Intracellular Ferritin Accumulation in Neural and Extraneural Tissue Characterizes a Neurodegenerative Disease Associated with a Mutation in theFerritin Light PolypeptideGene

Abstract

Abnormal accumulation of ferritin was found to be associated with an autosomal dominant slowly progressing neurodegenerative disease clinically characterized by tremor, cerebellar ataxia, parkinsonism and pyramidal signs, behavioral disturbances, and cognitive decline. These symptoms may appear sequentially over a period of 4 decades. Pathologically, intranuclear and intracytoplasmic bodies were found in glia and subsets of neurons in the central nervous system as well as in extraneural tissue. Biochemical analyses of these bodies isolated from the striatum and cerebellar cortex revealed that ferritin light polypeptide (FTL) and ferritin heavy polypeptide (FTH1) were the main constituents. Molecular genetic studies revealed a 2-bp insertion mutation in exon 4 of the FTL gene. The resulting mutant polypeptide is predicted to have a carboxy terminus that is altered in amino-acid sequence and length. In tissue sections, the bodies were immunolabeled by anti-ferritin and anti-ubiquitin antibodies and were stained by Perls' method for ferric iron. Synthetic peptides homologous to the altered and wild-type carboxy termini were used to raise polyclonal antibodies. These novel antibodies as well as an antibody recognizing FTH1 immunolabeled the bodies. This study of this disorder has provided additional knowledge and insights in the growing area of ferritin-related neurodegeneration.

Iron-mediated Aggregation and a Localized Structural Change Characterize Ferritin from a Mutant Light Chain Polypeptide That Causes Neurodegeneration

“…Samples treated with thermolysin and controls without thermolysin were boiled and loaded onto SDS-polyacrylamide gels (4 -20%) (Pierce). Gels were stained with Coomassie Blue (Total protein) or blotted against the C-terminal antibodies (MT-1283 or WT-1278) (9) or against the N-terminal antibody D18 (Santa Cruz Biotechnology, Inc), which recognized both polypeptides.…”

“…Here we characterize the protein structure and the iron storage function of ferritin formed by the polypeptide p.Phe167SerfsX26, generated by the FTL498 -499InsTC mutation (MT-FTL) (9). The mutant polypeptide assembled spontaneously into ferritin spherical shells in a soluble manner.…”

Neuroferritinopathy: a new inborn error of iron metabolism

“…Seven pathogenic mutations in FTL1 have since been described [1][2][3][4][5][6][7]. Six are frameshift mutations which alter the reading frame and are predicted to extend the ferritin light chain peptide at the site of the pore in the ferritin molecule.…”

“…The mutations result in the accumulation of ferritin and iron within central neurons, in particular within the basal ganglia [1][2][3][4], leading to oxidative stress and ultimately resulting in neurodegeneration [2,8].…”

Mutant Ferritin L-chains That Cause Neurodegeneration Act in a Dominant-negative Manner to Reduce Ferritin Iron Incorporation

“…Six pathogenic mutations have been identified so far (9,10,(12)(13)(14)(15)(16). They are all private mutations found in single families, except the 460InsA found in several patients of North Anglia.…”