Antizyme Inhibitor 2-Deficient Mice Exhibit Altered Brain Polyamine Levels and Reduced Locomotor Activity

BACKGROUND: Alterations in the neural polyamine system are known to be associated with different brain pathological conditions. In addition, the regulation of enzymes involved in polyamine metabolism such as ornithine decarboxylase (ODC), antizymes (AZs), and antizyme inhibitors (AZINs) is critical during brain development. However, while most studies focus on ODC and AZs, less is known about AZIN expression and function in the brain. Thus, our aim was to analyze the expression pattern of AZIN2 during postnatal development, its brain distribution, and its possible implication in phenotypical alterations.

METHODS: The expression pattern of Azin2 and other genes related to polyamine metabolism was analyzed by RT-qPCR. β-D-galactosidase staining was used to determine the anatomical distribution of AZIN2 in a Azin2 knockout model containing the βGeo marker. Brain polyamine content was determined by HPLC. The Rota-Rod and Pole functional tests were used to evaluate motor skills in Azin2-lacking mice.

RESULTS: Our results showed that expression of genes codifying for AZs and AZINs showed a similar increasing pattern over time that coincided with a decrease in ODC activity and putrescine levels. The analysis of AZIN2 distribution demonstrated that it is strongly expressed in the cerebellum and distributed along the neuron body and dendrites. The ablation of Azin2 showed a decrease in putrescine levels and is related to reduced motor skills.

CONCLUSIONS: Our study revealed that AZIN2 expression in the brain is particularly limited to the cerebellum. In addition, the ablation of Azin2 leads to a reduction in putrescine that relates to alterations in motor function, suggesting the role of AZIN2 in the functioning of dopaminergic neurons.