurodegenerative disorders that involve the dopamine system. Page 819

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