Neuroferritinopathy is a rare
genetic disease with a dominant autosomal transmission caused by mutations of the
ferritin light chain gene (FTL). It belongs to Neurodegeneration with Brain
Iron Accumulation, a group of disorders where
iron dysregulation is tightly associated with neurodegeneration. We studied the 498-499InsTC mutation which causes the substitution of the last 9
amino acids and an elongation of extra 16
amino acids at the C-terminus of
L-ferritin peptide. An analysis with cyclic voltammetry on the purified
protein showed that this structural modification severely reduces the ability of the
protein to store
iron. In order to analyze the impact of the mutation in vivo, we generated mouse models for the some pathogenic human FTL gene in FVB and C57BL/6J strains. Transgenic mice in the FVB background showed high accumulation of the mutated
ferritin in brain where it correlated with increased
iron deposition with age, as scored by magnetic resonance imaging. Notably, the accumulation of
iron-
ferritin bodies was accompanied by signs of oxidative damage. In the C57BL/6 background, both the expression of the mutant
ferritin and the
iron levels were lower than in the FVB strain. Nevertheless, also these mice showed oxidative alterations in the brain. Furthermore, post-natal hippocampal neurons obtained from these mice experienced a marked increased cell death in response to chronic
iron overload and/or acute oxidative stress, in comparison to wild-type neurons. Ultrastructural analyses revealed an accumulation of
lipofuscin granules associated with
iron deposits, particularly enriched in the cerebellum and striatum of our transgenic mice. Finally, experimental subjects were tested throughout development and aging at 2-, 8- and 18-months for behavioral phenotype. Rotarod test revealed a progressive impaired motor coordination building up with age, FTL mutant old mice showing a shorter latency to fall from the apparatus, according to higher accumulation of
iron aggregates in the striatum. Our data show that our 498-499InsTC mouse models recapitulate early pathological and clinical traits of the human
neuroferritinopathy, thus providing a valuable model for the study of the disease. Finally, we propose a mechanistic model of lipofuscine formation that can account for the etiopathogenesis of human
neuroferritinopathy.