Gene expression profile of oxidant stress and neurodegeneration in transgenic mice deficient in α-tocopherol transfer protein

Alpha-tocopherol transfer protein (TTP) regulates the retention and secretion of α-tocopherol (α-T) by the liver. Deletion of the TTP gene (Ttpa) in mice results in systemic deficiency of α-T and neurological dysfunctions described in patients with mutated Ttpa. We have explored genome-wide changes in mRNAs from brain cortex and liver of Ttpa-deficient (Ttpa^-/-) mice and wild-type (Ttpa^+/+) mice. Selective inductions of genes regulated by antioxidant response elements were detected in Ttpa^-/- livers compared to Ttpa^+/+ livers, suggesting increased oxidant stress in Ttpa^-/- livers. The activation of cell proliferation pathways in Ttpa^-/- livers was indicated by the induction of genes that encode growth factor-binding proteins, mitogen-activated protein kinase kinase 3, and apoptosis inhibitor 6. The induction of synuclein-α and repression of synuclein-β genes was detected in Ttpa^-/- cortex. This may predispose Ttpa^-/- cortex to increased formation of synuclein-α aggregates and Lewy body, often associated with oxidant stress. Cortex of Ttpa^-/- mice revealed repression of genes encoding synaptic proteins, protein kinase C family members, and myelin proteins. A 13-fold decrease in the expression of retinoic acid receptor-related orphan receptor-α mRNA predicts staggerer-like phenotype (ataxia and deficits of motor coordination) of Ttpa^-/- mice. The repression of specific genes that determine synaptic plasticity and neuronal development may account for suppressed electrophysiological activities of cortex and impaired behavior in Ttpa ^-/- mice.